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

#include <linux/backing-dev.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/pagevec.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/signal.h>
#include <linux/iversion.h>
#include <linux/ktime.h>
#include <linux/netfs.h>
#include <trace/events/netfs.h>

#include "super.h"
#include "mds_client.h"
#include "cache.h"
#include "metric.h"
#include "crypto.h"
#include <linux/ceph/osd_client.h>
#include <linux/ceph/striper.h>

/*
 * Ceph address space ops.
 *
 * There are a few funny things going on here.
 *
 * The page->private field is used to reference a struct
 * ceph_snap_context for _every_ dirty page.  This indicates which
 * snapshot the page was logically dirtied in, and thus which snap
 * context needs to be associated with the osd write during writeback.
 *
 * Similarly, struct ceph_inode_info maintains a set of counters to
 * count dirty pages on the inode.  In the absence of snapshots,
 * i_wrbuffer_ref == i_wrbuffer_ref_head == the dirty page count.
 *
 * When a snapshot is taken (that is, when the client receives
 * notification that a snapshot was taken), each inode with caps and
 * with dirty pages (dirty pages implies there is a cap) gets a new
 * ceph_cap_snap in the i_cap_snaps list (which is sorted in ascending
 * order, new snaps go to the tail).  The i_wrbuffer_ref_head count is
 * moved to capsnap->dirty. (Unless a sync write is currently in
 * progress.  In that case, the capsnap is said to be "pending", new
 * writes cannot start, and the capsnap isn't "finalized" until the
 * write completes (or fails) and a final size/mtime for the inode for
 * that snap can be settled upon.)  i_wrbuffer_ref_head is reset to 0.
 *
 * On writeback, we must submit writes to the osd IN SNAP ORDER.  So,
 * we look for the first capsnap in i_cap_snaps and write out pages in
 * that snap context _only_.  Then we move on to the next capsnap,
 * eventually reaching the "live" or "head" context (i.e., pages that
 * are not yet snapped) and are writing the most recently dirtied
 * pages.
 *
 * Invalidate and so forth must take care to ensure the dirty page
 * accounting is preserved.
 */

#define CONGESTION_ON_THRESH(congestion_kb) (congestion_kb >> (PAGE_SHIFT-10))
#define CONGESTION_OFF_THRESH(congestion_kb)				\
	(CONGESTION_ON_THRESH(congestion_kb) -				\
	 (CONGESTION_ON_THRESH(congestion_kb) >> 2))

static int ceph_netfs_check_write_begin(struct file *file, loff_t pos, unsigned int len,
					struct folio **foliop, void **_fsdata);

static inline struct ceph_snap_context *page_snap_context(struct page *page)
{
	if (PagePrivate(page))
		return (void *)page->private;
	return NULL;
}

/*
 * Dirty a page.  Optimistically adjust accounting, on the assumption
 * that we won't race with invalidate.  If we do, readjust.
 */
static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
{
	struct inode *inode = mapping->host;
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
	struct ceph_inode_info *ci;
	struct ceph_snap_context *snapc;

	if (folio_test_dirty(folio)) {
		doutc(cl, "%llx.%llx %p idx %lu -- already dirty\n",
		      ceph_vinop(inode), folio, folio->index);
		VM_BUG_ON_FOLIO(!folio_test_private(folio), folio);
		return false;
	}

	atomic64_inc(&mdsc->dirty_folios);

	ci = ceph_inode(inode);

	/* dirty the head */
	spin_lock(&ci->i_ceph_lock);
	if (__ceph_have_pending_cap_snap(ci)) {
		struct ceph_cap_snap *capsnap =
				list_last_entry(&ci->i_cap_snaps,
						struct ceph_cap_snap,
						ci_item);
		snapc = ceph_get_snap_context(capsnap->context);
		capsnap->dirty_pages++;
	} else {
		BUG_ON(!ci->i_head_snapc);
		snapc = ceph_get_snap_context(ci->i_head_snapc);
		++ci->i_wrbuffer_ref_head;
	}
	if (ci->i_wrbuffer_ref == 0)
		ihold(inode);
	++ci->i_wrbuffer_ref;
	doutc(cl, "%llx.%llx %p idx %lu head %d/%d -> %d/%d "
	      "snapc %p seq %lld (%d snaps)\n",
	      ceph_vinop(inode), folio, folio->index,
	      ci->i_wrbuffer_ref-1, ci->i_wrbuffer_ref_head-1,
	      ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
	      snapc, snapc->seq, snapc->num_snaps);
	spin_unlock(&ci->i_ceph_lock);

	/*
	 * Reference snap context in folio->private.  Also set
	 * PagePrivate so that we get invalidate_folio callback.
	 */
	VM_WARN_ON_FOLIO(folio->private, folio);
	folio_attach_private(folio, snapc);

	return ceph_fscache_dirty_folio(mapping, folio);
}

/*
 * If we are truncating the full folio (i.e. offset == 0), adjust the
 * dirty folio counters appropriately.  Only called if there is private
 * data on the folio.
 */
static void ceph_invalidate_folio(struct folio *folio, size_t offset,
				size_t length)
{
	struct inode *inode = folio->mapping->host;
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_snap_context *snapc;


	if (offset != 0 || length != folio_size(folio)) {
		doutc(cl, "%llx.%llx idx %lu partial dirty page %zu~%zu\n",
		      ceph_vinop(inode), folio->index, offset, length);
		return;
	}

	WARN_ON(!folio_test_locked(folio));
	if (folio_test_private(folio)) {
		doutc(cl, "%llx.%llx idx %lu full dirty page\n",
		      ceph_vinop(inode), folio->index);

		snapc = folio_detach_private(folio);
		ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
		ceph_put_snap_context(snapc);
	}

	netfs_invalidate_folio(folio, offset, length);
}

static void ceph_netfs_expand_readahead(struct netfs_io_request *rreq)
{
	struct inode *inode = rreq->inode;
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_file_layout *lo = &ci->i_layout;
	unsigned long max_pages = inode->i_sb->s_bdi->ra_pages;
	loff_t end = rreq->start + rreq->len, new_end;
	struct ceph_netfs_request_data *priv = rreq->netfs_priv;
	unsigned long max_len;
	u32 blockoff;

	if (priv) {
		/* Readahead is disabled by posix_fadvise POSIX_FADV_RANDOM */
		if (priv->file_ra_disabled)
			max_pages = 0;
		else
			max_pages = priv->file_ra_pages;

	}

	/* Readahead is disabled */
	if (!max_pages)
		return;

	max_len = max_pages << PAGE_SHIFT;

	/*
	 * Try to expand the length forward by rounding up it to the next
	 * block, but do not exceed the file size, unless the original
	 * request already exceeds it.
	 */
	new_end = umin(round_up(end, lo->stripe_unit), rreq->i_size);
	if (new_end > end && new_end <= rreq->start + max_len)
		rreq->len = new_end - rreq->start;

	/* Try to expand the start downward */
	div_u64_rem(rreq->start, lo->stripe_unit, &blockoff);
	if (rreq->len + blockoff <= max_len) {
		rreq->start -= blockoff;
		rreq->len += blockoff;
	}
}

static void finish_netfs_read(struct ceph_osd_request *req)
{
	struct inode *inode = req->r_inode;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct ceph_osd_data *osd_data = osd_req_op_extent_osd_data(req, 0);
	struct netfs_io_subrequest *subreq = req->r_priv;
	struct ceph_osd_req_op *op = &req->r_ops[0];
	int err = req->r_result;
	bool sparse = (op->op == CEPH_OSD_OP_SPARSE_READ);

	ceph_update_read_metrics(&fsc->mdsc->metric, req->r_start_latency,
				 req->r_end_latency, osd_data->length, err);

	doutc(cl, "result %d subreq->len=%zu i_size=%lld\n", req->r_result,
	      subreq->len, i_size_read(req->r_inode));

	/* no object means success but no data */
	if (err == -ENOENT) {
		__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
		__set_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags);
		err = 0;
	} else if (err == -EBLOCKLISTED) {
		fsc->blocklisted = true;
	}

	if (err >= 0) {
		if (sparse && err > 0)
			err = ceph_sparse_ext_map_end(op);
		if (err < subreq->len &&
		    subreq->rreq->origin != NETFS_UNBUFFERED_READ &&
		    subreq->rreq->origin != NETFS_DIO_READ)
			__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
		if (IS_ENCRYPTED(inode) && err > 0) {
			err = ceph_fscrypt_decrypt_extents(inode,
					osd_data->pages, subreq->start,
					op->extent.sparse_ext,
					op->extent.sparse_ext_cnt);
			if (err > subreq->len)
				err = subreq->len;
		}
		if (err > 0)
			__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
	}

	if (osd_data->type == CEPH_OSD_DATA_TYPE_PAGES) {
		ceph_put_page_vector(osd_data->pages,
				     calc_pages_for(osd_data->alignment,
					osd_data->length), false);
	}
	if (err > 0) {
		subreq->transferred = err;
		err = 0;
	}
	subreq->error = err;
	trace_netfs_sreq(subreq, netfs_sreq_trace_io_progress);
	netfs_read_subreq_terminated(subreq);
	iput(req->r_inode);
	ceph_dec_osd_stopping_blocker(fsc->mdsc);
}

static bool ceph_netfs_issue_op_inline(struct netfs_io_subrequest *subreq)
{
	struct netfs_io_request *rreq = subreq->rreq;
	struct inode *inode = rreq->inode;
	struct ceph_mds_reply_info_parsed *rinfo;
	struct ceph_mds_reply_info_in *iinfo;
	struct ceph_mds_request *req;
	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
	struct ceph_inode_info *ci = ceph_inode(inode);
	ssize_t err = 0;
	size_t len;
	int mode;

	if (rreq->origin != NETFS_UNBUFFERED_READ &&
	    rreq->origin != NETFS_DIO_READ)
		__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
	__clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);

	if (subreq->start >= inode->i_size)
		goto out;

	/* We need to fetch the inline data. */
	mode = ceph_try_to_choose_auth_mds(inode, CEPH_STAT_CAP_INLINE_DATA);
	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_GETATTR, mode);
	if (IS_ERR(req)) {
		err = PTR_ERR(req);
		goto out;
	}
	req->r_ino1 = ci->i_vino;
	req->r_args.getattr.mask = cpu_to_le32(CEPH_STAT_CAP_INLINE_DATA);
	req->r_num_caps = 2;

	trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
	err = ceph_mdsc_do_request(mdsc, NULL, req);
	if (err < 0)
		goto out;

	rinfo = &req->r_reply_info;
	iinfo = &rinfo->targeti;
	if (iinfo->inline_version == CEPH_INLINE_NONE) {
		/* The data got uninlined */
		ceph_mdsc_put_request(req);
		return false;
	}

	len = min_t(size_t, iinfo->inline_len - subreq->start, subreq->len);
	err = copy_to_iter(iinfo->inline_data + subreq->start, len, &subreq->io_iter);
	if (err == 0) {
		err = -EFAULT;
	} else {
		subreq->transferred += err;
		err = 0;
	}

	ceph_mdsc_put_request(req);
out:
	subreq->error = err;
	trace_netfs_sreq(subreq, netfs_sreq_trace_io_progress);
	netfs_read_subreq_terminated(subreq);
	return true;
}

static int ceph_netfs_prepare_read(struct netfs_io_subrequest *subreq)
{
	struct netfs_io_request *rreq = subreq->rreq;
	struct inode *inode = rreq->inode;
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	u64 objno, objoff;
	u32 xlen;

