fs/ceph/mds_client.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/ceph/ceph_debug.h>

#include <linux/fs.h>
#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/gfp.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/delay.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/ratelimit.h>
#include <linux/bits.h>
#include <linux/ktime.h>
#include <linux/bitmap.h>
#include <linux/mnt_idmapping.h>

#include "super.h"
#include "mds_client.h"
#include "crypto.h"

#include <linux/ceph/ceph_features.h>
#include <linux/ceph/messenger.h>
#include <linux/ceph/decode.h>
#include <linux/ceph/pagelist.h>
#include <linux/ceph/auth.h>
#include <linux/ceph/debugfs.h>
#include <trace/events/ceph.h>

#define RECONNECT_MAX_SIZE (INT_MAX - PAGE_SIZE)

/*
 * A cluster of MDS (metadata server) daemons is responsible for
 * managing the file system namespace (the directory hierarchy and
 * inodes) and for coordinating shared access to storage.  Metadata is
 * partitioning hierarchically across a number of servers, and that
 * partition varies over time as the cluster adjusts the distribution
 * in order to balance load.
 *
 * The MDS client is primarily responsible to managing synchronous
 * metadata requests for operations like open, unlink, and so forth.
 * If there is a MDS failure, we find out about it when we (possibly
 * request and) receive a new MDS map, and can resubmit affected
 * requests.
 *
 * For the most part, though, we take advantage of a lossless
 * communications channel to the MDS, and do not need to worry about
 * timing out or resubmitting requests.
 *
 * We maintain a stateful "session" with each MDS we interact with.
 * Within each session, we sent periodic heartbeat messages to ensure
 * any capabilities or leases we have been issues remain valid.  If
 * the session times out and goes stale, our leases and capabilities
 * are no longer valid.
 */

struct ceph_reconnect_state {
	struct ceph_mds_session *session;
	int nr_caps, nr_realms;
	struct ceph_pagelist *pagelist;
	unsigned msg_version;
	bool allow_multi;
};

static void __wake_requests(struct ceph_mds_client *mdsc,
			    struct list_head *head);
static void ceph_cap_release_work(struct work_struct *work);
static void ceph_cap_reclaim_work(struct work_struct *work);
static void ceph_mdsc_reset_workfn(struct work_struct *work);

static const struct ceph_connection_operations mds_con_ops;

static void ceph_metric_bind_session(struct ceph_mds_client *mdsc,
				     struct ceph_mds_session *session)
{
	struct ceph_mds_session *old;

	if (!mdsc || !session || disable_send_metrics)
		return;

	old = mdsc->metric.session;
	mdsc->metric.session = ceph_get_mds_session(session);
	if (old)
		ceph_put_mds_session(old);

	metric_schedule_delayed(&mdsc->metric);
}

/*
 * mds reply parsing
 */

static int parse_reply_info_quota(void **p, void *end,
				  struct ceph_mds_reply_info_in *info)
{
	u8 struct_v, struct_compat;
	u32 struct_len;

	ceph_decode_8_safe(p, end, struct_v, bad);
	ceph_decode_8_safe(p, end, struct_compat, bad);
	/* struct_v is expected to be >= 1. we only
	 * understand encoding with struct_compat == 1. */
	if (!struct_v || struct_compat != 1)
		goto bad;
	ceph_decode_32_safe(p, end, struct_len, bad);
	ceph_decode_need(p, end, struct_len, bad);
	end = *p + struct_len;
	ceph_decode_64_safe(p, end, info->max_bytes, bad);
	ceph_decode_64_safe(p, end, info->max_files, bad);
	*p = end;
	return 0;
bad:
	return -EIO;
}

static int parse_reply_info_in(void **p, void *end,
			       struct ceph_mds_reply_info_in *info,
			       u64 features,
			       struct ceph_mds_client *mdsc)
{
	int err = 0;
	u8 struct_v = 0;
	u8 struct_compat = 0;
	u32 struct_len = 0;

	info->subvolume_id = CEPH_SUBVOLUME_ID_NONE;

	if (features == (u64)-1) {
		ceph_decode_8_safe(p, end, struct_v, bad);
		ceph_decode_8_safe(p, end, struct_compat, bad);
		/* struct_v is expected to be >= 1. we only understand
		 * encoding with struct_compat == 1. */
		if (!struct_v || struct_compat != 1)
			goto bad;
		ceph_decode_32_safe(p, end, struct_len, bad);
		ceph_decode_need(p, end, struct_len, bad);
		end = *p + struct_len;
	}

	ceph_decode_need(p, end, sizeof(struct ceph_mds_reply_inode), bad);
	info->in = *p;
	*p += sizeof(struct ceph_mds_reply_inode) +
		sizeof(*info->in->fragtree.splits) *
		le32_to_cpu(info->in->fragtree.nsplits);

	ceph_decode_32_safe(p, end, info->symlink_len, bad);
	ceph_decode_need(p, end, info->symlink_len, bad);
	info->symlink = *p;
	*p += info->symlink_len;

	ceph_decode_copy_safe(p, end, &info->dir_layout,
			      sizeof(info->dir_layout), bad);
	ceph_decode_32_safe(p, end, info->xattr_len, bad);
	ceph_decode_need(p, end, info->xattr_len, bad);
	info->xattr_data = *p;
	*p += info->xattr_len;

	if (features == (u64)-1) {
		/* inline data */
		ceph_decode_64_safe(p, end, info->inline_version, bad);
		ceph_decode_32_safe(p, end, info->inline_len, bad);
		ceph_decode_need(p, end, info->inline_len, bad);
		info->inline_data = *p;
		*p += info->inline_len;
		/* quota */
		err = parse_reply_info_quota(p, end, info);
		if (err < 0)
			goto out_bad;
		/* pool namespace */
		ceph_decode_32_safe(p, end, info->pool_ns_len, bad);
		if (info->pool_ns_len > 0) {
			ceph_decode_need(p, end, info->pool_ns_len, bad);
			info->pool_ns_data = *p;
			*p += info->pool_ns_len;
		}

		/* btime */
		ceph_decode_need(p, end, sizeof(info->btime), bad);
		ceph_decode_copy(p, &info->btime, sizeof(info->btime));

		/* change attribute */
		ceph_decode_64_safe(p, end, info->change_attr, bad);

		/* dir pin */
		if (struct_v >= 2) {
			ceph_decode_32_safe(p, end, info->dir_pin, bad);
		} else {
			info->dir_pin = -ENODATA;
		}

		/* snapshot birth time, remains zero for v<=2 */
		if (struct_v >= 3) {
			ceph_decode_need(p, end, sizeof(info->snap_btime), bad);
			ceph_decode_copy(p, &info->snap_btime,
					 sizeof(info->snap_btime));
		} else {
			memset(&info->snap_btime, 0, sizeof(info->snap_btime));
		}

		/* snapshot count, remains zero for v<=3 */
		if (struct_v >= 4) {
			ceph_decode_64_safe(p, end, info->rsnaps, bad);
		} else {
			info->rsnaps = 0;
		}

		if (struct_v >= 5) {
			u32 alen;

			ceph_decode_32_safe(p, end, alen, bad);

			while (alen--) {
				u32 len;

				/* key */
				ceph_decode_32_safe(p, end, len, bad);
				ceph_decode_skip_n(p, end, len, bad);
				/* value */
				ceph_decode_32_safe(p, end, len, bad);
				ceph_decode_skip_n(p, end, len, bad);
			}
		}

		/* fscrypt flag -- ignore */
		if (struct_v >= 6)
			ceph_decode_skip_8(p, end, bad);

		info->fscrypt_auth = NULL;
		info->fscrypt_auth_len = 0;
		info->fscrypt_file = NULL;
		info->fscrypt_file_len = 0;
		if (struct_v >= 7) {
			ceph_decode_32_safe(p, end, info->fscrypt_auth_len, bad);
			if (info->fscrypt_auth_len) {
				info->fscrypt_auth = kmalloc(info->fscrypt_auth_len,
							     GFP_KERNEL);
				if (!info->fscrypt_auth)
					return -ENOMEM;
				ceph_decode_copy_safe(p, end, info->fscrypt_auth,
						      info->fscrypt_auth_len, bad);
			}
			ceph_decode_32_safe(p, end, info->fscrypt_file_len, bad);
			if (info->fscrypt_file_len) {
				info->fscrypt_file = kmalloc(info->fscrypt_file_len,
							     GFP_KERNEL);
				if (!info->fscrypt_file)
					return -ENOMEM;
				ceph_decode_copy_safe(p, end, info->fscrypt_file,
						      info->fscrypt_file_len, bad);
			}
		}

		/*
		 * InodeStat encoding versions:
		 *   v1-v7: various fields added over time
		 *   v8: added optmetadata (versioned sub-structure containing
		 *       optional inode metadata like charmap for case-insensitive
		 *       filesystems). The kernel client doesn't support
		 *       case-insensitive lookups, so we skip this field.
		 *   v9: added subvolume_id (parsed below)
		 */
		if (struct_v >= 8) {
			u32 v8_struct_len;

			/* skip optmetadata versioned sub-structure */
			ceph_decode_skip_8(p, end, bad);  /* struct_v */
			ceph_decode_skip_8(p, end, bad);  /* struct_compat */
			ceph_decode_32_safe(p, end, v8_struct_len, bad);
			ceph_decode_skip_n(p, end, v8_struct_len, bad);
		}

		/* struct_v 9 added subvolume_id */
		if (struct_v >= 9)
			ceph_decode_64_safe(p, end, info->subvolume_id, bad);

		*p = end;
	} else {
		/* legacy (unversioned) struct */
		if (features & CEPH_FEATURE_MDS_INLINE_DATA) {
			ceph_decode_64_safe(p, end, info->inline_version, bad);
			ceph_decode_32_safe(p, end, info->inline_len, bad);
			ceph_decode_need(p, end, info->inline_len, bad);
			info->inline_data = *p;
			*p += info->inline_len;
		} else
			info->inline_version = CEPH_INLINE_NONE;

		if (features & CEPH_FEATURE_MDS_QUOTA) {
			err = parse_reply_info_quota(p, end, info);
			if (err < 0)
				goto out_bad;
		} else {
			info->max_bytes = 0;
			info->max_files = 0;
		}

		info->pool_ns_len = 0;
		info->pool_ns_data = NULL;
		if (features & CEPH_FEATURE_FS_FILE_LAYOUT_V2) {
			ceph_decode_32_safe(p, end, info->pool_ns_len, bad);
			if (info->pool_ns_len > 0) {
				ceph_decode_need(p, end, info->pool_ns_len, bad);
				info->pool_ns_data = *p;
				*p += info->pool_ns_len;
			}
		}

		if (features & CEPH_FEATURE_FS_BTIME) {
			ceph_decode_need(p, end, sizeof(info->btime), bad);
			ceph_decode_copy(p, &info->btime, sizeof(info->btime));
			ceph_decode_64_safe(p, end, info->change_attr, bad);
		}

		info->dir_pin = -ENODATA;
		/* info->snap_btime and info->rsnaps remain zero */
	}
	return 0;
bad:
	err = -EIO;
out_bad:
	return err;
}

static int parse_reply_info_dir(void **p, void *end,
				struct ceph_mds_reply_dirfrag **dirfrag,
				u64 features)
{
	if (features == (u64)-1) {
		u8 struct_v, struct_compat;
		u32 struct_len;
		ceph_decode_8_safe(p, end, struct_v, bad);
		ceph_decode_8_safe(p, end, struct_compat, bad);
		/* struct_v is expected to be >= 1. we only understand
		 * encoding whose struct_compat == 1. */
		if (!struct_v || struct_compat != 1)
			goto bad;
		ceph_decode_32_safe(p, end, struct_len, bad);
		ceph_decode_need(p, end, struct_len, bad);
		end = *p + struct_len;
	}

	ceph_decode_need(p, end, sizeof(**dirfrag), bad);
	*dirfrag = *p;
	*p += sizeof(**dirfrag) + sizeof(u32) * le32_to_cpu((*dirfrag)->ndist);
	if (unlikely(*p > end))
		goto bad;
	if (features == (u64)-1)
		*p = end;
	return 0;
bad:
	return -EIO;
}

static int parse_reply_info_lease(void **p, void *end,
				  struct ceph_mds_reply_lease **lease,
				  u64 features, u32 *altname_len, u8 **altname)
{
	u8 struct_v;
	u32 struct_len;
	void *lend;

	if (features == (u64)-1) {
		u8 struct_compat;

		ceph_decode_8_safe(p, end, struct_v, bad);
		ceph_decode_8_safe(p, end, struct_compat, bad);

		/* struct_v is expected to be >= 1. we only understand
		 * encoding whose struct_compat == 1. */
		if (!struct_v || struct_compat != 1)
			goto bad;

		ceph_decode_32_safe(p, end, struct_len, bad);
	} else {
		struct_len = sizeof(**lease);
		*altname_len = 0;
		*altname = NULL;
	}

	lend = *p + struct_len;
	ceph_decode_need(p, end, struct_len, bad);
	*lease = *p;
	*p += sizeof(**lease);

	if (features == (u64)-1) {
		if (struct_v >= 2) {
			ceph_decode_32_safe(p, end, *altname_len, bad);
			ceph_decode_need(p, end, *altname_len, bad);
			*altname = *p;
			*p += *altname_len;
		} else {
			*altname = NULL;
			*altname_len = 0;
		}
	}
	*p = lend;
	return 0;
bad:
	return -EIO;
}

/*
 * parse a normal reply, which may contain a (dir+)dentry and/or a
 * target inode.
 */
static int parse_reply_info_trace(void **p, void *end,
				  struct ceph_mds_reply_info_parsed *info,
				  u64 features,
				  struct ceph_mds_client *mdsc)
{
	int err;

	if (info->head->is_dentry) {
		err = parse_reply_info_in(p, end, &info->diri, features, mdsc);
		if (err < 0)
			goto out_bad;

		err = parse_reply_info_dir(p, end, &info->dirfrag, features);
		if (err < 0)
			goto out_bad;

		ceph_decode_32_safe(p, end, info->dname_len, bad);
		ceph_decode_need(p, end, info->dname_len, bad);
		info->dname = *p;
		*p += info->dname_len;

		err = parse_reply_info_lease(p, end, &info->dlease, features,
					     &info->altname_len, &info->altname);
		if (err < 0)
			goto out_bad;
	}

	if (info->head->is_target) {
		err = parse_reply_info_in(p, end, &info->targeti, features,
					  mdsc);
		if (err < 0)
			goto out_bad;
	}

	if (unlikely(*p != end))
		goto bad;
	return 0;

bad:
	err = -EIO;
out_bad:
	pr_err("problem parsing mds trace %d\n", err);
	return err;
}

/*
 * parse readdir results
 */
static int parse_reply_info_readdir(void **p, void *end,
				    struct ceph_mds_request *req,
				    u64 features,
				    struct ceph_mds_client *mdsc)
{
	struct ceph_mds_reply_info_parsed *info = &req->r_reply_info;
	struct ceph_client *cl = req->r_mdsc->fsc->client;
	u32 num, i = 0;
	int err;

	err = parse_reply_info_dir(p, end, &info->dir_dir, features);
	if (err < 0)
		goto out_bad;

	ceph_decode_need(p, end, sizeof(num) + 2, bad);
	num = ceph_decode_32(p);
	{
		u16 flags = ceph_decode_16(p);
		info->dir_end = !!(flags & CEPH_READDIR_FRAG_END);
		info->dir_complete = !!(flags & CEPH_READDIR_FRAG_COMPLETE);
		info->hash_order = !!(flags & CEPH_READDIR_HASH_ORDER);
		info->offset_hash = !!(flags & CEPH_READDIR_OFFSET_HASH);
	}
	if (num == 0)
		goto done;

	BUG_ON(!info->dir_entries);
	if ((unsigned long)(info->dir_entries + num) >
	    (unsigned long)info->dir_entries + info->dir_buf_size) {
		pr_err_client(cl, "dir contents are larger than expected\n");
		WARN_ON(1);
		goto bad;
	}

	info->dir_nr = num;
	while (num) {
		struct inode *inode = d_inode(req->r_dentry);
		struct ceph_inode_info *ci = ceph_inode(inode);
		struct ceph_mds_reply_dir_entry *rde = info->dir_entries + i;
		struct fscrypt_str oname = FSTR_INIT(NULL, 0);
		struct ceph_fname fname;
		u32 altname_len, _name_len;
		u8 *altname, *_name;
		u8 *tname = NULL;

		/* dentry */
		ceph_decode_32_safe(p, end, _name_len, bad);
		ceph_decode_need(p, end, _name_len, bad);
		_name = *p;
		*p += _name_len;
		doutc(cl, "parsed dir dname '%.*s'\n", _name_len, _name);

		if (info->hash_order)
			rde->raw_hash = ceph_str_hash(ci->i_dir_layout.dl_dir_hash,
						      _name, _name_len);

		/* dentry lease */
		err = parse_reply_info_lease(p, end, &rde->lease, features,
					     &altname_len, &altname);
		if (err)
			goto out_bad;

		/*
		 * Try to dencrypt the dentry names and update them
		 * in the ceph_mds_reply_dir_entry struct.
		 */
		fname.dir = inode;
		fname.name = _name;
		fname.name_len = _name_len;
		fname.ctext = altname;
		fname.ctext_len = altname_len;
		/*
		 * The _name_len maybe larger than altname_len, such as
		 * when the human readable name length is in range of
		 * (CEPH_NOHASH_NAME_MAX, CEPH_NOHASH_NAME_MAX + SHA256_DIGEST_SIZE),
		 * then the copy in ceph_fname_to_usr will corrupt the
		 * data if there has no encryption key.
		 *
		 * Just set the no_copy flag and then if there has no
		 * encryption key the oname.name will be assigned to
		 * _name always.
		 */
		fname.no_copy = true;
		if (altname_len == 0) {
			/*
			 * Set tname to _name, and this will be used
			 * to do the base64_decode in-place. It's
			 * safe because the decoded string should
			 * always be shorter, which is 3/4 of origin
			 * string. If this message was allocated with
			 * vmalloc() (happens, but rarely), leave it
			 * NULL and let ceph_fname_to_usr() allocate
			 * suitable temporary working space instead.
			 */
			if (likely(!is_vmalloc_addr(_name)))
				tname = _name;

			/*
			 * Set oname to _name too, and this will be
			 * used to do the dencryption in-place.
			 */
			oname.name = _name;
			oname.len = _name_len;
		} else {
			/*
			 * This will do the decryption only in-place
			 * from altname cryptext directly.
			 */
			oname.name = altname;
			oname.len = altname_len;
		}
		rde->is_nokey = false;
		err = ceph_fname_to_usr(&fname, tname, &oname, &rde->is_nokey);
		if (err) {
			pr_err_client(cl, "unable to decode %.*s, got %d\n",
				      _name_len, _name, err);
			goto out_bad;
		}
		rde->name = oname.name;
		rde->name_len = oname.len;

		/* inode */
		err = parse_reply_info_in(p, end, &rde->inode, features, mdsc);
		if (err < 0)
			goto out_bad;
		/* ceph_readdir_prepopulate() will update it */
		rde->offset = 0;
		i++;
		num--;
	}

done:
	/* Skip over any unrecognized fields */
	*p = end;
	return 0;

bad:
	err = -EIO;
out_bad:
	pr_err_client(cl, "problem parsing dir contents %d\n", err);
	return err;
}

/*
 * parse fcntl F_GETLK results
 */
static int parse_reply_info_filelock(void **p, void *end,
				     struct ceph_mds_reply_info_parsed *info,
				     u64 features)
{
	if (*p + sizeof(*info->filelock_reply) > end)
		goto bad;

	info->filelock_reply = *p;

	/* Skip over any unrecognized fields */
	*p = end;
	return 0;
bad:
	return -EIO;
}


#if BITS_PER_LONG == 64

#define DELEGATED_INO_AVAILABLE		xa_mk_value(1)

static int ceph_insert_deleg_ino(struct ceph_mds_session *s, u64 ino)
{
	struct ceph_client *cl = s->s_mdsc->fsc->client;
	int err;

	/*
	 * Cap how many delegated inodes a single session may hold. This is
	 * the only place that grows the count, so atomic_add_unless() bounds
	 * it at exactly CEPH_MAX_DELEG_INOS; s_num_deleg_inos can never exceed
	 * that.
	 */
	if (!atomic_add_unless(&s->s_num_deleg_inos, 1, CEPH_MAX_DELEG_INOS)) {
		pr_warn_ratelimited_client(cl,
			"MDS session already holds %d delegated inodes\n",
			CEPH_MAX_DELEG_INOS);
		return -EOVERFLOW;
	}

	err = xa_insert(&s->s_delegated_inos, ino, DELEGATED_INO_AVAILABLE,
			GFP_KERNEL);
	if (err)
		atomic_dec(&s->s_num_deleg_inos);
	return err;
}

static int ceph_parse_deleg_inos(void **p, void *end,
				 struct ceph_mds_session *s)
{
	struct ceph_client *cl = s->s_mdsc->fsc->client;
	u64 msg_deleg_inos = 0;
	u32 sets;

	ceph_decode_32_safe(p, end, sets, bad);
	doutc(cl, "got %u sets of delegated inodes\n", sets);
	while (sets--) {
		u64 start, len;

		ceph_decode_64_safe(p, end, start, bad);
		ceph_decode_64_safe(p, end, len, bad);

		/* Don't accept a delegation of system inodes */
		if (start < CEPH_INO_SYSTEM_BASE) {
			pr_warn_ratelimited_client(cl,
				"ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
				start, len);
			continue;
		}

		/*
		 * Bound the number of inodes one reply may delegate.
		 * ceph_insert_deleg_ino() separately caps the per-session
		 * population, so this only has to stop one reply from spinning
		 * the insert loop under an attacker-controlled len.
		 */
		if (len > (u64)CEPH_MAX_DELEG_INOS ||
		    msg_deleg_inos > (u64)CEPH_MAX_DELEG_INOS - len) {
			pr_warn_ratelimited_client(cl,
				"MDS reply delegates too many inodes (have %llu, +%llu, max %d)\n",
				msg_deleg_inos, len, CEPH_MAX_DELEG_INOS);
			return -EIO;
		}
		msg_deleg_inos += len;

		while (len--) {
			int err = ceph_insert_deleg_ino(s, start++);

			if (!err) {
				doutc(cl, "added delegated inode 0x%llx\n", start - 1);
			} else if (err == -EBUSY) {
				pr_warn_client(cl,
					"MDS delegated inode 0x%llx more than once.\n",
					start - 1);
			} else if (err == -EOVERFLOW) {
				/* ceph_insert_deleg_ino() already warned. */
				return -EIO;
			} else {
				return err;
			}
		}
	}
	return 0;
bad:
	return -EIO;
}

u64 ceph_get_deleg_ino(struct ceph_mds_session *s)
{
	unsigned long ino;
	void *val;

	xa_for_each(&s->s_delegated_inos, ino, val) {
		val = xa_erase(&s->s_delegated_inos, ino);
		if (val == DELEGATED_INO_AVAILABLE) {
			atomic_dec(&s->s_num_deleg_inos);
			return ino;
		}
	}
	return 0;
}

int ceph_restore_deleg_ino(struct ceph_mds_session *s, u64 ino)
{
	return ceph_insert_deleg_ino(s, ino);
}
#else /* BITS_PER_LONG == 64 */
/*
 * FIXME: xarrays can't handle 64-bit indexes on a 32-bit arch. For now, just
 * ignore delegated_inos on 32 bit arch. Maybe eventually add xarrays for top
 * and bottom words?
 */
static int ceph_parse_deleg_inos(void **p, void *end,
				 struct ceph_mds_session *s)
{
	u32 sets;

	ceph_decode_32_safe(p, end, sets, bad);
	if (sets)
		ceph_decode_skip_n(p, end, sets * 2 * sizeof(__le64), bad);
	return 0;
bad:
	return -EIO;
}

u64 ceph_get_deleg_ino(struct ceph_mds_session *s)
{
	return 0;
}

int ceph_restore_deleg_ino(struct ceph_mds_session *s, u64 ino)
{
	return 0;
}
#endif /* BITS_PER_LONG == 64 */

/*
 * parse create results
 */
static int parse_reply_info_create(void **p, void *end,
				  struct ceph_mds_reply_info_parsed *info,
				  u64 features, struct ceph_mds_session *s)
{
	int ret;

	if (features == (u64)-1 ||
	    (features & CEPH_FEATURE_REPLY_CREATE_INODE)) {
		if (*p == end) {
			/* Malformed reply? */
			info->has_create_ino = false;
		} else if (test_bit(CEPHFS_FEATURE_DELEG_INO, &s->s_features)) {
			info->has_create_ino = true;
			/* struct_v, struct_compat, and len */
			ceph_decode_skip_n(p, end, 2 + sizeof(u32), bad);
			ceph_decode_64_safe(p, end, info->ino, bad);
			ret = ceph_parse_deleg_inos(p, end, s);
			if (ret)
				return ret;
		} else {
			/* legacy */
			ceph_decode_64_safe(p, end, info->ino, bad);
			info->has_create_ino = true;
		}
	} else {
		if (*p != end)
			goto bad;
	}

	/* Skip over any unrecognized fields */
	*p = end;
	return 0;
bad:
	return -EIO;
}

static int parse_reply_info_getvxattr(void **p, void *end,
				      struct ceph_mds_reply_info_parsed *info,
				      u64 features)
{
	u32 value_len;

	ceph_decode_skip_8(p, end, bad); /* skip current version: 1 */
	ceph_decode_skip_8(p, end, bad); /* skip first version: 1 */
	ceph_decode_skip_32(p, end, bad); /* skip payload length */

	ceph_decode_32_safe(p, end, value_len, bad);

	if (value_len == end - *p) {
	  info->xattr_info.xattr_value = *p;
	  info->xattr_info.xattr_value_len = value_len;
	  *p = end;
	  return value_len;
	}
bad:
	return -EIO;
}

/*
 * parse extra results
 */
static int parse_reply_info_extra(void **p, void *end,
				  struct ceph_mds_request *req,
				  u64 features, struct ceph_mds_session *s)
{
	struct ceph_mds_reply_info_parsed *info = &req->r_reply_info;
	u32 op = le32_to_cpu(info->head->op);

	if (op == CEPH_MDS_OP_GETFILELOCK)
		return parse_reply_info_filelock(p, end, info, features);
	else if (op == CEPH_MDS_OP_READDIR || op == CEPH_MDS_OP_LSSNAP)
		return parse_reply_info_readdir(p, end, req, features,
						req->r_mdsc);
	else if (op == CEPH_MDS_OP_CREATE)
		return parse_reply_info_create(p, end, info, features, s);
	else if (op == CEPH_MDS_OP_GETVXATTR)
		return parse_reply_info_getvxattr(p, end, info, features);
	else
		return -EIO;
}

/*
 * parse entire mds reply
 */
static int parse_reply_info(struct ceph_mds_session *s, struct ceph_msg *msg,
			    struct ceph_mds_request *req, u64 features)
{
	struct ceph_mds_reply_info_parsed *info = &req->r_reply_info;
	struct ceph_client *cl = s->s_mdsc->fsc->client;
	void *p, *end;
	u32 len;
	int err;

	info->head = msg->front.iov_base;
	p = msg->front.iov_base + sizeof(struct ceph_mds_reply_head);
	end = p + msg->front.iov_len - sizeof(struct ceph_mds_reply_head);

	/* trace */
	ceph_decode_32_safe(&p, end, len, bad);
	if (len > 0) {
		ceph_decode_need(&p, end, len, bad);
		err = parse_reply_info_trace(&p, p + len, info, features,
					     s->s_mdsc);
		if (err < 0)
			goto out_bad;
	}

	/* extra */
	ceph_decode_32_safe(&p, end, len, bad);
	if (len > 0) {
		ceph_decode_need(&p, end, len, bad);
		err = parse_reply_info_extra(&p, p + len, req, features, s);
		if (err < 0)
			goto out_bad;
	}

	/* snap blob */
	ceph_decode_32_safe(&p, end, len, bad);
	info->snapblob_len = len;
	info->snapblob = p;
	p += len;

	if (p != end)
		goto bad;
	return 0;

bad:
	err = -EIO;
out_bad:
	pr_err_client(cl, "mds parse_reply err %d\n", err);
	ceph_msg_dump(msg);
	return err;
}

static void destroy_reply_info(struct ceph_mds_reply_info_parsed *info)
{
	int i;

	kfree(info->diri.fscrypt_auth);
	kfree(info->diri.fscrypt_file);
	kfree(info->targeti.fscrypt_auth);
	kfree(info->targeti.fscrypt_file);
	if (!info->dir_entries)
		return;

	for (i = 0; i < info->dir_nr; i++) {
		struct ceph_mds_reply_dir_entry *rde = info->dir_entries + i;

		kfree(rde->inode.fscrypt_auth);
		kfree(rde->inode.fscrypt_file);
	}
	free_pages((unsigned long)info->dir_entries, get_order(info->dir_buf_size));
}

/*
 * In async unlink case the kclient won't wait for the first reply
 * from MDS and just drop all the links and unhash the dentry and then
 * succeeds immediately.
 *
 * For any new create/link/rename,etc requests followed by using the
 * same file names we must wait for the first reply of the inflight
 * unlink request, or the MDS possibly will fail these following
 * requests with -EEXIST if the inflight async unlink request was
 * delayed for some reasons.
 *
 * And the worst case is that for the none async openc request it will
 * successfully open the file if the CDentry hasn't been unlinked yet,
 * but later the previous delayed async unlink request will remove the
 * CDentry. That means the just created file is possibly deleted later
 * by accident.
 *
 * We need to wait for the inflight async unlink requests to finish
 * when creating new files/directories by using the same file names.
 */
int ceph_wait_on_conflict_unlink(struct dentry *dentry)
{
	struct ceph_fs_client *fsc = ceph_sb_to_fs_client(dentry->d_sb);
	struct ceph_client *cl = fsc->client;
	struct dentry *pdentry = dentry->d_parent;
	struct dentry *udentry, *found = NULL;
	struct ceph_dentry_info *di;
	struct qstr dname;
	u32 hash = dentry->d_name.hash;
	int err;

	dname.name = dentry->d_name.name;
	dname.len = dentry->d_name.len;

	rcu_read_lock();
	hash_for_each_possible_rcu(fsc->async_unlink_conflict, di,
				   hnode, hash) {
		udentry = di->dentry;

		spin_lock(&udentry->d_lock);
		if (udentry->d_name.hash != hash)
			goto next;
		if (unlikely(udentry->d_parent != pdentry))
			goto next;
		if (!hash_hashed(&di->hnode))
			goto next;

		if (!test_bit(CEPH_DENTRY_ASYNC_UNLINK_BIT, &di->flags))
			pr_warn_client(cl, "dentry %p:%pd async unlink bit is not set\n",
				       dentry, dentry);

		if (!d_same_name(udentry, pdentry, &dname))
			goto next;

		found = dget_dlock(udentry);
		spin_unlock(&udentry->d_lock);
		break;
next:
		spin_unlock(&udentry->d_lock);
	}
	rcu_read_unlock();

	if (likely(!found))
		return 0;

	doutc(cl, "dentry %p:%pd conflict with old %p:%pd\n", dentry, dentry,
	      found, found);

	err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_UNLINK_BIT,
			  TASK_KILLABLE);
	dput(found);
	return err;
}


