fs/overlayfs/copy_up.c - third_party/linux - Git at Google

 /*
  *
  * Copyright (C) 2011 Novell Inc.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 as published by
  * the Free Software Foundation.
  */

 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/file.h>
 #include <linux/splice.h>
 #include <linux/xattr.h>
 #include <linux/security.h>
 #include <linux/uaccess.h>
 #include <linux/sched/signal.h>
 #include <linux/cred.h>
 #include <linux/namei.h>
 #include <linux/fdtable.h>
 #include <linux/ratelimit.h>
 #include <linux/exportfs.h>
 #include "overlayfs.h"
 #include "ovl_entry.h"

 #define OVL_COPY_UP_CHUNK_SIZE (1 << 20)

 static bool __read_mostly ovl_check_copy_up;
 module_param_named(check_copy_up, ovl_check_copy_up, bool,
 		   S_IWUSR | S_IRUGO);
 MODULE_PARM_DESC(ovl_check_copy_up,
 		 "Warn on copy-up when causing process also has a R/O fd open");

 static int ovl_check_fd(const void *data, struct file *f, unsigned int fd)
 {
 	const struct dentry *dentry = data;

 	if (file_inode(f) == d_inode(dentry))
 		pr_warn_ratelimited("overlayfs: Warning: Copying up %pD, but open R/O on fd %u which will cease to be coherent [pid=%d %s]\n",
 				    f, fd, current->pid, current->comm);
 	return 0;
 }

 /*
  * Check the fds open by this process and warn if something like the following
  * scenario is about to occur:
  *
  *	fd1 = open("foo", O_RDONLY);
  *	fd2 = open("foo", O_RDWR);
  */
 static void ovl_do_check_copy_up(struct dentry *dentry)
 {
 	if (ovl_check_copy_up)
 		iterate_fd(current->files, 0, ovl_check_fd, dentry);
 }

 int ovl_copy_xattr(struct dentry *old, struct dentry *new)
 {
 	ssize_t list_size, size, value_size = 0;
 	char *buf, *name, *value = NULL;
 	int uninitialized_var(error);
 	size_t slen;

 	if (!(old->d_inode->i_opflags & IOP_XATTR) ||
 	    !(new->d_inode->i_opflags & IOP_XATTR))
 		return 0;

 	list_size = vfs_listxattr(old, NULL, 0);
 	if (list_size <= 0) {
 		if (list_size == -EOPNOTSUPP)
 			return 0;
 		return list_size;
 	}

 	buf = kzalloc(list_size, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;

 	list_size = vfs_listxattr(old, buf, list_size);
 	if (list_size <= 0) {
 		error = list_size;
 		goto out;
 	}

 	for (name = buf; list_size; name += slen) {
 		slen = strnlen(name, list_size) + 1;

 		/* underlying fs providing us with an broken xattr list? */
 		if (WARN_ON(slen > list_size)) {
 			error = -EIO;
 			break;
 		}
 		list_size -= slen;

 		if (ovl_is_private_xattr(name))
 			continue;
 retry:
 		size = vfs_getxattr(old, name, value, value_size);
 		if (size == -ERANGE)
 			size = vfs_getxattr(old, name, NULL, 0);

 		if (size < 0) {
 			error = size;
 			break;
 		}

 		if (size > value_size) {
 			void *new;

 			new = krealloc(value, size, GFP_KERNEL);
 			if (!new) {
 				error = -ENOMEM;
 				break;
 			}
 			value = new;
 			value_size = size;
 			goto retry;
 		}

 		error = security_inode_copy_up_xattr(name);
 		if (error < 0 && error != -EOPNOTSUPP)
 			break;
 		if (error == 1) {
 			error = 0;
 			continue; /* Discard */
 		}
 		error = vfs_setxattr(new, name, value, size, 0);
 		if (error)
 			break;
 	}
 	kfree(value);
 out:
 	kfree(buf);
 	return error;
 }

 static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 {
 	struct file *old_file;
 	struct file *new_file;
 	loff_t old_pos = 0;
 	loff_t new_pos = 0;
 	int error = 0;

 	if (len == 0)
 		return 0;

 	old_file = ovl_path_open(old, O_LARGEFILE | O_RDONLY);
 	if (IS_ERR(old_file))
 		return PTR_ERR(old_file);

 	new_file = ovl_path_open(new, O_LARGEFILE | O_WRONLY);
 	if (IS_ERR(new_file)) {
 		error = PTR_ERR(new_file);
 		goto out_fput;
 	}