	/* Truncate the extent at the end of the current block */
	ceph_calc_file_object_mapping(&ci->i_layout, subreq->start, subreq->len,
				      &objno, &objoff, &xlen);
	rreq->io_streams[0].sreq_max_len = umin(xlen, fsc->mount_options->rsize);
	return 0;
}

static void ceph_netfs_issue_read(struct netfs_io_subrequest *subreq)
{
	struct netfs_io_request *rreq = subreq->rreq;
	struct inode *inode = rreq->inode;
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct ceph_osd_request *req = NULL;
	struct ceph_vino vino = ceph_vino(inode);
	int err;
	u64 len;
	bool sparse = IS_ENCRYPTED(inode) || ceph_test_mount_opt(fsc, SPARSEREAD);
	u64 off = subreq->start;
	int extent_cnt;

	if (ceph_inode_is_shutdown(inode)) {
		err = -EIO;
		goto out;
	}

	if (ceph_has_inline_data(ci) && ceph_netfs_issue_op_inline(subreq))
		return;

	// TODO: This rounding here is slightly dodgy.  It *should* work, for
	// now, as the cache only deals in blocks that are a multiple of
	// PAGE_SIZE and fscrypt blocks are at most PAGE_SIZE.  What needs to
	// happen is for the fscrypt driving to be moved into netfslib and the
	// data in the cache also to be stored encrypted.
	len = subreq->len;
	ceph_fscrypt_adjust_off_and_len(inode, &off, &len);

	req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout, vino,
			off, &len, 0, 1, sparse ? CEPH_OSD_OP_SPARSE_READ : CEPH_OSD_OP_READ,
			CEPH_OSD_FLAG_READ, NULL, ci->i_truncate_seq,
			ci->i_truncate_size, false);
	if (IS_ERR(req)) {
		err = PTR_ERR(req);
		req = NULL;
		goto out;
	}

	if (sparse) {
		extent_cnt = __ceph_sparse_read_ext_count(inode, len);
		err = ceph_alloc_sparse_ext_map(&req->r_ops[0], extent_cnt);
		if (err)
			goto out;
	}

	doutc(cl, "%llx.%llx pos=%llu orig_len=%zu len=%llu\n",
	      ceph_vinop(inode), subreq->start, subreq->len, len);

	/*
	 * FIXME: For now, use CEPH_OSD_DATA_TYPE_PAGES instead of _ITER for
	 * encrypted inodes. We'd need infrastructure that handles an iov_iter
	 * instead of page arrays, and we don't have that as of yet. Once the
	 * dust settles on the write helpers and encrypt/decrypt routines for
	 * netfs, we should be able to rework this.
	 */
	if (IS_ENCRYPTED(inode)) {
		struct page **pages;
		size_t page_off;

		/*
		 * FIXME: io_iter.count needs to be corrected to aligned
		 * length. Otherwise, iov_iter_get_pages_alloc2() operates
		 * with the initial unaligned length value. As a result,
		 * ceph_msg_data_cursor_init() triggers BUG_ON() in the case
		 * if msg->sparse_read_total > msg->data_length.
		 */
		subreq->io_iter.count = len;

		err = iov_iter_get_pages_alloc2(&subreq->io_iter, &pages, len, &page_off);
		if (err < 0) {
			doutc(cl, "%llx.%llx failed to allocate pages, %d\n",
			      ceph_vinop(inode), err);
			goto out;
		}

		/* should always give us a page-aligned read */
		WARN_ON_ONCE(page_off);
		len = err;
		err = 0;

		osd_req_op_extent_osd_data_pages(req, 0, pages, len, 0, false,
						 false);
	} else {
		osd_req_op_extent_osd_iter(req, 0, &subreq->io_iter);
	}
	if (!ceph_inc_osd_stopping_blocker(fsc->mdsc)) {
		err = -EIO;
		goto out;
	}
	req->r_callback = finish_netfs_read;
	req->r_priv = subreq;
	req->r_inode = inode;
	ihold(inode);

	trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
	ceph_osdc_start_request(req->r_osdc, req);
out:
	ceph_osdc_put_request(req);
	if (err) {
		subreq->error = err;
		netfs_read_subreq_terminated(subreq);
	}
	doutc(cl, "%llx.%llx result %d\n", ceph_vinop(inode), err);
}

static int ceph_init_request(struct netfs_io_request *rreq, struct file *file)
{
	struct inode *inode = rreq->inode;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = ceph_inode_to_client(inode);
	int got = 0, want = CEPH_CAP_FILE_CACHE;
	struct ceph_netfs_request_data *priv;
	int ret = 0;

	/* [DEPRECATED] Use PG_private_2 to mark folio being written to the cache. */
	__set_bit(NETFS_RREQ_USE_PGPRIV2, &rreq->flags);

	if (rreq->origin != NETFS_READAHEAD)
		return 0;

	priv = kzalloc(sizeof(*priv), GFP_NOFS);
	if (!priv)
		return -ENOMEM;

	if (file) {
		struct ceph_rw_context *rw_ctx;
		struct ceph_file_info *fi = file->private_data;

		priv->file_ra_pages = file->f_ra.ra_pages;
		priv->file_ra_disabled = file->f_mode & FMODE_RANDOM;

		rw_ctx = ceph_find_rw_context(fi);
		if (rw_ctx) {
			rreq->netfs_priv = priv;
			return 0;
		}
	}

	/*
	 * readahead callers do not necessarily hold Fcb caps
	 * (e.g. fadvise, madvise).
	 */
	ret = ceph_try_get_caps(inode, CEPH_CAP_FILE_RD, want, true, &got);
	if (ret < 0) {
		doutc(cl, "%llx.%llx, error getting cap\n", ceph_vinop(inode));
		goto out;
	}

	if (!(got & want)) {
		doutc(cl, "%llx.%llx, no cache cap\n", ceph_vinop(inode));
		ret = -EACCES;
		goto out;
	}
	if (ret == 0) {
		ret = -EACCES;
		goto out;
	}

	priv->caps = got;
	rreq->netfs_priv = priv;
	rreq->io_streams[0].sreq_max_len = fsc->mount_options->rsize;

out:
	if (ret < 0) {
		if (got)
			ceph_put_cap_refs(ceph_inode(inode), got);
		kfree(priv);
	}

	return ret;
}

static void ceph_netfs_free_request(struct netfs_io_request *rreq)
{
	struct ceph_netfs_request_data *priv = rreq->netfs_priv;

	if (!priv)
		return;

	if (priv->caps)
		ceph_put_cap_refs(ceph_inode(rreq->inode), priv->caps);
	kfree(priv);
	rreq->netfs_priv = NULL;
}

const struct netfs_request_ops ceph_netfs_ops = {
	.init_request		= ceph_init_request,
	.free_request		= ceph_netfs_free_request,
	.prepare_read		= ceph_netfs_prepare_read,
	.issue_read		= ceph_netfs_issue_read,
	.expand_readahead	= ceph_netfs_expand_readahead,
	.check_write_begin	= ceph_netfs_check_write_begin,
};

#ifdef CONFIG_CEPH_FSCACHE
static void ceph_set_page_fscache(struct page *page)
{
	folio_start_private_2(page_folio(page)); /* [DEPRECATED] */
}

static void ceph_fscache_write_terminated(void *priv, ssize_t error)
{
	struct inode *inode = priv;

	if (IS_ERR_VALUE(error) && error != -ENOBUFS)
		ceph_fscache_invalidate(inode, false);
}

static void ceph_fscache_write_to_cache(struct inode *inode, u64 off, u64 len, bool caching)
{
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct fscache_cookie *cookie = ceph_fscache_cookie(ci);

	fscache_write_to_cache(cookie, inode->i_mapping, off, len, i_size_read(inode),
			       ceph_fscache_write_terminated, inode, true, caching);
}
#else
static inline void ceph_set_page_fscache(struct page *page)
{
}

static inline void ceph_fscache_write_to_cache(struct inode *inode, u64 off, u64 len, bool caching)
{
}
#endif /* CONFIG_CEPH_FSCACHE */

struct ceph_writeback_ctl
{
	loff_t i_size;
	u64 truncate_size;
	u32 truncate_seq;
	bool size_stable;

	bool head_snapc;
	struct ceph_snap_context *snapc;
	struct ceph_snap_context *last_snapc;

	bool done;
	bool should_loop;
	bool range_whole;
	pgoff_t start_index;
	pgoff_t index;
	pgoff_t end;
	xa_mark_t tag;

	pgoff_t strip_unit_end;
	unsigned int wsize;
	unsigned int nr_folios;
	unsigned int max_pages;
	unsigned int locked_pages;

	int op_idx;
	int num_ops;
	u64 offset;
	u64 len;

	struct folio_batch fbatch;
	unsigned int processed_in_fbatch;

	bool from_pool;
	struct page **pages;
	struct page **data_pages;
};

/*
 * Get ref for the oldest snapc for an inode with dirty data... that is, the
 * only snap context we are allowed to write back.
 */
static struct ceph_snap_context *
get_oldest_context(struct inode *inode, struct ceph_writeback_ctl *ctl,
		   struct ceph_snap_context *page_snapc)
{
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct ceph_snap_context *snapc = NULL;
	struct ceph_cap_snap *capsnap = NULL;

	spin_lock(&ci->i_ceph_lock);
	list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
		doutc(cl, " capsnap %p snapc %p has %d dirty pages\n",
		      capsnap, capsnap->context, capsnap->dirty_pages);
		if (!capsnap->dirty_pages)
			continue;