/*
 * sessions
 */
const char *ceph_session_state_name(int s)
{
	switch (s) {
	case CEPH_MDS_SESSION_NEW: return "new";
	case CEPH_MDS_SESSION_OPENING: return "opening";
	case CEPH_MDS_SESSION_OPEN: return "open";
	case CEPH_MDS_SESSION_HUNG: return "hung";
	case CEPH_MDS_SESSION_CLOSING: return "closing";
	case CEPH_MDS_SESSION_CLOSED: return "closed";
	case CEPH_MDS_SESSION_RESTARTING: return "restarting";
	case CEPH_MDS_SESSION_RECONNECTING: return "reconnecting";
	case CEPH_MDS_SESSION_REJECTED: return "rejected";
	default: return "???";
	}
}

struct ceph_mds_session *ceph_get_mds_session(struct ceph_mds_session *s)
{
	if (refcount_inc_not_zero(&s->s_ref))
		return s;
	return NULL;
}

void ceph_put_mds_session(struct ceph_mds_session *s)
{
	if (IS_ERR_OR_NULL(s))
		return;

	if (refcount_dec_and_test(&s->s_ref)) {
		if (s->s_auth.authorizer)
			ceph_auth_destroy_authorizer(s->s_auth.authorizer);
		WARN_ON(mutex_is_locked(&s->s_mutex));
		xa_destroy(&s->s_delegated_inos);
		kfree(s);
	}
}

/*
 * called under mdsc->mutex
 */
struct ceph_mds_session *__ceph_lookup_mds_session(struct ceph_mds_client *mdsc,
						   int mds)
{
	if (mds >= mdsc->max_sessions || !mdsc->sessions[mds])
		return NULL;
	return ceph_get_mds_session(mdsc->sessions[mds]);
}

static bool __have_session(struct ceph_mds_client *mdsc, int mds)
{
	if (mds >= mdsc->max_sessions || !mdsc->sessions[mds])
		return false;
	else
		return true;
}

static int __verify_registered_session(struct ceph_mds_client *mdsc,
				       struct ceph_mds_session *s)
{
	if (s->s_mds >= mdsc->max_sessions ||
	    mdsc->sessions[s->s_mds] != s)
		return -ENOENT;
	return 0;
}

/*
 * create+register a new session for given mds.
 * called under mdsc->mutex.
 */
static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
						 int mds)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_session *s;

	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_FENCE_IO)
		return ERR_PTR(-EIO);

	if (mds >= mdsc->mdsmap->possible_max_rank)
		return ERR_PTR(-EINVAL);

	s = kzalloc_obj(*s, GFP_NOFS);
	if (!s)
		return ERR_PTR(-ENOMEM);

	if (mds >= mdsc->max_sessions) {
		int newmax = 1 << get_count_order(mds + 1);
		struct ceph_mds_session **sa;
		size_t ptr_size = sizeof(struct ceph_mds_session *);

		doutc(cl, "realloc to %d\n", newmax);
		sa = kcalloc(newmax, ptr_size, GFP_NOFS);
		if (!sa)
			goto fail_realloc;
		if (mdsc->sessions) {
			memcpy(sa, mdsc->sessions,
			       mdsc->max_sessions * ptr_size);
			kfree(mdsc->sessions);
		}
		mdsc->sessions = sa;
		mdsc->max_sessions = newmax;
	}

	doutc(cl, "mds%d\n", mds);
	s->s_mdsc = mdsc;
	s->s_mds = mds;
	s->s_state = CEPH_MDS_SESSION_NEW;
	mutex_init(&s->s_mutex);

	ceph_con_init(&s->s_con, s, &mds_con_ops, &mdsc->fsc->client->msgr);

	atomic_set(&s->s_cap_gen, 1);
	s->s_cap_ttl = jiffies - 1;

	spin_lock_init(&s->s_cap_lock);
	INIT_LIST_HEAD(&s->s_caps);
	refcount_set(&s->s_ref, 1);
	INIT_LIST_HEAD(&s->s_waiting);
	INIT_LIST_HEAD(&s->s_unsafe);
	xa_init(&s->s_delegated_inos);
	atomic_set(&s->s_num_deleg_inos, 0);
	INIT_LIST_HEAD(&s->s_cap_releases);
	INIT_WORK(&s->s_cap_release_work, ceph_cap_release_work);

	INIT_LIST_HEAD(&s->s_cap_dirty);
	INIT_LIST_HEAD(&s->s_cap_flushing);

	mdsc->sessions[mds] = s;
	atomic_inc(&mdsc->num_sessions);
	refcount_inc(&s->s_ref);  /* one ref to sessions[], one to caller */

	ceph_con_open(&s->s_con, CEPH_ENTITY_TYPE_MDS, mds,
		      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

	return s;

fail_realloc:
	kfree(s);
	return ERR_PTR(-ENOMEM);
}

/*
 * called under mdsc->mutex
 */
static void __unregister_session(struct ceph_mds_client *mdsc,
			       struct ceph_mds_session *s)
{
	doutc(mdsc->fsc->client, "mds%d %p\n", s->s_mds, s);
	BUG_ON(mdsc->sessions[s->s_mds] != s);
	mdsc->sessions[s->s_mds] = NULL;
	ceph_con_close(&s->s_con);
	ceph_put_mds_session(s);
	atomic_dec(&mdsc->num_sessions);
}

/*
 * drop session refs in request.
 *
 * should be last request ref, or hold mdsc->mutex
 */
static void put_request_session(struct ceph_mds_request *req)
{
	if (req->r_session) {
		ceph_put_mds_session(req->r_session);
		req->r_session = NULL;
	}
}

void ceph_mdsc_iterate_sessions(struct ceph_mds_client *mdsc,
				void (*cb)(struct ceph_mds_session *),
				bool check_state)
{
	int mds;

	mutex_lock(&mdsc->mutex);
	for (mds = 0; mds < mdsc->max_sessions; ++mds) {
		struct ceph_mds_session *s;

		s = __ceph_lookup_mds_session(mdsc, mds);
		if (!s)
			continue;

		if (check_state && !check_session_state(s)) {
			ceph_put_mds_session(s);
			continue;
		}

		mutex_unlock(&mdsc->mutex);
		cb(s);
		ceph_put_mds_session(s);
		mutex_lock(&mdsc->mutex);
	}
	mutex_unlock(&mdsc->mutex);
}

void ceph_mdsc_release_request(struct kref *kref)
{
	struct ceph_mds_request *req = container_of(kref,
						    struct ceph_mds_request,
						    r_kref);
	ceph_mdsc_release_dir_caps_async(req);
	destroy_reply_info(&req->r_reply_info);
	if (req->r_request)
		ceph_msg_put(req->r_request);
	if (req->r_reply)
		ceph_msg_put(req->r_reply);
	if (req->r_inode) {
		ceph_put_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
		iput(req->r_inode);
	}
	if (req->r_parent) {
		ceph_put_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN);
		iput(req->r_parent);
	}
	iput(req->r_target_inode);
	iput(req->r_new_inode);
	if (req->r_dentry)
		dput(req->r_dentry);
	if (req->r_old_dentry)
		dput(req->r_old_dentry);
	if (req->r_old_dentry_dir) {
		/*
		 * track (and drop pins for) r_old_dentry_dir
		 * separately, since r_old_dentry's d_parent may have
		 * changed between the dir mutex being dropped and
		 * this request being freed.
		 */
		ceph_put_cap_refs(ceph_inode(req->r_old_dentry_dir),
				  CEPH_CAP_PIN);
		iput(req->r_old_dentry_dir);
	}
	kfree(req->r_path1);
	kfree(req->r_path2);
	put_cred(req->r_cred);
	if (req->r_mnt_idmap)
		mnt_idmap_put(req->r_mnt_idmap);
	if (req->r_pagelist)
		ceph_pagelist_release(req->r_pagelist);
	kfree(req->r_fscrypt_auth);
	kfree(req->r_altname);
	put_request_session(req);
	ceph_unreserve_caps(req->r_mdsc, &req->r_caps_reservation);
	WARN_ON_ONCE(!list_empty(&req->r_wait));
	kmem_cache_free(ceph_mds_request_cachep, req);
}

DEFINE_RB_FUNCS(request, struct ceph_mds_request, r_tid, r_node)

/*
 * lookup session, bump ref if found.
 *
 * called under mdsc->mutex.
 */
static struct ceph_mds_request *
lookup_get_request(struct ceph_mds_client *mdsc, u64 tid)
{
	struct ceph_mds_request *req;

	req = lookup_request(&mdsc->request_tree, tid);
	if (req)
		ceph_mdsc_get_request(req);

	return req;
}

/*
 * Register an in-flight request, and assign a tid.  Link to directory
 * are modifying (if any).
 *
 * Called under mdsc->mutex.
 */
static void __register_request(struct ceph_mds_client *mdsc,
			       struct ceph_mds_request *req,
			       struct inode *dir)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int ret = 0;

	req->r_tid = ++mdsc->last_tid;
	if (req->r_num_caps) {
		ret = ceph_reserve_caps(mdsc, &req->r_caps_reservation,
					req->r_num_caps);
		if (ret < 0) {
			pr_err_client(cl, "%p failed to reserve caps: %d\n",
				      req, ret);
			/* set req->r_err to fail early from __do_request */
			req->r_err = ret;
			return;
		}
	}
	doutc(cl, "%p tid %lld\n", req, req->r_tid);
	ceph_mdsc_get_request(req);
	insert_request(&mdsc->request_tree, req);

	req->r_cred = get_current_cred();
	if (!req->r_mnt_idmap)
		req->r_mnt_idmap = &nop_mnt_idmap;

	if (mdsc->oldest_tid == 0 && req->r_op != CEPH_MDS_OP_SETFILELOCK)
		mdsc->oldest_tid = req->r_tid;

	if (dir) {
		struct ceph_inode_info *ci = ceph_inode(dir);

		ihold(dir);
		req->r_unsafe_dir = dir;
		spin_lock(&ci->i_unsafe_lock);
		list_add_tail(&req->r_unsafe_dir_item, &ci->i_unsafe_dirops);
		spin_unlock(&ci->i_unsafe_lock);
	}
}

static void __unregister_request(struct ceph_mds_client *mdsc,
				 struct ceph_mds_request *req)
{
	doutc(mdsc->fsc->client, "%p tid %lld\n", req, req->r_tid);

	/* Never leave an unregistered request on an unsafe list! */
	list_del_init(&req->r_unsafe_item);

	if (req->r_tid == mdsc->oldest_tid) {
		struct rb_node *p = rb_next(&req->r_node);
		mdsc->oldest_tid = 0;
		while (p) {
			struct ceph_mds_request *next_req =
				rb_entry(p, struct ceph_mds_request, r_node);
			if (next_req->r_op != CEPH_MDS_OP_SETFILELOCK) {
				mdsc->oldest_tid = next_req->r_tid;
				break;
			}
			p = rb_next(p);
		}
	}

	erase_request(&mdsc->request_tree, req);

	if (req->r_unsafe_dir) {
		struct ceph_inode_info *ci = ceph_inode(req->r_unsafe_dir);
		spin_lock(&ci->i_unsafe_lock);
		list_del_init(&req->r_unsafe_dir_item);
		spin_unlock(&ci->i_unsafe_lock);
	}
	if (req->r_target_inode &&
	    test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
		struct ceph_inode_info *ci = ceph_inode(req->r_target_inode);
		spin_lock(&ci->i_unsafe_lock);
		list_del_init(&req->r_unsafe_target_item);
		spin_unlock(&ci->i_unsafe_lock);
	}

	if (req->r_unsafe_dir) {
		iput(req->r_unsafe_dir);
		req->r_unsafe_dir = NULL;
	}

	complete_all(&req->r_safe_completion);

	ceph_mdsc_put_request(req);
}

/*
 * Walk back up the dentry tree until we hit a dentry representing a
 * non-snapshot inode. We do this using the rcu_read_lock (which must be held
 * when calling this) to ensure that the objects won't disappear while we're
 * working with them. Once we hit a candidate dentry, we attempt to take a
 * reference to it, and return that as the result.
 */
static struct inode *get_nonsnap_parent(struct dentry *dentry)
{
	struct inode *inode = NULL;

	while (dentry && !IS_ROOT(dentry)) {
		inode = d_inode_rcu(dentry);
		if (!inode || ceph_snap(inode) == CEPH_NOSNAP)
			break;
		dentry = dentry->d_parent;
	}
	if (inode)
		inode = igrab(inode);
	return inode;
}

/*
 * Choose mds to send request to next.  If there is a hint set in the
 * request (e.g., due to a prior forward hint from the mds), use that.
 * Otherwise, consult frag tree and/or caps to identify the
 * appropriate mds.  If all else fails, choose randomly.
 *
 * Called under mdsc->mutex.
 */
static int __choose_mds(struct ceph_mds_client *mdsc,
			struct ceph_mds_request *req,
			bool *random)
{
	struct inode *inode;
	struct ceph_inode_info *ci;
	struct ceph_cap *cap;
	int mode = req->r_direct_mode;
	int mds = -1;
	u32 hash = req->r_direct_hash;
	bool is_hash = test_bit(CEPH_MDS_R_DIRECT_IS_HASH, &req->r_req_flags);
	struct ceph_client *cl = mdsc->fsc->client;

	if (random)
		*random = false;

	/*
	 * is there a specific mds we should try?  ignore hint if we have
	 * no session and the mds is not up (active or recovering).
	 */
	if (req->r_resend_mds >= 0 &&
	    (__have_session(mdsc, req->r_resend_mds) ||
	     ceph_mdsmap_get_state(mdsc->mdsmap, req->r_resend_mds) > 0)) {
		doutc(cl, "using resend_mds mds%d\n", req->r_resend_mds);
		return req->r_resend_mds;
	}

	if (mode == USE_RANDOM_MDS)
		goto random;

	inode = NULL;
	if (req->r_inode) {
		if (ceph_snap(req->r_inode) != CEPH_SNAPDIR) {
			inode = req->r_inode;
			ihold(inode);
		} else {
			/* req->r_dentry is non-null for LSSNAP request */
			rcu_read_lock();
			inode = get_nonsnap_parent(req->r_dentry);
			rcu_read_unlock();
			doutc(cl, "using snapdir's parent %p %llx.%llx\n",
			      inode, ceph_vinop(inode));
		}
	} else if (req->r_dentry) {
		/* ignore race with rename; old or new d_parent is okay */
		struct dentry *parent;
		struct inode *dir;

		rcu_read_lock();
		parent = READ_ONCE(req->r_dentry->d_parent);
		dir = req->r_parent ? : d_inode_rcu(parent);

		if (!dir || dir->i_sb != mdsc->fsc->sb) {
			/*  not this fs or parent went negative */
			inode = d_inode(req->r_dentry);
			if (inode)
				ihold(inode);
		} else if (ceph_snap(dir) != CEPH_NOSNAP) {
			/* direct snapped/virtual snapdir requests
			 * based on parent dir inode */
			inode = get_nonsnap_parent(parent);
			doutc(cl, "using nonsnap parent %p %llx.%llx\n",
			      inode, ceph_vinop(inode));
		} else {
			/* dentry target */
			inode = d_inode(req->r_dentry);
			if (!inode || mode == USE_AUTH_MDS) {
				/* dir + name */
				inode = igrab(dir);
				hash = ceph_dentry_hash(dir, req->r_dentry);
				is_hash = true;
			} else {
				ihold(inode);
			}
		}
		rcu_read_unlock();
	}

	if (!inode)
		goto random;

	doutc(cl, "%p %llx.%llx is_hash=%d (0x%x) mode %d\n", inode,
	      ceph_vinop(inode), (int)is_hash, hash, mode);
	ci = ceph_inode(inode);

	if (is_hash && S_ISDIR(inode->i_mode)) {
		struct ceph_inode_frag frag;
		int found;

		ceph_choose_frag(ci, hash, &frag, &found);
		if (found) {
			if (mode == USE_ANY_MDS && frag.ndist > 0) {
				u8 r;

				/* choose a random replica */
				get_random_bytes(&r, 1);
				r %= frag.ndist;
				mds = frag.dist[r];
				doutc(cl, "%p %llx.%llx frag %u mds%d (%d/%d)\n",
				      inode, ceph_vinop(inode), frag.frag,
				      mds, (int)r, frag.ndist);
				if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
				    CEPH_MDS_STATE_ACTIVE &&
				    !ceph_mdsmap_is_laggy(mdsc->mdsmap, mds))
					goto out;
			}

			/* since this file/dir wasn't known to be
			 * replicated, then we want to look for the
			 * authoritative mds. */
			if (frag.mds >= 0) {
				/* choose auth mds */
				mds = frag.mds;
				doutc(cl, "%p %llx.%llx frag %u mds%d (auth)\n",
				      inode, ceph_vinop(inode), frag.frag, mds);
				if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
				    CEPH_MDS_STATE_ACTIVE) {
					if (!ceph_mdsmap_is_laggy(mdsc->mdsmap,
								  mds))
						goto out;
				}
			}
			mode = USE_AUTH_MDS;
		}
	}

	spin_lock(&ci->i_ceph_lock);
	cap = NULL;
	if (mode == USE_AUTH_MDS)
		cap = ci->i_auth_cap;
	if (!cap && !RB_EMPTY_ROOT(&ci->i_caps))
		cap = rb_entry(rb_first(&ci->i_caps), struct ceph_cap, ci_node);
	if (!cap) {
		spin_unlock(&ci->i_ceph_lock);
		iput(inode);
		goto random;
	}
	mds = cap->session->s_mds;
	doutc(cl, "%p %llx.%llx mds%d (%scap %p)\n", inode,
	      ceph_vinop(inode), mds,
	      cap == ci->i_auth_cap ? "auth " : "", cap);
	spin_unlock(&ci->i_ceph_lock);
out:
	iput(inode);
	return mds;

random:
	if (random)
		*random = true;

	mds = ceph_mdsmap_get_random_mds(mdsc->mdsmap);
	doutc(cl, "chose random mds%d\n", mds);
	return mds;
}


/*
 * session messages
 */
struct ceph_msg *ceph_create_session_msg(u32 op, u64 seq)
{
	struct ceph_msg *msg;
	struct ceph_mds_session_head *h;

	msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h), GFP_NOFS,
			   false);
	if (!msg) {
		pr_err("ENOMEM creating session %s msg\n",
		       ceph_session_op_name(op));
		return NULL;
	}
	h = msg->front.iov_base;
	h->op = cpu_to_le32(op);
	h->seq = cpu_to_le64(seq);

	return msg;
}

static const unsigned char feature_bits[] = CEPHFS_FEATURES_CLIENT_SUPPORTED;
#define FEATURE_BYTES(c) (DIV_ROUND_UP((size_t)feature_bits[c - 1] + 1, 64) * 8)
static int encode_supported_features(void **p, void *end)
{
	static const size_t count = ARRAY_SIZE(feature_bits);

	if (count > 0) {
		size_t i;
		size_t size = FEATURE_BYTES(count);
		unsigned long bit;

		if (WARN_ON_ONCE(*p + 4 + size > end))
			return -ERANGE;

		ceph_encode_32(p, size);
		memset(*p, 0, size);
		for (i = 0; i < count; i++) {
			bit = feature_bits[i];
			((unsigned char *)(*p))[bit / 8] |= BIT(bit % 8);
		}
		*p += size;
	} else {
		if (WARN_ON_ONCE(*p + 4 > end))
			return -ERANGE;

		ceph_encode_32(p, 0);
	}

	return 0;
}

static const unsigned char metric_bits[] = CEPHFS_METRIC_SPEC_CLIENT_SUPPORTED;
#define METRIC_BYTES(cnt) (DIV_ROUND_UP((size_t)metric_bits[cnt - 1] + 1, 64) * 8)
static int encode_metric_spec(void **p, void *end)
{
	static const size_t count = ARRAY_SIZE(metric_bits);

	/* header */
	if (WARN_ON_ONCE(*p + 2 > end))
		return -ERANGE;

	ceph_encode_8(p, 1); /* version */
	ceph_encode_8(p, 1); /* compat */

	if (count > 0) {
		size_t i;
		size_t size = METRIC_BYTES(count);

		if (WARN_ON_ONCE(*p + 4 + 4 + size > end))
			return -ERANGE;

		/* metric spec info length */
		ceph_encode_32(p, 4 + size);

		/* metric spec */
		ceph_encode_32(p, size);
		memset(*p, 0, size);
		for (i = 0; i < count; i++)
			((unsigned char *)(*p))[i / 8] |= BIT(metric_bits[i] % 8);
		*p += size;
	} else {
		if (WARN_ON_ONCE(*p + 4 + 4 > end))
			return -ERANGE;

		/* metric spec info length */
		ceph_encode_32(p, 4);
		/* metric spec */
		ceph_encode_32(p, 0);
	}

	return 0;
}

/*
 * session message, specialization for CEPH_SESSION_REQUEST_OPEN
 * to include additional client metadata fields.
 */
static struct ceph_msg *
create_session_full_msg(struct ceph_mds_client *mdsc, int op, u64 seq)
{
	struct ceph_msg *msg;
	struct ceph_mds_session_head *h;
	int i;
	int extra_bytes = 0;
	int metadata_key_count = 0;
	struct ceph_options *opt = mdsc->fsc->client->options;
	struct ceph_mount_options *fsopt = mdsc->fsc->mount_options;
	struct ceph_client *cl = mdsc->fsc->client;
	size_t size, count;
	void *p, *end;
	int ret;

	const char* metadata[][2] = {
		{"hostname", mdsc->nodename},
		{"kernel_version", init_utsname()->release},
		{"entity_id", opt->name ? : ""},
		{"root", fsopt->server_path ? : "/"},
		{NULL, NULL}
	};

	/* Calculate serialized length of metadata */
	extra_bytes = 4;  /* map length */
	for (i = 0; metadata[i][0]; ++i) {
		extra_bytes += 8 + strlen(metadata[i][0]) +
			strlen(metadata[i][1]);
		metadata_key_count++;
	}

	/* supported feature */
	size = 0;
	count = ARRAY_SIZE(feature_bits);
	if (count > 0)
		size = FEATURE_BYTES(count);
	extra_bytes += 4 + size;

	/* metric spec */
	size = 0;
	count = ARRAY_SIZE(metric_bits);
	if (count > 0)
		size = METRIC_BYTES(count);
	extra_bytes += 2 + 4 + 4 + size;

	/* flags, mds auth caps and oldest_client_tid */
	extra_bytes += 4 + 4 + 8;

	/* Allocate the message */
	msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h) + extra_bytes,
			   GFP_NOFS, false);
	if (!msg) {
		pr_err_client(cl, "ENOMEM creating session open msg\n");
		return ERR_PTR(-ENOMEM);
	}
	p = msg->front.iov_base;
	end = p + msg->front.iov_len;

	h = p;
	h->op = cpu_to_le32(op);
	h->seq = cpu_to_le64(seq);

	/*
	 * Serialize client metadata into waiting buffer space, using
	 * the format that userspace expects for map<string, string>
	 *
	 * ClientSession messages with metadata are v7
	 */
	msg->hdr.version = cpu_to_le16(7);
	msg->hdr.compat_version = cpu_to_le16(1);

	/* The write pointer, following the session_head structure */
	p += sizeof(*h);

	/* Number of entries in the map */
	ceph_encode_32(&p, metadata_key_count);

	/* Two length-prefixed strings for each entry in the map */
	for (i = 0; metadata[i][0]; ++i) {
		size_t const key_len = strlen(metadata[i][0]);
		size_t const val_len = strlen(metadata[i][1]);

		ceph_encode_32(&p, key_len);
		memcpy(p, metadata[i][0], key_len);
		p += key_len;
		ceph_encode_32(&p, val_len);
		memcpy(p, metadata[i][1], val_len);
		p += val_len;
	}

	ret = encode_supported_features(&p, end);
	if (ret) {
		pr_err_client(cl, "encode_supported_features failed!\n");
		ceph_msg_put(msg);
		return ERR_PTR(ret);
	}

	ret = encode_metric_spec(&p, end);
	if (ret) {
		pr_err_client(cl, "encode_metric_spec failed!\n");
		ceph_msg_put(msg);
		return ERR_PTR(ret);
	}

	/* version == 5, flags */
	ceph_encode_32(&p, 0);

	/* version == 6, mds auth caps */
	ceph_encode_32(&p, 0);

	/* version == 7, oldest_client_tid */
	ceph_encode_64(&p, mdsc->oldest_tid);

	msg->front.iov_len = p - msg->front.iov_base;
	msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);

	return msg;
}

/*
 * send session open request.
 *
 * called under mdsc->mutex
 */
static int __open_session(struct ceph_mds_client *mdsc,
			  struct ceph_mds_session *session)
{
	struct ceph_msg *msg;
	int mstate;
	int mds = session->s_mds;

	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_FENCE_IO)
		return -EIO;

	/* wait for mds to go active? */
	mstate = ceph_mdsmap_get_state(mdsc->mdsmap, mds);
	doutc(mdsc->fsc->client, "open_session to mds%d (%s)\n", mds,
	      ceph_mds_state_name(mstate));
	session->s_state = CEPH_MDS_SESSION_OPENING;
	session->s_renew_requested = jiffies;

	/* send connect message */
	msg = create_session_full_msg(mdsc, CEPH_SESSION_REQUEST_OPEN,
				      session->s_seq);
	if (IS_ERR(msg))
		return PTR_ERR(msg);
	ceph_con_send(&session->s_con, msg);
	return 0;
}

/*
 * open sessions for any export targets for the given mds
 *
 * called under mdsc->mutex
 */
static struct ceph_mds_session *
__open_export_target_session(struct ceph_mds_client *mdsc, int target)
{
	struct ceph_mds_session *session;
	int ret;

	session = __ceph_lookup_mds_session(mdsc, target);
	if (!session) {
		session = register_session(mdsc, target);
		if (IS_ERR(session))
			return session;
	}
	if (session->s_state == CEPH_MDS_SESSION_NEW ||
	    session->s_state == CEPH_MDS_SESSION_CLOSING) {
		ret = __open_session(mdsc, session);
		if (ret)
			return ERR_PTR(ret);
	}

	return session;
}

struct ceph_mds_session *
ceph_mdsc_open_export_target_session(struct ceph_mds_client *mdsc, int target)
{
	struct ceph_mds_session *session;
	struct ceph_client *cl = mdsc->fsc->client;

	doutc(cl, "to mds%d\n", target);

	mutex_lock(&mdsc->mutex);
	session = __open_export_target_session(mdsc, target);
	mutex_unlock(&mdsc->mutex);

	return session;
}

static void __open_export_target_sessions(struct ceph_mds_client *mdsc,
					  struct ceph_mds_session *session)
{
	struct ceph_mds_info *mi;
	struct ceph_mds_session *ts;
	int i, mds = session->s_mds;
	struct ceph_client *cl = mdsc->fsc->client;

	if (mds >= mdsc->mdsmap->possible_max_rank)
		return;

	mi = &mdsc->mdsmap->m_info[mds];
	doutc(cl, "for mds%d (%d targets)\n", session->s_mds,
	      mi->num_export_targets);

	for (i = 0; i < mi->num_export_targets; i++) {
		ts = __open_export_target_session(mdsc, mi->export_targets[i]);
		ceph_put_mds_session(ts);
	}
}

/*
 * session caps
 */

static int detach_cap_releases(struct ceph_mds_session *session,
			       struct list_head *target)
{
	struct ceph_client *cl = session->s_mdsc->fsc->client;
	const int num_cap_releases = session->s_num_cap_releases;

	lockdep_assert_held(&session->s_cap_lock);

	list_splice_init(&session->s_cap_releases, target);
	session->s_num_cap_releases = 0;
	doutc(cl, "mds%d\n", session->s_mds);

	return num_cap_releases;
}

static void dispose_cap_releases(struct ceph_mds_client *mdsc,
				 struct list_head *dispose)
{
	while (!list_empty(dispose)) {
		struct ceph_cap *cap;
		/* zero out the in-progress message */
		cap = list_first_entry(dispose, struct ceph_cap, session_caps);
		list_del(&cap->session_caps);
		ceph_put_cap(mdsc, cap);
	}
}

static void cleanup_session_requests(struct ceph_mds_client *mdsc,
				     struct ceph_mds_session *session)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_request *req;
	struct rb_node *p;

	doutc(cl, "mds%d\n", session->s_mds);
	mutex_lock(&mdsc->mutex);
	while (!list_empty(&session->s_unsafe)) {
		req = list_first_entry(&session->s_unsafe,
				       struct ceph_mds_request, r_unsafe_item);
		pr_warn_ratelimited_client(cl, " dropping unsafe request %llu\n",
					   req->r_tid);
		if (req->r_target_inode)
			mapping_set_error(req->r_target_inode->i_mapping, -EIO);
		if (req->r_unsafe_dir)
			mapping_set_error(req->r_unsafe_dir->i_mapping, -EIO);
		__unregister_request(mdsc, req);
	}
	/* zero r_attempts, so kick_requests() will re-send requests */
	p = rb_first(&mdsc->request_tree);
	while (p) {
		req = rb_entry(p, struct ceph_mds_request, r_node);
		p = rb_next(p);
		if (req->r_session &&
		    req->r_session->s_mds == session->s_mds)
			req->r_attempts = 0;
	}
	mutex_unlock(&mdsc->mutex);
}

/*
 * Helper to safely iterate over all caps associated with a session, with
 * special care taken to handle a racing __ceph_remove_cap().
 *
 * Caller must hold session s_mutex.
 */
int ceph_iterate_session_caps(struct ceph_mds_session *session,
			      int (*cb)(struct inode *, int mds, void *),
			      void *arg)
{
	struct ceph_client *cl = session->s_mdsc->fsc->client;
	struct list_head *p;
	struct ceph_cap *cap;
	struct inode *inode, *last_inode = NULL;
	struct ceph_cap *old_cap = NULL;
	int ret;

	doutc(cl, "%p mds%d\n", session, session->s_mds);
	spin_lock(&session->s_cap_lock);
	p = session->s_caps.next;
	while (p != &session->s_caps) {
		int mds;

		cap = list_entry(p, struct ceph_cap, session_caps);
		inode = igrab(&cap->ci->netfs.inode);
		if (!inode) {
			p = p->next;
			continue;
		}
		session->s_cap_iterator = cap;
		mds = cap->mds;
		spin_unlock(&session->s_cap_lock);

		if (last_inode) {
			iput(last_inode);
			last_inode = NULL;
		}
		if (old_cap) {
			ceph_put_cap(session->s_mdsc, old_cap);
			old_cap = NULL;
		}

		ret = cb(inode, mds, arg);
		last_inode = inode;

		spin_lock(&session->s_cap_lock);
		p = p->next;
		if (ceph_cap_is_removed(cap)) {
			doutc(cl, "finishing cap %p removal\n", cap);
			BUG_ON(cap->session != session);
			cap->session = NULL;
			list_del_init(&cap->session_caps);
			session->s_nr_caps--;
			atomic64_dec(&session->s_mdsc->metric.total_caps);
			if (cap->queue_release)
				__ceph_queue_cap_release(session, cap);
			else
				old_cap = cap;  /* put_cap it w/o locks held */
		}
		if (ret < 0)
			goto out;
	}
	ret = 0;
out:
	session->s_cap_iterator = NULL;
	spin_unlock(&session->s_cap_lock);

	iput(last_inode);
	if (old_cap)
		ceph_put_cap(session->s_mdsc, old_cap);

	return ret;
}

static int remove_session_caps_cb(struct inode *inode, int mds, void *arg)
{
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_client *cl = ceph_inode_to_client(inode);
	bool invalidate = false;
	struct ceph_cap *cap;
	int iputs = 0;

	spin_lock(&ci->i_ceph_lock);
	cap = __get_cap_for_mds(ci, mds);
	if (cap) {
		doutc(cl, " removing cap %p, ci is %p, inode is %p\n",
		      cap, ci, &ci->netfs.inode);

		iputs = ceph_purge_inode_cap(inode, cap, &invalidate);
	}
	spin_unlock(&ci->i_ceph_lock);

	if (cap)
		wake_up_all(&ci->i_cap_wq);
	if (invalidate)
		ceph_queue_invalidate(inode);
	while (iputs--)
		iput(inode);
	return 0;
}