 	/* Try to use clone_file_range to clone up within the same fs */
 	error = vfs_clone_file_range(old_file, 0, new_file, 0, len);
 	if (!error)
 		goto out;
 	/* Couldn't clone, so now we try to copy the data */
 	error = 0;

 	/* FIXME: copy up sparse files efficiently */
 	while (len) {
 		size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
 		long bytes;

 		if (len < this_len)
 			this_len = len;

 		if (signal_pending_state(TASK_KILLABLE, current)) {
 			error = -EINTR;
 			break;
 		}

 		bytes = do_splice_direct(old_file, &old_pos,
 					 new_file, &new_pos,
 					 this_len, SPLICE_F_MOVE);
 		if (bytes <= 0) {
 			error = bytes;
 			break;
 		}
 		WARN_ON(old_pos != new_pos);

 		len -= bytes;
 	}
 out:
 	if (!error)
 		error = vfs_fsync(new_file, 0);
 	fput(new_file);
 out_fput:
 	fput(old_file);
 	return error;
 }

 static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
 {
 	struct iattr attr = {
 		.ia_valid =
 		     ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
 		.ia_atime = stat->atime,
 		.ia_mtime = stat->mtime,
 	};

 	return notify_change(upperdentry, &attr, NULL);
 }

 int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
 {
 	int err = 0;

 	if (!S_ISLNK(stat->mode)) {
 		struct iattr attr = {
 			.ia_valid = ATTR_MODE,
 			.ia_mode = stat->mode,
 		};
 		err = notify_change(upperdentry, &attr, NULL);
 	}
 	if (!err) {
 		struct iattr attr = {
 			.ia_valid = ATTR_UID | ATTR_GID,
 			.ia_uid = stat->uid,
 			.ia_gid = stat->gid,
 		};
 		err = notify_change(upperdentry, &attr, NULL);
 	}
 	if (!err)
 		ovl_set_timestamps(upperdentry, stat);

 	return err;
 }

 static struct ovl_fh *ovl_encode_fh(struct dentry *lower, uuid_t *uuid)
 {
 	struct ovl_fh *fh;
 	int fh_type, fh_len, dwords;
 	void *buf;
 	int buflen = MAX_HANDLE_SZ;

 	buf = kmalloc(buflen, GFP_TEMPORARY);
 	if (!buf)
 		return ERR_PTR(-ENOMEM);

 	/*
 	 * We encode a non-connectable file handle for non-dir, because we
 	 * only need to find the lower inode number and we don't want to pay
 	 * the price or reconnecting the dentry.
 	 */
 	dwords = buflen >> 2;
 	fh_type = exportfs_encode_fh(lower, buf, &dwords, 0);
 	buflen = (dwords << 2);

 	fh = ERR_PTR(-EIO);
 	if (WARN_ON(fh_type < 0) ||
 	    WARN_ON(buflen > MAX_HANDLE_SZ) ||
 	    WARN_ON(fh_type == FILEID_INVALID))
 		goto out;

 	BUILD_BUG_ON(MAX_HANDLE_SZ + offsetof(struct ovl_fh, fid) > 255);
 	fh_len = offsetof(struct ovl_fh, fid) + buflen;
 	fh = kmalloc(fh_len, GFP_KERNEL);
 	if (!fh) {
 		fh = ERR_PTR(-ENOMEM);
 		goto out;
 	}

 	fh->version = OVL_FH_VERSION;
 	fh->magic = OVL_FH_MAGIC;
 	fh->type = fh_type;
 	fh->flags = OVL_FH_FLAG_CPU_ENDIAN;
 	fh->len = fh_len;
 	fh->uuid = *uuid;
 	memcpy(fh->fid, buf, buflen);

 out:
 	kfree(buf);
 	return fh;
 }

 static int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
 			  struct dentry *upper)
 {
 	struct super_block *sb = lower->d_sb;
 	const struct ovl_fh *fh = NULL;
 	int err;