		/* get i_size, truncate_{seq,size} for page_snapc? */
		if (snapc && capsnap->context != page_snapc)
			continue;

		if (ctl) {
			if (capsnap->writing) {
				ctl->i_size = i_size_read(inode);
				ctl->size_stable = false;
			} else {
				ctl->i_size = capsnap->size;
				ctl->size_stable = true;
			}
			ctl->truncate_size = capsnap->truncate_size;
			ctl->truncate_seq = capsnap->truncate_seq;
			ctl->head_snapc = false;
		}

		if (snapc)
			break;

		snapc = ceph_get_snap_context(capsnap->context);
		if (!page_snapc ||
		    page_snapc == snapc ||
		    page_snapc->seq > snapc->seq)
			break;
	}
	if (!snapc && ci->i_wrbuffer_ref_head) {
		snapc = ceph_get_snap_context(ci->i_head_snapc);
		doutc(cl, " head snapc %p has %d dirty pages\n", snapc,
		      ci->i_wrbuffer_ref_head);
		if (ctl) {
			ctl->i_size = i_size_read(inode);
			ctl->truncate_size = ci->i_truncate_size;
			ctl->truncate_seq = ci->i_truncate_seq;
			ctl->size_stable = false;
			ctl->head_snapc = true;
		}
	}
	spin_unlock(&ci->i_ceph_lock);
	return snapc;
}

static u64 get_writepages_data_length(struct inode *inode,
				      struct page *page, u64 start)
{
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_snap_context *snapc;
	struct ceph_cap_snap *capsnap = NULL;
	u64 end = i_size_read(inode);
	u64 ret;

	snapc = page_snap_context(ceph_fscrypt_pagecache_page(page));
	if (snapc != ci->i_head_snapc) {
		bool found = false;
		spin_lock(&ci->i_ceph_lock);
		list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
			if (capsnap->context == snapc) {
				if (!capsnap->writing)
					end = capsnap->size;
				found = true;
				break;
			}
		}
		spin_unlock(&ci->i_ceph_lock);
		WARN_ON(!found);
	}
	if (end > ceph_fscrypt_page_offset(page) + thp_size(page))
		end = ceph_fscrypt_page_offset(page) + thp_size(page);
	ret = end > start ? end - start : 0;
	if (ret && fscrypt_is_bounce_page(page))
		ret = round_up(ret, CEPH_FSCRYPT_BLOCK_SIZE);
	return ret;
}

/*
 * Write a folio, but leave it locked.
 *
 * If we get a write error, mark the mapping for error, but still adjust the
 * dirty page accounting (i.e., folio is no longer dirty).
 */
static int write_folio_nounlock(struct folio *folio,
		struct writeback_control *wbc)
{
	struct page *page = &folio->page;
	struct inode *inode = folio->mapping->host;
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct ceph_snap_context *snapc, *oldest;
	loff_t page_off = folio_pos(folio);
	int err;
	loff_t len = folio_size(folio);
	loff_t wlen;
	struct ceph_writeback_ctl ceph_wbc;
	struct ceph_osd_client *osdc = &fsc->client->osdc;
	struct ceph_osd_request *req;
	bool caching = ceph_is_cache_enabled(inode);
	struct page *bounce_page = NULL;

	doutc(cl, "%llx.%llx folio %p idx %lu\n", ceph_vinop(inode), folio,
	      folio->index);

	if (ceph_inode_is_shutdown(inode))
		return -EIO;

	/* verify this is a writeable snap context */
	snapc = page_snap_context(&folio->page);
	if (!snapc) {
		doutc(cl, "%llx.%llx folio %p not dirty?\n", ceph_vinop(inode),
		      folio);
		return 0;
	}
	oldest = get_oldest_context(inode, &ceph_wbc, snapc);
	if (snapc->seq > oldest->seq) {
		doutc(cl, "%llx.%llx folio %p snapc %p not writeable - noop\n",
		      ceph_vinop(inode), folio, snapc);
		/* we should only noop if called by kswapd */
		WARN_ON(!(current->flags & PF_MEMALLOC));
		ceph_put_snap_context(oldest);
		folio_redirty_for_writepage(wbc, folio);
		return 0;
	}
	ceph_put_snap_context(oldest);

	/* is this a partial page at end of file? */
	if (page_off >= ceph_wbc.i_size) {
		doutc(cl, "%llx.%llx folio at %lu beyond eof %llu\n",
		      ceph_vinop(inode), folio->index, ceph_wbc.i_size);
		folio_invalidate(folio, 0, folio_size(folio));
		return 0;
	}

	if (ceph_wbc.i_size < page_off + len)
		len = ceph_wbc.i_size - page_off;

	wlen = IS_ENCRYPTED(inode) ? round_up(len, CEPH_FSCRYPT_BLOCK_SIZE) : len;
	doutc(cl, "%llx.%llx folio %p index %lu on %llu~%llu snapc %p seq %lld\n",
	      ceph_vinop(inode), folio, folio->index, page_off, wlen, snapc,
	      snapc->seq);

	if (atomic_long_inc_return(&fsc->writeback_count) >
	    CONGESTION_ON_THRESH(fsc->mount_options->congestion_kb))
		fsc->write_congested = true;

	req = ceph_osdc_new_request(osdc, &ci->i_layout, ceph_vino(inode),
				    page_off, &wlen, 0, 1, CEPH_OSD_OP_WRITE,
				    CEPH_OSD_FLAG_WRITE, snapc,
				    ceph_wbc.truncate_seq,
				    ceph_wbc.truncate_size, true);
	if (IS_ERR(req)) {
		folio_redirty_for_writepage(wbc, folio);
		return PTR_ERR(req);
	}

	if (wlen < len)
		len = wlen;

	folio_start_writeback(folio);
	if (caching)
		ceph_set_page_fscache(&folio->page);
	ceph_fscache_write_to_cache(inode, page_off, len, caching);

	if (IS_ENCRYPTED(inode)) {
		bounce_page = fscrypt_encrypt_pagecache_blocks(folio,
						    CEPH_FSCRYPT_BLOCK_SIZE, 0,
						    GFP_NOFS);
		if (IS_ERR(bounce_page)) {
			folio_redirty_for_writepage(wbc, folio);
			folio_end_writeback(folio);
			ceph_osdc_put_request(req);
			return PTR_ERR(bounce_page);
		}
	}

	/* it may be a short write due to an object boundary */
	WARN_ON_ONCE(len > folio_size(folio));
	osd_req_op_extent_osd_data_pages(req, 0,
			bounce_page ? &bounce_page : &page, wlen, 0,
			false, false);
	doutc(cl, "%llx.%llx %llu~%llu (%llu bytes, %sencrypted)\n",
	      ceph_vinop(inode), page_off, len, wlen,
	      IS_ENCRYPTED(inode) ? "" : "not ");

	req->r_mtime = inode_get_mtime(inode);
	ceph_osdc_start_request(osdc, req);
	err = ceph_osdc_wait_request(osdc, req);

	ceph_update_write_metrics(&fsc->mdsc->metric, req->r_start_latency,
				  req->r_end_latency, len, err);
	fscrypt_free_bounce_page(bounce_page);
	ceph_osdc_put_request(req);
	if (err == 0)
		err = len;

	if (err < 0) {
		struct writeback_control tmp_wbc;
		if (!wbc)
			wbc = &tmp_wbc;
		if (err == -ERESTARTSYS) {
			/* killed by SIGKILL */
			doutc(cl, "%llx.%llx interrupted page %p\n",
			      ceph_vinop(inode), folio);
			folio_redirty_for_writepage(wbc, folio);
			folio_end_writeback(folio);
			return err;
		}
		if (err == -EBLOCKLISTED)
			fsc->blocklisted = true;
		doutc(cl, "%llx.%llx setting mapping error %d %p\n",
		      ceph_vinop(inode), err, folio);
		mapping_set_error(&inode->i_data, err);
		wbc->pages_skipped++;
	} else {
		doutc(cl, "%llx.%llx cleaned page %p\n",
		      ceph_vinop(inode), folio);
		err = 0;  /* vfs expects us to return 0 */
	}
	oldest = folio_detach_private(folio);
	WARN_ON_ONCE(oldest != snapc);
	folio_end_writeback(folio);
	ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
	ceph_put_snap_context(snapc);  /* page's reference */

	if (atomic_long_dec_return(&fsc->writeback_count) <
	    CONGESTION_OFF_THRESH(fsc->mount_options->congestion_kb))
		fsc->write_congested = false;

	return err;
}

/*
 * async writeback completion handler.
 *
 * If we get an error, set the mapping error bit, but not the individual
 * page error bits.
 */
static void writepages_finish(struct ceph_osd_request *req)
{
	struct inode *inode = req->r_inode;
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct ceph_osd_data *osd_data;
	struct page *page;
	int num_pages, total_pages = 0;
	int i, j;
	int rc = req->r_result;
	struct ceph_snap_context *snapc = req->r_snapc;
	struct address_space *mapping = inode->i_mapping;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
	unsigned int len = 0;
	bool remove_page;

	doutc(cl, "%llx.%llx rc %d\n", ceph_vinop(inode), rc);
	if (rc < 0) {
		mapping_set_error(mapping, rc);
		ceph_set_error_write(ci);
		if (rc == -EBLOCKLISTED)
			fsc->blocklisted = true;
	} else {
		ceph_clear_error_write(ci);
	}

	/*
	 * We lost the cache cap, need to truncate the page before
	 * it is unlocked, otherwise we'd truncate it later in the
	 * page truncation thread, possibly losing some data that
	 * raced its way in
	 */
	remove_page = !(ceph_caps_issued(ci) &
			(CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO));

	/* clean all pages */
	for (i = 0; i < req->r_num_ops; i++) {
		if (req->r_ops[i].op != CEPH_OSD_OP_WRITE) {
			pr_warn_client(cl,
				"%llx.%llx incorrect op %d req %p index %d tid %llu\n",
				ceph_vinop(inode), req->r_ops[i].op, req, i,
				req->r_tid);
			break;
		}

		osd_data = osd_req_op_extent_osd_data(req, i);
		BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_PAGES);
		len += osd_data->length;
		num_pages = calc_pages_for((u64)osd_data->alignment,
					   (u64)osd_data->length);
		total_pages += num_pages;
		for (j = 0; j < num_pages; j++) {
			page = osd_data->pages[j];
			if (fscrypt_is_bounce_page(page)) {
				page = fscrypt_pagecache_page(page);
				fscrypt_free_bounce_page(osd_data->pages[j]);
				osd_data->pages[j] = page;
			}
			BUG_ON(!page);
			WARN_ON(!PageUptodate(page));

			if (atomic_long_dec_return(&fsc->writeback_count) <
			     CONGESTION_OFF_THRESH(
					fsc->mount_options->congestion_kb))
				fsc->write_congested = false;

			ceph_put_snap_context(detach_page_private(page));
			end_page_writeback(page);

			if (atomic64_dec_return(&mdsc->dirty_folios) <= 0) {
				wake_up_all(&mdsc->flush_end_wq);
				WARN_ON(atomic64_read(&mdsc->dirty_folios) < 0);
			}

			doutc(cl, "unlocking %p\n", page);

			if (remove_page)
				generic_error_remove_folio(inode->i_mapping,
							  page_folio(page));

			unlock_page(page);
		}
		doutc(cl, "%llx.%llx wrote %llu bytes cleaned %d pages\n",
		      ceph_vinop(inode), osd_data->length,
		      rc >= 0 ? num_pages : 0);