/*
 * caller must hold session s_mutex
 */
static void remove_session_caps(struct ceph_mds_session *session)
{
	struct ceph_fs_client *fsc = session->s_mdsc->fsc;
	struct super_block *sb = fsc->sb;
	LIST_HEAD(dispose);

	doutc(fsc->client, "on %p\n", session);
	ceph_iterate_session_caps(session, remove_session_caps_cb, fsc);

	wake_up_all(&fsc->mdsc->cap_flushing_wq);

	spin_lock(&session->s_cap_lock);
	if (session->s_nr_caps > 0) {
		struct inode *inode;
		struct ceph_cap *cap, *prev = NULL;
		struct ceph_vino vino;
		/*
		 * iterate_session_caps() skips inodes that are being
		 * deleted, we need to wait until deletions are complete.
		 * __wait_on_freeing_inode() is designed for the job,
		 * but it is not exported, so use lookup inode function
		 * to access it.
		 */
		while (!list_empty(&session->s_caps)) {
			cap = list_entry(session->s_caps.next,
					 struct ceph_cap, session_caps);
			if (cap == prev)
				break;
			prev = cap;
			vino = cap->ci->i_vino;
			spin_unlock(&session->s_cap_lock);

			inode = ceph_find_inode(sb, vino);
			iput(inode);

			spin_lock(&session->s_cap_lock);
		}
	}

	// drop cap expires and unlock s_cap_lock
	detach_cap_releases(session, &dispose);

	BUG_ON(session->s_nr_caps > 0);
	BUG_ON(!list_empty(&session->s_cap_flushing));
	spin_unlock(&session->s_cap_lock);
	dispose_cap_releases(session->s_mdsc, &dispose);
}

enum {
	RECONNECT,
	RENEWCAPS,
	FORCE_RO,
};

/*
 * wake up any threads waiting on this session's caps.  if the cap is
 * old (didn't get renewed on the client reconnect), remove it now.
 *
 * caller must hold s_mutex.
 */
static int wake_up_session_cb(struct inode *inode, int mds, void *arg)
{
	struct ceph_inode_info *ci = ceph_inode(inode);
	unsigned long ev = (unsigned long)arg;

	if (ev == RECONNECT) {
		spin_lock(&ci->i_ceph_lock);
		ci->i_wanted_max_size = 0;
		ci->i_requested_max_size = 0;
		spin_unlock(&ci->i_ceph_lock);
	} else if (ev == RENEWCAPS) {
		struct ceph_cap *cap;

		spin_lock(&ci->i_ceph_lock);
		cap = __get_cap_for_mds(ci, mds);
		/* mds did not re-issue stale cap */
		if (cap && cap->cap_gen < atomic_read(&cap->session->s_cap_gen))
			cap->issued = cap->implemented = CEPH_CAP_PIN;
		spin_unlock(&ci->i_ceph_lock);
	} else if (ev == FORCE_RO) {
	}
	wake_up_all(&ci->i_cap_wq);
	return 0;
}

static void wake_up_session_caps(struct ceph_mds_session *session, int ev)
{
	struct ceph_client *cl = session->s_mdsc->fsc->client;

	doutc(cl, "session %p mds%d\n", session, session->s_mds);
	ceph_iterate_session_caps(session, wake_up_session_cb,
				  (void *)(unsigned long)ev);
}

/*
 * Send periodic message to MDS renewing all currently held caps.  The
 * ack will reset the expiration for all caps from this session.
 *
 * caller holds s_mutex
 */
static int send_renew_caps(struct ceph_mds_client *mdsc,
			   struct ceph_mds_session *session)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_msg *msg;
	int state;

	if (time_after_eq(jiffies, session->s_cap_ttl) &&
	    time_after_eq(session->s_cap_ttl, session->s_renew_requested))
		pr_info_client(cl, "mds%d caps stale\n", session->s_mds);
	session->s_renew_requested = jiffies;

	/* do not try to renew caps until a recovering mds has reconnected
	 * with its clients. */
	state = ceph_mdsmap_get_state(mdsc->mdsmap, session->s_mds);
	if (state < CEPH_MDS_STATE_RECONNECT) {
		doutc(cl, "ignoring mds%d (%s)\n", session->s_mds,
		      ceph_mds_state_name(state));
		return 0;
	}

	doutc(cl, "to mds%d (%s)\n", session->s_mds,
	      ceph_mds_state_name(state));
	msg = create_session_full_msg(mdsc, CEPH_SESSION_REQUEST_RENEWCAPS,
				      ++session->s_renew_seq);
	if (IS_ERR(msg))
		return PTR_ERR(msg);
	ceph_con_send(&session->s_con, msg);
	return 0;
}

static int send_flushmsg_ack(struct ceph_mds_client *mdsc,
			     struct ceph_mds_session *session, u64 seq)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_msg *msg;

	doutc(cl, "to mds%d (%s)s seq %lld\n", session->s_mds,
	      ceph_session_state_name(session->s_state), seq);
	msg = ceph_create_session_msg(CEPH_SESSION_FLUSHMSG_ACK, seq);
	if (!msg)
		return -ENOMEM;
	ceph_con_send(&session->s_con, msg);
	return 0;
}


/*
 * Note new cap ttl, and any transition from stale -> not stale (fresh?).
 *
 * Called under session->s_mutex
 */
static void renewed_caps(struct ceph_mds_client *mdsc,
			 struct ceph_mds_session *session, int is_renew)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int was_stale;
	int wake = 0;

	spin_lock(&session->s_cap_lock);
	was_stale = is_renew && time_after_eq(jiffies, session->s_cap_ttl);

	session->s_cap_ttl = session->s_renew_requested +
		mdsc->mdsmap->m_session_timeout*HZ;

	if (was_stale) {
		if (time_before(jiffies, session->s_cap_ttl)) {
			pr_info_client(cl, "mds%d caps renewed\n",
				       session->s_mds);
			wake = 1;
		} else {
			pr_info_client(cl, "mds%d caps still stale\n",
				       session->s_mds);
		}
	}
	doutc(cl, "mds%d ttl now %lu, was %s, now %s\n", session->s_mds,
	      session->s_cap_ttl, was_stale ? "stale" : "fresh",
	      time_before(jiffies, session->s_cap_ttl) ? "stale" : "fresh");
	spin_unlock(&session->s_cap_lock);

	if (wake)
		wake_up_session_caps(session, RENEWCAPS);
}

/*
 * send a session close request
 */
static int request_close_session(struct ceph_mds_session *session)
{
	struct ceph_client *cl = session->s_mdsc->fsc->client;
	struct ceph_msg *msg;

	doutc(cl, "mds%d state %s seq %lld\n", session->s_mds,
	      ceph_session_state_name(session->s_state), session->s_seq);
	msg = ceph_create_session_msg(CEPH_SESSION_REQUEST_CLOSE,
				      session->s_seq);
	if (!msg)
		return -ENOMEM;
	ceph_con_send(&session->s_con, msg);
	return 1;
}

/*
 * Called with s_mutex held.
 */
static int __close_session(struct ceph_mds_client *mdsc,
			 struct ceph_mds_session *session)
{
	if (session->s_state >= CEPH_MDS_SESSION_CLOSING)
		return 0;
	session->s_state = CEPH_MDS_SESSION_CLOSING;
	return request_close_session(session);
}

static bool drop_negative_children(struct dentry *dentry)
{
	struct dentry *child;
	bool all_negative = true;

	if (!d_is_dir(dentry))
		goto out;

	spin_lock(&dentry->d_lock);
	hlist_for_each_entry(child, &dentry->d_children, d_sib) {
		if (d_really_is_positive(child)) {
			all_negative = false;
			break;
		}
	}
	spin_unlock(&dentry->d_lock);

	if (all_negative)
		shrink_dcache_parent(dentry);
out:
	return all_negative;
}

/*
 * Trim old(er) caps.
 *
 * Because we can't cache an inode without one or more caps, we do
 * this indirectly: if a cap is unused, we prune its aliases, at which
 * point the inode will hopefully get dropped to.
 *
 * Yes, this is a bit sloppy.  Our only real goal here is to respond to
 * memory pressure from the MDS, though, so it needn't be perfect.
 */
static int trim_caps_cb(struct inode *inode, int mds, void *arg)
{
	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
	struct ceph_client *cl = mdsc->fsc->client;
	int *remaining = arg;
	struct ceph_inode_info *ci = ceph_inode(inode);
	int used, wanted, oissued, mine;
	struct ceph_cap *cap;

	if (*remaining <= 0)
		return -1;

	spin_lock(&ci->i_ceph_lock);
	cap = __get_cap_for_mds(ci, mds);
	if (!cap) {
		spin_unlock(&ci->i_ceph_lock);
		return 0;
	}
	mine = cap->issued | cap->implemented;
	used = __ceph_caps_used(ci);
	wanted = __ceph_caps_file_wanted(ci);
	oissued = __ceph_caps_issued_other(ci, cap);

	doutc(cl, "%p %llx.%llx cap %p mine %s oissued %s used %s wanted %s\n",
	      inode, ceph_vinop(inode), cap, ceph_cap_string(mine),
	      ceph_cap_string(oissued), ceph_cap_string(used),
	      ceph_cap_string(wanted));
	if (cap == ci->i_auth_cap) {
		if (ci->i_dirty_caps || ci->i_flushing_caps ||
		    !list_empty(&ci->i_cap_snaps))
			goto out;
		if ((used | wanted) & CEPH_CAP_ANY_WR)
			goto out;
		/* Note: it's possible that i_filelock_ref becomes non-zero
		 * after dropping auth caps. It doesn't hurt because reply
		 * of lock mds request will re-add auth caps. */
		if (atomic_read(&ci->i_filelock_ref) > 0)
			goto out;
	}
	/* The inode has cached pages, but it's no longer used.
	 * we can safely drop it */
	if (S_ISREG(inode->i_mode) &&
	    wanted == 0 && used == CEPH_CAP_FILE_CACHE &&
	    !(oissued & CEPH_CAP_FILE_CACHE)) {
	  used = 0;
	  oissued = 0;
	}
	if ((used | wanted) & ~oissued & mine)
		goto out;   /* we need these caps */

	if (oissued) {
		/* we aren't the only cap.. just remove us */
		ceph_remove_cap(mdsc, cap, ci, true);
		(*remaining)--;
	} else {
		struct dentry *dentry;
		/* try dropping referring dentries */
		spin_unlock(&ci->i_ceph_lock);
		dentry = d_find_any_alias(inode);
		if (dentry && drop_negative_children(dentry)) {
			int count;
			dput(dentry);
			d_prune_aliases(inode);
			count = icount_read_once(inode);
			if (count == 1)
				(*remaining)--;
			doutc(cl, "%p %llx.%llx cap %p pruned, count now %d\n",
			      inode, ceph_vinop(inode), cap, count);
		} else {
			dput(dentry);
		}
		return 0;
	}

out:
	spin_unlock(&ci->i_ceph_lock);
	return 0;
}

/*
 * Trim session cap count down to some max number.
 */
int ceph_trim_caps(struct ceph_mds_client *mdsc,
		   struct ceph_mds_session *session,
		   int max_caps)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int trim_caps = session->s_nr_caps - max_caps;

	doutc(cl, "mds%d start: %d / %d, trim %d\n", session->s_mds,
	      session->s_nr_caps, max_caps, trim_caps);
	if (trim_caps > 0) {
		int remaining = trim_caps;

		ceph_iterate_session_caps(session, trim_caps_cb, &remaining);
		doutc(cl, "mds%d done: %d / %d, trimmed %d\n",
		      session->s_mds, session->s_nr_caps, max_caps,
		      trim_caps - remaining);
	}

	ceph_flush_session_cap_releases(mdsc, session);
	return 0;
}

static int check_caps_flush(struct ceph_mds_client *mdsc,
			    u64 want_flush_tid)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int ret = 1;

	spin_lock(&mdsc->cap_dirty_lock);
	if (!list_empty(&mdsc->cap_flush_list)) {
		struct ceph_cap_flush *cf =
			list_first_entry(&mdsc->cap_flush_list,
					 struct ceph_cap_flush, g_list);
		if (cf->tid <= want_flush_tid) {
			doutc(cl, "still flushing tid %llu <= %llu\n",
			      cf->tid, want_flush_tid);
			ret = 0;
		}
	}
	spin_unlock(&mdsc->cap_dirty_lock);
	return ret;
}

/*
 * Snapshot of a single cap_flush entry for diagnostic dump.
 * Collected under cap_dirty_lock, printed after releasing it.
 */
struct flush_dump_entry {
	u64 ino;		/* inode number */
	u64 snap;		/* snap id */
	int caps;		/* dirty cap bits */
	u64 tid;		/* flush transaction id */
	u64 last_ack;		/* most recent ack tid for this inode */
	bool wake;		/* whether completion was requested */
	bool is_capsnap;	/* true if this is a cap snap flush */
	bool ci_null;		/* true if cf->ci was unexpectedly NULL */
};

/*
 * Dump pending cap flushes for diagnostic purposes.
 *
 * cf->ci is safe to dereference here: cap_flush entries hold a
 * reference on the inode (via the cap), and entries are removed from
 * cap_flush_list under cap_dirty_lock before the cap (and thus the
 * inode reference) is released.  Holding cap_dirty_lock therefore
 * guarantees the inode remains valid for the lifetime of the scan.
 */

static void dump_cap_flushes(struct ceph_mds_client *mdsc, u64 want_tid)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct flush_dump_entry entries[CEPH_CAP_FLUSH_MAX_DUMP_ENTRIES];
	struct ceph_cap_flush *cf;
	int n = 0, remaining = 0;
	int i;

	spin_lock(&mdsc->cap_dirty_lock);
	list_for_each_entry(cf, &mdsc->cap_flush_list, g_list) {
		if (cf->tid > want_tid)
			break;
		if (n < CEPH_CAP_FLUSH_MAX_DUMP_ENTRIES) {
			struct flush_dump_entry *e = &entries[n++];

			e->ci_null = WARN_ON_ONCE(!cf->ci);
			if (!e->ci_null) {
				e->ino = ceph_ino(&cf->ci->netfs.inode);
				e->snap = ceph_snap(&cf->ci->netfs.inode);
				e->last_ack = READ_ONCE(cf->ci->i_last_cap_flush_ack);
			}
			e->caps = cf->caps;
			e->tid = cf->tid;
			e->wake = cf->wake;
			e->is_capsnap = cf->is_capsnap;
		} else {
			remaining++;
		}
	}
	spin_unlock(&mdsc->cap_dirty_lock);

	pr_info_client(cl, "still waiting for cap flushes through %llu:\n",
		       want_tid);
	for (i = 0; i < n; i++) {
		struct flush_dump_entry *e = &entries[i];

		if (e->ci_null)
			pr_info_client(cl,
				       "  (null ci) %s tid=%llu wake=%d%s\n",
				       ceph_cap_string(e->caps), e->tid,
				       e->wake,
				       e->is_capsnap ? " is_capsnap" : "");
		else
			pr_info_client(cl,
				       "  %llx.%llx %s tid=%llu last_ack=%llu wake=%d%s\n",
				       e->ino, e->snap,
				       ceph_cap_string(e->caps), e->tid,
				       e->last_ack, e->wake,
				       e->is_capsnap ? " is_capsnap" : "");
	}
	if (remaining)
		pr_info_client(cl, "  ... and %d more pending flushes\n",
			       remaining);
}

/*
 * Wait for all cap flushes through @want_flush_tid to complete.
 * Periodically dumps pending cap flush state for diagnostics.
 */
static void wait_caps_flush(struct ceph_mds_client *mdsc,
			    u64 want_flush_tid)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int i = 0;
	long ret;

	doutc(cl, "want %llu\n", want_flush_tid);

	do {
		/* 60 * HZ fits in a long on all supported architectures. */
		ret = wait_event_timeout(mdsc->cap_flushing_wq,
			   check_caps_flush(mdsc, want_flush_tid),
			   CEPH_CAP_FLUSH_WAIT_TIMEOUT_SEC * HZ);
		if (ret == 0) {
			if (i < CEPH_CAP_FLUSH_MAX_DUMP_ITERS)
				dump_cap_flushes(mdsc, want_flush_tid);
			else if (i == CEPH_CAP_FLUSH_MAX_DUMP_ITERS)
				pr_info_client(cl,
					       "still waiting for cap flushes; suppressing further dumps\n");
			i++;
		}
	} while (ret == 0);

	doutc(cl, "ok, flushed thru %llu\n", want_flush_tid);
}

/*
 * called under s_mutex
 */
static void ceph_send_cap_releases(struct ceph_mds_client *mdsc,
				   struct ceph_mds_session *session)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_msg *msg = NULL;
	struct ceph_mds_cap_release *head;
	struct ceph_mds_cap_item *item;
	struct ceph_osd_client *osdc = &mdsc->fsc->client->osdc;
	struct ceph_cap *cap;
	LIST_HEAD(tmp_list);
	int num_cap_releases;
	__le32	barrier, *cap_barrier;

	down_read(&osdc->lock);
	barrier = cpu_to_le32(osdc->epoch_barrier);
	up_read(&osdc->lock);

	spin_lock(&session->s_cap_lock);
again:
	num_cap_releases = detach_cap_releases(session, &tmp_list);
	spin_unlock(&session->s_cap_lock);

	while (!list_empty(&tmp_list)) {
		if (!msg) {
			msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPRELEASE,
					PAGE_SIZE, GFP_NOFS, false);
			if (!msg)
				goto out_err;
			head = msg->front.iov_base;
			head->num = cpu_to_le32(0);
			msg->front.iov_len = sizeof(*head);

			msg->hdr.version = cpu_to_le16(2);
			msg->hdr.compat_version = cpu_to_le16(1);
		}

		cap = list_first_entry(&tmp_list, struct ceph_cap,
					session_caps);
		list_del(&cap->session_caps);
		num_cap_releases--;

		head = msg->front.iov_base;
		put_unaligned_le32(get_unaligned_le32(&head->num) + 1,
				   &head->num);
		item = msg->front.iov_base + msg->front.iov_len;
		item->ino = cpu_to_le64(cap->cap_ino);
		item->cap_id = cpu_to_le64(cap->cap_id);
		item->migrate_seq = cpu_to_le32(cap->mseq);
		item->issue_seq = cpu_to_le32(cap->issue_seq);
		msg->front.iov_len += sizeof(*item);

		ceph_put_cap(mdsc, cap);

		if (le32_to_cpu(head->num) == CEPH_CAPS_PER_RELEASE) {
			// Append cap_barrier field
			cap_barrier = msg->front.iov_base + msg->front.iov_len;
			*cap_barrier = barrier;
			msg->front.iov_len += sizeof(*cap_barrier);

			msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
			doutc(cl, "mds%d %p\n", session->s_mds, msg);
			ceph_con_send(&session->s_con, msg);
			msg = NULL;
		}
	}

	BUG_ON(num_cap_releases != 0);

	spin_lock(&session->s_cap_lock);
	if (!list_empty(&session->s_cap_releases))
		goto again;
	spin_unlock(&session->s_cap_lock);

	if (msg) {
		// Append cap_barrier field
		cap_barrier = msg->front.iov_base + msg->front.iov_len;
		*cap_barrier = barrier;
		msg->front.iov_len += sizeof(*cap_barrier);

		msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
		doutc(cl, "mds%d %p\n", session->s_mds, msg);
		ceph_con_send(&session->s_con, msg);
	}
	return;
out_err:
	pr_err_client(cl, "mds%d, failed to allocate message\n",
		      session->s_mds);
	spin_lock(&session->s_cap_lock);
	list_splice(&tmp_list, &session->s_cap_releases);
	session->s_num_cap_releases += num_cap_releases;
	spin_unlock(&session->s_cap_lock);
}

static void ceph_cap_release_work(struct work_struct *work)
{
	struct ceph_mds_session *session =
		container_of(work, struct ceph_mds_session, s_cap_release_work);

	mutex_lock(&session->s_mutex);
	if (session->s_state == CEPH_MDS_SESSION_OPEN ||
	    session->s_state == CEPH_MDS_SESSION_HUNG)
		ceph_send_cap_releases(session->s_mdsc, session);
	mutex_unlock(&session->s_mutex);
	ceph_put_mds_session(session);
}

void ceph_flush_session_cap_releases(struct ceph_mds_client *mdsc,
		             struct ceph_mds_session *session)
{
	struct ceph_client *cl = mdsc->fsc->client;
	if (mdsc->stopping)
		return;

	ceph_get_mds_session(session);
	if (queue_work(mdsc->fsc->cap_wq,
		       &session->s_cap_release_work)) {
		doutc(cl, "cap release work queued\n");
	} else {
		ceph_put_mds_session(session);
		doutc(cl, "failed to queue cap release work\n");
	}
}

/*
 * caller holds session->s_cap_lock
 */
void __ceph_queue_cap_release(struct ceph_mds_session *session,
			      struct ceph_cap *cap)
{
	list_add_tail(&cap->session_caps, &session->s_cap_releases);
	session->s_num_cap_releases++;

	if (!(session->s_num_cap_releases % CEPH_CAPS_PER_RELEASE))
		ceph_flush_session_cap_releases(session->s_mdsc, session);
}

static void ceph_cap_reclaim_work(struct work_struct *work)
{
	struct ceph_mds_client *mdsc =
		container_of(work, struct ceph_mds_client, cap_reclaim_work);
	int ret = ceph_trim_dentries(mdsc);
	if (ret == -EAGAIN)
		ceph_queue_cap_reclaim_work(mdsc);
}

void ceph_queue_cap_reclaim_work(struct ceph_mds_client *mdsc)
{
	struct ceph_client *cl = mdsc->fsc->client;
	if (mdsc->stopping)
		return;

        if (queue_work(mdsc->fsc->cap_wq, &mdsc->cap_reclaim_work)) {
                doutc(cl, "caps reclaim work queued\n");
        } else {
                doutc(cl, "failed to queue caps release work\n");
        }
}

void ceph_reclaim_caps_nr(struct ceph_mds_client *mdsc, int nr)
{
	int val;
	if (!nr)
		return;
	val = atomic_add_return(nr, &mdsc->cap_reclaim_pending);
	if ((val % CEPH_CAPS_PER_RELEASE) < nr) {
		atomic_set(&mdsc->cap_reclaim_pending, 0);
		ceph_queue_cap_reclaim_work(mdsc);
	}
}

void ceph_queue_cap_unlink_work(struct ceph_mds_client *mdsc)
{
	struct ceph_client *cl = mdsc->fsc->client;
	if (mdsc->stopping)
		return;

        if (queue_work(mdsc->fsc->cap_wq, &mdsc->cap_unlink_work)) {
                doutc(cl, "caps unlink work queued\n");
        } else {
                doutc(cl, "failed to queue caps unlink work\n");
        }
}

static void ceph_cap_unlink_work(struct work_struct *work)
{
	struct ceph_mds_client *mdsc =
		container_of(work, struct ceph_mds_client, cap_unlink_work);
	struct ceph_client *cl = mdsc->fsc->client;

	doutc(cl, "begin\n");
	spin_lock(&mdsc->cap_delay_lock);
	while (!list_empty(&mdsc->cap_unlink_delay_list)) {
		struct ceph_inode_info *ci;
		struct inode *inode;

		ci = list_first_entry(&mdsc->cap_unlink_delay_list,
				      struct ceph_inode_info,
				      i_cap_delay_list);
		list_del_init(&ci->i_cap_delay_list);

		inode = igrab(&ci->netfs.inode);
		if (inode) {
			spin_unlock(&mdsc->cap_delay_lock);
			doutc(cl, "on %p %llx.%llx\n", inode,
			      ceph_vinop(inode));
			ceph_check_caps(ci, CHECK_CAPS_FLUSH);
			iput(inode);
			spin_lock(&mdsc->cap_delay_lock);
		}
	}
	spin_unlock(&mdsc->cap_delay_lock);
	doutc(cl, "done\n");
}

/*
 * requests
 */

int ceph_alloc_readdir_reply_buffer(struct ceph_mds_request *req,
				    struct inode *dir)
{
	struct ceph_inode_info *ci = ceph_inode(dir);
	struct ceph_mds_reply_info_parsed *rinfo = &req->r_reply_info;
	struct ceph_mount_options *opt = req->r_mdsc->fsc->mount_options;
	size_t size = sizeof(struct ceph_mds_reply_dir_entry);
	unsigned int num_entries;
	u64 bytes_count;
	int order;

	spin_lock(&ci->i_ceph_lock);
	num_entries = ci->i_files + ci->i_subdirs;
	spin_unlock(&ci->i_ceph_lock);
	num_entries = max(num_entries, 1U);
	num_entries = min(num_entries, opt->max_readdir);

	bytes_count = (u64)size * num_entries;
	if (unlikely(bytes_count > ULONG_MAX))
		bytes_count = ULONG_MAX;

	order = get_order((unsigned long)bytes_count);
	while (order >= 0) {
		rinfo->dir_entries = (void*)__get_free_pages(GFP_KERNEL |
							     __GFP_NOWARN |
							     __GFP_ZERO,
							     order);
		if (rinfo->dir_entries)
			break;
		order--;
	}
	if (!rinfo->dir_entries || unlikely(order < 0))
		return -ENOMEM;

	num_entries = (PAGE_SIZE << order) / size;
	num_entries = min(num_entries, opt->max_readdir);

	rinfo->dir_buf_size = PAGE_SIZE << order;
	req->r_num_caps = num_entries + 1;
	req->r_args.readdir.max_entries = cpu_to_le32(num_entries);
	req->r_args.readdir.max_bytes = cpu_to_le32(opt->max_readdir_bytes);
	return 0;
}

/*
 * Create an mds request.
 */
struct ceph_mds_request *
ceph_mdsc_create_request(struct ceph_mds_client *mdsc, int op, int mode)
{
	struct ceph_mds_request *req;

	req = kmem_cache_zalloc(ceph_mds_request_cachep, GFP_NOFS);
	if (!req)
		return ERR_PTR(-ENOMEM);

	mutex_init(&req->r_fill_mutex);
	req->r_mdsc = mdsc;
	req->r_started = jiffies;
	req->r_start_latency = ktime_get();
	req->r_resend_mds = -1;
	INIT_LIST_HEAD(&req->r_unsafe_dir_item);
	INIT_LIST_HEAD(&req->r_unsafe_target_item);
	req->r_fmode = -1;
	req->r_feature_needed = -1;
	kref_init(&req->r_kref);
	RB_CLEAR_NODE(&req->r_node);
	INIT_LIST_HEAD(&req->r_wait);
	init_completion(&req->r_completion);
	init_completion(&req->r_safe_completion);
	INIT_LIST_HEAD(&req->r_unsafe_item);

	ktime_get_coarse_real_ts64(&req->r_stamp);

	req->r_op = op;
	req->r_direct_mode = mode;
	return req;
}

/*
 * return oldest (lowest) request, tid in request tree, 0 if none.
 *
 * called under mdsc->mutex.
 */
static struct ceph_mds_request *__get_oldest_req(struct ceph_mds_client *mdsc)
{
	if (RB_EMPTY_ROOT(&mdsc->request_tree))
		return NULL;
	return rb_entry(rb_first(&mdsc->request_tree),
			struct ceph_mds_request, r_node);
}

static inline  u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
{
	return mdsc->oldest_tid;
}

#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
static u8 *get_fscrypt_altname(const struct ceph_mds_request *req, u32 *plen)
{
	struct inode *dir = req->r_parent;
	struct dentry *dentry = req->r_dentry;
	const struct qstr *name = req->r_dname;
	u8 *cryptbuf = NULL;
	u32 len = 0;
	int ret = 0;

	/* only encode if we have parent and dentry */
	if (!dir || !dentry)
		goto success;

	/* No-op unless this is encrypted */
	if (!IS_ENCRYPTED(dir))
		goto success;

	ret = ceph_fscrypt_prepare_readdir(dir);
	if (ret < 0)
		return ERR_PTR(ret);

	/* No key? Just ignore it. */
	if (!fscrypt_has_encryption_key(dir))
		goto success;

	if (!name)
		name = &dentry->d_name;

	if (!fscrypt_fname_encrypted_size(dir, name->len, NAME_MAX, &len)) {
		WARN_ON_ONCE(1);
		return ERR_PTR(-ENAMETOOLONG);
	}

	/* No need to append altname if name is short enough */
	if (len <= CEPH_NOHASH_NAME_MAX) {
		len = 0;
		goto success;
	}

	cryptbuf = kmalloc(len, GFP_KERNEL);
	if (!cryptbuf)
		return ERR_PTR(-ENOMEM);

	ret = fscrypt_fname_encrypt(dir, name, cryptbuf, len);
	if (ret) {
		kfree(cryptbuf);
		return ERR_PTR(ret);
	}
success:
	*plen = len;
	return cryptbuf;
}
#else
static u8 *get_fscrypt_altname(const struct ceph_mds_request *req, u32 *plen)
{
	*plen = 0;
	return NULL;
}
#endif