 	/*
 	 * When lower layer doesn't support export operations store a 'null' fh,
 	 * so we can use the overlay.origin xattr to distignuish between a copy
 	 * up and a pure upper inode.
 	 */
 	if (sb->s_export_op && sb->s_export_op->fh_to_dentry &&
 	    !uuid_is_null(&sb->s_uuid)) {
 		fh = ovl_encode_fh(lower, &sb->s_uuid);
 		if (IS_ERR(fh))
 			return PTR_ERR(fh);
 	}

 	/*
 	 * Do not fail when upper doesn't support xattrs.
 	 */
 	err = ovl_check_setxattr(dentry, upper, OVL_XATTR_ORIGIN, fh,
 				 fh ? fh->len : 0, 0);
 	kfree(fh);

 	return err;
 }

 static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
 			      struct dentry *dentry, struct path *lowerpath,
 			      struct kstat *stat, const char *link,
 			      struct kstat *pstat, bool tmpfile)
 {
 	struct inode *wdir = workdir->d_inode;
 	struct inode *udir = upperdir->d_inode;
 	struct dentry *newdentry = NULL;
 	struct dentry *upper = NULL;
 	struct dentry *temp = NULL;
 	int err;
 	const struct cred *old_creds = NULL;
 	struct cred *new_creds = NULL;
 	struct cattr cattr = {
 		/* Can't properly set mode on creation because of the umask */
 		.mode = stat->mode & S_IFMT,
 		.rdev = stat->rdev,
 		.link = link
 	};

 	err = security_inode_copy_up(dentry, &new_creds);
 	if (err < 0)
 		goto out;

 	if (new_creds)
 		old_creds = override_creds(new_creds);

 	if (tmpfile)
 		temp = ovl_do_tmpfile(upperdir, stat->mode);
 	else
 		temp = ovl_lookup_temp(workdir);
 	err = 0;
 	if (IS_ERR(temp)) {
 		err = PTR_ERR(temp);
 		temp = NULL;
 	}

 	if (!err && !tmpfile)
 		err = ovl_create_real(wdir, temp, &cattr, NULL, true);

 	if (new_creds) {
 		revert_creds(old_creds);
 		put_cred(new_creds);
 	}

 	if (err)
 		goto out;

 	if (S_ISREG(stat->mode)) {
 		struct path upperpath;

 		ovl_path_upper(dentry, &upperpath);
 		BUG_ON(upperpath.dentry != NULL);
 		upperpath.dentry = temp;

 		if (tmpfile) {
 			inode_unlock(udir);
 			err = ovl_copy_up_data(lowerpath, &upperpath,
 					       stat->size);
 			inode_lock_nested(udir, I_MUTEX_PARENT);
 		} else {
 			err = ovl_copy_up_data(lowerpath, &upperpath,
 					       stat->size);
 		}

 		if (err)
 			goto out_cleanup;
 	}

 	err = ovl_copy_xattr(lowerpath->dentry, temp);
 	if (err)
 		goto out_cleanup;

 	inode_lock(temp->d_inode);
 	err = ovl_set_attr(temp, stat);
 	inode_unlock(temp->d_inode);
 	if (err)
 		goto out_cleanup;

 	/*
 	 * Store identifier of lower inode in upper inode xattr to
 	 * allow lookup of the copy up origin inode.
 	 *
 	 * Don't set origin when we are breaking the association with a lower
 	 * hard link.
 	 */
 	if (S_ISDIR(stat->mode) || stat->nlink == 1) {
 		err = ovl_set_origin(dentry, lowerpath->dentry, temp);
 		if (err)
 			goto out_cleanup;
 	}

 	upper = lookup_one_len(dentry->d_name.name, upperdir,
 			       dentry->d_name.len);
 	if (IS_ERR(upper)) {
 		err = PTR_ERR(upper);
 		upper = NULL;
 		goto out_cleanup;
 	}

 	if (tmpfile)
 		err = ovl_do_link(temp, udir, upper, true);
 	else
 		err = ovl_do_rename(wdir, temp, udir, upper, 0);
 	if (err)
 		goto out_cleanup;

 	newdentry = dget(tmpfile ? upper : temp);
 	ovl_dentry_update(dentry, newdentry);
 	ovl_inode_update(d_inode(dentry), d_inode(newdentry));