		release_pages(osd_data->pages, num_pages);
	}

	ceph_update_write_metrics(&fsc->mdsc->metric, req->r_start_latency,
				  req->r_end_latency, len, rc);

	ceph_put_wrbuffer_cap_refs(ci, total_pages, snapc);

	osd_data = osd_req_op_extent_osd_data(req, 0);
	if (osd_data->pages_from_pool)
		mempool_free(osd_data->pages, ceph_wb_pagevec_pool);
	else
		kfree(osd_data->pages);
	ceph_osdc_put_request(req);
	ceph_dec_osd_stopping_blocker(fsc->mdsc);
}

static inline
bool is_forced_umount(struct address_space *mapping)
{
	struct inode *inode = mapping->host;
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;

	if (ceph_inode_is_shutdown(inode)) {
		if (ci->i_wrbuffer_ref > 0) {
			pr_warn_ratelimited_client(cl,
				"%llx.%llx %lld forced umount\n",
				ceph_vinop(inode), ceph_ino(inode));
		}
		mapping_set_error(mapping, -EIO);
		return true;
	}

	return false;
}

static inline
unsigned int ceph_define_write_size(struct address_space *mapping)
{
	struct inode *inode = mapping->host;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	unsigned int wsize = i_blocksize(inode);

	if (fsc->mount_options->wsize < wsize)
		wsize = fsc->mount_options->wsize;

	return wsize;
}

static inline
void ceph_folio_batch_init(struct ceph_writeback_ctl *ceph_wbc)
{
	folio_batch_init(&ceph_wbc->fbatch);
	ceph_wbc->processed_in_fbatch = 0;
}

static inline
void ceph_folio_batch_reinit(struct ceph_writeback_ctl *ceph_wbc)
{
	folio_batch_release(&ceph_wbc->fbatch);
	ceph_folio_batch_init(ceph_wbc);
}

static inline
void ceph_init_writeback_ctl(struct address_space *mapping,
			     struct writeback_control *wbc,
			     struct ceph_writeback_ctl *ceph_wbc)
{
	ceph_wbc->snapc = NULL;
	ceph_wbc->last_snapc = NULL;

	ceph_wbc->strip_unit_end = 0;
	ceph_wbc->wsize = ceph_define_write_size(mapping);

	ceph_wbc->nr_folios = 0;
	ceph_wbc->max_pages = 0;
	ceph_wbc->locked_pages = 0;

	ceph_wbc->done = false;
	ceph_wbc->should_loop = false;
	ceph_wbc->range_whole = false;

	ceph_wbc->start_index = wbc->range_cyclic ? mapping->writeback_index : 0;
	ceph_wbc->index = ceph_wbc->start_index;
	ceph_wbc->end = -1;

	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) {
		ceph_wbc->tag = PAGECACHE_TAG_TOWRITE;
	} else {
		ceph_wbc->tag = PAGECACHE_TAG_DIRTY;
	}

	ceph_wbc->op_idx = -1;
	ceph_wbc->num_ops = 0;
	ceph_wbc->offset = 0;
	ceph_wbc->len = 0;
	ceph_wbc->from_pool = false;

	ceph_folio_batch_init(ceph_wbc);

	ceph_wbc->pages = NULL;
	ceph_wbc->data_pages = NULL;
}

static inline
int ceph_define_writeback_range(struct address_space *mapping,
				struct writeback_control *wbc,
				struct ceph_writeback_ctl *ceph_wbc)
{
	struct inode *inode = mapping->host;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;

	/* find oldest snap context with dirty data */
	ceph_wbc->snapc = get_oldest_context(inode, ceph_wbc, NULL);
	if (!ceph_wbc->snapc) {
		/* hmm, why does writepages get called when there
		   is no dirty data? */
		doutc(cl, " no snap context with dirty data?\n");
		return -ENODATA;
	}

	doutc(cl, " oldest snapc is %p seq %lld (%d snaps)\n",
	      ceph_wbc->snapc, ceph_wbc->snapc->seq,
	      ceph_wbc->snapc->num_snaps);

	ceph_wbc->should_loop = false;

	if (ceph_wbc->head_snapc && ceph_wbc->snapc != ceph_wbc->last_snapc) {
		/* where to start/end? */
		if (wbc->range_cyclic) {
			ceph_wbc->index = ceph_wbc->start_index;
			ceph_wbc->end = -1;
			if (ceph_wbc->index > 0)
				ceph_wbc->should_loop = true;
			doutc(cl, " cyclic, start at %lu\n", ceph_wbc->index);
		} else {
			ceph_wbc->index = wbc->range_start >> PAGE_SHIFT;
			ceph_wbc->end = wbc->range_end >> PAGE_SHIFT;
			if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
				ceph_wbc->range_whole = true;
			doutc(cl, " not cyclic, %lu to %lu\n",
				ceph_wbc->index, ceph_wbc->end);
		}
	} else if (!ceph_wbc->head_snapc) {
		/* Do not respect wbc->range_{start,end}. Dirty pages
		 * in that range can be associated with newer snapc.
		 * They are not writeable until we write all dirty pages
		 * associated with 'snapc' get written */
		if (ceph_wbc->index > 0)
			ceph_wbc->should_loop = true;
		doutc(cl, " non-head snapc, range whole\n");
	}

	ceph_put_snap_context(ceph_wbc->last_snapc);
	ceph_wbc->last_snapc = ceph_wbc->snapc;

	return 0;
}

static inline
bool has_writeback_done(struct ceph_writeback_ctl *ceph_wbc)
{
	return ceph_wbc->done && ceph_wbc->index > ceph_wbc->end;
}

static inline
bool can_next_page_be_processed(struct ceph_writeback_ctl *ceph_wbc,
				unsigned index)
{
	return index < ceph_wbc->nr_folios &&
		ceph_wbc->locked_pages < ceph_wbc->max_pages;
}

static
int ceph_check_page_before_write(struct address_space *mapping,
				 struct writeback_control *wbc,
				 struct ceph_writeback_ctl *ceph_wbc,
				 struct folio *folio)
{
	struct inode *inode = mapping->host;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct ceph_snap_context *pgsnapc;

	/* only dirty folios, or our accounting breaks */
	if (unlikely(!folio_test_dirty(folio) || folio->mapping != mapping)) {
		doutc(cl, "!dirty or !mapping %p\n", folio);
		return -ENODATA;
	}

	/* only if matching snap context */
	pgsnapc = page_snap_context(&folio->page);
	if (pgsnapc != ceph_wbc->snapc) {
		doutc(cl, "folio snapc %p %lld != oldest %p %lld\n",
		      pgsnapc, pgsnapc->seq,
		      ceph_wbc->snapc, ceph_wbc->snapc->seq);

		if (!ceph_wbc->should_loop && !ceph_wbc->head_snapc &&
		    wbc->sync_mode != WB_SYNC_NONE)
			ceph_wbc->should_loop = true;

		return -ENODATA;
	}

	if (folio_pos(folio) >= ceph_wbc->i_size) {
		doutc(cl, "folio at %lu beyond eof %llu\n",
		      folio->index, ceph_wbc->i_size);

		if ((ceph_wbc->size_stable ||
		    folio_pos(folio) >= i_size_read(inode)) &&
		    folio_clear_dirty_for_io(folio))
			folio_invalidate(folio, 0, folio_size(folio));

		return -ENODATA;
	}

	if (ceph_wbc->strip_unit_end &&
	    (folio->index > ceph_wbc->strip_unit_end)) {
		doutc(cl, "end of strip unit %p\n", folio);
		return -E2BIG;
	}

	return 0;
}

static inline
void __ceph_allocate_page_array(struct ceph_writeback_ctl *ceph_wbc,
				unsigned int max_pages)
{
	ceph_wbc->pages = kmalloc_array(max_pages,
					sizeof(*ceph_wbc->pages),
					GFP_NOFS);
	if (!ceph_wbc->pages) {
		ceph_wbc->from_pool = true;
		ceph_wbc->pages = mempool_alloc(ceph_wb_pagevec_pool, GFP_NOFS);
		BUG_ON(!ceph_wbc->pages);
	}
}

static inline
void ceph_allocate_page_array(struct address_space *mapping,
			      struct ceph_writeback_ctl *ceph_wbc,
			      struct folio *folio)
{
	struct inode *inode = mapping->host;
	struct ceph_inode_info *ci = ceph_inode(inode);
	u64 objnum;
	u64 objoff;
	u32 xlen;

	/* prepare async write request */
	ceph_wbc->offset = (u64)folio_pos(folio);
	ceph_calc_file_object_mapping(&ci->i_layout,
					ceph_wbc->offset, ceph_wbc->wsize,
					&objnum, &objoff, &xlen);

	ceph_wbc->num_ops = 1;
	ceph_wbc->strip_unit_end = folio->index + ((xlen - 1) >> PAGE_SHIFT);

	BUG_ON(ceph_wbc->pages);
	ceph_wbc->max_pages = calc_pages_for(0, (u64)xlen);
	__ceph_allocate_page_array(ceph_wbc, ceph_wbc->max_pages);

	ceph_wbc->len = 0;
}

static inline
bool is_folio_index_contiguous(const struct ceph_writeback_ctl *ceph_wbc,
			      const struct folio *folio)
{
	return folio->index == (ceph_wbc->offset + ceph_wbc->len) >> PAGE_SHIFT;
}

static inline
bool is_num_ops_too_big(struct ceph_writeback_ctl *ceph_wbc)
{
	return ceph_wbc->num_ops >=
		(ceph_wbc->from_pool ?  CEPH_OSD_SLAB_OPS : CEPH_OSD_MAX_OPS);
}

static inline
bool is_write_congestion_happened(struct ceph_fs_client *fsc)
{
	return atomic_long_inc_return(&fsc->writeback_count) >
		CONGESTION_ON_THRESH(fsc->mount_options->congestion_kb);
}

static inline int move_dirty_folio_in_page_array(struct address_space *mapping,
		struct writeback_control *wbc,
		struct ceph_writeback_ctl *ceph_wbc, struct folio *folio)
{
	struct inode *inode = mapping->host;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct page **pages = ceph_wbc->pages;
	unsigned int index = ceph_wbc->locked_pages;
	gfp_t gfp_flags = ceph_wbc->locked_pages ? GFP_NOWAIT : GFP_NOFS;

	if (IS_ENCRYPTED(inode)) {
		pages[index] = fscrypt_encrypt_pagecache_blocks(folio,
								PAGE_SIZE,
								0,
								gfp_flags);
		if (IS_ERR(pages[index])) {
			int err = PTR_ERR(pages[index]);

			if (err == -EINVAL) {
				pr_err_client(cl, "inode->i_blkbits=%hhu\n",
						inode->i_blkbits);
			}