/**
 * ceph_mdsc_build_path - build a path string to a given dentry
 * @mdsc: mds client
 * @dentry: dentry to which path should be built
 * @path_info: output path, length, base ino+snap, and freepath ownership flag
 * @for_wire: is this path going to be sent to the MDS?
 *
 * Build a string that represents the path to the dentry. This is mostly called
 * for two different purposes:
 *
 * 1) we need to build a path string to send to the MDS (for_wire == true)
 * 2) we need a path string for local presentation (e.g. debugfs)
 *    (for_wire == false)
 *
 * The path is built in reverse, starting with the dentry. Walk back up toward
 * the root, building the path until the first non-snapped inode is reached
 * (for_wire) or the root inode is reached (!for_wire).
 *
 * Encode hidden .snap dirs as a double /, i.e.
 *   foo/.snap/bar -> foo//bar
 */
char *ceph_mdsc_build_path(struct ceph_mds_client *mdsc, struct dentry *dentry,
			   struct ceph_path_info *path_info, int for_wire)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct dentry *cur;
	struct inode *inode;
	char *path;
	int pos;
	unsigned seq;
	u64 base;

	if (!dentry)
		return ERR_PTR(-EINVAL);

	path = __getname();
	if (!path)
		return ERR_PTR(-ENOMEM);
retry:
	pos = PATH_MAX - 1;
	path[pos] = '\0';

	seq = read_seqbegin(&rename_lock);
	cur = dget(dentry);
	for (;;) {
		struct dentry *parent;

		spin_lock(&cur->d_lock);
		inode = d_inode(cur);
		if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
			doutc(cl, "path+%d: %p SNAPDIR\n", pos, cur);
			spin_unlock(&cur->d_lock);
			parent = dget_parent(cur);
		} else if (for_wire && inode && dentry != cur &&
			   ceph_snap(inode) == CEPH_NOSNAP) {
			spin_unlock(&cur->d_lock);
			pos++; /* get rid of any prepended '/' */
			break;
		} else if (!for_wire || !IS_ENCRYPTED(d_inode(cur->d_parent))) {
			pos -= cur->d_name.len;
			if (pos < 0) {
				spin_unlock(&cur->d_lock);
				break;
			}
			memcpy(path + pos, cur->d_name.name, cur->d_name.len);
			spin_unlock(&cur->d_lock);
			parent = dget_parent(cur);
		} else {
			int len, ret;
			char buf[NAME_MAX];

			/*
			 * Proactively copy name into buf, in case we need to
			 * present it as-is.
			 */
			memcpy(buf, cur->d_name.name, cur->d_name.len);
			len = cur->d_name.len;
			spin_unlock(&cur->d_lock);
			parent = dget_parent(cur);

			ret = ceph_fscrypt_prepare_readdir(d_inode(parent));
			if (ret < 0) {
				dput(parent);
				dput(cur);
				__putname(path);
				return ERR_PTR(ret);
			}

			if (fscrypt_has_encryption_key(d_inode(parent))) {
				len = ceph_encode_encrypted_dname(d_inode(parent),
								  buf, len);
				if (len < 0) {
					dput(parent);
					dput(cur);
					__putname(path);
					return ERR_PTR(len);
				}
			}
			pos -= len;
			if (pos < 0) {
				dput(parent);
				break;
			}
			memcpy(path + pos, buf, len);
		}
		dput(cur);
		cur = parent;

		/* Are we at the root? */
		if (IS_ROOT(cur))
			break;

		/* Are we out of buffer? */
		if (--pos < 0)
			break;

		path[pos] = '/';
	}
	inode = d_inode(cur);
	base = inode ? ceph_ino(inode) : 0;
	dput(cur);

	if (read_seqretry(&rename_lock, seq))
		goto retry;

	if (pos < 0) {
		/*
		 * The path is longer than PATH_MAX and this function
		 * cannot ever succeed.  Creating paths that long is
		 * possible with Ceph, but Linux cannot use them.
		 */
		__putname(path);
		return ERR_PTR(-ENAMETOOLONG);
	}

	/* Initialize the output structure */
	memset(path_info, 0, sizeof(*path_info));

	path_info->vino.ino = base;
	path_info->pathlen = PATH_MAX - 1 - pos;
	path_info->path = path + pos;
	path_info->freepath = true;

	/* Set snap from dentry if available */
	if (d_inode(dentry))
		path_info->vino.snap = ceph_snap(d_inode(dentry));
	else
		path_info->vino.snap = CEPH_NOSNAP;

	doutc(cl, "on %p %d built %llx '%.*s'\n", dentry, d_count(dentry),
	      base, PATH_MAX - 1 - pos, path + pos);
	return path + pos;
}

static int build_dentry_path(struct ceph_mds_client *mdsc, struct dentry *dentry,
			     struct inode *dir, struct ceph_path_info *path_info,
			     bool parent_locked)
{
	char *path;

	rcu_read_lock();
	if (!dir)
		dir = d_inode_rcu(dentry->d_parent);
	if (dir && parent_locked && ceph_snap(dir) == CEPH_NOSNAP &&
	    !IS_ENCRYPTED(dir)) {
		path_info->vino.ino = ceph_ino(dir);
		path_info->vino.snap = ceph_snap(dir);
		rcu_read_unlock();
		path_info->path = dentry->d_name.name;
		path_info->pathlen = dentry->d_name.len;
		path_info->freepath = false;
		return 0;
	}
	rcu_read_unlock();
	path = ceph_mdsc_build_path(mdsc, dentry, path_info, 1);
	if (IS_ERR(path))
		return PTR_ERR(path);
	/*
	 * ceph_mdsc_build_path already fills path_info, including snap handling.
	 */
	return 0;
}

static int build_inode_path(struct inode *inode, struct ceph_path_info *path_info)
{
	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
	struct dentry *dentry;
	char *path;

	if (ceph_snap(inode) == CEPH_NOSNAP) {
		path_info->vino.ino = ceph_ino(inode);
		path_info->vino.snap = ceph_snap(inode);
		path_info->pathlen = 0;
		path_info->freepath = false;
		return 0;
	}
	dentry = d_find_alias(inode);
	path = ceph_mdsc_build_path(mdsc, dentry, path_info, 1);
	dput(dentry);
	if (IS_ERR(path))
		return PTR_ERR(path);
	/*
	 * ceph_mdsc_build_path already fills path_info, including snap from dentry.
	 * Override with inode's snap since that's what this function is for.
	 */
	path_info->vino.snap = ceph_snap(inode);
	return 0;
}

/*
 * request arguments may be specified via an inode *, a dentry *, or
 * an explicit ino+path.
 */
static int set_request_path_attr(struct ceph_mds_client *mdsc, struct inode *rinode,
				 struct dentry *rdentry, struct inode *rdiri,
				 const char *rpath, u64 rino,
				 struct ceph_path_info *path_info,
				 bool parent_locked)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int r = 0;

	/* Initialize the output structure */
	memset(path_info, 0, sizeof(*path_info));

	if (rinode) {
		r = build_inode_path(rinode, path_info);
		doutc(cl, " inode %p %llx.%llx\n", rinode, ceph_ino(rinode),
		      ceph_snap(rinode));
	} else if (rdentry) {
		r = build_dentry_path(mdsc, rdentry, rdiri, path_info, parent_locked);
		doutc(cl, " dentry %p %llx/%.*s\n", rdentry, path_info->vino.ino,
		      path_info->pathlen, path_info->path);
	} else if (rpath || rino) {
		path_info->vino.ino = rino;
		path_info->vino.snap = CEPH_NOSNAP;
		path_info->path = rpath;
		path_info->pathlen = rpath ? strlen(rpath) : 0;
		path_info->freepath = false;

		doutc(cl, " path %.*s\n", path_info->pathlen, rpath);
	}

	return r;
}

static void encode_mclientrequest_tail(void **p,
				       const struct ceph_mds_request *req)
{
	struct ceph_timespec ts;
	int i;

	ceph_encode_timespec64(&ts, &req->r_stamp);
	ceph_encode_copy(p, &ts, sizeof(ts));

	/* v4: gid_list */
	ceph_encode_32(p, req->r_cred->group_info->ngroups);
	for (i = 0; i < req->r_cred->group_info->ngroups; i++)
		ceph_encode_64(p, from_kgid(&init_user_ns,
					    req->r_cred->group_info->gid[i]));

	/* v5: altname */
	ceph_encode_32(p, req->r_altname_len);
	ceph_encode_copy(p, req->r_altname, req->r_altname_len);

	/* v6: fscrypt_auth and fscrypt_file */
	if (req->r_fscrypt_auth) {
		u32 authlen = ceph_fscrypt_auth_len(req->r_fscrypt_auth);

		ceph_encode_32(p, authlen);
		ceph_encode_copy(p, req->r_fscrypt_auth, authlen);
	} else {
		ceph_encode_32(p, 0);
	}
	if (test_bit(CEPH_MDS_R_FSCRYPT_FILE, &req->r_req_flags)) {
		ceph_encode_32(p, sizeof(__le64));
		ceph_encode_64(p, req->r_fscrypt_file);
	} else {
		ceph_encode_32(p, 0);
	}
}

static inline u16 mds_supported_head_version(struct ceph_mds_session *session)
{
	if (!test_bit(CEPHFS_FEATURE_32BITS_RETRY_FWD, &session->s_features))
		return 1;

	if (!test_bit(CEPHFS_FEATURE_HAS_OWNER_UIDGID, &session->s_features))
		return 2;

	return CEPH_MDS_REQUEST_HEAD_VERSION;
}

static struct ceph_mds_request_head_legacy *
find_legacy_request_head(void *p, u64 features)
{
	bool legacy = !(features & CEPH_FEATURE_FS_BTIME);
	struct ceph_mds_request_head *head;

	if (legacy)
		return (struct ceph_mds_request_head_legacy *)p;
	head = (struct ceph_mds_request_head *)p;
	return (struct ceph_mds_request_head_legacy *)&head->oldest_client_tid;
}

/*
 * called under mdsc->mutex
 */
static struct ceph_msg *create_request_message(struct ceph_mds_session *session,
					       struct ceph_mds_request *req,
					       bool drop_cap_releases)
{
	int mds = session->s_mds;
	struct ceph_mds_client *mdsc = session->s_mdsc;
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_msg *msg;
	struct ceph_mds_request_head_legacy *lhead;
	struct ceph_path_info path_info1 = {0};
	struct ceph_path_info path_info2 = {0};
	struct dentry *old_dentry = NULL;
	int len;
	u16 releases;
	void *p, *end;
	int ret;
	bool legacy = !(session->s_con.peer_features & CEPH_FEATURE_FS_BTIME);
	u16 request_head_version = mds_supported_head_version(session);
	kuid_t caller_fsuid = req->r_cred->fsuid;
	kgid_t caller_fsgid = req->r_cred->fsgid;
	bool parent_locked = test_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);

	ret = set_request_path_attr(mdsc, req->r_inode, req->r_dentry,
				    req->r_parent, req->r_path1, req->r_ino1.ino,
				    &path_info1, parent_locked);
	if (ret < 0) {
		msg = ERR_PTR(ret);
		goto out;
	}

	/*
	 * When the parent directory's i_rwsem is *not* locked, req->r_parent may
	 * have become stale (e.g. after a concurrent rename) between the time the
	 * dentry was looked up and now.  If we detect that the stored r_parent
	 * does not match the inode number we just encoded for the request, switch
	 * to the correct inode so that the MDS receives a valid parent reference.
	 */
	if (!parent_locked && req->r_parent && path_info1.vino.ino &&
	    ceph_ino(req->r_parent) != path_info1.vino.ino) {
		struct inode *old_parent = req->r_parent;
		struct inode *correct_dir = ceph_get_inode(mdsc->fsc->sb, path_info1.vino, NULL);
		if (!IS_ERR(correct_dir)) {
			WARN_ONCE(1, "ceph: r_parent mismatch (had %llx wanted %llx) - updating\n",
			          ceph_ino(old_parent), path_info1.vino.ino);
			/*
			 * Transfer CEPH_CAP_PIN from the old parent to the new one.
			 * The pin was taken earlier in ceph_mdsc_submit_request().
			 */
			ceph_put_cap_refs(ceph_inode(old_parent), CEPH_CAP_PIN);
			iput(old_parent);
			req->r_parent = correct_dir;
			ceph_get_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN);
		}
	}

	/* If r_old_dentry is set, then assume that its parent is locked */
	if (req->r_old_dentry &&
	    !(req->r_old_dentry->d_flags & DCACHE_DISCONNECTED))
		old_dentry = req->r_old_dentry;
	ret = set_request_path_attr(mdsc, NULL, old_dentry,
				    req->r_old_dentry_dir,
				    req->r_path2, req->r_ino2.ino,
				    &path_info2, true);
	if (ret < 0) {
		msg = ERR_PTR(ret);
		goto out_free1;
	}

	req->r_altname = get_fscrypt_altname(req, &req->r_altname_len);
	if (IS_ERR(req->r_altname)) {
		msg = ERR_CAST(req->r_altname);
		req->r_altname = NULL;
		goto out_free2;
	}

	/*
	 * For old cephs without supporting the 32bit retry/fwd feature
	 * it will copy the raw memories directly when decoding the
	 * requests. While new cephs will decode the head depending the
	 * version member, so we need to make sure it will be compatible
	 * with them both.
	 */
	if (legacy)
		len = sizeof(struct ceph_mds_request_head_legacy);
	else if (request_head_version == 1)
		len = offsetofend(struct ceph_mds_request_head, args);
	else if (request_head_version == 2)
		len = offsetofend(struct ceph_mds_request_head, ext_num_fwd);
	else
		len = sizeof(struct ceph_mds_request_head);

	/* filepaths */
	len += 2 * (1 + sizeof(u32) + sizeof(u64));
	len += path_info1.pathlen + path_info2.pathlen;

	/* cap releases */
	len += sizeof(struct ceph_mds_request_release) *
		(!!req->r_inode_drop + !!req->r_dentry_drop +
		 !!req->r_old_inode_drop + !!req->r_old_dentry_drop);

	if (req->r_dentry_drop)
		len += path_info1.pathlen;
	if (req->r_old_dentry_drop)
		len += path_info2.pathlen;

	/* MClientRequest tail */

	/* req->r_stamp */
	len += sizeof(struct ceph_timespec);

	/* gid list */
	len += sizeof(u32) + (sizeof(u64) * req->r_cred->group_info->ngroups);

	/* alternate name */
	len += sizeof(u32) + req->r_altname_len;

	/* fscrypt_auth */
	len += sizeof(u32); // fscrypt_auth
	if (req->r_fscrypt_auth)
		len += ceph_fscrypt_auth_len(req->r_fscrypt_auth);

	/* fscrypt_file */
	len += sizeof(u32);
	if (test_bit(CEPH_MDS_R_FSCRYPT_FILE, &req->r_req_flags))
		len += sizeof(__le64);

	msg = ceph_msg_new2(CEPH_MSG_CLIENT_REQUEST, len, 1, GFP_NOFS, false);
	if (!msg) {
		msg = ERR_PTR(-ENOMEM);
		goto out_free2;
	}

	msg->hdr.tid = cpu_to_le64(req->r_tid);

	lhead = find_legacy_request_head(msg->front.iov_base,
					 session->s_con.peer_features);

	if ((req->r_mnt_idmap != &nop_mnt_idmap) &&
	    !test_bit(CEPHFS_FEATURE_HAS_OWNER_UIDGID, &session->s_features)) {
		WARN_ON_ONCE(!IS_CEPH_MDS_OP_NEWINODE(req->r_op));

		if (enable_unsafe_idmap) {
			pr_warn_once_client(cl,
				"idmapped mount is used and CEPHFS_FEATURE_HAS_OWNER_UIDGID"
				" is not supported by MDS. UID/GID-based restrictions may"
				" not work properly.\n");

			caller_fsuid = from_vfsuid(req->r_mnt_idmap, &init_user_ns,
						   VFSUIDT_INIT(req->r_cred->fsuid));
			caller_fsgid = from_vfsgid(req->r_mnt_idmap, &init_user_ns,
						   VFSGIDT_INIT(req->r_cred->fsgid));
		} else {
			pr_err_ratelimited_client(cl,
				"idmapped mount is used and CEPHFS_FEATURE_HAS_OWNER_UIDGID"
				" is not supported by MDS. Fail request with -EIO.\n");

			ret = -EIO;
			goto out_err;
		}
	}

	/*
	 * The ceph_mds_request_head_legacy didn't contain a version field, and
	 * one was added when we moved the message version from 3->4.
	 */
	if (legacy) {
		msg->hdr.version = cpu_to_le16(3);
		p = msg->front.iov_base + sizeof(*lhead);
	} else if (request_head_version == 1) {
		struct ceph_mds_request_head *nhead = msg->front.iov_base;

		msg->hdr.version = cpu_to_le16(4);
		nhead->version = cpu_to_le16(1);
		p = msg->front.iov_base + offsetofend(struct ceph_mds_request_head, args);
	} else if (request_head_version == 2) {
		struct ceph_mds_request_head *nhead = msg->front.iov_base;

		msg->hdr.version = cpu_to_le16(6);
		nhead->version = cpu_to_le16(2);

		p = msg->front.iov_base + offsetofend(struct ceph_mds_request_head, ext_num_fwd);
	} else {
		struct ceph_mds_request_head *nhead = msg->front.iov_base;
		kuid_t owner_fsuid;
		kgid_t owner_fsgid;

		msg->hdr.version = cpu_to_le16(6);
		nhead->version = cpu_to_le16(CEPH_MDS_REQUEST_HEAD_VERSION);
		nhead->struct_len = cpu_to_le32(sizeof(struct ceph_mds_request_head));

		if (IS_CEPH_MDS_OP_NEWINODE(req->r_op)) {
			owner_fsuid = from_vfsuid(req->r_mnt_idmap, &init_user_ns,
						VFSUIDT_INIT(req->r_cred->fsuid));
			owner_fsgid = from_vfsgid(req->r_mnt_idmap, &init_user_ns,
						VFSGIDT_INIT(req->r_cred->fsgid));
			nhead->owner_uid = cpu_to_le32(from_kuid(&init_user_ns, owner_fsuid));
			nhead->owner_gid = cpu_to_le32(from_kgid(&init_user_ns, owner_fsgid));
		} else {
			nhead->owner_uid = cpu_to_le32(-1);
			nhead->owner_gid = cpu_to_le32(-1);
		}

		p = msg->front.iov_base + sizeof(*nhead);
	}

	end = msg->front.iov_base + msg->front.iov_len;

	lhead->mdsmap_epoch = cpu_to_le32(mdsc->mdsmap->m_epoch);
	lhead->op = cpu_to_le32(req->r_op);
	lhead->caller_uid = cpu_to_le32(from_kuid(&init_user_ns,
						  caller_fsuid));
	lhead->caller_gid = cpu_to_le32(from_kgid(&init_user_ns,
						  caller_fsgid));
	lhead->ino = cpu_to_le64(req->r_deleg_ino);
	lhead->args = req->r_args;

	ceph_encode_filepath(&p, end, path_info1.vino.ino, path_info1.path);
	ceph_encode_filepath(&p, end, path_info2.vino.ino, path_info2.path);

	/* make note of release offset, in case we need to replay */
	req->r_request_release_offset = p - msg->front.iov_base;

	/* cap releases */
	releases = 0;
	if (req->r_inode_drop)
		releases += ceph_encode_inode_release(&p,
		      req->r_inode ? req->r_inode : d_inode(req->r_dentry),
		      mds, req->r_inode_drop, req->r_inode_unless,
		      req->r_op == CEPH_MDS_OP_READDIR);
	if (req->r_dentry_drop) {
		ret = ceph_encode_dentry_release(&p, req->r_dentry,
				req->r_parent, mds, req->r_dentry_drop,
				req->r_dentry_unless);
		if (ret < 0)
			goto out_err;
		releases += ret;
	}
	if (req->r_old_dentry_drop) {
		ret = ceph_encode_dentry_release(&p, req->r_old_dentry,
				req->r_old_dentry_dir, mds,
				req->r_old_dentry_drop,
				req->r_old_dentry_unless);
		if (ret < 0)
			goto out_err;
		releases += ret;
	}
	if (req->r_old_inode_drop)
		releases += ceph_encode_inode_release(&p,
		      d_inode(req->r_old_dentry),
		      mds, req->r_old_inode_drop, req->r_old_inode_unless, 0);

	if (drop_cap_releases) {
		releases = 0;
		p = msg->front.iov_base + req->r_request_release_offset;
	}

	lhead->num_releases = cpu_to_le16(releases);

	encode_mclientrequest_tail(&p, req);

	if (WARN_ON_ONCE(p > end)) {
		ceph_msg_put(msg);
		msg = ERR_PTR(-ERANGE);
		goto out_free2;
	}

	msg->front.iov_len = p - msg->front.iov_base;
	msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);

	if (req->r_pagelist) {
		struct ceph_pagelist *pagelist = req->r_pagelist;
		ceph_msg_data_add_pagelist(msg, pagelist);
		msg->hdr.data_len = cpu_to_le32(pagelist->length);
	} else {
		msg->hdr.data_len = 0;
	}

	msg->hdr.data_off = cpu_to_le16(0);

out_free2:
	ceph_mdsc_free_path_info(&path_info2);
out_free1:
	ceph_mdsc_free_path_info(&path_info1);
out:
	return msg;
out_err:
	ceph_msg_put(msg);
	msg = ERR_PTR(ret);
	goto out_free2;
}

/*
 * called under mdsc->mutex if error, under no mutex if
 * success.
 */
static void complete_request(struct ceph_mds_client *mdsc,
			     struct ceph_mds_request *req)
{
	req->r_end_latency = ktime_get();

	trace_ceph_mdsc_complete_request(mdsc, req);

	if (req->r_callback)
		req->r_callback(mdsc, req);
	complete_all(&req->r_completion);
}

/*
 * called under mdsc->mutex
 */
static int __prepare_send_request(struct ceph_mds_session *session,
				  struct ceph_mds_request *req,
				  bool drop_cap_releases)
{
	int mds = session->s_mds;
	struct ceph_mds_client *mdsc = session->s_mdsc;
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_request_head_legacy *lhead;
	struct ceph_mds_request_head *nhead;
	struct ceph_msg *msg;
	int flags = 0, old_max_retry;
	bool old_version = !test_bit(CEPHFS_FEATURE_32BITS_RETRY_FWD,
				     &session->s_features);

	/*
	 * Avoid infinite retrying after overflow. The client will
	 * increase the retry count and if the MDS is old version,
	 * so we limit to retry at most 256 times.
	 */
	if (req->r_attempts) {
	       old_max_retry = sizeof_field(struct ceph_mds_request_head,
					    num_retry);
	       old_max_retry = 1 << (old_max_retry * BITS_PER_BYTE);
	       if ((old_version && req->r_attempts >= old_max_retry) ||
		   ((uint32_t)req->r_attempts >= U32_MAX)) {
			pr_warn_ratelimited_client(cl, "request tid %llu seq overflow\n",
						   req->r_tid);
			return -EMULTIHOP;
	       }
	}

	req->r_attempts++;
	if (req->r_inode) {
		struct ceph_cap *cap =
			ceph_get_cap_for_mds(ceph_inode(req->r_inode), mds);

		if (cap)
			req->r_sent_on_mseq = cap->mseq;
		else
			req->r_sent_on_mseq = -1;
	}
	doutc(cl, "%p tid %lld %s (attempt %d)\n", req, req->r_tid,
	      ceph_mds_op_name(req->r_op), req->r_attempts);

	if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
		void *p;

		/*
		 * Replay.  Do not regenerate message (and rebuild
		 * paths, etc.); just use the original message.
		 * Rebuilding paths will break for renames because
		 * d_move mangles the src name.
		 */
		msg = req->r_request;
		lhead = find_legacy_request_head(msg->front.iov_base,
						 session->s_con.peer_features);

		flags = le32_to_cpu(lhead->flags);
		flags |= CEPH_MDS_FLAG_REPLAY;
		lhead->flags = cpu_to_le32(flags);

		if (req->r_target_inode)
			lhead->ino = cpu_to_le64(ceph_ino(req->r_target_inode));

		lhead->num_retry = req->r_attempts - 1;
		if (!old_version) {
			nhead = (struct ceph_mds_request_head*)msg->front.iov_base;
			nhead->ext_num_retry = cpu_to_le32(req->r_attempts - 1);
		}

		/* remove cap/dentry releases from message */
		lhead->num_releases = 0;

		p = msg->front.iov_base + req->r_request_release_offset;
		encode_mclientrequest_tail(&p, req);

		msg->front.iov_len = p - msg->front.iov_base;
		msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
		return 0;
	}

	if (req->r_request) {
		ceph_msg_put(req->r_request);
		req->r_request = NULL;
	}
	msg = create_request_message(session, req, drop_cap_releases);
	if (IS_ERR(msg)) {
		req->r_err = PTR_ERR(msg);
		return PTR_ERR(msg);
	}
	req->r_request = msg;

	lhead = find_legacy_request_head(msg->front.iov_base,
					 session->s_con.peer_features);
	lhead->oldest_client_tid = cpu_to_le64(__get_oldest_tid(mdsc));
	if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
		flags |= CEPH_MDS_FLAG_REPLAY;
	if (test_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags))
		flags |= CEPH_MDS_FLAG_ASYNC;
	if (req->r_parent)
		flags |= CEPH_MDS_FLAG_WANT_DENTRY;
	lhead->flags = cpu_to_le32(flags);
	lhead->num_fwd = req->r_num_fwd;
	lhead->num_retry = req->r_attempts - 1;
	if (!old_version) {
		nhead = (struct ceph_mds_request_head*)msg->front.iov_base;
		nhead->ext_num_fwd = cpu_to_le32(req->r_num_fwd);
		nhead->ext_num_retry = cpu_to_le32(req->r_attempts - 1);
	}

	doutc(cl, " r_parent = %p\n", req->r_parent);
	return 0;
}

/*
 * called under mdsc->mutex
 */
static int __send_request(struct ceph_mds_session *session,
			  struct ceph_mds_request *req,
			  bool drop_cap_releases)
{
	int err;

	trace_ceph_mdsc_send_request(session, req);

	err = __prepare_send_request(session, req, drop_cap_releases);
	if (!err) {
		ceph_msg_get(req->r_request);
		ceph_con_send(&session->s_con, req->r_request);
	}

	return err;
}

/*
 * send request, or put it on the appropriate wait list.
 */
static void __do_request(struct ceph_mds_client *mdsc,
			struct ceph_mds_request *req)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_session *session = NULL;
	int mds = -1;
	int err = 0;
	bool random;

	if (req->r_err || test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags)) {
		if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags))
			__unregister_request(mdsc, req);
		return;
	}

	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_FENCE_IO) {
		doutc(cl, "metadata corrupted\n");
		err = -EIO;
		goto finish;
	}
	if (req->r_timeout &&
	    time_after_eq(jiffies, req->r_started + req->r_timeout)) {
		doutc(cl, "timed out\n");
		err = -ETIMEDOUT;
		goto finish;
	}
	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
		doutc(cl, "forced umount\n");
		err = -EIO;
		goto finish;
	}
	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_MOUNTING) {
		if (mdsc->mdsmap_err) {
			err = mdsc->mdsmap_err;
			doutc(cl, "mdsmap err %d\n", err);
			goto finish;
		}
		if (mdsc->mdsmap->m_epoch == 0) {
			doutc(cl, "no mdsmap, waiting for map\n");
			trace_ceph_mdsc_suspend_request(mdsc, session, req,
							ceph_mdsc_suspend_reason_no_mdsmap);
			list_add(&req->r_wait, &mdsc->waiting_for_map);
			return;
		}
		if (!(mdsc->fsc->mount_options->flags &
		      CEPH_MOUNT_OPT_MOUNTWAIT) &&
		    !ceph_mdsmap_is_cluster_available(mdsc->mdsmap)) {
			err = -EHOSTUNREACH;
			goto finish;
		}
	}

	put_request_session(req);

	mds = __choose_mds(mdsc, req, &random);
	if (mds < 0 ||
	    ceph_mdsmap_get_state(mdsc->mdsmap, mds) < CEPH_MDS_STATE_ACTIVE) {
		if (test_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags)) {
			err = -EJUKEBOX;
			goto finish;
		}
		doutc(cl, "no mds or not active, waiting for map\n");
		trace_ceph_mdsc_suspend_request(mdsc, session, req,
						ceph_mdsc_suspend_reason_no_active_mds);
		list_add(&req->r_wait, &mdsc->waiting_for_map);
		return;
	}

	/* get, open session */
	session = __ceph_lookup_mds_session(mdsc, mds);
	if (!session) {
		session = register_session(mdsc, mds);
		if (IS_ERR(session)) {
			err = PTR_ERR(session);
			goto finish;
		}
	}
	req->r_session = ceph_get_mds_session(session);

	doutc(cl, "mds%d session %p state %s\n", mds, session,
	      ceph_session_state_name(session->s_state));

	/*
	 * The old ceph will crash the MDSs when see unknown OPs
	 */
	if (req->r_feature_needed > 0 &&
	    !test_bit(req->r_feature_needed, &session->s_features)) {
		err = -EOPNOTSUPP;
		goto out_session;
	}

	if (session->s_state != CEPH_MDS_SESSION_OPEN &&
	    session->s_state != CEPH_MDS_SESSION_HUNG) {
		/*
		 * We cannot queue async requests since the caps and delegated
		 * inodes are bound to the session. Just return -EJUKEBOX and
		 * let the caller retry a sync request in that case.
		 */
		if (test_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags)) {
			err = -EJUKEBOX;
			goto out_session;
		}

		/*
		 * If the session has been REJECTED, then return a hard error,
		 * unless it's a CLEANRECOVER mount, in which case we'll queue
		 * it to the mdsc queue.
		 */
		if (session->s_state == CEPH_MDS_SESSION_REJECTED) {
			if (ceph_test_mount_opt(mdsc->fsc, CLEANRECOVER)) {
				trace_ceph_mdsc_suspend_request(mdsc, session, req,
								ceph_mdsc_suspend_reason_rejected);
				list_add(&req->r_wait, &mdsc->waiting_for_map);
			} else
				err = -EACCES;
			goto out_session;
		}

		if (session->s_state == CEPH_MDS_SESSION_NEW ||
		    session->s_state == CEPH_MDS_SESSION_CLOSING) {
			err = __open_session(mdsc, session);
			if (err)
				goto out_session;
			/* retry the same mds later */
			if (random)
				req->r_resend_mds = mds;
		}
		trace_ceph_mdsc_suspend_request(mdsc, session, req,
						ceph_mdsc_suspend_reason_session);
		list_add(&req->r_wait, &session->s_waiting);
		goto out_session;
	}

	/* send request */
	req->r_resend_mds = -1;   /* forget any previous mds hint */

	if (req->r_request_started == 0)   /* note request start time */
		req->r_request_started = jiffies;

	/*
	 * For async create we will choose the auth MDS of frag in parent
	 * directory to send the request and usually this works fine, but
	 * if the migrated the dirtory to another MDS before it could handle
	 * it the request will be forwarded.
	 *
	 * And then the auth cap will be changed.
	 */
	if (test_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags) && req->r_num_fwd) {
		struct ceph_dentry_info *di = ceph_dentry(req->r_dentry);
		struct ceph_inode_info *ci;
		struct ceph_cap *cap;

		/*
		 * The request maybe handled very fast and the new inode
		 * hasn't been linked to the dentry yet. We need to wait
		 * for the ceph_finish_async_create(), which shouldn't be
		 * stuck too long or fail in thoery, to finish when forwarding
		 * the request.
		 */
		if (!d_inode(req->r_dentry)) {
			err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_CREATE_BIT,
					  TASK_KILLABLE);
			if (err) {
				mutex_lock(&req->r_fill_mutex);
				set_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags);
				mutex_unlock(&req->r_fill_mutex);
				goto out_session;
			}
		}

		ci = ceph_inode(d_inode(req->r_dentry));

		spin_lock(&ci->i_ceph_lock);
		cap = ci->i_auth_cap;
		if (test_bit(CEPH_I_ASYNC_CREATE_BIT, &ci->i_ceph_flags) &&
		    mds != cap->mds) {
			doutc(cl, "session changed for auth cap %d -> %d\n",
			      cap->session->s_mds, session->s_mds);

			/* Remove the auth cap from old session */
			spin_lock(&cap->session->s_cap_lock);
			cap->session->s_nr_caps--;
			list_del_init(&cap->session_caps);
			spin_unlock(&cap->session->s_cap_lock);

			/* Add the auth cap to the new session */
			cap->mds = mds;
			cap->session = session;
			spin_lock(&session->s_cap_lock);
			session->s_nr_caps++;
			list_add_tail(&cap->session_caps, &session->s_caps);
			spin_unlock(&session->s_cap_lock);

			change_auth_cap_ses(ci, session);
		}
		spin_unlock(&ci->i_ceph_lock);
	}

	err = __send_request(session, req, false);

out_session:
	ceph_put_mds_session(session);
finish:
	if (err) {
		doutc(cl, "early error %d\n", err);
		req->r_err = err;
		complete_request(mdsc, req);
		__unregister_request(mdsc, req);
	}
	return;
}

/*
 * called under mdsc->mutex
 */
static void __wake_requests(struct ceph_mds_client *mdsc,
			    struct list_head *head)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_request *req;
	LIST_HEAD(tmp_list);

	list_splice_init(head, &tmp_list);

	while (!list_empty(&tmp_list)) {
		req = list_entry(tmp_list.next,
				 struct ceph_mds_request, r_wait);
		list_del_init(&req->r_wait);
		doutc(cl, " wake request %p tid %llu\n", req,
		      req->r_tid);
		trace_ceph_mdsc_resume_request(mdsc, req);
		__do_request(mdsc, req);
	}
}

/*
 * Wake up threads with requests pending for @mds, so that they can
 * resubmit their requests to a possibly different mds.
 */
static void kick_requests(struct ceph_mds_client *mdsc, int mds)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_request *req;
	struct rb_node *p = rb_first(&mdsc->request_tree);

	doutc(cl, "kick_requests mds%d\n", mds);
	while (p) {
		req = rb_entry(p, struct ceph_mds_request, r_node);
		p = rb_next(p);
		if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
			continue;
		if (req->r_attempts > 0)
			continue; /* only new requests */
		if (req->r_session &&
		    req->r_session->s_mds == mds) {
			doutc(cl, " kicking tid %llu\n", req->r_tid);
			list_del_init(&req->r_wait);
			trace_ceph_mdsc_resume_request(mdsc, req);
			__do_request(mdsc, req);
		}
	}
}

int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
			      struct ceph_mds_request *req)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int err = 0;

	/*
	 * If a reset is in progress, wait for it to complete.
	 *
	 * This is best-effort: a request can pass this check just
	 * before the phase leaves IDLE and proceed concurrently with
	 * reset.  That is acceptable because (a) such requests will
	 * either complete normally or fail and be retried by the
	 * caller, and (b) adding lock serialization here would
	 * penalize every request for a rare manual operation.
	 */
	err = ceph_mdsc_wait_for_reset(mdsc);
	if (err) {
		doutc(cl, "wait_for_reset failed: %d\n", err);
		return err;
	}

	/* take CAP_PIN refs for r_inode, r_parent, r_old_dentry */
	if (req->r_inode)
		ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
	if (req->r_parent) {
		struct ceph_inode_info *ci = ceph_inode(req->r_parent);
		int fmode = (req->r_op & CEPH_MDS_OP_WRITE) ?
			    CEPH_FILE_MODE_WR : CEPH_FILE_MODE_RD;
		spin_lock(&ci->i_ceph_lock);
		ceph_take_cap_refs(ci, CEPH_CAP_PIN, false);
		__ceph_touch_fmode(ci, mdsc, fmode);
		spin_unlock(&ci->i_ceph_lock);
	}
	if (req->r_old_dentry_dir)
		ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
				  CEPH_CAP_PIN);

	if (req->r_inode) {
		err = ceph_wait_on_async_create(req->r_inode);
		if (err) {
			doutc(cl, "wait for async create returned: %d\n", err);
			return err;
		}
	}

	if (!err && req->r_old_inode) {
		err = ceph_wait_on_async_create(req->r_old_inode);
		if (err) {
			doutc(cl, "wait for async create returned: %d\n", err);
			return err;
		}
	}

	doutc(cl, "submit_request on %p for inode %p\n", req, dir);
	mutex_lock(&mdsc->mutex);
	__register_request(mdsc, req, dir);
	trace_ceph_mdsc_submit_request(mdsc, req);
	__do_request(mdsc, req);
	err = req->r_err;
	mutex_unlock(&mdsc->mutex);
	return err;
}

int ceph_mdsc_wait_request(struct ceph_mds_client *mdsc,
			   struct ceph_mds_request *req,
			   ceph_mds_request_wait_callback_t wait_func)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int err;

	/* wait */
	doutc(cl, "do_request waiting\n");
	if (wait_func) {
		err = wait_func(mdsc, req);
	} else {
		long timeleft = wait_for_completion_killable_timeout(
					&req->r_completion,
					ceph_timeout_jiffies(req->r_timeout));
		if (timeleft > 0)
			err = 0;
		else if (!timeleft)
			err = -ETIMEDOUT;  /* timed out */
		else
			err = timeleft;  /* killed */
	}
	doutc(cl, "do_request waited, got %d\n", err);
	mutex_lock(&mdsc->mutex);

	/* only abort if we didn't race with a real reply */
	if (test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags)) {
		err = le32_to_cpu(req->r_reply_info.head->result);
	} else if (err < 0) {
		doutc(cl, "aborted request %lld with %d\n", req->r_tid, err);

		/*
		 * ensure we aren't running concurrently with
		 * ceph_fill_trace or ceph_readdir_prepopulate, which
		 * rely on locks (dir mutex) held by our caller.
		 */
		mutex_lock(&req->r_fill_mutex);
		req->r_err = err;
		set_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags);
		mutex_unlock(&req->r_fill_mutex);

		if (req->r_parent &&
		    (req->r_op & CEPH_MDS_OP_WRITE))
			ceph_invalidate_dir_request(req);
	} else {
		err = req->r_err;
	}

	mutex_unlock(&mdsc->mutex);
	return err;
}

/*
 * Synchrously perform an mds request.  Take care of all of the
 * session setup, forwarding, retry details.
 */
int ceph_mdsc_do_request(struct ceph_mds_client *mdsc,
			 struct inode *dir,
			 struct ceph_mds_request *req)
{
	struct ceph_client *cl = mdsc->fsc->client;
	int err;

	doutc(cl, "do_request on %p\n", req);

	/* issue */
	err = ceph_mdsc_submit_request(mdsc, dir, req);
	if (!err)
		err = ceph_mdsc_wait_request(mdsc, req, NULL);
	doutc(cl, "do_request %p done, result %d\n", req, err);
	return err;
}

/*
 * Invalidate dir's completeness, dentry lease state on an aborted MDS
 * namespace request.
 */
void ceph_invalidate_dir_request(struct ceph_mds_request *req)
{
	struct inode *dir = req->r_parent;
	struct inode *old_dir = req->r_old_dentry_dir;
	struct ceph_client *cl = req->r_mdsc->fsc->client;

	doutc(cl, "invalidate_dir_request %p %p (complete, lease(s))\n",
	      dir, old_dir);

	ceph_dir_clear_complete(dir);
	if (old_dir)
		ceph_dir_clear_complete(old_dir);
	if (req->r_dentry)
		ceph_invalidate_dentry_lease(req->r_dentry);
	if (req->r_old_dentry)
		ceph_invalidate_dentry_lease(req->r_old_dentry);
}

/*
 * Handle mds reply.
 *
 * We take the session mutex and parse and process the reply immediately.
 * This preserves the logical ordering of replies, capabilities, etc., sent
 * by the MDS as they are applied to our local cache.
 */
static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
{
	struct ceph_mds_client *mdsc = session->s_mdsc;
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_request *req;
	struct ceph_mds_reply_head *head = msg->front.iov_base;
	struct ceph_mds_reply_info_parsed *rinfo;  /* parsed reply info */
	struct ceph_snap_realm *realm;
	unsigned int nofs_flags;
	u64 tid;
	int err, result;
	int mds = session->s_mds;
	bool close_sessions = false;

	if (msg->front.iov_len < sizeof(*head)) {
		pr_err_client(cl, "got corrupt (short) reply\n");
		ceph_msg_dump(msg);
		return;
	}

	/* get request, session */
	tid = le64_to_cpu(msg->hdr.tid);
	mutex_lock(&mdsc->mutex);
	req = lookup_get_request(mdsc, tid);
	if (!req) {
		doutc(cl, "on unknown tid %llu\n", tid);
		mutex_unlock(&mdsc->mutex);
		return;
	}
	doutc(cl, "handle_reply %p\n", req);

	/* correct session? */
	if (req->r_session != session) {
		pr_err_client(cl, "got %llu on session mds%d not mds%d\n",
			      tid, session->s_mds,
			      req->r_session ? req->r_session->s_mds : -1);
		mutex_unlock(&mdsc->mutex);
		goto out;
	}

	/* dup? */
	if ((test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags) && !head->safe) ||
	    (test_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags) && head->safe)) {
		pr_warn_client(cl, "got a dup %s reply on %llu from mds%d\n",
			       head->safe ? "safe" : "unsafe", tid, mds);
		mutex_unlock(&mdsc->mutex);
		goto out;
	}
	if (test_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags)) {
		pr_warn_client(cl, "got unsafe after safe on %llu from mds%d\n",
			       tid, mds);
		mutex_unlock(&mdsc->mutex);
		goto out;
	}

	result = le32_to_cpu(head->result);

	if (head->safe) {
		set_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags);
		__unregister_request(mdsc, req);

		/* last request during umount? */
		if (mdsc->stopping && !__get_oldest_req(mdsc))
			complete_all(&mdsc->safe_umount_waiters);

		if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
			/*
			 * We already handled the unsafe response, now do the
			 * cleanup.  No need to examine the response; the MDS
			 * doesn't include any result info in the safe
			 * response.  And even if it did, there is nothing
			 * useful we could do with a revised return value.
			 */
			doutc(cl, "got safe reply %llu, mds%d\n", tid, mds);

			mutex_unlock(&mdsc->mutex);
			goto out;
		}
	} else {
		set_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags);
		list_add_tail(&req->r_unsafe_item, &req->r_session->s_unsafe);
	}

	/*
	 * Now that all mutex-protected state has been updated above
	 * (the request has been unregistered or added to the
	 * session's unsafe list), we can unlock it.
	 */
	mutex_unlock(&mdsc->mutex);

	doutc(cl, "tid %lld result %d\n", tid, result);
	if (test_bit(CEPHFS_FEATURE_REPLY_ENCODING, &session->s_features))
		err = parse_reply_info(session, msg, req, (u64)-1);
	else
		err = parse_reply_info(session, msg, req,
				       session->s_con.peer_features);

	/* Must find target inode outside of mutexes to avoid deadlocks */
	rinfo = &req->r_reply_info;
	if ((err >= 0) && rinfo->head->is_target) {
		struct inode *in = xchg(&req->r_new_inode, NULL);
		struct ceph_vino tvino = {
			.ino  = le64_to_cpu(rinfo->targeti.in->ino),
			.snap = le64_to_cpu(rinfo->targeti.in->snapid)
		};

		/*
		 * If we ended up opening an existing inode, discard
		 * r_new_inode
		 */
		if (req->r_op == CEPH_MDS_OP_CREATE &&
		    !req->r_reply_info.has_create_ino) {
			/* This should never happen on an async create */
			WARN_ON_ONCE(req->r_deleg_ino);
			iput(in);
			in = NULL;
		}

		in = ceph_get_inode(mdsc->fsc->sb, tvino, in);
		if (IS_ERR(in)) {
			err = PTR_ERR(in);
			mutex_lock(&session->s_mutex);
			goto out_err;
		}
		req->r_target_inode = in;
		ceph_inode_set_subvolume(in, rinfo->targeti.subvolume_id);
	}

	mutex_lock(&session->s_mutex);
	if (err < 0) {
		pr_err_client(cl, "got corrupt reply mds%d(tid:%lld)\n",
			      mds, tid);
		ceph_msg_dump(msg);
		goto out_err;
	}

	/* snap trace */
	realm = NULL;
	if (rinfo->snapblob_len) {
		down_write(&mdsc->snap_rwsem);
		err = ceph_update_snap_trace(mdsc, rinfo->snapblob,
				rinfo->snapblob + rinfo->snapblob_len,
				le32_to_cpu(head->op) == CEPH_MDS_OP_RMSNAP,
				&realm);
		if (err) {
			up_write(&mdsc->snap_rwsem);
			close_sessions = true;
			if (err == -EIO)
				ceph_msg_dump(msg);
			goto out_err;
		}
		downgrade_write(&mdsc->snap_rwsem);
	} else {
		down_read(&mdsc->snap_rwsem);
	}

	/* insert trace into our cache */
	mutex_lock(&req->r_fill_mutex);

	/* disable fs reclaim while we are using current->journal_info
	 * for our own purposes, or else shrinkers of other
	 * filesystems might dereference this pointer as a different
	 * type
	 */
	nofs_flags = memalloc_nofs_save();

	current->journal_info = req;
	err = ceph_fill_trace(mdsc->fsc->sb, req);
	if (err == 0) {
		if (result == 0 && (req->r_op == CEPH_MDS_OP_READDIR ||
				    req->r_op == CEPH_MDS_OP_LSSNAP))
			err = ceph_readdir_prepopulate(req, req->r_session);
	}
	current->journal_info = NULL;
	memalloc_nofs_restore(nofs_flags);
	mutex_unlock(&req->r_fill_mutex);

	up_read(&mdsc->snap_rwsem);
	if (realm)
		ceph_put_snap_realm(mdsc, realm);

	if (err == 0) {
		if (req->r_target_inode &&
		    test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
			struct ceph_inode_info *ci =
				ceph_inode(req->r_target_inode);
			spin_lock(&ci->i_unsafe_lock);
			list_add_tail(&req->r_unsafe_target_item,
				      &ci->i_unsafe_iops);
			spin_unlock(&ci->i_unsafe_lock);
		}

		ceph_unreserve_caps(mdsc, &req->r_caps_reservation);
	}
out_err:
	mutex_lock(&mdsc->mutex);
	if (!test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {
		if (err) {
			req->r_err = err;
		} else {
			req->r_reply =  ceph_msg_get(msg);
			set_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags);
		}
	} else {
		doutc(cl, "reply arrived after request %lld was aborted\n", tid);
	}
	mutex_unlock(&mdsc->mutex);

	mutex_unlock(&session->s_mutex);

	/* kick calling process */
	complete_request(mdsc, req);

	ceph_update_metadata_metrics(&mdsc->metric, req->r_start_latency,
				     req->r_end_latency, err);
out:
	ceph_mdsc_put_request(req);

	/* Defer closing the sessions after s_mutex lock being released */
	if (close_sessions)
		ceph_mdsc_close_sessions(mdsc);
	return;
}



/*
 * handle mds notification that our request has been forwarded.
 */
static void handle_forward(struct ceph_mds_client *mdsc,
			   struct ceph_mds_session *session,
			   struct ceph_msg *msg)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_request *req;
	u64 tid = le64_to_cpu(msg->hdr.tid);
	u32 next_mds;
	u32 fwd_seq;
	int err = -EINVAL;
	void *p = msg->front.iov_base;
	void *end = p + msg->front.iov_len;
	bool aborted = false;

	ceph_decode_need(&p, end, 2*sizeof(u32), bad);
	next_mds = ceph_decode_32(&p);
	fwd_seq = ceph_decode_32(&p);

	mutex_lock(&mdsc->mutex);
	req = lookup_get_request(mdsc, tid);
	if (!req) {
		mutex_unlock(&mdsc->mutex);
		doutc(cl, "forward tid %llu to mds%d - req dne\n", tid, next_mds);
		return;  /* dup reply? */
	}

	if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {
		doutc(cl, "forward tid %llu aborted, unregistering\n", tid);
		__unregister_request(mdsc, req);
	} else if (fwd_seq <= req->r_num_fwd || (uint32_t)fwd_seq >= U32_MAX) {
		/*
		 * Avoid infinite retrying after overflow.
		 *
		 * The MDS will increase the fwd count and in client side
		 * if the num_fwd is less than the one saved in request
		 * that means the MDS is an old version and overflowed of
		 * 8 bits.
		 */
		mutex_lock(&req->r_fill_mutex);
		req->r_err = -EMULTIHOP;
		set_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags);
		mutex_unlock(&req->r_fill_mutex);
		aborted = true;
		pr_warn_ratelimited_client(cl, "forward tid %llu seq overflow\n",
					   tid);
	} else {
		/* resend. forward race not possible; mds would drop */
		doutc(cl, "forward tid %llu to mds%d (we resend)\n", tid, next_mds);
		BUG_ON(req->r_err);
		BUG_ON(test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags));
		req->r_attempts = 0;
		req->r_num_fwd = fwd_seq;
		req->r_resend_mds = next_mds;
		put_request_session(req);
		__do_request(mdsc, req);
	}
	mutex_unlock(&mdsc->mutex);

	/* kick calling process */
	if (aborted)
		complete_request(mdsc, req);
	ceph_mdsc_put_request(req);
	return;

bad:
	pr_err_client(cl, "decode error err=%d\n", err);
	ceph_msg_dump(msg);
}

static int __decode_session_metadata(void **p, void *end,
				     bool *blocklisted)
{
	/* map<string,string> */
	u32 n;
	bool err_str;
	ceph_decode_32_safe(p, end, n, bad);
	while (n-- > 0) {
		u32 len;
		ceph_decode_32_safe(p, end, len, bad);
		ceph_decode_need(p, end, len, bad);
		err_str = !strncmp(*p, "error_string", len);
		*p += len;
		ceph_decode_32_safe(p, end, len, bad);
		ceph_decode_need(p, end, len, bad);
		/*
		 * Match "blocklisted (blacklisted)" from newer MDSes,
		 * or "blacklisted" from older MDSes.
		 */
		if (err_str && strnstr(*p, "blacklisted", len))
			*blocklisted = true;
		*p += len;
	}
	return 0;
bad:
	return -1;
}

/*
 * handle a mds session control message
 */
static void handle_session(struct ceph_mds_session *session,
			   struct ceph_msg *msg)
{
	struct ceph_mds_client *mdsc = session->s_mdsc;
	struct ceph_client *cl = mdsc->fsc->client;
	int mds = session->s_mds;
	int msg_version = le16_to_cpu(msg->hdr.version);
	void *p = msg->front.iov_base;
	void *end = p + msg->front.iov_len;
	struct ceph_mds_session_head *h;
	struct ceph_mds_cap_auth *cap_auths = NULL;
	u32 op, cap_auths_num = 0;
	u64 seq, features = 0;
	int wake = 0;
	bool blocklisted = false;
	u32 i;


	/* decode */
	ceph_decode_need(&p, end, sizeof(*h), bad);
	h = p;
	p += sizeof(*h);

	op = le32_to_cpu(h->op);
	seq = le64_to_cpu(h->seq);

	if (msg_version >= 3) {
		u32 len;
		/* version >= 2 and < 5, decode metadata, skip otherwise
		 * as it's handled via flags.
		 */
		if (msg_version >= 5)
			ceph_decode_skip_map(&p, end, string, string, bad);
		else if (__decode_session_metadata(&p, end, &blocklisted) < 0)
			goto bad;

		/* version >= 3, feature bits */
		ceph_decode_32_safe(&p, end, len, bad);
		if (len) {
			ceph_decode_64_safe(&p, end, features, bad);
			p += len - sizeof(features);
		}
	}

	if (msg_version >= 5) {
		u32 flags, len;

		/* version >= 4 */
		ceph_decode_skip_16(&p, end, bad); /* struct_v, struct_cv */
		ceph_decode_32_safe(&p, end, len, bad); /* len */
		ceph_decode_skip_n(&p, end, len, bad); /* metric_spec */

		/* version >= 5, flags   */
		ceph_decode_32_safe(&p, end, flags, bad);
		if (flags & CEPH_SESSION_BLOCKLISTED) {
			pr_warn_client(cl, "mds%d session blocklisted\n",
				       session->s_mds);
			blocklisted = true;
		}
	}

	if (msg_version >= 6) {
		ceph_decode_32_safe(&p, end, cap_auths_num, bad);
		doutc(cl, "cap_auths_num %d\n", cap_auths_num);

		if (cap_auths_num && op != CEPH_SESSION_OPEN) {
			WARN_ON_ONCE(op != CEPH_SESSION_OPEN);
			goto skip_cap_auths;
		}

		cap_auths = kzalloc_objs(struct ceph_mds_cap_auth,
					 cap_auths_num);
		if (!cap_auths) {
			pr_err_client(cl, "No memory for cap_auths\n");
			return;
		}

		for (i = 0; i < cap_auths_num; i++) {
			u32 _len, j;

			/* struct_v, struct_compat, and struct_len in MDSCapAuth */
			ceph_decode_skip_n(&p, end, 2 + sizeof(u32), bad);

			/* struct_v, struct_compat, and struct_len in MDSCapMatch */
			ceph_decode_skip_n(&p, end, 2 + sizeof(u32), bad);
			ceph_decode_64_safe(&p, end, cap_auths[i].match.uid, bad);
			ceph_decode_32_safe(&p, end, _len, bad);
			if (_len) {
				cap_auths[i].match.gids = kcalloc(_len, sizeof(u32),
								  GFP_KERNEL);
				if (!cap_auths[i].match.gids) {
					pr_err_client(cl, "No memory for gids\n");
					goto fail;
				}

				cap_auths[i].match.num_gids = _len;
				for (j = 0; j < _len; j++)
					ceph_decode_32_safe(&p, end,
							    cap_auths[i].match.gids[j],
							    bad);
			}

			ceph_decode_32_safe(&p, end, _len, bad);
			if (_len) {
				cap_auths[i].match.path = kcalloc(_len + 1, sizeof(char),
								  GFP_KERNEL);
				if (!cap_auths[i].match.path) {
					pr_err_client(cl, "No memory for path\n");
					goto fail;
				}
				ceph_decode_copy_safe(&p, end,
						      cap_auths[i].match.path,
						      _len, bad);

				/* Remove the tailing '/' */
				while (_len && cap_auths[i].match.path[_len - 1] == '/') {
					cap_auths[i].match.path[_len - 1] = '\0';
					_len -= 1;
				}
			}

			ceph_decode_32_safe(&p, end, _len, bad);
			if (_len) {
				cap_auths[i].match.fs_name = kcalloc(_len + 1, sizeof(char),
								     GFP_KERNEL);
				if (!cap_auths[i].match.fs_name) {
					pr_err_client(cl, "No memory for fs_name\n");
					goto fail;
				}
				ceph_decode_copy_safe(&p, end,
						      cap_auths[i].match.fs_name,
						      _len, bad);
			}

			ceph_decode_8_safe(&p, end, cap_auths[i].match.root_squash, bad);
			ceph_decode_8_safe(&p, end, cap_auths[i].readable, bad);
			ceph_decode_8_safe(&p, end, cap_auths[i].writeable, bad);
			doutc(cl, "uid %lld, num_gids %u, path %s, fs_name %s, root_squash %d, readable %d, writeable %d\n",
			      cap_auths[i].match.uid, cap_auths[i].match.num_gids,
			      cap_auths[i].match.path, cap_auths[i].match.fs_name,
			      cap_auths[i].match.root_squash,
			      cap_auths[i].readable, cap_auths[i].writeable);
		}
	}

skip_cap_auths:
	mutex_lock(&mdsc->mutex);
	if (op == CEPH_SESSION_OPEN) {
		if (mdsc->s_cap_auths) {
			for (i = 0; i < mdsc->s_cap_auths_num; i++) {
				kfree(mdsc->s_cap_auths[i].match.gids);
				kfree(mdsc->s_cap_auths[i].match.path);
				kfree(mdsc->s_cap_auths[i].match.fs_name);
			}
			kfree(mdsc->s_cap_auths);
		}
		mdsc->s_cap_auths_num = cap_auths_num;
		mdsc->s_cap_auths = cap_auths;

		session->s_features = features;
		if (test_bit(CEPHFS_FEATURE_METRIC_COLLECT,
			     &session->s_features))
			ceph_metric_bind_session(mdsc, session);
	}
	if (op == CEPH_SESSION_CLOSE) {
		ceph_get_mds_session(session);
		__unregister_session(mdsc, session);
	}
	/* FIXME: this ttl calculation is generous */
	session->s_ttl = jiffies + HZ*mdsc->mdsmap->m_session_autoclose;
	mutex_unlock(&mdsc->mutex);

	mutex_lock(&session->s_mutex);

	doutc(cl, "mds%d %s %p state %s seq %llu\n", mds,
	      ceph_session_op_name(op), session,
	      ceph_session_state_name(session->s_state), seq);

	if (session->s_state == CEPH_MDS_SESSION_HUNG) {
		session->s_state = CEPH_MDS_SESSION_OPEN;
		pr_info_client(cl, "mds%d came back\n", session->s_mds);
	}

	switch (op) {
	case CEPH_SESSION_OPEN:
		if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
			pr_info_client(cl, "mds%d reconnect success\n",
				       session->s_mds);

		if (test_bit(CEPHFS_FEATURE_SUBVOLUME_METRICS,
			     &session->s_features))
			ceph_subvolume_metrics_enable(&mdsc->subvol_metrics, true);
		else
			ceph_subvolume_metrics_enable(&mdsc->subvol_metrics, false);
		if (session->s_state == CEPH_MDS_SESSION_OPEN) {
			pr_notice_client(cl, "mds%d is already opened\n",
					 session->s_mds);
		} else {
			session->s_state = CEPH_MDS_SESSION_OPEN;
			renewed_caps(mdsc, session, 0);
			if (test_bit(CEPHFS_FEATURE_METRIC_COLLECT,
				     &session->s_features))
				metric_schedule_delayed(&mdsc->metric);
		}

		/*
		 * The connection maybe broken and the session in client
		 * side has been reinitialized, need to update the seq
		 * anyway.
		 */
		if (!session->s_seq && seq)
			session->s_seq = seq;

		wake = 1;
		if (mdsc->stopping)
			__close_session(mdsc, session);
		break;

	case CEPH_SESSION_RENEWCAPS:
		if (session->s_renew_seq == seq)
			renewed_caps(mdsc, session, 1);
		break;

	case CEPH_SESSION_CLOSE:
		if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
			pr_info_client(cl, "mds%d reconnect denied\n",
				       session->s_mds);
		session->s_state = CEPH_MDS_SESSION_CLOSED;
		cleanup_session_requests(mdsc, session);
		remove_session_caps(session);
		wake = 2; /* for good measure */
		wake_up_all(&mdsc->session_close_wq);
		break;

	case CEPH_SESSION_STALE:
		pr_info_client(cl, "mds%d caps went stale, renewing\n",
			       session->s_mds);
		atomic_inc(&session->s_cap_gen);
		session->s_cap_ttl = jiffies - 1;
		send_renew_caps(mdsc, session);
		break;

	case CEPH_SESSION_RECALL_STATE:
		ceph_trim_caps(mdsc, session, le32_to_cpu(h->max_caps));
		break;

	case CEPH_SESSION_FLUSHMSG:
		/* flush cap releases */
		spin_lock(&session->s_cap_lock);
		if (session->s_num_cap_releases)
			ceph_flush_session_cap_releases(mdsc, session);
		spin_unlock(&session->s_cap_lock);

		send_flushmsg_ack(mdsc, session, seq);
		break;

	case CEPH_SESSION_FORCE_RO:
		doutc(cl, "force_session_readonly %p\n", session);
		spin_lock(&session->s_cap_lock);
		session->s_readonly = true;
		spin_unlock(&session->s_cap_lock);
		wake_up_session_caps(session, FORCE_RO);
		break;

	case CEPH_SESSION_REJECT:
		WARN_ON(session->s_state != CEPH_MDS_SESSION_OPENING &&
			session->s_state != CEPH_MDS_SESSION_RECONNECTING);
		if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
			pr_info_client(cl, "mds%d reconnect rejected\n",
				       session->s_mds);
		else
			pr_info_client(cl, "mds%d rejected session\n",
				       session->s_mds);
		session->s_state = CEPH_MDS_SESSION_REJECTED;
		cleanup_session_requests(mdsc, session);
		remove_session_caps(session);
		if (blocklisted)
			mdsc->fsc->blocklisted = true;
		wake = 2; /* for good measure */
		break;

	default:
		pr_err_client(cl, "bad op %d mds%d\n", op, mds);
		WARN_ON(1);
	}

	mutex_unlock(&session->s_mutex);
	if (wake) {
		mutex_lock(&mdsc->mutex);
		__wake_requests(mdsc, &session->s_waiting);
		if (wake == 2)
			kick_requests(mdsc, mds);
		mutex_unlock(&mdsc->mutex);
	}
	if (op == CEPH_SESSION_CLOSE)
		ceph_put_mds_session(session);
	return;

bad:
	pr_err_client(cl, "corrupt message mds%d len %d\n", mds,
		      (int)msg->front.iov_len);
	ceph_msg_dump(msg);
fail:
	for (i = 0; i < cap_auths_num; i++) {
		kfree(cap_auths[i].match.gids);
		kfree(cap_auths[i].match.path);
		kfree(cap_auths[i].match.fs_name);
	}
	kfree(cap_auths);
	return;
}

void ceph_mdsc_release_dir_caps(struct ceph_mds_request *req)
{
	struct ceph_client *cl = req->r_mdsc->fsc->client;
	int dcaps;

	dcaps = xchg(&req->r_dir_caps, 0);
	if (dcaps) {
		doutc(cl, "releasing r_dir_caps=%s\n", ceph_cap_string(dcaps));
		ceph_put_cap_refs(ceph_inode(req->r_parent), dcaps);
	}
}

void ceph_mdsc_release_dir_caps_async(struct ceph_mds_request *req)
{
	struct ceph_client *cl = req->r_mdsc->fsc->client;
	int dcaps;

	dcaps = xchg(&req->r_dir_caps, 0);
	if (dcaps) {
		doutc(cl, "releasing r_dir_caps=%s\n", ceph_cap_string(dcaps));
		ceph_put_cap_refs_async(ceph_inode(req->r_parent), dcaps);
	}
}

/*
 * called under session->mutex.
 */
static void replay_unsafe_requests(struct ceph_mds_client *mdsc,
				   struct ceph_mds_session *session)
{
	struct ceph_mds_request *req, *nreq;
	struct rb_node *p;

	doutc(mdsc->fsc->client, "mds%d\n", session->s_mds);

	mutex_lock(&mdsc->mutex);
	list_for_each_entry_safe(req, nreq, &session->s_unsafe, r_unsafe_item)
		__send_request(session, req, true);