			/* better not fail on first page! */
			BUG_ON(ceph_wbc->locked_pages == 0);

			pages[index] = NULL;
			return err;
		}
	} else {
		pages[index] = &folio->page;
	}

	ceph_wbc->locked_pages++;

	return 0;
}

static
int ceph_process_folio_batch(struct address_space *mapping,
			     struct writeback_control *wbc,
			     struct ceph_writeback_ctl *ceph_wbc)
{
	struct inode *inode = mapping->host;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct folio *folio = NULL;
	unsigned i;
	int rc = 0;

	for (i = 0; can_next_page_be_processed(ceph_wbc, i); i++) {
		folio = ceph_wbc->fbatch.folios[i];

		if (!folio)
			continue;

		doutc(cl, "? %p idx %lu, folio_test_writeback %#x, "
			"folio_test_dirty %#x, folio_test_locked %#x\n",
			folio, folio->index, folio_test_writeback(folio),
			folio_test_dirty(folio),
			folio_test_locked(folio));

		if (folio_test_writeback(folio) ||
		    folio_test_private_2(folio) /* [DEPRECATED] */) {
			doutc(cl, "waiting on writeback %p\n", folio);
			folio_wait_writeback(folio);
			folio_wait_private_2(folio); /* [DEPRECATED] */
			continue;
		}

		if (ceph_wbc->locked_pages == 0)
			folio_lock(folio);
		else if (!folio_trylock(folio))
			break;

		rc = ceph_check_page_before_write(mapping, wbc,
						  ceph_wbc, folio);
		if (rc == -ENODATA) {
			rc = 0;
			folio_unlock(folio);
			ceph_wbc->fbatch.folios[i] = NULL;
			continue;
		} else if (rc == -E2BIG) {
			rc = 0;
			folio_unlock(folio);
			ceph_wbc->fbatch.folios[i] = NULL;
			break;
		}

		if (!folio_clear_dirty_for_io(folio)) {
			doutc(cl, "%p !folio_clear_dirty_for_io\n", folio);
			folio_unlock(folio);
			ceph_wbc->fbatch.folios[i] = NULL;
			continue;
		}

		/*
		 * We have something to write.  If this is
		 * the first locked page this time through,
		 * calculate max possible write size and
		 * allocate a page array
		 */
		if (ceph_wbc->locked_pages == 0) {
			ceph_allocate_page_array(mapping, ceph_wbc, folio);
		} else if (!is_folio_index_contiguous(ceph_wbc, folio)) {
			if (is_num_ops_too_big(ceph_wbc)) {
				folio_redirty_for_writepage(wbc, folio);
				folio_unlock(folio);
				break;
			}

			ceph_wbc->num_ops++;
			ceph_wbc->offset = (u64)folio_pos(folio);
			ceph_wbc->len = 0;
		}

		/* note position of first page in fbatch */
		doutc(cl, "%llx.%llx will write folio %p idx %lu\n",
		      ceph_vinop(inode), folio, folio->index);

		fsc->write_congested = is_write_congestion_happened(fsc);

		rc = move_dirty_folio_in_page_array(mapping, wbc, ceph_wbc,
				folio);
		if (rc) {
			folio_redirty_for_writepage(wbc, folio);
			folio_unlock(folio);
			break;
		}

		ceph_wbc->fbatch.folios[i] = NULL;
		ceph_wbc->len += folio_size(folio);
	}

	ceph_wbc->processed_in_fbatch = i;

	return rc;
}

static inline
void ceph_shift_unused_folios_left(struct folio_batch *fbatch)
{
	unsigned j, n = 0;

	/* shift unused page to beginning of fbatch */
	for (j = 0; j < folio_batch_count(fbatch); j++) {
		if (!fbatch->folios[j])
			continue;

		if (n < j) {
			fbatch->folios[n] = fbatch->folios[j];
		}

		n++;
	}

	fbatch->nr = n;
}

static
int ceph_submit_write(struct address_space *mapping,
			struct writeback_control *wbc,
			struct ceph_writeback_ctl *ceph_wbc)
{
	struct inode *inode = mapping->host;
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct ceph_vino vino = ceph_vino(inode);
	struct ceph_osd_request *req = NULL;
	struct page *page = NULL;
	bool caching = ceph_is_cache_enabled(inode);
	u64 offset;
	u64 len;
	unsigned i;

new_request:
	offset = ceph_fscrypt_page_offset(ceph_wbc->pages[0]);
	len = ceph_wbc->wsize;

	req = ceph_osdc_new_request(&fsc->client->osdc,
				    &ci->i_layout, vino,
				    offset, &len, 0, ceph_wbc->num_ops,
				    CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
				    ceph_wbc->snapc, ceph_wbc->truncate_seq,
				    ceph_wbc->truncate_size, false);
	if (IS_ERR(req)) {
		req = ceph_osdc_new_request(&fsc->client->osdc,
					    &ci->i_layout, vino,
					    offset, &len, 0,
					    min(ceph_wbc->num_ops,
						CEPH_OSD_SLAB_OPS),
					    CEPH_OSD_OP_WRITE,
					    CEPH_OSD_FLAG_WRITE,
					    ceph_wbc->snapc,
					    ceph_wbc->truncate_seq,
					    ceph_wbc->truncate_size,
					    true);
		BUG_ON(IS_ERR(req));
	}

	page = ceph_wbc->pages[ceph_wbc->locked_pages - 1];
	BUG_ON(len < ceph_fscrypt_page_offset(page) + thp_size(page) - offset);

	if (!ceph_inc_osd_stopping_blocker(fsc->mdsc)) {
		for (i = 0; i < folio_batch_count(&ceph_wbc->fbatch); i++) {
			struct folio *folio = ceph_wbc->fbatch.folios[i];

			if (!folio)
				continue;

			page = &folio->page;
			redirty_page_for_writepage(wbc, page);
			unlock_page(page);
		}

		for (i = 0; i < ceph_wbc->locked_pages; i++) {
			page = ceph_fscrypt_pagecache_page(ceph_wbc->pages[i]);

			if (!page)
				continue;

			redirty_page_for_writepage(wbc, page);
			unlock_page(page);
		}

		ceph_osdc_put_request(req);
		return -EIO;
	}

	req->r_callback = writepages_finish;
	req->r_inode = inode;

	/* Format the osd request message and submit the write */
	len = 0;
	ceph_wbc->data_pages = ceph_wbc->pages;
	ceph_wbc->op_idx = 0;
	for (i = 0; i < ceph_wbc->locked_pages; i++) {
		u64 cur_offset;

		page = ceph_fscrypt_pagecache_page(ceph_wbc->pages[i]);
		cur_offset = page_offset(page);

		/*
		 * Discontinuity in page range? Ceph can handle that by just passing
		 * multiple extents in the write op.
		 */
		if (offset + len != cur_offset) {
			/* If it's full, stop here */
			if (ceph_wbc->op_idx + 1 == req->r_num_ops)
				break;

			/* Kick off an fscache write with what we have so far. */
			ceph_fscache_write_to_cache(inode, offset, len, caching);

			/* Start a new extent */
			osd_req_op_extent_dup_last(req, ceph_wbc->op_idx,
						   cur_offset - offset);

			doutc(cl, "got pages at %llu~%llu\n", offset, len);

			osd_req_op_extent_osd_data_pages(req, ceph_wbc->op_idx,
							 ceph_wbc->data_pages,
							 len, 0,
							 ceph_wbc->from_pool,
							 false);
			osd_req_op_extent_update(req, ceph_wbc->op_idx, len);

			len = 0;
			offset = cur_offset;
			ceph_wbc->data_pages = ceph_wbc->pages + i;
			ceph_wbc->op_idx++;
		}

		set_page_writeback(page);

		if (caching)
			ceph_set_page_fscache(page);

		len += thp_size(page);
	}

	ceph_fscache_write_to_cache(inode, offset, len, caching);

	if (ceph_wbc->size_stable) {
		len = min(len, ceph_wbc->i_size - offset);
	} else if (i == ceph_wbc->locked_pages) {
		/* writepages_finish() clears writeback pages
		 * according to the data length, so make sure
		 * data length covers all locked pages */
		u64 min_len = len + 1 - thp_size(page);
		len = get_writepages_data_length(inode,
						 ceph_wbc->pages[i - 1],
						 offset);
		len = max(len, min_len);
	}

	if (IS_ENCRYPTED(inode))
		len = round_up(len, CEPH_FSCRYPT_BLOCK_SIZE);

	doutc(cl, "got pages at %llu~%llu\n", offset, len);

	if (IS_ENCRYPTED(inode) &&
	    ((offset | len) & ~CEPH_FSCRYPT_BLOCK_MASK)) {
		pr_warn_client(cl,
			"bad encrypted write offset=%lld len=%llu\n",
			offset, len);
	}

	osd_req_op_extent_osd_data_pages(req, ceph_wbc->op_idx,
					 ceph_wbc->data_pages, len,
					 0, ceph_wbc->from_pool, false);
	osd_req_op_extent_update(req, ceph_wbc->op_idx, len);

	BUG_ON(ceph_wbc->op_idx + 1 != req->r_num_ops);

	ceph_wbc->from_pool = false;
	if (i < ceph_wbc->locked_pages) {
		BUG_ON(ceph_wbc->num_ops <= req->r_num_ops);
		ceph_wbc->num_ops -= req->r_num_ops;
		ceph_wbc->locked_pages -= i;