	/*
	 * also re-send old requests when MDS enters reconnect stage. So that MDS
	 * can process completed request in clientreplay stage.
	 */
	p = rb_first(&mdsc->request_tree);
	while (p) {
		req = rb_entry(p, struct ceph_mds_request, r_node);
		p = rb_next(p);
		if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
			continue;
		if (req->r_attempts == 0)
			continue; /* only old requests */
		if (!req->r_session)
			continue;
		if (req->r_session->s_mds != session->s_mds)
			continue;

		ceph_mdsc_release_dir_caps_async(req);

		__send_request(session, req, true);
	}
	mutex_unlock(&mdsc->mutex);
}

static int send_reconnect_partial(struct ceph_reconnect_state *recon_state)
{
	struct ceph_msg *reply;
	struct ceph_pagelist *_pagelist;
	struct page *page;
	__le32 *addr;
	int err = -ENOMEM;

	if (!recon_state->allow_multi)
		return -ENOSPC;

	/* can't handle message that contains both caps and realm */
	BUG_ON(!recon_state->nr_caps == !recon_state->nr_realms);

	/* pre-allocate new pagelist */
	_pagelist = ceph_pagelist_alloc(GFP_NOFS);
	if (!_pagelist)
		return -ENOMEM;

	reply = ceph_msg_new2(CEPH_MSG_CLIENT_RECONNECT, 0, 1, GFP_NOFS, false);
	if (!reply)
		goto fail_msg;

	/* placeholder for nr_caps */
	err = ceph_pagelist_encode_32(_pagelist, 0);
	if (err < 0)
		goto fail;

	if (recon_state->nr_caps) {
		/* currently encoding caps */
		err = ceph_pagelist_encode_32(recon_state->pagelist, 0);
		if (err)
			goto fail;
	} else {
		/* placeholder for nr_realms (currently encoding relams) */
		err = ceph_pagelist_encode_32(_pagelist, 0);
		if (err < 0)
			goto fail;
	}

	err = ceph_pagelist_encode_8(recon_state->pagelist, 1);
	if (err)
		goto fail;

	page = list_first_entry(&recon_state->pagelist->head, struct page, lru);
	addr = kmap_atomic(page);
	if (recon_state->nr_caps) {
		/* currently encoding caps */
		*addr = cpu_to_le32(recon_state->nr_caps);
	} else {
		/* currently encoding relams */
		*(addr + 1) = cpu_to_le32(recon_state->nr_realms);
	}
	kunmap_atomic(addr);

	reply->hdr.version = cpu_to_le16(5);
	reply->hdr.compat_version = cpu_to_le16(4);

	reply->hdr.data_len = cpu_to_le32(recon_state->pagelist->length);
	ceph_msg_data_add_pagelist(reply, recon_state->pagelist);

	ceph_con_send(&recon_state->session->s_con, reply);
	ceph_pagelist_release(recon_state->pagelist);

	recon_state->pagelist = _pagelist;
	recon_state->nr_caps = 0;
	recon_state->nr_realms = 0;
	recon_state->msg_version = 5;
	return 0;
fail:
	ceph_msg_put(reply);
fail_msg:
	ceph_pagelist_release(_pagelist);
	return err;
}

static struct dentry* d_find_primary(struct inode *inode)
{
	struct dentry *alias, *dn = NULL;

	if (hlist_empty(&inode->i_dentry))
		return NULL;

	spin_lock(&inode->i_lock);
	if (hlist_empty(&inode->i_dentry))
		goto out_unlock;

	if (S_ISDIR(inode->i_mode)) {
		alias = hlist_entry(inode->i_dentry.first, struct dentry, d_alias);
		if (!IS_ROOT(alias))
			dn = dget(alias);
		goto out_unlock;
	}

	for_each_alias(alias, inode) {
		spin_lock(&alias->d_lock);
		if (!d_unhashed(alias) &&
		    (ceph_dentry(alias)->flags & CEPH_DENTRY_PRIMARY_LINK)) {
			dn = dget_dlock(alias);
		}
		spin_unlock(&alias->d_lock);
		if (dn)
			break;
	}
out_unlock:
	spin_unlock(&inode->i_lock);
	return dn;
}

/*
 * Encode information about a cap for a reconnect with the MDS.
 */
static int reconnect_caps_cb(struct inode *inode, int mds, void *arg)
{
	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
	struct ceph_client *cl = ceph_inode_to_client(inode);
	union {
		struct ceph_mds_cap_reconnect v2;
		struct ceph_mds_cap_reconnect_v1 v1;
	} rec;
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_reconnect_state *recon_state = arg;
	struct ceph_pagelist *pagelist = recon_state->pagelist;
	struct dentry *dentry;
	struct ceph_cap *cap;
	struct ceph_path_info path_info = {0};
	int err;
	u64 snap_follows;

	dentry = d_find_primary(inode);
	if (dentry) {
		/* set pathbase to parent dir when msg_version >= 2 */
		char *path = ceph_mdsc_build_path(mdsc, dentry, &path_info,
					    recon_state->msg_version >= 2);
		dput(dentry);
		if (IS_ERR(path)) {
			err = PTR_ERR(path);
			goto out_err;
		}
	}

	spin_lock(&ci->i_ceph_lock);
	cap = __get_cap_for_mds(ci, mds);
	if (!cap) {
		spin_unlock(&ci->i_ceph_lock);
		err = 0;
		goto out_err;
	}
	doutc(cl, " adding %p ino %llx.%llx cap %p %lld %s\n", inode,
	      ceph_vinop(inode), cap, cap->cap_id,
	      ceph_cap_string(cap->issued));

	cap->seq = 0;        /* reset cap seq */
	cap->issue_seq = 0;  /* and issue_seq */
	cap->mseq = 0;       /* and migrate_seq */
	cap->cap_gen = atomic_read(&cap->session->s_cap_gen);

	/*
	 * Note: CEPH_I_ERROR_FILELOCK is not set during reconnect.
	 * Instead, locks are submitted for best-effort MDS reclaim
	 * via the flock_len field below.  If reclaim fails (e.g.,
	 * another client grabbed a conflicting lock), future lock
	 * operations will fail and set the error flag at that point.
	 */

	/* These are lost when the session goes away */
	if (S_ISDIR(inode->i_mode)) {
		if (cap->issued & CEPH_CAP_DIR_CREATE) {
			ceph_put_string(rcu_dereference_raw(ci->i_cached_layout.pool_ns));
			memset(&ci->i_cached_layout, 0, sizeof(ci->i_cached_layout));
		}
		cap->issued &= ~CEPH_CAP_ANY_DIR_OPS;
	}

	if (recon_state->msg_version >= 2) {
		rec.v2.cap_id = cpu_to_le64(cap->cap_id);
		rec.v2.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
		rec.v2.issued = cpu_to_le32(cap->issued);
		rec.v2.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
		rec.v2.pathbase = cpu_to_le64(path_info.vino.ino);
		rec.v2.flock_len = cpu_to_le32(
			test_bit(CEPH_I_ERROR_FILELOCK_BIT,
				 &ci->i_ceph_flags) ? 0 : 1);
	} else {
		struct timespec64 ts;

		rec.v1.cap_id = cpu_to_le64(cap->cap_id);
		rec.v1.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
		rec.v1.issued = cpu_to_le32(cap->issued);
		rec.v1.size = cpu_to_le64(i_size_read(inode));
		ts = inode_get_mtime(inode);
		ceph_encode_timespec64(&rec.v1.mtime, &ts);
		ts = inode_get_atime(inode);
		ceph_encode_timespec64(&rec.v1.atime, &ts);
		rec.v1.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
		rec.v1.pathbase = cpu_to_le64(path_info.vino.ino);
	}

	if (list_empty(&ci->i_cap_snaps)) {
		snap_follows = ci->i_head_snapc ? ci->i_head_snapc->seq : 0;
	} else {
		struct ceph_cap_snap *capsnap =
			list_first_entry(&ci->i_cap_snaps,
					 struct ceph_cap_snap, ci_item);
		snap_follows = capsnap->follows;
	}
	spin_unlock(&ci->i_ceph_lock);

	if (recon_state->msg_version >= 2) {
		int num_fcntl_locks, num_flock_locks;
		struct ceph_filelock *flocks = NULL;
		size_t struct_len, total_len = sizeof(u64);
		u8 struct_v = 0;

encode_again:
		if (rec.v2.flock_len) {
			ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
		} else {
			num_fcntl_locks = 0;
			num_flock_locks = 0;
		}
		if (num_fcntl_locks + num_flock_locks > 0) {
			flocks = kmalloc_objs(struct ceph_filelock,
					      num_fcntl_locks + num_flock_locks,
					      GFP_NOFS);
			if (!flocks) {
				err = -ENOMEM;
				goto out_err;
			}
			err = ceph_encode_locks_to_buffer(inode, flocks,
							  num_fcntl_locks,
							  num_flock_locks);
			if (err) {
				kfree(flocks);
				flocks = NULL;
				if (err == -ENOSPC)
					goto encode_again;
				goto out_err;
			}
		} else {
			kfree(flocks);
			flocks = NULL;
		}

		if (recon_state->msg_version >= 3) {
			/* version, compat_version and struct_len */
			total_len += 2 * sizeof(u8) + sizeof(u32);
			struct_v = 2;
		}
		/*
		 * number of encoded locks is stable, so copy to pagelist
		 */
		struct_len = 2 * sizeof(u32) +
			    (num_fcntl_locks + num_flock_locks) *
			    sizeof(struct ceph_filelock);
		rec.v2.flock_len = cpu_to_le32(struct_len);

		struct_len += sizeof(u32) + path_info.pathlen + sizeof(rec.v2);

		if (struct_v >= 2)
			struct_len += sizeof(u64); /* snap_follows */

		total_len += struct_len;

		if (pagelist->length + total_len > RECONNECT_MAX_SIZE) {
			err = send_reconnect_partial(recon_state);
			if (err)
				goto out_freeflocks;
			pagelist = recon_state->pagelist;
		}

		err = ceph_pagelist_reserve(pagelist, total_len);
		if (err)
			goto out_freeflocks;

		ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
		if (recon_state->msg_version >= 3) {
			ceph_pagelist_encode_8(pagelist, struct_v);
			ceph_pagelist_encode_8(pagelist, 1);
			ceph_pagelist_encode_32(pagelist, struct_len);
		}
		ceph_pagelist_encode_string(pagelist, (char *)path_info.path, path_info.pathlen);
		ceph_pagelist_append(pagelist, &rec, sizeof(rec.v2));
		ceph_locks_to_pagelist(flocks, pagelist,
				       num_fcntl_locks, num_flock_locks);
		if (struct_v >= 2)
			ceph_pagelist_encode_64(pagelist, snap_follows);
out_freeflocks:
		kfree(flocks);
	} else {
		err = ceph_pagelist_reserve(pagelist,
					    sizeof(u64) + sizeof(u32) +
					    path_info.pathlen + sizeof(rec.v1));
		if (err)
			goto out_err;

		ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
		ceph_pagelist_encode_string(pagelist, (char *)path_info.path, path_info.pathlen);
		ceph_pagelist_append(pagelist, &rec, sizeof(rec.v1));
	}

out_err:
	ceph_mdsc_free_path_info(&path_info);
	if (!err)
		recon_state->nr_caps++;
	return err;
}

static int encode_snap_realms(struct ceph_mds_client *mdsc,
			      struct ceph_reconnect_state *recon_state)
{
	struct rb_node *p;
	struct ceph_pagelist *pagelist = recon_state->pagelist;
	struct ceph_client *cl = mdsc->fsc->client;
	int err = 0;

	if (recon_state->msg_version >= 4) {
		err = ceph_pagelist_encode_32(pagelist, mdsc->num_snap_realms);
		if (err < 0)
			goto fail;
	}

	/*
	 * snaprealms.  we provide mds with the ino, seq (version), and
	 * parent for all of our realms.  If the mds has any newer info,
	 * it will tell us.
	 */
	for (p = rb_first(&mdsc->snap_realms); p; p = rb_next(p)) {
		struct ceph_snap_realm *realm =
		       rb_entry(p, struct ceph_snap_realm, node);
		struct ceph_mds_snaprealm_reconnect sr_rec;

		if (recon_state->msg_version >= 4) {
			size_t need = sizeof(u8) * 2 + sizeof(u32) +
				      sizeof(sr_rec);

			if (pagelist->length + need > RECONNECT_MAX_SIZE) {
				err = send_reconnect_partial(recon_state);
				if (err)
					goto fail;
				pagelist = recon_state->pagelist;
			}

			err = ceph_pagelist_reserve(pagelist, need);
			if (err)
				goto fail;

			ceph_pagelist_encode_8(pagelist, 1);
			ceph_pagelist_encode_8(pagelist, 1);
			ceph_pagelist_encode_32(pagelist, sizeof(sr_rec));
		}

		doutc(cl, " adding snap realm %llx seq %lld parent %llx\n",
		      realm->ino, realm->seq, realm->parent_ino);
		sr_rec.ino = cpu_to_le64(realm->ino);
		sr_rec.seq = cpu_to_le64(realm->seq);
		sr_rec.parent = cpu_to_le64(realm->parent_ino);

		err = ceph_pagelist_append(pagelist, &sr_rec, sizeof(sr_rec));
		if (err)
			goto fail;

		recon_state->nr_realms++;
	}
fail:
	return err;
}


/*
 * If an MDS fails and recovers, clients need to reconnect in order to
 * reestablish shared state.  This includes all caps issued through
 * this session _and_ the snap_realm hierarchy.  Because it's not
 * clear which snap realms the mds cares about, we send everything we
 * know about.. that ensures we'll then get any new info the
 * recovering MDS might have.
 *
 * This is a relatively heavyweight operation, but it's rare.
 */
static int send_mds_reconnect(struct ceph_mds_client *mdsc,
			      struct ceph_mds_session *session)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_msg *reply;
	int mds = session->s_mds;
	int err = -ENOMEM;
	int old_state;
	struct ceph_reconnect_state recon_state = {
		.session = session,
	};
	LIST_HEAD(dispose);

	recon_state.pagelist = ceph_pagelist_alloc(GFP_NOFS);
	if (!recon_state.pagelist)
		goto fail_nopagelist;

	reply = ceph_msg_new2(CEPH_MSG_CLIENT_RECONNECT, 0, 1, GFP_NOFS, false);
	if (!reply)
		goto fail_nomsg;

	mutex_lock(&session->s_mutex);

	/* Serialized by s_mutex against concurrent ceph_get_deleg_ino(). */
	xa_destroy(&session->s_delegated_inos);
	atomic_set(&session->s_num_deleg_inos, 0);
	if (session->s_state == CEPH_MDS_SESSION_CLOSED ||
	    session->s_state == CEPH_MDS_SESSION_REJECTED) {
		pr_info_client(cl, "mds%d skipping reconnect, session %s\n",
			       mds,
			       ceph_session_state_name(session->s_state));
		mutex_unlock(&session->s_mutex);
		ceph_msg_put(reply);
		err = -ESTALE;
		goto fail_return;
	}

	/* s_mutex -> mdsc->mutex matches cleanup_session_requests() order. */
	mutex_lock(&mdsc->mutex);
	if (mds >= mdsc->max_sessions || mdsc->sessions[mds] != session) {
		mutex_unlock(&mdsc->mutex);
		pr_info_client(cl,
			       "mds%d skipping reconnect, session unregistered\n",
			       mds);
		mutex_unlock(&session->s_mutex);
		ceph_msg_put(reply);
		err = -ENOENT;
		goto fail_return;
	}
	mutex_unlock(&mdsc->mutex);

	pr_info_client(cl, "mds%d reconnect start\n", mds);
	old_state = session->s_state;
	session->s_state = CEPH_MDS_SESSION_RECONNECTING;
	session->s_seq = 0;

	doutc(cl, "session %p state %s\n", session,
	      ceph_session_state_name(session->s_state));

	atomic_inc(&session->s_cap_gen);

	spin_lock(&session->s_cap_lock);
	/* don't know if session is readonly */
	session->s_readonly = 0;
	/*
	 * notify __ceph_remove_cap() that we are composing cap reconnect.
	 * If a cap get released before being added to the cap reconnect,
	 * __ceph_remove_cap() should skip queuing cap release.
	 */
	session->s_cap_reconnect = 1;
	/* drop old cap expires; we're about to reestablish that state */
	detach_cap_releases(session, &dispose);
	spin_unlock(&session->s_cap_lock);
	dispose_cap_releases(mdsc, &dispose);

	/* trim unused caps to reduce MDS's cache rejoin time */
	if (mdsc->fsc->sb->s_root)
		shrink_dcache_parent(mdsc->fsc->sb->s_root);

	ceph_con_close(&session->s_con);
	ceph_con_open(&session->s_con,
		      CEPH_ENTITY_TYPE_MDS, mds,
		      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

	/* replay unsafe requests */
	replay_unsafe_requests(mdsc, session);

	ceph_early_kick_flushing_caps(mdsc, session);

	down_read(&mdsc->snap_rwsem);

	/* placeholder for nr_caps */
	err = ceph_pagelist_encode_32(recon_state.pagelist, 0);
	if (err)
		goto fail_clear_cap_reconnect;

	if (test_bit(CEPHFS_FEATURE_MULTI_RECONNECT, &session->s_features)) {
		recon_state.msg_version = 3;
		recon_state.allow_multi = true;
	} else if (session->s_con.peer_features & CEPH_FEATURE_MDSENC) {
		recon_state.msg_version = 3;
	} else {
		recon_state.msg_version = 2;
	}
	/* traverse this session's caps */
	err = ceph_iterate_session_caps(session, reconnect_caps_cb, &recon_state);

	spin_lock(&session->s_cap_lock);
	session->s_cap_reconnect = 0;
	spin_unlock(&session->s_cap_lock);

	if (err < 0)
		goto fail;

	/* check if all realms can be encoded into current message */
	if (mdsc->num_snap_realms) {
		size_t total_len =
			recon_state.pagelist->length +
			mdsc->num_snap_realms *
			sizeof(struct ceph_mds_snaprealm_reconnect);
		if (recon_state.msg_version >= 4) {
			/* number of realms */
			total_len += sizeof(u32);
			/* version, compat_version and struct_len */
			total_len += mdsc->num_snap_realms *
				     (2 * sizeof(u8) + sizeof(u32));
		}
		if (total_len > RECONNECT_MAX_SIZE) {
			if (!recon_state.allow_multi) {
				err = -ENOSPC;
				goto fail;
			}
			if (recon_state.nr_caps) {
				err = send_reconnect_partial(&recon_state);
				if (err)
					goto fail;
			}
			recon_state.msg_version = 5;
		}
	}

	err = encode_snap_realms(mdsc, &recon_state);
	if (err < 0)
		goto fail;

	if (recon_state.msg_version >= 5) {
		err = ceph_pagelist_encode_8(recon_state.pagelist, 0);
		if (err < 0)
			goto fail;
	}

	if (recon_state.nr_caps || recon_state.nr_realms) {
		struct page *page =
			list_first_entry(&recon_state.pagelist->head,
					struct page, lru);
		__le32 *addr = kmap_atomic(page);
		if (recon_state.nr_caps) {
			WARN_ON(recon_state.nr_realms != mdsc->num_snap_realms);
			*addr = cpu_to_le32(recon_state.nr_caps);
		} else if (recon_state.msg_version >= 4) {
			*(addr + 1) = cpu_to_le32(recon_state.nr_realms);
		}
		kunmap_atomic(addr);
	}

	reply->hdr.version = cpu_to_le16(recon_state.msg_version);
	if (recon_state.msg_version >= 4)
		reply->hdr.compat_version = cpu_to_le16(4);

	reply->hdr.data_len = cpu_to_le32(recon_state.pagelist->length);
	ceph_msg_data_add_pagelist(reply, recon_state.pagelist);

	ceph_con_send(&session->s_con, reply);

	mutex_unlock(&session->s_mutex);

	mutex_lock(&mdsc->mutex);
	__wake_requests(mdsc, &session->s_waiting);
	mutex_unlock(&mdsc->mutex);

	up_read(&mdsc->snap_rwsem);
	ceph_pagelist_release(recon_state.pagelist);
	return 0;

fail_clear_cap_reconnect:
	spin_lock(&session->s_cap_lock);
	session->s_cap_reconnect = 0;
	spin_unlock(&session->s_cap_lock);
fail:
	ceph_msg_put(reply);
	up_read(&mdsc->snap_rwsem);
	/*
	 * Restore prior session state so map-driven reconnect logic
	 * (check_new_map) can retry.  Without this, a transient build
	 * failure strands the session in RECONNECTING indefinitely.
	 */
	session->s_state = old_state;
	mutex_unlock(&session->s_mutex);
fail_nomsg:
	ceph_pagelist_release(recon_state.pagelist);
fail_nopagelist:
	pr_err_client(cl, "error %d preparing reconnect for mds%d\n",
		      err, mds);
	return err;

fail_return:
	/*
	 * Early-exit path for expected concurrent-teardown races
	 * (-ESTALE for closed/rejected sessions, -ENOENT for
	 * unregistered sessions).  Skip the pr_err_client diagnostic
	 * since these are not genuine reconnect build failures.
	 */
	ceph_pagelist_release(recon_state.pagelist);
	return err;
}

const char *ceph_reset_phase_name(enum ceph_client_reset_phase phase)
{
	switch (phase) {
	case CEPH_CLIENT_RESET_IDLE:	  return "idle";
	case CEPH_CLIENT_RESET_QUIESCING: return "quiescing";
	case CEPH_CLIENT_RESET_DRAINING:  return "draining";
	case CEPH_CLIENT_RESET_TEARDOWN:  return "teardown";
	default:			  return "unknown";
	}
}

/**
 * ceph_mdsc_wait_for_reset - wait for an active reset to complete
 * @mdsc: MDS client
 *
 * Returns 0 if reset completed successfully or no reset was active.
 * Returns -EAGAIN if reset completed with an error, signalling the
 * caller to retry.  The internal error (e.g. -ENOMEM) is not propagated
 * because callers like open() or flock() have no way to act on
 * work-function internals.  The detailed error is available via debugfs
 * reset/status and tracepoints.
 * Returns -ETIMEDOUT if we timed out waiting.
 * Returns -ERESTARTSYS if interrupted by signal.
 */
int ceph_mdsc_wait_for_reset(struct ceph_mds_client *mdsc)
{
	struct ceph_client_reset_state *st = &mdsc->reset_state;
	struct ceph_client *cl = mdsc->fsc->client;
	unsigned long deadline = jiffies + CEPH_CLIENT_RESET_WAIT_TIMEOUT_SEC * HZ;
	int blocked_count;
	long remaining;
	long wait_ret;
	int ret;

	if (ceph_reset_is_idle(st))
		return 0;

	blocked_count = atomic_inc_return(&st->blocked_requests);
	doutc(cl, "request blocked during reset, %d total blocked\n",
	      blocked_count);
	trace_ceph_client_reset_blocked(mdsc, blocked_count);

retry:
	remaining = max_t(long, deadline - jiffies, 1);
	wait_ret = wait_event_interruptible_timeout(st->blocked_wq,
						    ceph_reset_is_idle(st),
						    remaining);

	if (wait_ret == 0) {
		atomic_dec(&st->blocked_requests);
		pr_warn_client(cl, "timed out waiting for reset to complete\n");
		trace_ceph_client_reset_unblocked(mdsc, -ETIMEDOUT);
		return -ETIMEDOUT;
	}
	if (wait_ret < 0) {
		atomic_dec(&st->blocked_requests);
		trace_ceph_client_reset_unblocked(mdsc, (int)wait_ret);
		return (int)wait_ret;  /* -ERESTARTSYS */
	}

	/*
	 * Verify phase is still IDLE under the lock.  If another reset
	 * was scheduled between the wake-up and this check, loop back
	 * and wait for it to finish rather than returning a stale result.
	 */
	spin_lock(&st->lock);
	if (st->phase != CEPH_CLIENT_RESET_IDLE) {
		spin_unlock(&st->lock);
		if (time_before(jiffies, deadline))
			goto retry;
		atomic_dec(&st->blocked_requests);
		trace_ceph_client_reset_unblocked(mdsc, -ETIMEDOUT);
		return -ETIMEDOUT;
	}
	ret = st->last_errno;
	spin_unlock(&st->lock);

	atomic_dec(&st->blocked_requests);
	trace_ceph_client_reset_unblocked(mdsc, ret);
	return ret ? -EAGAIN : 0;
}

static void ceph_mdsc_reset_complete(struct ceph_mds_client *mdsc, int ret)
{
	struct ceph_client_reset_state *st = &mdsc->reset_state;

	spin_lock(&st->lock);
	/*
	 * If destroy already marked us as shut down, it owns the
	 * final bookkeeping and waiter wakeup.  Just bail so we
	 * don't overwrite its state.
	 */
	if (st->shutdown) {
		spin_unlock(&st->lock);
		return;
	}
	st->last_finish = jiffies;
	st->last_errno = ret;
	st->phase = CEPH_CLIENT_RESET_IDLE;
	if (ret)
		st->failure_count++;
	else
		st->success_count++;
	spin_unlock(&st->lock);

	/* Wake up all requests that were blocked waiting for reset */
	wake_up_all(&st->blocked_wq);

	trace_ceph_client_reset_complete(mdsc, ret);
}

static void ceph_mdsc_reset_workfn(struct work_struct *work)
{
	struct ceph_mds_client *mdsc =
		container_of(work, struct ceph_mds_client, reset_work);
	struct ceph_client_reset_state *st = &mdsc->reset_state;
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_session **sessions = NULL;
	char reason[CEPH_CLIENT_RESET_REASON_LEN];
	unsigned long drain_deadline;
	int max_sessions, i, n = 0, torn_down = 0;
	int ret = 0;

	spin_lock(&st->lock);
	strscpy(reason, st->last_reason, sizeof(reason));
	spin_unlock(&st->lock);

	mutex_lock(&mdsc->mutex);
	max_sessions = mdsc->max_sessions;
	if (max_sessions <= 0) {
		mutex_unlock(&mdsc->mutex);
		goto out_complete;
	}

	sessions = kzalloc_objs(*sessions, max_sessions);
	if (!sessions) {
		mutex_unlock(&mdsc->mutex);
		ret = -ENOMEM;
		pr_err_client(cl,
			      "manual session reset failed to allocate session array\n");
		ceph_mdsc_reset_complete(mdsc, ret);
		return;
	}

	for (i = 0; i < max_sessions; i++) {
		struct ceph_mds_session *session = mdsc->sessions[i];

		if (!session)
			continue;

		/*
		 * Read session state without s_mutex to avoid nesting
		 * mdsc->mutex -> s_mutex, which would invert the
		 * s_mutex -> mdsc->mutex order used by
		 * cleanup_session_requests().  s_state is an int
		 * so loads are atomic; the teardown loop below
		 * handles races with concurrent state transitions.
		 */
		switch (READ_ONCE(session->s_state)) {
		case CEPH_MDS_SESSION_OPEN:
		case CEPH_MDS_SESSION_HUNG:
		case CEPH_MDS_SESSION_OPENING:
		case CEPH_MDS_SESSION_RESTARTING:
		case CEPH_MDS_SESSION_RECONNECTING:
		case CEPH_MDS_SESSION_CLOSING:
			sessions[n++] = ceph_get_mds_session(session);
			break;
		default:
			pr_info_client(cl,
				       "mds%d in state %s, skipping reset\n",
				       session->s_mds,
				       ceph_session_state_name(session->s_state));
			break;
		}
	}
	mutex_unlock(&mdsc->mutex);

	pr_info_client(cl,
		       "manual session reset executing (sessions=%d, reason=\"%s\")\n",
		       n, reason);

	if (n == 0) {
		kfree(sessions);
		goto out_complete;
	}

	spin_lock(&st->lock);
	if (st->shutdown) {
		spin_unlock(&st->lock);
		goto out_sessions;
	}
	st->phase = CEPH_CLIENT_RESET_DRAINING;
	spin_unlock(&st->lock);

	/*
	 * Best-effort drain: flush dirty state while sessions are still
	 * alive.  New requests are blocked while phase != IDLE.
	 * The sessions are functional, so non-stuck state drains normally.
	 * Stuck state (the cause of the stalemate the operator is trying
	 * to break) will not drain -- that is expected, and we proceed to
	 * forced teardown after the timeout.
	 *
	 * Four things are drained:
	 *  1. MDS journal -- send_flush_mdlog asks each MDS to journal
	 *     pending unsafe operations (creates, renames, setattrs).
	 *  2. Unsafe requests -- bounded wait for each unsafe write
	 *     request to reach safe status via r_safe_completion.
	 *  3. Dirty caps -- ceph_flush_dirty_caps triggers cap flush on
	 *     all sessions.  Non-stuck caps flush in milliseconds.
	 *  4. Cap releases -- push pending cap release messages.
	 *
	 * The unsafe-request wait and cap-flush wait below provide
	 * the bounded drain window during which all categories can
	 * make progress.
	 */
	for (i = 0; i < n; i++)
		send_flush_mdlog(sessions[i]);

	/*
	 * Both drain legs (unsafe requests and cap flushes) share a
	 * single deadline so the total drain time is bounded at
	 * CEPH_CLIENT_RESET_DRAIN_SEC.
	 */
	drain_deadline = jiffies + CEPH_CLIENT_RESET_DRAIN_SEC * HZ;

	/*
	 * Wait for unsafe write requests (creates, renames, setattrs)
	 * to reach safe status.  Uses the same pattern as
	 * flush_mdlog_and_wait_mdsc_unsafe_requests() but bounded by
	 * the shared drain deadline.  Requests that do not complete within
	 * the window are force-dropped during teardown.
	 */
	{
		struct ceph_mds_request *req;
		struct rb_node *rn;
		u64 last_tid;

		mutex_lock(&mdsc->mutex);
		last_tid = mdsc->last_tid;
		mutex_unlock(&mdsc->mutex);

		mutex_lock(&mdsc->mutex);
		rn = rb_first(&mdsc->request_tree);
		while (rn) {
			req = rb_entry(rn, struct ceph_mds_request, r_node);
			if (req->r_tid > last_tid)
				break;
			if (req->r_op == CEPH_MDS_OP_SETFILELOCK ||
			    !(req->r_op & CEPH_MDS_OP_WRITE)) {
				rn = rb_next(rn);
				continue;
			}
			ceph_mdsc_get_request(req);
			mutex_unlock(&mdsc->mutex);

			wait_for_completion_timeout(&req->r_safe_completion,
				max_t(long, drain_deadline - jiffies, 1));

			mutex_lock(&mdsc->mutex);
			ceph_mdsc_put_request(req);
			if (time_after(jiffies, drain_deadline))
				break;
			rn = rb_first(&mdsc->request_tree);
		}
		mutex_unlock(&mdsc->mutex);

		if (time_after_eq(jiffies, drain_deadline))
			WRITE_ONCE(st->drain_timed_out, true);
	}

	ceph_flush_dirty_caps(mdsc);
	ceph_flush_cap_releases(mdsc);

	spin_lock(&mdsc->cap_dirty_lock);
	if (!list_empty(&mdsc->cap_flush_list)) {
		struct ceph_cap_flush *cf =
			list_last_entry(&mdsc->cap_flush_list,
					struct ceph_cap_flush, g_list);
		u64 want_flush = mdsc->last_cap_flush_tid;
		long drain_ret;

		/*
		 * Setting wake on the last entry is sufficient: flush
		 * entries complete in order, so when this entry finishes
		 * all earlier ones are already done.
		 */
		cf->wake = true;
		spin_unlock(&mdsc->cap_dirty_lock);
		pr_info_client(cl,
			       "draining (want_flush=%llu, %d sessions)\n",
			       want_flush, n);
		drain_ret = wait_event_timeout(mdsc->cap_flushing_wq,
					       check_caps_flush(mdsc,
								want_flush),
					       max_t(long,
						     drain_deadline - jiffies,
						     1));
		if (drain_ret == 0) {
			pr_info_client(cl,
				       "drain timed out, proceeding with forced teardown\n");
			WRITE_ONCE(st->drain_timed_out, true);
		} else {
			pr_info_client(cl, "drain completed successfully\n");
		}
	} else {
		spin_unlock(&mdsc->cap_dirty_lock);
	}

	spin_lock(&st->lock);
	if (st->shutdown) {
		spin_unlock(&st->lock);
		goto out_sessions;
	}
	st->phase = CEPH_CLIENT_RESET_TEARDOWN;
	spin_unlock(&st->lock);

	/*
	 * Ask each MDS to close the session before we tear it down
	 * locally.  Without this the MDS sees only a connection drop and
	 * waits for the client to reconnect (up to session_autoclose
	 * seconds) before evicting the session and releasing locks.
	 *
	 * Reuse the normal close machinery so the session state/sequence
	 * snapshot is serialized under s_mutex and a racing s_seq bump
	 * retransmits REQUEST_CLOSE while the session remains CLOSING.
	 * We send all close requests first, then yield briefly to let the
	 * network stack transmit them before __unregister_session()
	 * closes the connections.
	 */
	for (i = 0; i < n; i++) {
		int err;

		mutex_lock(&sessions[i]->s_mutex);
		err = __close_session(mdsc, sessions[i]);
		mutex_unlock(&sessions[i]->s_mutex);
		if (err < 0)
			pr_warn_client(cl,
				       "mds%d failed to queue close request before reset: %d\n",
				       sessions[i]->s_mds, err);
	}
	/*
	 * Best-effort grace period: yield briefly so the network stack
	 * can transmit the queued REQUEST_CLOSE messages before we tear
	 * down connections.  Not a correctness requirement -- the MDS
	 * will still evict via session_autoclose if it never receives
	 * the close request.
	 *
	 * Event-based waiting is not viable here: there is no completion
	 * event for "message left the NIC," and waiting for the MDS
	 * SESSION_CLOSE response would re-create the stalemate that the
	 * reset is meant to break.
	 */
	if (n > 0)
		msleep(CEPH_CLIENT_RESET_CLOSE_GRACE_MS);

	/*
	 * Tear down each session: close the connection, remove all
	 * caps, clean up requests, then kick pending requests so they
	 * re-open a fresh session on the next attempt.
	 *
	 * This is modeled on the check_new_map() forced-close path
	 * for stopped MDS ranks - a proven pattern for hard session
	 * teardown.  We do NOT attempt send_mds_reconnect() because
	 * the MDS only accepts reconnects during its own RECONNECT
	 * phase (after MDS restart), not from an active client.
	 *
	 * Any state that did not drain (caps that didn't flush, unsafe
	 * requests that the MDS didn't journal) is force-dropped here.
	 * This is intentional: that state is stuck and is the reason
	 * the operator triggered the reset.
	 */
	for (i = 0; i < n; i++) {
		int mds = sessions[i]->s_mds;

		pr_info_client(cl, "mds%d resetting session\n", mds);

		mutex_lock(&mdsc->mutex);
		if (mds >= mdsc->max_sessions ||
		    mdsc->sessions[mds] != sessions[i]) {
			pr_info_client(cl,
				       "mds%d session already torn down, skipping\n",
				       mds);
			mutex_unlock(&mdsc->mutex);
			ceph_put_mds_session(sessions[i]);
			sessions[i] = NULL;
			continue;
		}
		sessions[i]->s_state = CEPH_MDS_SESSION_CLOSED;
		__unregister_session(mdsc, sessions[i]);
		__wake_requests(mdsc, &sessions[i]->s_waiting);
		mutex_unlock(&mdsc->mutex);

		mutex_lock(&sessions[i]->s_mutex);
		cleanup_session_requests(mdsc, sessions[i]);
		remove_session_caps(sessions[i]);
		mutex_unlock(&sessions[i]->s_mutex);

		wake_up_all(&mdsc->session_close_wq);

		ceph_put_mds_session(sessions[i]);

		mutex_lock(&mdsc->mutex);
		kick_requests(mdsc, mds);
		mutex_unlock(&mdsc->mutex);

		torn_down++;
		pr_info_client(cl, "mds%d session reset complete\n", mds);
	}

	kfree(sessions);

	spin_lock(&st->lock);
	st->sessions_reset = torn_down;
	spin_unlock(&st->lock);

out_complete:
	ceph_mdsc_reset_complete(mdsc, ret);
	return;

out_sessions:
	/* shutdown == true: ceph_mdsc_destroy() owns the final transition. */
	for (i = 0; i < n; i++)
		ceph_put_mds_session(sessions[i]);
	kfree(sessions);
}

int ceph_mdsc_schedule_reset(struct ceph_mds_client *mdsc,
			     const char *reason)
{
	struct ceph_client_reset_state *st = &mdsc->reset_state;
	struct ceph_fs_client *fsc = mdsc->fsc;
	const char *msg = (reason && reason[0]) ? reason : "manual";
	int mount_state;

	mount_state = READ_ONCE(fsc->mount_state);
	if (mount_state != CEPH_MOUNT_MOUNTED) {
		pr_warn_client(fsc->client,
			       "reset rejected: mount_state=%d (not mounted)\n",
			       mount_state);
		return -EINVAL;
	}

	spin_lock(&st->lock);
	if (st->phase != CEPH_CLIENT_RESET_IDLE) {
		spin_unlock(&st->lock);
		return -EBUSY;
	}

	st->phase = CEPH_CLIENT_RESET_QUIESCING;
	st->last_start = jiffies;
	st->last_errno = 0;
	st->drain_timed_out = false;
	st->sessions_reset = 0;
	st->trigger_count++;
	strscpy(st->last_reason, msg, sizeof(st->last_reason));
	spin_unlock(&st->lock);

	if (WARN_ON_ONCE(!queue_work(system_dfl_wq, &mdsc->reset_work))) {
		spin_lock(&st->lock);
		st->phase = CEPH_CLIENT_RESET_IDLE;
		st->last_errno = -EALREADY;
		st->last_finish = jiffies;
		st->failure_count++;
		spin_unlock(&st->lock);
		wake_up_all(&st->blocked_wq);
		return -EALREADY;
	}

	pr_info_client(mdsc->fsc->client,
		       "manual session reset scheduled (reason=\"%s\")\n",
		       msg);
	trace_ceph_client_reset_schedule(mdsc, msg);
	return 0;
}


/*
 * compare old and new mdsmaps, kicking requests
 * and closing out old connections as necessary
 *
 * called under mdsc->mutex.
 */
static void check_new_map(struct ceph_mds_client *mdsc,
			  struct ceph_mdsmap *newmap,
			  struct ceph_mdsmap *oldmap)
{
	int i, j, err;
	int oldstate, newstate;
	struct ceph_mds_session *s;
	unsigned long targets[DIV_ROUND_UP(CEPH_MAX_MDS, sizeof(unsigned long))] = {0};
	struct ceph_client *cl = mdsc->fsc->client;

	doutc(cl, "new %u old %u\n", newmap->m_epoch, oldmap->m_epoch);

	if (newmap->m_info) {
		for (i = 0; i < newmap->possible_max_rank; i++) {
			for (j = 0; j < newmap->m_info[i].num_export_targets; j++)
				set_bit(newmap->m_info[i].export_targets[j], targets);
		}
	}

	for (i = 0; i < oldmap->possible_max_rank && i < mdsc->max_sessions; i++) {
		if (!mdsc->sessions[i])
			continue;
		s = mdsc->sessions[i];
		oldstate = ceph_mdsmap_get_state(oldmap, i);
		newstate = ceph_mdsmap_get_state(newmap, i);

		doutc(cl, "mds%d state %s%s -> %s%s (session %s)\n",
		      i, ceph_mds_state_name(oldstate),
		      ceph_mdsmap_is_laggy(oldmap, i) ? " (laggy)" : "",
		      ceph_mds_state_name(newstate),
		      ceph_mdsmap_is_laggy(newmap, i) ? " (laggy)" : "",
		      ceph_session_state_name(s->s_state));

		if (i >= newmap->possible_max_rank) {
			/* force close session for stopped mds */
			ceph_get_mds_session(s);
			__unregister_session(mdsc, s);
			__wake_requests(mdsc, &s->s_waiting);
			mutex_unlock(&mdsc->mutex);

			mutex_lock(&s->s_mutex);
			cleanup_session_requests(mdsc, s);
			remove_session_caps(s);
			mutex_unlock(&s->s_mutex);

			ceph_put_mds_session(s);

			mutex_lock(&mdsc->mutex);
			kick_requests(mdsc, i);
			continue;
		}

		if (memcmp(ceph_mdsmap_get_addr(oldmap, i),
			   ceph_mdsmap_get_addr(newmap, i),
			   sizeof(struct ceph_entity_addr))) {
			/* just close it */
			ceph_get_mds_session(s);
			mutex_unlock(&mdsc->mutex);
			mutex_lock(&s->s_mutex);
			mutex_lock(&mdsc->mutex);
			ceph_put_mds_session(s);
			ceph_con_close(&s->s_con);
			mutex_unlock(&s->s_mutex);
			s->s_state = CEPH_MDS_SESSION_RESTARTING;
		} else if (oldstate == newstate) {
			continue;  /* nothing new with this mds */
		}

		/*
		 * send reconnect?
		 */
		if (s->s_state == CEPH_MDS_SESSION_RESTARTING &&
		    newstate >= CEPH_MDS_STATE_RECONNECT) {
			int rc;

			ceph_get_mds_session(s);
			mutex_unlock(&mdsc->mutex);
			clear_bit(i, targets);
			rc = send_mds_reconnect(mdsc, s);
			if (rc)
				pr_warn_client(cl,
					       "mds%d reconnect failed: %d\n",
					       i, rc);
			mutex_lock(&mdsc->mutex);
			ceph_put_mds_session(s);
		}

		/*
		 * kick request on any mds that has gone active.
		 */
		if (oldstate < CEPH_MDS_STATE_ACTIVE &&
		    newstate >= CEPH_MDS_STATE_ACTIVE) {
			if (oldstate != CEPH_MDS_STATE_CREATING &&
			    oldstate != CEPH_MDS_STATE_STARTING)
				pr_info_client(cl, "mds%d recovery completed\n",
					       s->s_mds);
			kick_requests(mdsc, i);
			ceph_get_mds_session(s);
			mutex_unlock(&mdsc->mutex);
			mutex_lock(&s->s_mutex);
			mutex_lock(&mdsc->mutex);
			ceph_put_mds_session(s);
			ceph_kick_flushing_caps(mdsc, s);
			mutex_unlock(&s->s_mutex);
			wake_up_session_caps(s, RECONNECT);
		}
	}

	/*
	 * Only open and reconnect sessions that don't exist yet.
	 */
	for (i = 0; i < newmap->possible_max_rank; i++) {
		/*
		 * In case the import MDS is crashed just after
		 * the EImportStart journal is flushed, so when
		 * a standby MDS takes over it and is replaying
		 * the EImportStart journal the new MDS daemon
		 * will wait the client to reconnect it, but the
		 * client may never register/open the session yet.
		 *
		 * Will try to reconnect that MDS daemon if the
		 * rank number is in the export targets array and
		 * is the up:reconnect state.
		 */
		newstate = ceph_mdsmap_get_state(newmap, i);
		if (!test_bit(i, targets) || newstate != CEPH_MDS_STATE_RECONNECT)
			continue;

		/*
		 * The session maybe registered and opened by some
		 * requests which were choosing random MDSes during
		 * the mdsc->mutex's unlock/lock gap below in rare
		 * case. But the related MDS daemon will just queue
		 * that requests and be still waiting for the client's
		 * reconnection request in up:reconnect state.
		 */
		s = __ceph_lookup_mds_session(mdsc, i);
		if (likely(!s)) {
			s = __open_export_target_session(mdsc, i);
			if (IS_ERR(s)) {
				err = PTR_ERR(s);
				pr_err_client(cl,
					      "failed to open export target session, err %d\n",
					      err);
				continue;
			}
		}
		doutc(cl, "send reconnect to export target mds.%d\n", i);
		mutex_unlock(&mdsc->mutex);
		err = send_mds_reconnect(mdsc, s);
		if (err)
			pr_warn_client(cl,
				       "mds%d export target reconnect failed: %d\n",
				       i, err);
		ceph_put_mds_session(s);
		mutex_lock(&mdsc->mutex);
	}

	for (i = 0; i < newmap->possible_max_rank && i < mdsc->max_sessions; i++) {
		s = mdsc->sessions[i];
		if (!s)
			continue;
		if (!ceph_mdsmap_is_laggy(newmap, i))
			continue;
		if (s->s_state == CEPH_MDS_SESSION_OPEN ||
		    s->s_state == CEPH_MDS_SESSION_HUNG ||
		    s->s_state == CEPH_MDS_SESSION_CLOSING) {
			doutc(cl, " connecting to export targets of laggy mds%d\n", i);
			__open_export_target_sessions(mdsc, s);
		}
	}
}



/*
 * leases
 */

/*
 * caller must hold session s_mutex, dentry->d_lock
 */
void __ceph_mdsc_drop_dentry_lease(struct dentry *dentry)
{
	struct ceph_dentry_info *di = ceph_dentry(dentry);

	ceph_put_mds_session(di->lease_session);
	di->lease_session = NULL;
}

static void handle_lease(struct ceph_mds_client *mdsc,
			 struct ceph_mds_session *session,
			 struct ceph_msg *msg)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct super_block *sb = mdsc->fsc->sb;
	struct inode *inode;
	struct dentry *parent, *dentry;
	struct ceph_dentry_info *di;
	int mds = session->s_mds;
	struct ceph_mds_lease *h = msg->front.iov_base;
	u32 seq;
	struct ceph_vino vino;
	struct qstr dname;
	int release = 0;

	doutc(cl, "from mds%d\n", mds);

	if (!ceph_inc_mds_stopping_blocker(mdsc, session))
		return;

	/* decode */
	if (msg->front.iov_len < sizeof(*h) + sizeof(u32))
		goto bad;
	vino.ino = le64_to_cpu(h->ino);
	vino.snap = CEPH_NOSNAP;
	seq = le32_to_cpu(h->seq);
	dname.len = get_unaligned_le32(h + 1);
	if (msg->front.iov_len < sizeof(*h) + sizeof(u32) + dname.len)
		goto bad;
	dname.name = (void *)(h + 1) + sizeof(u32);

	/* lookup inode */
	inode = ceph_find_inode(sb, vino);
	doutc(cl, "%s, ino %llx %p %.*s\n", ceph_lease_op_name(h->action),
	      vino.ino, inode, dname.len, dname.name);

	mutex_lock(&session->s_mutex);
	if (!inode) {
		doutc(cl, "no inode %llx\n", vino.ino);
		goto release;
	}

	/* dentry */
	parent = d_find_alias(inode);
	if (!parent) {
		doutc(cl, "no parent dentry on inode %p\n", inode);
		WARN_ON(1);
		goto release;  /* hrm... */
	}
	dname.hash = full_name_hash(parent, dname.name, dname.len);
	dentry = d_lookup(parent, &dname);
	dput(parent);
	if (!dentry)
		goto release;

	spin_lock(&dentry->d_lock);
	di = ceph_dentry(dentry);
	switch (h->action) {
	case CEPH_MDS_LEASE_REVOKE:
		if (di->lease_session == session) {
			if (ceph_seq_cmp(di->lease_seq, seq) > 0)
				h->seq = cpu_to_le32(di->lease_seq);
			__ceph_mdsc_drop_dentry_lease(dentry);
		}
		release = 1;
		break;

	case CEPH_MDS_LEASE_RENEW:
		if (di->lease_session == session &&
		    di->lease_gen == atomic_read(&session->s_cap_gen) &&
		    di->lease_renew_from &&
		    di->lease_renew_after == 0) {
			unsigned long duration =
				msecs_to_jiffies(le32_to_cpu(h->duration_ms));

			di->lease_seq = seq;
			di->time = di->lease_renew_from + duration;
			di->lease_renew_after = di->lease_renew_from +
				(duration >> 1);
			di->lease_renew_from = 0;
		}
		break;
	}
	spin_unlock(&dentry->d_lock);
	dput(dentry);

	if (!release)
		goto out;

release:
	/* let's just reuse the same message */
	h->action = CEPH_MDS_LEASE_REVOKE_ACK;
	ceph_msg_get(msg);
	ceph_con_send(&session->s_con, msg);

out:
	mutex_unlock(&session->s_mutex);
	iput(inode);

	ceph_dec_mds_stopping_blocker(mdsc);
	return;

bad:
	ceph_dec_mds_stopping_blocker(mdsc);

	pr_err_client(cl, "corrupt lease message\n");
	ceph_msg_dump(msg);
}

void ceph_mdsc_lease_send_msg(struct ceph_mds_session *session,
			      struct dentry *dentry, char action,
			      u32 seq)
{
	struct ceph_client *cl = session->s_mdsc->fsc->client;
	struct ceph_msg *msg;
	struct ceph_mds_lease *lease;
	struct inode *dir;
	int len = sizeof(*lease) + sizeof(u32) + NAME_MAX;

	doutc(cl, "identry %p %s to mds%d\n", dentry, ceph_lease_op_name(action),
	      session->s_mds);

	msg = ceph_msg_new(CEPH_MSG_CLIENT_LEASE, len, GFP_NOFS, false);
	if (!msg)
		return;
	lease = msg->front.iov_base;
	lease->action = action;
	lease->seq = cpu_to_le32(seq);

	spin_lock(&dentry->d_lock);
	dir = d_inode(dentry->d_parent);
	lease->ino = cpu_to_le64(ceph_ino(dir));
	lease->first = lease->last = cpu_to_le64(ceph_snap(dir));

	put_unaligned_le32(dentry->d_name.len, lease + 1);
	memcpy((void *)(lease + 1) + 4,
	       dentry->d_name.name, dentry->d_name.len);
	spin_unlock(&dentry->d_lock);

	ceph_con_send(&session->s_con, msg);
}

/*
 * lock unlock the session, to wait ongoing session activities
 */
static void lock_unlock_session(struct ceph_mds_session *s)
{
	mutex_lock(&s->s_mutex);
	mutex_unlock(&s->s_mutex);
}

static void maybe_recover_session(struct ceph_mds_client *mdsc)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_fs_client *fsc = mdsc->fsc;

	if (!ceph_test_mount_opt(fsc, CLEANRECOVER))
		return;

	if (READ_ONCE(fsc->mount_state) != CEPH_MOUNT_MOUNTED)
		return;

	if (!READ_ONCE(fsc->blocklisted))
		return;

	pr_info_client(cl, "auto reconnect after blocklisted\n");
	ceph_force_reconnect(fsc->sb);
}

bool check_session_state(struct ceph_mds_session *s)
{
	struct ceph_client *cl = s->s_mdsc->fsc->client;

	switch (s->s_state) {
	case CEPH_MDS_SESSION_OPEN:
		if (s->s_ttl && time_after(jiffies, s->s_ttl)) {
			s->s_state = CEPH_MDS_SESSION_HUNG;
			pr_info_client(cl, "mds%d hung\n", s->s_mds);
		}
		break;
	case CEPH_MDS_SESSION_CLOSING:
	case CEPH_MDS_SESSION_NEW:
	case CEPH_MDS_SESSION_RESTARTING:
	case CEPH_MDS_SESSION_CLOSED:
	case CEPH_MDS_SESSION_REJECTED:
		return false;
	}

	return true;
}

/*
 * If the sequence is incremented while we're waiting on a REQUEST_CLOSE reply,
 * then we need to retransmit that request.
 */
void inc_session_sequence(struct ceph_mds_session *s)
{
	struct ceph_client *cl = s->s_mdsc->fsc->client;

	lockdep_assert_held(&s->s_mutex);

	s->s_seq++;

	if (s->s_state == CEPH_MDS_SESSION_CLOSING) {
		int ret;

		doutc(cl, "resending session close request for mds%d\n", s->s_mds);
		ret = request_close_session(s);
		if (ret < 0)
			pr_err_client(cl, "unable to close session to mds%d: %d\n",
				      s->s_mds, ret);
	}
}

/*
 * delayed work -- periodically trim expired leases, renew caps with mds.  If
 * the @delay parameter is set to 0 or if it's more than 5 secs, the default
 * workqueue delay value of 5 secs will be used.
 */
static void schedule_delayed(struct ceph_mds_client *mdsc, unsigned long delay)
{
	unsigned long max_delay = HZ * 5;

	/* 5 secs default delay */
	if (!delay || (delay > max_delay))
		delay = max_delay;
	schedule_delayed_work(&mdsc->delayed_work,
			      round_jiffies_relative(delay));
}

static void delayed_work(struct work_struct *work)
{
	struct ceph_mds_client *mdsc =
		container_of(work, struct ceph_mds_client, delayed_work.work);
	unsigned long delay;
	int renew_interval;
	int renew_caps;
	int i;

	doutc(mdsc->fsc->client, "mdsc delayed_work\n");

	if (mdsc->stopping >= CEPH_MDSC_STOPPING_FLUSHED)
		return;

	mutex_lock(&mdsc->mutex);
	renew_interval = mdsc->mdsmap->m_session_timeout >> 2;
	renew_caps = time_after_eq(jiffies, HZ*renew_interval +
				   mdsc->last_renew_caps);
	if (renew_caps)
		mdsc->last_renew_caps = jiffies;

	for (i = 0; i < mdsc->max_sessions; i++) {
		struct ceph_mds_session *s = __ceph_lookup_mds_session(mdsc, i);
		if (!s)
			continue;

		if (!check_session_state(s)) {
			ceph_put_mds_session(s);
			continue;
		}
		mutex_unlock(&mdsc->mutex);

		ceph_flush_session_cap_releases(mdsc, s);

		mutex_lock(&s->s_mutex);
		if (renew_caps)
			send_renew_caps(mdsc, s);
		else
			ceph_con_keepalive(&s->s_con);
		if (s->s_state == CEPH_MDS_SESSION_OPEN ||
		    s->s_state == CEPH_MDS_SESSION_HUNG)
			ceph_send_cap_releases(mdsc, s);
		mutex_unlock(&s->s_mutex);
		ceph_put_mds_session(s);

		mutex_lock(&mdsc->mutex);
	}
	mutex_unlock(&mdsc->mutex);

	delay = ceph_check_delayed_caps(mdsc);

	ceph_queue_cap_reclaim_work(mdsc);

	ceph_trim_snapid_map(mdsc);

	maybe_recover_session(mdsc);

	schedule_delayed(mdsc, delay);
}

int ceph_mdsc_init(struct ceph_fs_client *fsc)

{
	struct ceph_mds_client *mdsc;
	int err;

	mdsc = kzalloc_obj(struct ceph_mds_client, GFP_NOFS);
	if (!mdsc)
		return -ENOMEM;
	mdsc->fsc = fsc;
	mutex_init(&mdsc->mutex);
	mdsc->mdsmap = kzalloc_obj(*mdsc->mdsmap, GFP_NOFS);
	if (!mdsc->mdsmap) {
		err = -ENOMEM;
		goto err_mdsc;
	}

	init_completion(&mdsc->safe_umount_waiters);
	spin_lock_init(&mdsc->stopping_lock);
	atomic_set(&mdsc->stopping_blockers, 0);
	init_completion(&mdsc->stopping_waiter);
	atomic64_set(&mdsc->dirty_folios, 0);
	init_waitqueue_head(&mdsc->flush_end_wq);
	init_waitqueue_head(&mdsc->session_close_wq);
	INIT_LIST_HEAD(&mdsc->waiting_for_map);
	mdsc->quotarealms_inodes = RB_ROOT;
	mutex_init(&mdsc->quotarealms_inodes_mutex);
	init_rwsem(&mdsc->snap_rwsem);
	mdsc->snap_realms = RB_ROOT;
	INIT_LIST_HEAD(&mdsc->snap_empty);
	spin_lock_init(&mdsc->snap_empty_lock);
	mdsc->request_tree = RB_ROOT;
	INIT_DELAYED_WORK(&mdsc->delayed_work, delayed_work);
	mdsc->last_renew_caps = jiffies;
	INIT_LIST_HEAD(&mdsc->cap_delay_list);
#ifdef CONFIG_DEBUG_FS
	INIT_LIST_HEAD(&mdsc->cap_wait_list);
#endif
	spin_lock_init(&mdsc->cap_delay_lock);
	INIT_LIST_HEAD(&mdsc->cap_unlink_delay_list);
	INIT_LIST_HEAD(&mdsc->snap_flush_list);
	spin_lock_init(&mdsc->snap_flush_lock);
	mdsc->last_cap_flush_tid = 1;
	INIT_LIST_HEAD(&mdsc->cap_flush_list);
	INIT_LIST_HEAD(&mdsc->cap_dirty_migrating);
	spin_lock_init(&mdsc->cap_dirty_lock);
	init_waitqueue_head(&mdsc->cap_flushing_wq);
	INIT_WORK(&mdsc->cap_reclaim_work, ceph_cap_reclaim_work);
	INIT_WORK(&mdsc->cap_unlink_work, ceph_cap_unlink_work);
	err = ceph_metric_init(&mdsc->metric);
	if (err)
		goto err_mdsmap;
	ceph_subvolume_metrics_init(&mdsc->subvol_metrics);
	mutex_init(&mdsc->subvol_metrics_last_mutex);
	mdsc->subvol_metrics_last = NULL;
	mdsc->subvol_metrics_last_nr = 0;
	mdsc->subvol_metrics_sent = 0;
	mdsc->subvol_metrics_nonzero_sends = 0;

	spin_lock_init(&mdsc->dentry_list_lock);
	INIT_LIST_HEAD(&mdsc->dentry_leases);
	INIT_LIST_HEAD(&mdsc->dentry_dir_leases);

	spin_lock_init(&mdsc->reset_state.lock);
	init_waitqueue_head(&mdsc->reset_state.blocked_wq);
	atomic_set(&mdsc->reset_state.blocked_requests, 0);
	INIT_WORK(&mdsc->reset_work, ceph_mdsc_reset_workfn);

	ceph_caps_init(mdsc);
	ceph_adjust_caps_max_min(mdsc, fsc->mount_options);

	spin_lock_init(&mdsc->snapid_map_lock);
	mdsc->snapid_map_tree = RB_ROOT;
	INIT_LIST_HEAD(&mdsc->snapid_map_lru);

	init_rwsem(&mdsc->pool_perm_rwsem);
	mdsc->pool_perm_tree = RB_ROOT;

	strscpy(mdsc->nodename, utsname()->nodename,
		sizeof(mdsc->nodename));

	fsc->mdsc = mdsc;
	return 0;

err_mdsmap:
	kfree(mdsc->mdsmap);
err_mdsc:
	kfree(mdsc);
	return err;
}

/*
 * Wait for safe replies on open mds requests.  If we time out, drop
 * all requests from the tree to avoid dangling dentry refs.
 */
static void wait_requests(struct ceph_mds_client *mdsc)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_options *opts = mdsc->fsc->client->options;
	struct ceph_mds_request *req;

	mutex_lock(&mdsc->mutex);
	if (__get_oldest_req(mdsc)) {
		mutex_unlock(&mdsc->mutex);

		doutc(cl, "waiting for requests\n");
		wait_for_completion_timeout(&mdsc->safe_umount_waiters,
				    ceph_timeout_jiffies(opts->mount_timeout));

		/* tear down remaining requests */
		mutex_lock(&mdsc->mutex);
		while ((req = __get_oldest_req(mdsc))) {
			doutc(cl, "timed out on tid %llu\n", req->r_tid);
			list_del_init(&req->r_wait);
			__unregister_request(mdsc, req);
		}
	}
	mutex_unlock(&mdsc->mutex);
	doutc(cl, "done\n");
}

void send_flush_mdlog(struct ceph_mds_session *s)
{
	struct ceph_client *cl = s->s_mdsc->fsc->client;
	struct ceph_msg *msg;

	/*
	 * Pre-luminous MDS crashes when it sees an unknown session request
	 */
	if (!CEPH_HAVE_FEATURE(s->s_con.peer_features, SERVER_LUMINOUS))
		return;

	mutex_lock(&s->s_mutex);
	doutc(cl, "request mdlog flush to mds%d (%s)s seq %lld\n",
	      s->s_mds, ceph_session_state_name(s->s_state), s->s_seq);
	msg = ceph_create_session_msg(CEPH_SESSION_REQUEST_FLUSH_MDLOG,
				      s->s_seq);
	if (!msg) {
		pr_err_client(cl, "failed to request mdlog flush to mds%d (%s) seq %lld\n",
			      s->s_mds, ceph_session_state_name(s->s_state), s->s_seq);
	} else {
		ceph_con_send(&s->s_con, msg);
	}
	mutex_unlock(&s->s_mutex);
}

static int ceph_mds_auth_match(struct ceph_mds_client *mdsc,
			       struct ceph_mds_cap_auth *auth,
			       const struct cred *cred,
			       char *tpath)
{
	u32 caller_uid = from_kuid(&init_user_ns, cred->fsuid);
	u32 caller_gid = from_kgid(&init_user_ns, cred->fsgid);
	struct ceph_client *cl = mdsc->fsc->client;
	const char *fs_name = mdsc->mdsmap->m_fs_name;
	const char *spath = mdsc->fsc->mount_options->server_path;
	bool gid_matched = false;
	u32 gid, tlen, len;
	int i, j;

	doutc(cl, "fsname check fs_name=%s  match.fs_name=%s\n",
	      fs_name, auth->match.fs_name ? auth->match.fs_name : "");

	if (!ceph_namespace_match(auth->match.fs_name, fs_name)) {
		/* fsname mismatch, try next one */
		return 0;
	}

	doutc(cl, "match.uid %lld\n", auth->match.uid);
	if (auth->match.uid != MDS_AUTH_UID_ANY) {
		if (auth->match.uid != caller_uid)
			return 0;
		if (auth->match.num_gids) {
			for (i = 0; i < auth->match.num_gids; i++) {
				if (caller_gid == auth->match.gids[i])
					gid_matched = true;
			}
			if (!gid_matched && cred->group_info->ngroups) {
				for (i = 0; i < cred->group_info->ngroups; i++) {
					gid = from_kgid(&init_user_ns,
							cred->group_info->gid[i]);
					for (j = 0; j < auth->match.num_gids; j++) {
						if (gid == auth->match.gids[j]) {
							gid_matched = true;
							break;
						}
					}
					if (gid_matched)
						break;
				}
			}
			if (!gid_matched)
				return 0;
		}
	}