		/* allocate new pages array for next request */
		ceph_wbc->data_pages = ceph_wbc->pages;
		__ceph_allocate_page_array(ceph_wbc, ceph_wbc->locked_pages);
		memcpy(ceph_wbc->pages, ceph_wbc->data_pages + i,
			ceph_wbc->locked_pages * sizeof(*ceph_wbc->pages));
		memset(ceph_wbc->data_pages + i, 0,
			ceph_wbc->locked_pages * sizeof(*ceph_wbc->pages));
	} else {
		BUG_ON(ceph_wbc->num_ops != req->r_num_ops);
		/* request message now owns the pages array */
		ceph_wbc->pages = NULL;
	}

	req->r_mtime = inode_get_mtime(inode);
	ceph_osdc_start_request(&fsc->client->osdc, req);
	req = NULL;

	wbc->nr_to_write -= i;
	if (ceph_wbc->pages)
		goto new_request;

	return 0;
}

static
void ceph_wait_until_current_writes_complete(struct address_space *mapping,
					     struct writeback_control *wbc,
					     struct ceph_writeback_ctl *ceph_wbc)
{
	struct page *page;
	unsigned i, nr;

	if (wbc->sync_mode != WB_SYNC_NONE &&
	    ceph_wbc->start_index == 0 && /* all dirty pages were checked */
	    !ceph_wbc->head_snapc) {
		ceph_wbc->index = 0;

		while ((ceph_wbc->index <= ceph_wbc->end) &&
			(nr = filemap_get_folios_tag(mapping,
						     &ceph_wbc->index,
						     (pgoff_t)-1,
						     PAGECACHE_TAG_WRITEBACK,
						     &ceph_wbc->fbatch))) {
			for (i = 0; i < nr; i++) {
				page = &ceph_wbc->fbatch.folios[i]->page;
				if (page_snap_context(page) != ceph_wbc->snapc)
					continue;
				wait_on_page_writeback(page);
			}

			folio_batch_release(&ceph_wbc->fbatch);
			cond_resched();
		}
	}
}

/*
 * initiate async writeback
 */
static int ceph_writepages_start(struct address_space *mapping,
				 struct writeback_control *wbc)
{
	struct inode *inode = mapping->host;
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct ceph_writeback_ctl ceph_wbc;
	int rc = 0;

	if (wbc->sync_mode == WB_SYNC_NONE && fsc->write_congested)
		return 0;

	doutc(cl, "%llx.%llx (mode=%s)\n", ceph_vinop(inode),
	      wbc->sync_mode == WB_SYNC_NONE ? "NONE" :
	      (wbc->sync_mode == WB_SYNC_ALL ? "ALL" : "HOLD"));

	if (is_forced_umount(mapping)) {
		/* we're in a forced umount, don't write! */
		return -EIO;
	}

	ceph_init_writeback_ctl(mapping, wbc, &ceph_wbc);

	if (!ceph_inc_osd_stopping_blocker(fsc->mdsc)) {
		rc = -EIO;
		goto out;
	}

retry:
	rc = ceph_define_writeback_range(mapping, wbc, &ceph_wbc);
	if (rc == -ENODATA) {
		/* hmm, why does writepages get called when there
		   is no dirty data? */
		rc = 0;
		goto dec_osd_stopping_blocker;
	}

	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
		tag_pages_for_writeback(mapping, ceph_wbc.index, ceph_wbc.end);

	while (!has_writeback_done(&ceph_wbc)) {
		ceph_wbc.locked_pages = 0;
		ceph_wbc.max_pages = ceph_wbc.wsize >> PAGE_SHIFT;

get_more_pages:
		ceph_folio_batch_reinit(&ceph_wbc);

		ceph_wbc.nr_folios = filemap_get_folios_tag(mapping,
							    &ceph_wbc.index,
							    ceph_wbc.end,
							    ceph_wbc.tag,
							    &ceph_wbc.fbatch);
		doutc(cl, "pagevec_lookup_range_tag for tag %#x got %d\n",
			ceph_wbc.tag, ceph_wbc.nr_folios);

		if (!ceph_wbc.nr_folios && !ceph_wbc.locked_pages)
			break;

process_folio_batch:
		rc = ceph_process_folio_batch(mapping, wbc, &ceph_wbc);
		ceph_shift_unused_folios_left(&ceph_wbc.fbatch);
		if (rc)
			goto release_folios;

		/* did we get anything? */
		if (!ceph_wbc.locked_pages)
			goto release_folios;

		if (ceph_wbc.processed_in_fbatch) {
			if (folio_batch_count(&ceph_wbc.fbatch) == 0 &&
			    ceph_wbc.locked_pages < ceph_wbc.max_pages) {
				doutc(cl, "reached end fbatch, trying for more\n");
				goto get_more_pages;
			}
		}

		rc = ceph_submit_write(mapping, wbc, &ceph_wbc);
		if (rc)
			goto release_folios;

		ceph_wbc.locked_pages = 0;
		ceph_wbc.strip_unit_end = 0;

		if (folio_batch_count(&ceph_wbc.fbatch) > 0) {
			ceph_wbc.nr_folios =
				folio_batch_count(&ceph_wbc.fbatch);
			goto process_folio_batch;
		}

		/*
		 * We stop writing back only if we are not doing
		 * integrity sync. In case of integrity sync we have to
		 * keep going until we have written all the pages
		 * we tagged for writeback prior to entering this loop.
		 */
		if (wbc->nr_to_write <= 0 && wbc->sync_mode == WB_SYNC_NONE)
			ceph_wbc.done = true;

release_folios:
		doutc(cl, "folio_batch release on %d folios (%p)\n",
		      (int)ceph_wbc.fbatch.nr,
		      ceph_wbc.fbatch.nr ? ceph_wbc.fbatch.folios[0] : NULL);
		folio_batch_release(&ceph_wbc.fbatch);
	}

	if (ceph_wbc.should_loop && !ceph_wbc.done) {
		/* more to do; loop back to beginning of file */
		doutc(cl, "looping back to beginning of file\n");
		/* OK even when start_index == 0 */
		ceph_wbc.end = ceph_wbc.start_index - 1;

		/* to write dirty pages associated with next snapc,
		 * we need to wait until current writes complete */
		ceph_wait_until_current_writes_complete(mapping, wbc, &ceph_wbc);

		ceph_wbc.start_index = 0;
		ceph_wbc.index = 0;
		goto retry;
	}

	if (wbc->range_cyclic || (ceph_wbc.range_whole && wbc->nr_to_write > 0))
		mapping->writeback_index = ceph_wbc.index;

dec_osd_stopping_blocker:
	ceph_dec_osd_stopping_blocker(fsc->mdsc);

out:
	ceph_put_snap_context(ceph_wbc.last_snapc);
	doutc(cl, "%llx.%llx dend - startone, rc = %d\n", ceph_vinop(inode),
	      rc);

	return rc;
}

/*
 * See if a given @snapc is either writeable, or already written.
 */
static int context_is_writeable_or_written(struct inode *inode,
					   struct ceph_snap_context *snapc)
{
	struct ceph_snap_context *oldest = get_oldest_context(inode, NULL, NULL);
	int ret = !oldest || snapc->seq <= oldest->seq;

	ceph_put_snap_context(oldest);
	return ret;
}

/**
 * ceph_find_incompatible - find an incompatible context and return it
 * @folio: folio being dirtied
 *
 * We are only allowed to write into/dirty a folio if the folio is
 * clean, or already dirty within the same snap context. Returns a
 * conflicting context if there is one, NULL if there isn't, or a
 * negative error code on other errors.
 *
 * Must be called with folio lock held.
 */
static struct ceph_snap_context *
ceph_find_incompatible(struct folio *folio)
{
	struct inode *inode = folio->mapping->host;
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct ceph_inode_info *ci = ceph_inode(inode);

	if (ceph_inode_is_shutdown(inode)) {
		doutc(cl, " %llx.%llx folio %p is shutdown\n",
		      ceph_vinop(inode), folio);
		return ERR_PTR(-ESTALE);
	}

	for (;;) {
		struct ceph_snap_context *snapc, *oldest;

		folio_wait_writeback(folio);

		snapc = page_snap_context(&folio->page);
		if (!snapc || snapc == ci->i_head_snapc)
			break;

		/*
		 * this folio is already dirty in another (older) snap
		 * context!  is it writeable now?
		 */
		oldest = get_oldest_context(inode, NULL, NULL);
		if (snapc->seq > oldest->seq) {
			/* not writeable -- return it for the caller to deal with */
			ceph_put_snap_context(oldest);
			doutc(cl, " %llx.%llx folio %p snapc %p not current or oldest\n",
			      ceph_vinop(inode), folio, snapc);
			return ceph_get_snap_context(snapc);
		}
		ceph_put_snap_context(oldest);

		/* yay, writeable, do it now (without dropping folio lock) */
		doutc(cl, " %llx.%llx folio %p snapc %p not current, but oldest\n",
		      ceph_vinop(inode), folio, snapc);
		if (folio_clear_dirty_for_io(folio)) {
			int r = write_folio_nounlock(folio, NULL);
			if (r < 0)
				return ERR_PTR(r);
		}
	}
	return NULL;
}

static int ceph_netfs_check_write_begin(struct file *file, loff_t pos, unsigned int len,
					struct folio **foliop, void **_fsdata)
{
	struct inode *inode = file_inode(file);
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_snap_context *snapc;

	snapc = ceph_find_incompatible(*foliop);
	if (snapc) {
		int r;

		folio_unlock(*foliop);
		folio_put(*foliop);
		*foliop = NULL;
		if (IS_ERR(snapc))
			return PTR_ERR(snapc);

		ceph_queue_writeback(inode);
		r = wait_event_killable(ci->i_cap_wq,
					context_is_writeable_or_written(inode, snapc));
		ceph_put_snap_context(snapc);
		return r == 0 ? -EAGAIN : r;
	}
	return 0;
}

/*
 * We are only allowed to write into/dirty the page if the page is
 * clean, or already dirty within the same snap context.
 */
static int ceph_write_begin(struct file *file, struct address_space *mapping,
			    loff_t pos, unsigned len,
			    struct folio **foliop, void **fsdata)
{
	struct inode *inode = file_inode(file);
	struct ceph_inode_info *ci = ceph_inode(inode);
	int r;

	r = netfs_write_begin(&ci->netfs, file, inode->i_mapping, pos, len, foliop, NULL);
	if (r < 0)
		return r;

	folio_wait_private_2(*foliop); /* [DEPRECATED] */
	WARN_ON_ONCE(!folio_test_locked(*foliop));
	return 0;
}

/*
 * we don't do anything in here that simple_write_end doesn't do
 * except adjust dirty page accounting
 */
static int ceph_write_end(struct file *file, struct address_space *mapping,
			  loff_t pos, unsigned len, unsigned copied,
			  struct folio *folio, void *fsdata)
{
	struct inode *inode = file_inode(file);
	struct ceph_client *cl = ceph_inode_to_client(inode);
	bool check_cap = false;

	doutc(cl, "%llx.%llx file %p folio %p %d~%d (%d)\n", ceph_vinop(inode),
	      file, folio, (int)pos, (int)copied, (int)len);

	if (!folio_test_uptodate(folio)) {
		/* just return that nothing was copied on a short copy */
		if (copied < len) {
			copied = 0;
			goto out;
		}
		folio_mark_uptodate(folio);
	}

	/* did file size increase? */
	if (pos+copied > i_size_read(inode))
		check_cap = ceph_inode_set_size(inode, pos+copied);

	folio_mark_dirty(folio);

out:
	folio_unlock(folio);
	folio_put(folio);

	if (check_cap)
		ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY);

	return copied;
}

const struct address_space_operations ceph_aops = {
	.read_folio = netfs_read_folio,
	.readahead = netfs_readahead,
	.writepages = ceph_writepages_start,
	.write_begin = ceph_write_begin,
	.write_end = ceph_write_end,
	.dirty_folio = ceph_dirty_folio,
	.invalidate_folio = ceph_invalidate_folio,
	.release_folio = netfs_release_folio,
	.direct_IO = noop_direct_IO,
	.migrate_folio = filemap_migrate_folio,
};

static void ceph_block_sigs(sigset_t *oldset)
{
	sigset_t mask;
	siginitsetinv(&mask, sigmask(SIGKILL));
	sigprocmask(SIG_BLOCK, &mask, oldset);
}

static void ceph_restore_sigs(sigset_t *oldset)
{
	sigprocmask(SIG_SETMASK, oldset, NULL);
}