	/* path match */
	if (auth->match.path) {
		if (!tpath)
			return 0;

		tlen = strlen(tpath);
		len = strlen(auth->match.path);
		if (len) {
			char *_tpath = tpath;
			bool free_tpath = false;
			int m, n;

			doutc(cl, "server path %s, tpath %s, match.path %s\n",
			      spath, tpath, auth->match.path);
			if (spath && (m = strlen(spath)) != 1) {
				/* mount path + '/' + tpath + an extra space */
				n = m + 1 + tlen + 1;
				_tpath = kmalloc(n, GFP_NOFS);
				if (!_tpath)
					return -ENOMEM;
				/* remove the leading '/' */
				snprintf(_tpath, n, "%s/%s", spath + 1, tpath);
				free_tpath = true;
				tlen = strlen(_tpath);
			}

			/*
			 * Please note the tailing '/' for match.path has already
			 * been removed when parsing.
			 *
			 * Remove the tailing '/' for the target path.
			 */
			while (tlen && _tpath[tlen - 1] == '/') {
				_tpath[tlen - 1] = '\0';
				tlen -= 1;
			}
			doutc(cl, "_tpath %s\n", _tpath);

			/*
			 * In case first == _tpath && tlen == len:
			 *  match.path=/foo  --> /foo _path=/foo     --> match
			 *  match.path=/foo/ --> /foo _path=/foo     --> match
			 *
			 * In case first == _tmatch.path && tlen > len:
			 *  match.path=/foo/ --> /foo _path=/foo/    --> match
			 *  match.path=/foo  --> /foo _path=/foo/    --> match
			 *  match.path=/foo/ --> /foo _path=/foo/d   --> match
			 *  match.path=/foo  --> /foo _path=/food    --> mismatch
			 *
			 * All the other cases                       --> mismatch
			 */
			bool path_matched = true;
			char *first = strstr(_tpath, auth->match.path);
			if (first != _tpath ||
			    (tlen > len && _tpath[len] != '/')) {
				path_matched = false;
			}

			if (free_tpath)
				kfree(_tpath);

			if (!path_matched)
				return 0;
		}
	}

	doutc(cl, "matched\n");
	return 1;
}

int ceph_mds_check_access(struct ceph_mds_client *mdsc, char *tpath, int mask)
{
	const struct cred *cred = get_current_cred();
	u32 caller_uid = from_kuid(&init_user_ns, cred->fsuid);
	u32 caller_gid = from_kgid(&init_user_ns, cred->fsgid);
	struct ceph_mds_cap_auth *rw_perms_s = NULL;
	struct ceph_client *cl = mdsc->fsc->client;
	bool root_squash_perms = true;
	int i, err;

	doutc(cl, "tpath '%s', mask %d, caller_uid %d, caller_gid %d\n",
	      tpath, mask, caller_uid, caller_gid);

	mutex_lock(&mdsc->mutex);
	for (i = 0; i < mdsc->s_cap_auths_num; i++) {
		struct ceph_mds_cap_auth *s = &mdsc->s_cap_auths[i];

		err = ceph_mds_auth_match(mdsc, s, cred, tpath);
		if (err < 0) {
			mutex_unlock(&mdsc->mutex);
			put_cred(cred);
			return err;
		} else if (err > 0) {
			/* always follow the last auth caps' permission */
			root_squash_perms = true;
			rw_perms_s = NULL;
			if ((mask & MAY_WRITE) && s->writeable &&
			    s->match.root_squash && (!caller_uid || !caller_gid))
				root_squash_perms = false;

			if (((mask & MAY_WRITE) && !s->writeable) ||
			    ((mask & MAY_READ) && !s->readable))
				rw_perms_s = s;
		}
	}

	put_cred(cred);

	doutc(cl, "root_squash_perms %d, rw_perms_s %p\n", root_squash_perms,
	      rw_perms_s);
	if (root_squash_perms && rw_perms_s == NULL) {
		mutex_unlock(&mdsc->mutex);
		doutc(cl, "access allowed\n");
		return 0;
	}

	if (!root_squash_perms) {
		doutc(cl, "root_squash is enabled and user(%d %d) isn't allowed to write",
		      caller_uid, caller_gid);
	}
	if (rw_perms_s) {
		doutc(cl, "mds auth caps readable/writeable %d/%d while request r/w %d/%d",
		      rw_perms_s->readable, rw_perms_s->writeable,
		      !!(mask & MAY_READ), !!(mask & MAY_WRITE));
	}
	doutc(cl, "access denied\n");
	mutex_unlock(&mdsc->mutex);
	return -EACCES;
}

/*
 * called before mount is ro, and before dentries are torn down.
 * (hmm, does this still race with new lookups?)
 */
void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc)
{
	doutc(mdsc->fsc->client, "begin\n");
	mdsc->stopping = CEPH_MDSC_STOPPING_BEGIN;

	ceph_mdsc_iterate_sessions(mdsc, send_flush_mdlog, true);
	ceph_mdsc_iterate_sessions(mdsc, lock_unlock_session, false);
	ceph_flush_dirty_caps(mdsc);
	wait_requests(mdsc);

	/*
	 * wait for reply handlers to drop their request refs and
	 * their inode/dcache refs
	 */
	ceph_msgr_flush();

	ceph_cleanup_quotarealms_inodes(mdsc);
	doutc(mdsc->fsc->client, "done\n");
}

/*
 * flush the mdlog and wait for all write mds requests to flush.
 */
static void flush_mdlog_and_wait_mdsc_unsafe_requests(struct ceph_mds_client *mdsc,
						 u64 want_tid)
{
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_request *req = NULL, *nextreq;
	struct ceph_mds_session *last_session = NULL;
	struct rb_node *n;

	mutex_lock(&mdsc->mutex);
	doutc(cl, "want %lld\n", want_tid);
restart:
	req = __get_oldest_req(mdsc);
	while (req && req->r_tid <= want_tid) {
		/* find next request */
		n = rb_next(&req->r_node);
		if (n)
			nextreq = rb_entry(n, struct ceph_mds_request, r_node);
		else
			nextreq = NULL;
		if (req->r_op != CEPH_MDS_OP_SETFILELOCK &&
		    (req->r_op & CEPH_MDS_OP_WRITE)) {
			struct ceph_mds_session *s = req->r_session;

			if (!s) {
				req = nextreq;
				continue;
			}

			/* write op */
			ceph_mdsc_get_request(req);
			if (nextreq)
				ceph_mdsc_get_request(nextreq);
			s = ceph_get_mds_session(s);
			mutex_unlock(&mdsc->mutex);

			/* send flush mdlog request to MDS */
			if (last_session != s) {
				send_flush_mdlog(s);
				ceph_put_mds_session(last_session);
				last_session = s;
			} else {
				ceph_put_mds_session(s);
			}
			doutc(cl, "wait on %llu (want %llu)\n",
			      req->r_tid, want_tid);
			wait_for_completion(&req->r_safe_completion);

			mutex_lock(&mdsc->mutex);
			ceph_mdsc_put_request(req);
			if (!nextreq)
				break;  /* next dne before, so we're done! */
			if (RB_EMPTY_NODE(&nextreq->r_node)) {
				/* next request was removed from tree */
				ceph_mdsc_put_request(nextreq);
				goto restart;
			}
			ceph_mdsc_put_request(nextreq);  /* won't go away */
		}
		req = nextreq;
	}
	mutex_unlock(&mdsc->mutex);
	ceph_put_mds_session(last_session);
	doutc(cl, "done\n");
}

void ceph_mdsc_sync(struct ceph_mds_client *mdsc)
{
	struct ceph_client *cl = mdsc->fsc->client;
	u64 want_tid, want_flush;

	if (READ_ONCE(mdsc->fsc->mount_state) >= CEPH_MOUNT_SHUTDOWN)
		return;

	doutc(cl, "sync\n");
	mutex_lock(&mdsc->mutex);
	want_tid = mdsc->last_tid;
	mutex_unlock(&mdsc->mutex);

	ceph_flush_dirty_caps(mdsc);
	ceph_flush_cap_releases(mdsc);
	spin_lock(&mdsc->cap_dirty_lock);
	want_flush = mdsc->last_cap_flush_tid;
	if (!list_empty(&mdsc->cap_flush_list)) {
		struct ceph_cap_flush *cf =
			list_last_entry(&mdsc->cap_flush_list,
					struct ceph_cap_flush, g_list);
		cf->wake = true;
	}
	spin_unlock(&mdsc->cap_dirty_lock);

	doutc(cl, "sync want tid %lld flush_seq %lld\n", want_tid, want_flush);

	flush_mdlog_and_wait_mdsc_unsafe_requests(mdsc, want_tid);
	wait_caps_flush(mdsc, want_flush);
}

/*
 * true if all sessions are closed, or we force unmount
 */
static bool done_closing_sessions(struct ceph_mds_client *mdsc, int skipped)
{
	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_SHUTDOWN)
		return true;
	return atomic_read(&mdsc->num_sessions) <= skipped;
}

/*
 * called after sb is ro or when metadata corrupted.
 */
void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
{
	struct ceph_options *opts = mdsc->fsc->client->options;
	struct ceph_client *cl = mdsc->fsc->client;
	struct ceph_mds_session *session;
	int i;
	int skipped = 0;

	doutc(cl, "begin\n");

	/* close sessions */
	mutex_lock(&mdsc->mutex);
	for (i = 0; i < mdsc->max_sessions; i++) {
		session = __ceph_lookup_mds_session(mdsc, i);
		if (!session)
			continue;
		mutex_unlock(&mdsc->mutex);
		mutex_lock(&session->s_mutex);
		if (__close_session(mdsc, session) <= 0)
			skipped++;
		mutex_unlock(&session->s_mutex);
		ceph_put_mds_session(session);
		mutex_lock(&mdsc->mutex);
	}
	mutex_unlock(&mdsc->mutex);

	doutc(cl, "waiting for sessions to close\n");
	wait_event_timeout(mdsc->session_close_wq,
			   done_closing_sessions(mdsc, skipped),
			   ceph_timeout_jiffies(opts->mount_timeout));

	/* tear down remaining sessions */
	mutex_lock(&mdsc->mutex);
	for (i = 0; i < mdsc->max_sessions; i++) {
		if (mdsc->sessions[i]) {
			session = ceph_get_mds_session(mdsc->sessions[i]);
			__unregister_session(mdsc, session);
			mutex_unlock(&mdsc->mutex);
			mutex_lock(&session->s_mutex);
			remove_session_caps(session);
			mutex_unlock(&session->s_mutex);
			ceph_put_mds_session(session);
			mutex_lock(&mdsc->mutex);
		}
	}
	WARN_ON(!list_empty(&mdsc->cap_delay_list));
	mutex_unlock(&mdsc->mutex);

	ceph_cleanup_snapid_map(mdsc);
	ceph_cleanup_global_and_empty_realms(mdsc);

	cancel_work_sync(&mdsc->cap_reclaim_work);
	cancel_work_sync(&mdsc->cap_unlink_work);
	cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */

	doutc(cl, "done\n");
}

void ceph_mdsc_force_umount(struct ceph_mds_client *mdsc)
{
	struct ceph_mds_session *session;
	int mds;

	doutc(mdsc->fsc->client, "force umount\n");

	mutex_lock(&mdsc->mutex);
	for (mds = 0; mds < mdsc->max_sessions; mds++) {
		session = __ceph_lookup_mds_session(mdsc, mds);
		if (!session)
			continue;

		if (session->s_state == CEPH_MDS_SESSION_REJECTED)
			__unregister_session(mdsc, session);
		__wake_requests(mdsc, &session->s_waiting);
		mutex_unlock(&mdsc->mutex);

		mutex_lock(&session->s_mutex);
		__close_session(mdsc, session);
		if (session->s_state == CEPH_MDS_SESSION_CLOSING) {
			cleanup_session_requests(mdsc, session);
			remove_session_caps(session);
		}
		mutex_unlock(&session->s_mutex);
		ceph_put_mds_session(session);

		mutex_lock(&mdsc->mutex);
		kick_requests(mdsc, mds);
	}
	__wake_requests(mdsc, &mdsc->waiting_for_map);
	mutex_unlock(&mdsc->mutex);
}

static void ceph_mdsc_stop(struct ceph_mds_client *mdsc)
{
	doutc(mdsc->fsc->client, "stop\n");
	/*
	 * Make sure the delayed work stopped before releasing
	 * the resources.
	 *
	 * Because the cancel_delayed_work_sync() will only
	 * guarantee that the work finishes executing. But the
	 * delayed work will re-arm itself again after that.
	 */
	flush_delayed_work(&mdsc->delayed_work);

	if (mdsc->mdsmap)
		ceph_mdsmap_destroy(mdsc->mdsmap);
	kfree(mdsc->sessions);
	ceph_caps_finalize(mdsc);

	if (mdsc->s_cap_auths) {
		int i;

		for (i = 0; i < mdsc->s_cap_auths_num; i++) {
			kfree(mdsc->s_cap_auths[i].match.gids);
			kfree(mdsc->s_cap_auths[i].match.path);
			kfree(mdsc->s_cap_auths[i].match.fs_name);
		}
		kfree(mdsc->s_cap_auths);
	}

	ceph_pool_perm_destroy(mdsc);
}

void ceph_mdsc_destroy(struct ceph_fs_client *fsc)
{
	struct ceph_mds_client *mdsc = fsc->mdsc;
	doutc(fsc->client, "%p\n", mdsc);

	if (!mdsc)
		return;

	/* flush out any connection work with references to us */
	ceph_msgr_flush();

	/*
	 * Mark reset as failed and wake any blocked waiters before
	 * cancelling, so unmount doesn't stall on blocked_wq timeout
	 * if cancel_work_sync() prevents the work from running.
	 */
	spin_lock(&mdsc->reset_state.lock);
	mdsc->reset_state.shutdown = true;
	if (mdsc->reset_state.phase != CEPH_CLIENT_RESET_IDLE) {
		mdsc->reset_state.phase = CEPH_CLIENT_RESET_IDLE;
		mdsc->reset_state.last_errno = -ESHUTDOWN;
		mdsc->reset_state.last_finish = jiffies;
		mdsc->reset_state.failure_count++;
	}
	spin_unlock(&mdsc->reset_state.lock);
	wake_up_all(&mdsc->reset_state.blocked_wq);

	cancel_work_sync(&mdsc->reset_work);
	ceph_mdsc_stop(mdsc);

	ceph_metric_destroy(&mdsc->metric);
	ceph_subvolume_metrics_destroy(&mdsc->subvol_metrics);
	kfree(mdsc->subvol_metrics_last);

	fsc->mdsc = NULL;
	kfree(mdsc);
	doutc(fsc->client, "%p done\n", mdsc);
}

void ceph_mdsc_handle_fsmap(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
{
	struct ceph_fs_client *fsc = mdsc->fsc;
	struct ceph_client *cl = fsc->client;
	const char *mds_namespace = fsc->mount_options->mds_namespace;
	void *p = msg->front.iov_base;
	void *end = p + msg->front.iov_len;
	u32 epoch;
	u32 num_fs;
	u32 mount_fscid = (u32)-1;
	int err = -EINVAL;

	ceph_decode_need(&p, end, sizeof(u32), bad);
	epoch = ceph_decode_32(&p);

	doutc(cl, "epoch %u\n", epoch);

	/* struct_v, struct_cv, map_len, epoch, legacy_client_fscid */
	ceph_decode_skip_n(&p, end, 2 + sizeof(u32) * 3, bad);

	ceph_decode_32_safe(&p, end, num_fs, bad);
	while (num_fs-- > 0) {
		void *info_p, *info_end;
		u32 info_len;
		u32 fscid, namelen;

		ceph_decode_need(&p, end, 2 + sizeof(u32), bad);
		p += 2;		// info_v, info_cv
		info_len = ceph_decode_32(&p);
		ceph_decode_need(&p, end, info_len, bad);
		info_p = p;
		info_end = p + info_len;
		p = info_end;

		ceph_decode_need(&info_p, info_end, sizeof(u32) * 2, bad);
		fscid = ceph_decode_32(&info_p);
		namelen = ceph_decode_32(&info_p);
		ceph_decode_need(&info_p, info_end, namelen, bad);

		if (mds_namespace &&
		    strlen(mds_namespace) == namelen &&
		    !strncmp(mds_namespace, (char *)info_p, namelen)) {
			mount_fscid = fscid;
			break;
		}
	}

	ceph_monc_got_map(&fsc->client->monc, CEPH_SUB_FSMAP, epoch);
	if (mount_fscid != (u32)-1) {
		fsc->client->monc.fs_cluster_id = mount_fscid;
		ceph_monc_want_map(&fsc->client->monc, CEPH_SUB_MDSMAP,
				   0, true);
		ceph_monc_renew_subs(&fsc->client->monc);
	} else {
		err = -ENOENT;
		goto err_out;
	}
	return;

bad:
	pr_err_client(cl, "error decoding fsmap %d. Shutting down mount.\n",
		      err);
	ceph_umount_begin(mdsc->fsc->sb);
	ceph_msg_dump(msg);
err_out:
	mutex_lock(&mdsc->mutex);
	mdsc->mdsmap_err = err;
	__wake_requests(mdsc, &mdsc->waiting_for_map);
	mutex_unlock(&mdsc->mutex);
}

/*
 * handle mds map update.
 */
void ceph_mdsc_handle_mdsmap(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
{
	struct ceph_client *cl = mdsc->fsc->client;
	u32 epoch;
	u32 maplen;
	void *p = msg->front.iov_base;
	void *end = p + msg->front.iov_len;
	struct ceph_mdsmap *newmap, *oldmap;
	struct ceph_fsid fsid;
	int err = -EINVAL;

	ceph_decode_need(&p, end, sizeof(fsid)+2*sizeof(u32), bad);
	ceph_decode_copy(&p, &fsid, sizeof(fsid));
	if (ceph_check_fsid(mdsc->fsc->client, &fsid) < 0)
		return;
	epoch = ceph_decode_32(&p);
	maplen = ceph_decode_32(&p);
	doutc(cl, "epoch %u len %d\n", epoch, (int)maplen);

	/* do we need it? */
	mutex_lock(&mdsc->mutex);
	if (mdsc->mdsmap && epoch <= mdsc->mdsmap->m_epoch) {
		doutc(cl, "epoch %u <= our %u\n", epoch, mdsc->mdsmap->m_epoch);
		mutex_unlock(&mdsc->mutex);
		return;
	}

	newmap = ceph_mdsmap_decode(mdsc, &p, end, ceph_msgr2(mdsc->fsc->client));
	if (IS_ERR(newmap)) {
		err = PTR_ERR(newmap);
		goto bad_unlock;
	}

	/* swap into place */
	if (mdsc->mdsmap) {
		oldmap = mdsc->mdsmap;
		mdsc->mdsmap = newmap;
		check_new_map(mdsc, newmap, oldmap);
		ceph_mdsmap_destroy(oldmap);
	} else {
		mdsc->mdsmap = newmap;  /* first mds map */
	}
	mdsc->fsc->max_file_size = min((loff_t)mdsc->mdsmap->m_max_file_size,
					MAX_LFS_FILESIZE);

	__wake_requests(mdsc, &mdsc->waiting_for_map);
	ceph_monc_got_map(&mdsc->fsc->client->monc, CEPH_SUB_MDSMAP,
			  mdsc->mdsmap->m_epoch);

	mutex_unlock(&mdsc->mutex);
	schedule_delayed(mdsc, 0);
	return;

bad_unlock:
	mutex_unlock(&mdsc->mutex);
bad:
	pr_err_client(cl, "error decoding mdsmap %d. Shutting down mount.\n",
		      err);
	ceph_umount_begin(mdsc->fsc->sb);
	ceph_msg_dump(msg);
	return;
}

static struct ceph_connection *mds_get_con(struct ceph_connection *con)
{
	struct ceph_mds_session *s = con->private;

	if (ceph_get_mds_session(s))
		return con;
	return NULL;
}

static void mds_put_con(struct ceph_connection *con)
{
	struct ceph_mds_session *s = con->private;

	ceph_put_mds_session(s);
}

/*
 * if the client is unresponsive for long enough, the mds will kill
 * the session entirely.
 */
static void mds_peer_reset(struct ceph_connection *con)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_mds_client *mdsc = s->s_mdsc;
	int session_state;

	pr_warn_client(mdsc->fsc->client, "mds%d closed our session\n",
		       s->s_mds);

	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_FENCE_IO ||
	    ceph_mdsmap_get_state(mdsc->mdsmap, s->s_mds) < CEPH_MDS_STATE_RECONNECT)
		return;

	/*
	 * Only reconnect if MDS is in its RECONNECT phase.  An MDS past
	 * RECONNECT (REJOIN, CLIENTREPLAY, ACTIVE) will reject reconnect
	 * attempts, so those states fall through to session teardown below.
	 */
	if (ceph_mdsmap_get_state(mdsc->mdsmap, s->s_mds) == CEPH_MDS_STATE_RECONNECT) {
		int rc = send_mds_reconnect(mdsc, s);

		if (rc)
			pr_warn_client(mdsc->fsc->client,
				       "mds%d reconnect failed: %d\n",
				       s->s_mds, rc);
		return;
	}

	/*
	 * MDS is active (past RECONNECT).  It will not accept a
	 * CLIENT_RECONNECT from us, so tear the session down locally
	 * and let new requests re-open a fresh session.
	 *
	 * Snapshot session state with READ_ONCE, then revalidate under
	 * mdsc->mutex before acting.  The subsequent mdsc->mutex
	 * section rechecks s_state to catch concurrent transitions, so
	 * the lockless snapshot here is safe.  s->s_mutex is taken
	 * separately for cleanup after unregistration, which avoids
	 * introducing a new s->s_mutex + mdsc->mutex nesting.
	 */
	session_state = READ_ONCE(s->s_state);

	switch (session_state) {
	case CEPH_MDS_SESSION_RESTARTING:
	case CEPH_MDS_SESSION_RECONNECTING:
	case CEPH_MDS_SESSION_CLOSING:
	case CEPH_MDS_SESSION_OPEN:
	case CEPH_MDS_SESSION_HUNG:
	case CEPH_MDS_SESSION_OPENING:
		mutex_lock(&mdsc->mutex);
		if (s->s_mds >= mdsc->max_sessions ||
		    mdsc->sessions[s->s_mds] != s ||
		    s->s_state != session_state) {
			pr_info_client(mdsc->fsc->client,
				       "mds%d state changed to %s during peer reset\n",
				       s->s_mds,
				       ceph_session_state_name(s->s_state));
			mutex_unlock(&mdsc->mutex);
			return;
		}

		ceph_get_mds_session(s);
		s->s_state = CEPH_MDS_SESSION_CLOSED;
		__unregister_session(mdsc, s);
		__wake_requests(mdsc, &s->s_waiting);
		mutex_unlock(&mdsc->mutex);

		mutex_lock(&s->s_mutex);
		cleanup_session_requests(mdsc, s);
		remove_session_caps(s);
		mutex_unlock(&s->s_mutex);

		wake_up_all(&mdsc->session_close_wq);

		mutex_lock(&mdsc->mutex);
		kick_requests(mdsc, s->s_mds);
		mutex_unlock(&mdsc->mutex);

		ceph_put_mds_session(s);
		break;
	case CEPH_MDS_SESSION_CLOSED:
	case CEPH_MDS_SESSION_REJECTED:
		break;
	default:
		pr_warn_client(mdsc->fsc->client,
			       "mds%d peer reset in unexpected state %s\n",
			       s->s_mds,
			       ceph_session_state_name(session_state));
		break;
	}
}

static void mds_dispatch(struct ceph_connection *con, struct ceph_msg *msg)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_mds_client *mdsc = s->s_mdsc;
	struct ceph_client *cl = mdsc->fsc->client;
	int type = le16_to_cpu(msg->hdr.type);

	mutex_lock(&mdsc->mutex);
	if (__verify_registered_session(mdsc, s) < 0) {
		doutc(cl, "dropping tid %llu from unregistered session %d\n",
		      le64_to_cpu(msg->hdr.tid), s->s_mds);
		mutex_unlock(&mdsc->mutex);
		goto out;
	}
	mutex_unlock(&mdsc->mutex);

	switch (type) {
	case CEPH_MSG_MDS_MAP:
		ceph_mdsc_handle_mdsmap(mdsc, msg);
		break;
	case CEPH_MSG_FS_MAP_USER:
		ceph_mdsc_handle_fsmap(mdsc, msg);
		break;
	case CEPH_MSG_CLIENT_SESSION:
		handle_session(s, msg);
		break;
	case CEPH_MSG_CLIENT_REPLY:
		handle_reply(s, msg);
		break;
	case CEPH_MSG_CLIENT_REQUEST_FORWARD:
		handle_forward(mdsc, s, msg);
		break;
	case CEPH_MSG_CLIENT_CAPS:
		ceph_handle_caps(s, msg);
		break;
	case CEPH_MSG_CLIENT_SNAP:
		ceph_handle_snap(mdsc, s, msg);
		break;
	case CEPH_MSG_CLIENT_LEASE:
		handle_lease(mdsc, s, msg);
		break;
	case CEPH_MSG_CLIENT_QUOTA:
		ceph_handle_quota(mdsc, s, msg);
		break;

	default:
		pr_err_client(cl, "received unknown message type %d %s\n",
			      type, ceph_msg_type_name(type));
	}
out:
	ceph_msg_put(msg);
}

/*
 * authentication
 */

/*
 * Note: returned pointer is the address of a structure that's
 * managed separately.  Caller must *not* attempt to free it.
 */
static struct ceph_auth_handshake *
mds_get_authorizer(struct ceph_connection *con, int *proto, int force_new)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_mds_client *mdsc = s->s_mdsc;
	struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
	struct ceph_auth_handshake *auth = &s->s_auth;
	int ret;

	ret = __ceph_auth_get_authorizer(ac, auth, CEPH_ENTITY_TYPE_MDS,
					 force_new, proto, NULL, NULL);
	if (ret)
		return ERR_PTR(ret);

	return auth;
}

static int mds_add_authorizer_challenge(struct ceph_connection *con,
				    void *challenge_buf, int challenge_buf_len)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_mds_client *mdsc = s->s_mdsc;
	struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;

	return ceph_auth_add_authorizer_challenge(ac, s->s_auth.authorizer,
					    challenge_buf, challenge_buf_len);
}

static int mds_verify_authorizer_reply(struct ceph_connection *con)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_mds_client *mdsc = s->s_mdsc;
	struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
	struct ceph_auth_handshake *auth = &s->s_auth;

	return ceph_auth_verify_authorizer_reply(ac, auth->authorizer,
		auth->authorizer_reply_buf, auth->authorizer_reply_buf_len,
		NULL, NULL, NULL, NULL);
}

static int mds_invalidate_authorizer(struct ceph_connection *con)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_mds_client *mdsc = s->s_mdsc;
	struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;

	ceph_auth_invalidate_authorizer(ac, CEPH_ENTITY_TYPE_MDS);

	return ceph_monc_validate_auth(&mdsc->fsc->client->monc);
}

static int mds_get_auth_request(struct ceph_connection *con,
				void *buf, int *buf_len,
				void **authorizer, int *authorizer_len)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_auth_client *ac = s->s_mdsc->fsc->client->monc.auth;
	struct ceph_auth_handshake *auth = &s->s_auth;
	int ret;

	ret = ceph_auth_get_authorizer(ac, auth, CEPH_ENTITY_TYPE_MDS,
				       buf, buf_len);
	if (ret)
		return ret;

	*authorizer = auth->authorizer_buf;
	*authorizer_len = auth->authorizer_buf_len;
	return 0;
}

static int mds_handle_auth_reply_more(struct ceph_connection *con,
				      void *reply, int reply_len,
				      void *buf, int *buf_len,
				      void **authorizer, int *authorizer_len)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_auth_client *ac = s->s_mdsc->fsc->client->monc.auth;
	struct ceph_auth_handshake *auth = &s->s_auth;
	int ret;

	ret = ceph_auth_handle_svc_reply_more(ac, auth, reply, reply_len,
					      buf, buf_len);
	if (ret)
		return ret;

	*authorizer = auth->authorizer_buf;
	*authorizer_len = auth->authorizer_buf_len;
	return 0;
}

static int mds_handle_auth_done(struct ceph_connection *con,
				u64 global_id, void *reply, int reply_len,
				u8 *session_key, int *session_key_len,
				u8 *con_secret, int *con_secret_len)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_auth_client *ac = s->s_mdsc->fsc->client->monc.auth;
	struct ceph_auth_handshake *auth = &s->s_auth;

	return ceph_auth_handle_svc_reply_done(ac, auth, reply, reply_len,
					       session_key, session_key_len,
					       con_secret, con_secret_len);
}

static int mds_handle_auth_bad_method(struct ceph_connection *con,
				      int used_proto, int result,
				      const int *allowed_protos, int proto_cnt,
				      const int *allowed_modes, int mode_cnt)
{
	struct ceph_mds_session *s = con->private;
	struct ceph_mon_client *monc = &s->s_mdsc->fsc->client->monc;
	int ret;

	if (ceph_auth_handle_bad_authorizer(monc->auth, CEPH_ENTITY_TYPE_MDS,
					    used_proto, result,
					    allowed_protos, proto_cnt,
					    allowed_modes, mode_cnt)) {
		ret = ceph_monc_validate_auth(monc);
		if (ret)
			return ret;
	}

	return -EACCES;
}

static struct ceph_msg *mds_alloc_msg(struct ceph_connection *con,
				struct ceph_msg_header *hdr, int *skip)
{
	struct ceph_msg *msg;
	int type = (int) le16_to_cpu(hdr->type);
	int front_len = (int) le32_to_cpu(hdr->front_len);

	if (con->in_msg)
		return con->in_msg;

	*skip = 0;
	msg = ceph_msg_new(type, front_len, GFP_NOFS, false);
	if (!msg) {
		pr_err("unable to allocate msg type %d len %d\n",
		       type, front_len);
		return NULL;
	}

	return msg;
}

static int mds_sign_message(struct ceph_msg *msg)
{
       struct ceph_mds_session *s = msg->con->private;
       struct ceph_auth_handshake *auth = &s->s_auth;

       return ceph_auth_sign_message(auth, msg);
}

static int mds_check_message_signature(struct ceph_msg *msg)
{
       struct ceph_mds_session *s = msg->con->private;
       struct ceph_auth_handshake *auth = &s->s_auth;

       return ceph_auth_check_message_signature(auth, msg);
}

static const struct ceph_connection_operations mds_con_ops = {
	.get = mds_get_con,
	.put = mds_put_con,
	.alloc_msg = mds_alloc_msg,
	.dispatch = mds_dispatch,
	.peer_reset = mds_peer_reset,
	.get_authorizer = mds_get_authorizer,
	.add_authorizer_challenge = mds_add_authorizer_challenge,
	.verify_authorizer_reply = mds_verify_authorizer_reply,
	.invalidate_authorizer = mds_invalidate_authorizer,
	.sign_message = mds_sign_message,
	.check_message_signature = mds_check_message_signature,
	.get_auth_request = mds_get_auth_request,
	.handle_auth_reply_more = mds_handle_auth_reply_more,
	.handle_auth_done = mds_handle_auth_done,
	.handle_auth_bad_method = mds_handle_auth_bad_method,
};

/* eof */