/*
 * vm ops
 */
static vm_fault_t ceph_filemap_fault(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct inode *inode = file_inode(vma->vm_file);
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct ceph_file_info *fi = vma->vm_file->private_data;
	loff_t off = (loff_t)vmf->pgoff << PAGE_SHIFT;
	int want, got, err;
	sigset_t oldset;
	vm_fault_t ret = VM_FAULT_SIGBUS;

	if (ceph_inode_is_shutdown(inode))
		return ret;

	ceph_block_sigs(&oldset);

	doutc(cl, "%llx.%llx %llu trying to get caps\n",
	      ceph_vinop(inode), off);
	if (fi->fmode & CEPH_FILE_MODE_LAZY)
		want = CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO;
	else
		want = CEPH_CAP_FILE_CACHE;

	got = 0;
	err = ceph_get_caps(vma->vm_file, CEPH_CAP_FILE_RD, want, -1, &got);
	if (err < 0)
		goto out_restore;

	doutc(cl, "%llx.%llx %llu got cap refs on %s\n", ceph_vinop(inode),
	      off, ceph_cap_string(got));

	if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) ||
	    !ceph_has_inline_data(ci)) {
		CEPH_DEFINE_RW_CONTEXT(rw_ctx, got);
		ceph_add_rw_context(fi, &rw_ctx);
		ret = filemap_fault(vmf);
		ceph_del_rw_context(fi, &rw_ctx);
		doutc(cl, "%llx.%llx %llu drop cap refs %s ret %x\n",
		      ceph_vinop(inode), off, ceph_cap_string(got), ret);
	} else
		err = -EAGAIN;

	ceph_put_cap_refs(ci, got);

	if (err != -EAGAIN)
		goto out_restore;

	/* read inline data */
	if (off >= PAGE_SIZE) {
		/* does not support inline data > PAGE_SIZE */
		ret = VM_FAULT_SIGBUS;
	} else {
		struct address_space *mapping = inode->i_mapping;
		struct page *page;

		filemap_invalidate_lock_shared(mapping);
		page = find_or_create_page(mapping, 0,
				mapping_gfp_constraint(mapping, ~__GFP_FS));
		if (!page) {
			ret = VM_FAULT_OOM;
			goto out_inline;
		}
		err = __ceph_do_getattr(inode, page,
					 CEPH_STAT_CAP_INLINE_DATA, true);
		if (err < 0 || off >= i_size_read(inode)) {
			unlock_page(page);
			put_page(page);
			ret = vmf_error(err);
			goto out_inline;
		}
		if (err < PAGE_SIZE)
			zero_user_segment(page, err, PAGE_SIZE);
		else
			flush_dcache_page(page);
		SetPageUptodate(page);
		vmf->page = page;
		ret = VM_FAULT_MAJOR | VM_FAULT_LOCKED;
out_inline:
		filemap_invalidate_unlock_shared(mapping);
		doutc(cl, "%llx.%llx %llu read inline data ret %x\n",
		      ceph_vinop(inode), off, ret);
	}
out_restore:
	ceph_restore_sigs(&oldset);
	if (err < 0)
		ret = vmf_error(err);

	return ret;
}

static vm_fault_t ceph_page_mkwrite(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct inode *inode = file_inode(vma->vm_file);
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_file_info *fi = vma->vm_file->private_data;
	struct ceph_cap_flush *prealloc_cf;
	struct folio *folio = page_folio(vmf->page);
	loff_t off = folio_pos(folio);
	loff_t size = i_size_read(inode);
	size_t len;
	int want, got, err;
	sigset_t oldset;
	vm_fault_t ret = VM_FAULT_SIGBUS;

	if (ceph_inode_is_shutdown(inode))
		return ret;

	prealloc_cf = ceph_alloc_cap_flush();
	if (!prealloc_cf)
		return VM_FAULT_OOM;

	sb_start_pagefault(inode->i_sb);
	ceph_block_sigs(&oldset);

	if (off + folio_size(folio) <= size)
		len = folio_size(folio);
	else
		len = offset_in_folio(folio, size);

	doutc(cl, "%llx.%llx %llu~%zd getting caps i_size %llu\n",
	      ceph_vinop(inode), off, len, size);
	if (fi->fmode & CEPH_FILE_MODE_LAZY)
		want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
	else
		want = CEPH_CAP_FILE_BUFFER;

	got = 0;
	err = ceph_get_caps(vma->vm_file, CEPH_CAP_FILE_WR, want, off + len, &got);
	if (err < 0)
		goto out_free;

	doutc(cl, "%llx.%llx %llu~%zd got cap refs on %s\n", ceph_vinop(inode),
	      off, len, ceph_cap_string(got));

	/* Update time before taking folio lock */
	file_update_time(vma->vm_file);
	inode_inc_iversion_raw(inode);

	do {
		struct ceph_snap_context *snapc;

		folio_lock(folio);

		if (folio_mkwrite_check_truncate(folio, inode) < 0) {
			folio_unlock(folio);
			ret = VM_FAULT_NOPAGE;
			break;
		}

		snapc = ceph_find_incompatible(folio);
		if (!snapc) {
			/* success.  we'll keep the folio locked. */
			folio_mark_dirty(folio);
			ret = VM_FAULT_LOCKED;
			break;
		}

		folio_unlock(folio);

		if (IS_ERR(snapc)) {
			ret = VM_FAULT_SIGBUS;
			break;
		}

		ceph_queue_writeback(inode);
		err = wait_event_killable(ci->i_cap_wq,
				context_is_writeable_or_written(inode, snapc));
		ceph_put_snap_context(snapc);
	} while (err == 0);

	if (ret == VM_FAULT_LOCKED) {
		int dirty;
		spin_lock(&ci->i_ceph_lock);
		dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR,
					       &prealloc_cf);
		spin_unlock(&ci->i_ceph_lock);
		if (dirty)
			__mark_inode_dirty(inode, dirty);
	}

	doutc(cl, "%llx.%llx %llu~%zd dropping cap refs on %s ret %x\n",
	      ceph_vinop(inode), off, len, ceph_cap_string(got), ret);
	ceph_put_cap_refs_async(ci, got);
out_free:
	ceph_restore_sigs(&oldset);
	sb_end_pagefault(inode->i_sb);
	ceph_free_cap_flush(prealloc_cf);
	if (err < 0)
		ret = vmf_error(err);
	return ret;
}

void ceph_fill_inline_data(struct inode *inode, struct page *locked_page,
			   char	*data, size_t len)
{
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct address_space *mapping = inode->i_mapping;
	struct page *page;

	if (locked_page) {
		page = locked_page;
	} else {
		if (i_size_read(inode) == 0)
			return;
		page = find_or_create_page(mapping, 0,
					   mapping_gfp_constraint(mapping,
					   ~__GFP_FS));
		if (!page)
			return;
		if (PageUptodate(page)) {
			unlock_page(page);
			put_page(page);
			return;
		}
	}

	doutc(cl, "%p %llx.%llx len %zu locked_page %p\n", inode,
	      ceph_vinop(inode), len, locked_page);

	if (len > 0) {
		void *kaddr = kmap_atomic(page);
		memcpy(kaddr, data, len);
		kunmap_atomic(kaddr);
	}

	if (page != locked_page) {
		if (len < PAGE_SIZE)
			zero_user_segment(page, len, PAGE_SIZE);
		else
			flush_dcache_page(page);

		SetPageUptodate(page);
		unlock_page(page);
		put_page(page);
	}
}

int ceph_uninline_data(struct file *file)
{
	struct inode *inode = file_inode(file);
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
	struct ceph_client *cl = fsc->client;
	struct ceph_osd_request *req = NULL;
	struct ceph_cap_flush *prealloc_cf = NULL;
	struct folio *folio = NULL;
	u64 inline_version = CEPH_INLINE_NONE;
	struct page *pages[1];
	int err = 0;
	u64 len;

	spin_lock(&ci->i_ceph_lock);
	inline_version = ci->i_inline_version;
	spin_unlock(&ci->i_ceph_lock);

	doutc(cl, "%llx.%llx inline_version %llu\n", ceph_vinop(inode),
	      inline_version);

	if (ceph_inode_is_shutdown(inode)) {
		err = -EIO;
		goto out;
	}

	if (inline_version == CEPH_INLINE_NONE)
		return 0;

	prealloc_cf = ceph_alloc_cap_flush();
	if (!prealloc_cf)
		return -ENOMEM;

	if (inline_version == 1) /* initial version, no data */
		goto out_uninline;

	folio = read_mapping_folio(inode->i_mapping, 0, file);
	if (IS_ERR(folio)) {
		err = PTR_ERR(folio);
		goto out;
	}

	folio_lock(folio);

	len = i_size_read(inode);
	if (len > folio_size(folio))
		len = folio_size(folio);

	req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
				    ceph_vino(inode), 0, &len, 0, 1,
				    CEPH_OSD_OP_CREATE, CEPH_OSD_FLAG_WRITE,
				    NULL, 0, 0, false);
	if (IS_ERR(req)) {
		err = PTR_ERR(req);
		goto out_unlock;
	}

	req->r_mtime = inode_get_mtime(inode);
	ceph_osdc_start_request(&fsc->client->osdc, req);
	err = ceph_osdc_wait_request(&fsc->client->osdc, req);
	ceph_osdc_put_request(req);
	if (err < 0)
		goto out_unlock;

	req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
				    ceph_vino(inode), 0, &len, 1, 3,
				    CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
				    NULL, ci->i_truncate_seq,
				    ci->i_truncate_size, false);
	if (IS_ERR(req)) {
		err = PTR_ERR(req);
		goto out_unlock;
	}

	pages[0] = folio_page(folio, 0);
	osd_req_op_extent_osd_data_pages(req, 1, pages, len, 0, false, false);

	{
		__le64 xattr_buf = cpu_to_le64(inline_version);
		err = osd_req_op_xattr_init(req, 0, CEPH_OSD_OP_CMPXATTR,
					    "inline_version", &xattr_buf,
					    sizeof(xattr_buf),
					    CEPH_OSD_CMPXATTR_OP_GT,
					    CEPH_OSD_CMPXATTR_MODE_U64);
		if (err)
			goto out_put_req;
	}

	{
		char xattr_buf[32];
		int xattr_len = snprintf(xattr_buf, sizeof(xattr_buf),
					 "%llu", inline_version);
		err = osd_req_op_xattr_init(req, 2, CEPH_OSD_OP_SETXATTR,
					    "inline_version",
					    xattr_buf, xattr_len, 0, 0);
		if (err)
			goto out_put_req;
	}

	req->r_mtime = inode_get_mtime(inode);
	ceph_osdc_start_request(&fsc->client->osdc, req);
	err = ceph_osdc_wait_request(&fsc->client->osdc, req);

	ceph_update_write_metrics(&fsc->mdsc->metric, req->r_start_latency,
				  req->r_end_latency, len, err);

out_uninline:
	if (!err) {
		int dirty;

		/* Set to CAP_INLINE_NONE and dirty the caps */
		down_read(&fsc->mdsc->snap_rwsem);
		spin_lock(&ci->i_ceph_lock);
		ci->i_inline_version = CEPH_INLINE_NONE;
		dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR, &prealloc_cf);
		spin_unlock(&ci->i_ceph_lock);
		up_read(&fsc->mdsc->snap_rwsem);
		if (dirty)
			__mark_inode_dirty(inode, dirty);
	}
out_put_req:
	ceph_osdc_put_request(req);
	if (err == -ECANCELED)
		err = 0;
out_unlock:
	if (folio) {
		folio_unlock(folio);
		folio_put(folio);
	}
out:
	ceph_free_cap_flush(prealloc_cf);
	doutc(cl, "%llx.%llx inline_version %llu = %d\n",
	      ceph_vinop(inode), inline_version, err);
	return err;
}

static const struct vm_operations_struct ceph_vmops = {
	.fault		= ceph_filemap_fault,
	.page_mkwrite	= ceph_page_mkwrite,
};

int ceph_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct address_space *mapping = file->f_mapping;

	if (!mapping->a_ops->read_folio)
		return -ENOEXEC;
	vma->vm_ops = &ceph_vmops;
	return 0;
}

enum {
	POOL_READ	= 1,
	POOL_WRITE	= 2,
};

static int __ceph_pool_perm_get(struct ceph_inode_info *ci,
				s64 pool, struct ceph_string *pool_ns)
{
	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(&ci->netfs.inode);
	struct ceph_mds_client *mdsc = fsc->mdsc;
	struct ceph_client *cl = fsc->client;
	struct ceph_osd_request *rd_req = NULL, *wr_req = NULL;
	struct rb_node **p, *parent;
	struct ceph_pool_perm *perm;
	struct page **pages;
	size_t pool_ns_len;
	int err = 0, err2 = 0, have = 0;

	down_read(&mdsc->pool_perm_rwsem);
	p = &mdsc->pool_perm_tree.rb_node;
	while (*p) {
		perm = rb_entry(*p, struct ceph_pool_perm, node);
		if (pool < perm->pool)
			p = &(*p)->rb_left;
		else if (pool > perm->pool)
			p = &(*p)->rb_right;
		else {
			int ret = ceph_compare_string(pool_ns,
						perm->pool_ns,
						perm->pool_ns_len);
			if (ret < 0)
				p = &(*p)->rb_left;
			else if (ret > 0)
				p = &(*p)->rb_right;
			else {
				have = perm->perm;
				break;
			}
		}
	}
	up_read(&mdsc->pool_perm_rwsem);
	if (*p)
		goto out;

	if (pool_ns)
		doutc(cl, "pool %lld ns %.*s no perm cached\n", pool,
		      (int)pool_ns->len, pool_ns->str);
	else
		doutc(cl, "pool %lld no perm cached\n", pool);

	down_write(&mdsc->pool_perm_rwsem);
	p = &mdsc->pool_perm_tree.rb_node;
	parent = NULL;
	while (*p) {
		parent = *p;
		perm = rb_entry(parent, struct ceph_pool_perm, node);
		if (pool < perm->pool)
			p = &(*p)->rb_left;
		else if (pool > perm->pool)
			p = &(*p)->rb_right;
		else {
			int ret = ceph_compare_string(pool_ns,
						perm->pool_ns,
						perm->pool_ns_len);
			if (ret < 0)
				p = &(*p)->rb_left;
			else if (ret > 0)
				p = &(*p)->rb_right;
			else {
				have = perm->perm;
				break;
			}
		}
	}
	if (*p) {
		up_write(&mdsc->pool_perm_rwsem);
		goto out;
	}

	rd_req = ceph_osdc_alloc_request(&fsc->client->osdc, NULL,
					 1, false, GFP_NOFS);
	if (!rd_req) {
		err = -ENOMEM;
		goto out_unlock;
	}

	rd_req->r_flags = CEPH_OSD_FLAG_READ;
	osd_req_op_init(rd_req, 0, CEPH_OSD_OP_STAT, 0);
	rd_req->r_base_oloc.pool = pool;
	if (pool_ns)
		rd_req->r_base_oloc.pool_ns = ceph_get_string(pool_ns);
	ceph_oid_printf(&rd_req->r_base_oid, "%llx.00000000", ci->i_vino.ino);

	err = ceph_osdc_alloc_messages(rd_req, GFP_NOFS);
	if (err)
		goto out_unlock;

	wr_req = ceph_osdc_alloc_request(&fsc->client->osdc, NULL,
					 1, false, GFP_NOFS);
	if (!wr_req) {
		err = -ENOMEM;
		goto out_unlock;
	}

	wr_req->r_flags = CEPH_OSD_FLAG_WRITE;
	osd_req_op_init(wr_req, 0, CEPH_OSD_OP_CREATE, CEPH_OSD_OP_FLAG_EXCL);
	ceph_oloc_copy(&wr_req->r_base_oloc, &rd_req->r_base_oloc);
	ceph_oid_copy(&wr_req->r_base_oid, &rd_req->r_base_oid);

	err = ceph_osdc_alloc_messages(wr_req, GFP_NOFS);
	if (err)
		goto out_unlock;

	/* one page should be large enough for STAT data */
	pages = ceph_alloc_page_vector(1, GFP_KERNEL);
	if (IS_ERR(pages)) {
		err = PTR_ERR(pages);
		goto out_unlock;
	}

	osd_req_op_raw_data_in_pages(rd_req, 0, pages, PAGE_SIZE,
				     0, false, true);
	ceph_osdc_start_request(&fsc->client->osdc, rd_req);

	wr_req->r_mtime = inode_get_mtime(&ci->netfs.inode);
	ceph_osdc_start_request(&fsc->client->osdc, wr_req);

	err = ceph_osdc_wait_request(&fsc->client->osdc, rd_req);
	err2 = ceph_osdc_wait_request(&fsc->client->osdc, wr_req);

	if (err >= 0 || err == -ENOENT)
		have |= POOL_READ;
	else if (err != -EPERM) {
		if (err == -EBLOCKLISTED)
			fsc->blocklisted = true;
		goto out_unlock;
	}

	if (err2 == 0 || err2 == -EEXIST)
		have |= POOL_WRITE;
	else if (err2 != -EPERM) {
		if (err2 == -EBLOCKLISTED)
			fsc->blocklisted = true;
		err = err2;
		goto out_unlock;
	}

	pool_ns_len = pool_ns ? pool_ns->len : 0;
	perm = kmalloc(struct_size(perm, pool_ns, pool_ns_len + 1), GFP_NOFS);
	if (!perm) {
		err = -ENOMEM;
		goto out_unlock;
	}

	perm->pool = pool;
	perm->perm = have;
	perm->pool_ns_len = pool_ns_len;
	if (pool_ns_len > 0)
		memcpy(perm->pool_ns, pool_ns->str, pool_ns_len);
	perm->pool_ns[pool_ns_len] = 0;

	rb_link_node(&perm->node, parent, p);
	rb_insert_color(&perm->node, &mdsc->pool_perm_tree);
	err = 0;
out_unlock:
	up_write(&mdsc->pool_perm_rwsem);

	ceph_osdc_put_request(rd_req);
	ceph_osdc_put_request(wr_req);
out:
	if (!err)
		err = have;
	if (pool_ns)
		doutc(cl, "pool %lld ns %.*s result = %d\n", pool,
		      (int)pool_ns->len, pool_ns->str, err);
	else
		doutc(cl, "pool %lld result = %d\n", pool, err);
	return err;
}

int ceph_pool_perm_check(struct inode *inode, int need)
{
	struct ceph_client *cl = ceph_inode_to_client(inode);
	struct ceph_inode_info *ci = ceph_inode(inode);
	struct ceph_string *pool_ns;
	s64 pool;
	int ret, flags;

	/* Only need to do this for regular files */
	if (!S_ISREG(inode->i_mode))
		return 0;

	if (ci->i_vino.snap != CEPH_NOSNAP) {
		/*
		 * Pool permission check needs to write to the first object.
		 * But for snapshot, head of the first object may have already
		 * been deleted. Skip check to avoid creating orphan object.
		 */
		return 0;
	}

	if (ceph_test_mount_opt(ceph_inode_to_fs_client(inode),
				NOPOOLPERM))
		return 0;

	spin_lock(&ci->i_ceph_lock);
	flags = ci->i_ceph_flags;
	pool = ci->i_layout.pool_id;
	spin_unlock(&ci->i_ceph_lock);
check:
	if (flags & CEPH_I_POOL_PERM) {
		if ((need & CEPH_CAP_FILE_RD) && !(flags & CEPH_I_POOL_RD)) {
			doutc(cl, "pool %lld no read perm\n", pool);
			return -EPERM;
		}
		if ((need & CEPH_CAP_FILE_WR) && !(flags & CEPH_I_POOL_WR)) {
			doutc(cl, "pool %lld no write perm\n", pool);
			return -EPERM;
		}
		return 0;
	}

	pool_ns = ceph_try_get_string(ci->i_layout.pool_ns);
	ret = __ceph_pool_perm_get(ci, pool, pool_ns);
	ceph_put_string(pool_ns);
	if (ret < 0)
		return ret;

	flags = CEPH_I_POOL_PERM;
	if (ret & POOL_READ)
		flags |= CEPH_I_POOL_RD;
	if (ret & POOL_WRITE)
		flags |= CEPH_I_POOL_WR;

	spin_lock(&ci->i_ceph_lock);
	if (pool == ci->i_layout.pool_id &&
	    pool_ns == rcu_dereference_raw(ci->i_layout.pool_ns)) {
		ci->i_ceph_flags |= flags;
        } else {
		pool = ci->i_layout.pool_id;
		flags = ci->i_ceph_flags;
	}
	spin_unlock(&ci->i_ceph_lock);
	goto check;
}

void ceph_pool_perm_destroy(struct ceph_mds_client *mdsc)
{
	struct ceph_pool_perm *perm;
	struct rb_node *n;

	while (!RB_EMPTY_ROOT(&mdsc->pool_perm_tree)) {
		n = rb_first(&mdsc->pool_perm_tree);
		perm = rb_entry(n, struct ceph_pool_perm, node);
		rb_erase(n, &mdsc->pool_perm_tree);
		kfree(perm);
	}
}