 	/* Restore timestamps on parent (best effort) */
 	ovl_set_timestamps(upperdir, pstat);
 out:
 	dput(temp);
 	dput(upper);
 	return err;

 out_cleanup:
 	if (!tmpfile)
 		ovl_cleanup(wdir, temp);
 	goto out;
 }

 /*
  * Copy up a single dentry
  *
  * All renames start with copy up of source if necessary.  The actual
  * rename will only proceed once the copy up was successful.  Copy up uses
  * upper parent i_mutex for exclusion.  Since rename can change d_parent it
  * is possible that the copy up will lock the old parent.  At that point
  * the file will have already been copied up anyway.
  */
 static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 			   struct path *lowerpath, struct kstat *stat)
 {
 	DEFINE_DELAYED_CALL(done);
 	struct dentry *workdir = ovl_workdir(dentry);
 	int err;
 	struct kstat pstat;
 	struct path parentpath;
 	struct dentry *lowerdentry = lowerpath->dentry;
 	struct dentry *upperdir;
 	const char *link = NULL;
 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;

 	if (WARN_ON(!workdir))
 		return -EROFS;

 	ovl_do_check_copy_up(lowerdentry);

 	ovl_path_upper(parent, &parentpath);
 	upperdir = parentpath.dentry;

 	/* Mark parent "impure" because it may now contain non-pure upper */
 	err = ovl_set_impure(parent, upperdir);
 	if (err)
 		return err;

 	err = vfs_getattr(&parentpath, &pstat,
 			  STATX_ATIME | STATX_MTIME, AT_STATX_SYNC_AS_STAT);
 	if (err)
 		return err;

 	if (S_ISLNK(stat->mode)) {
 		link = vfs_get_link(lowerdentry, &done);
 		if (IS_ERR(link))
 			return PTR_ERR(link);
 	}

 	/* Should we copyup with O_TMPFILE or with workdir? */
 	if (S_ISREG(stat->mode) && ofs->tmpfile) {
 		err = ovl_copy_up_start(dentry);
 		/* err < 0: interrupted, err > 0: raced with another copy-up */
 		if (unlikely(err)) {
 			pr_debug("ovl_copy_up_start(%pd2) = %i\n", dentry, err);
 			if (err > 0)
 				err = 0;
 			goto out_done;
 		}

 		inode_lock_nested(upperdir->d_inode, I_MUTEX_PARENT);
 		err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
 					 stat, link, &pstat, true);
 		inode_unlock(upperdir->d_inode);
 		ovl_copy_up_end(dentry);
 		goto out_done;
 	}

 	err = -EIO;
 	if (lock_rename(workdir, upperdir) != NULL) {
 		pr_err("overlayfs: failed to lock workdir+upperdir\n");
 		goto out_unlock;
 	}
 	if (ovl_dentry_upper(dentry)) {
 		/* Raced with another copy-up?  Nothing to do, then... */
 		err = 0;
 		goto out_unlock;
 	}

 	err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
 				 stat, link, &pstat, false);
 out_unlock:
 	unlock_rename(workdir, upperdir);
 out_done:
 	do_delayed_call(&done);

 	return err;
 }

 int ovl_copy_up_flags(struct dentry *dentry, int flags)
 {
 	int err = 0;
 	const struct cred *old_cred = ovl_override_creds(dentry->d_sb);

 	while (!err) {
 		struct dentry *next;
 		struct dentry *parent;
 		struct path lowerpath;
 		struct kstat stat;
 		enum ovl_path_type type = ovl_path_type(dentry);

 		if (OVL_TYPE_UPPER(type))
 			break;

 		next = dget(dentry);
 		/* find the topmost dentry not yet copied up */
 		for (;;) {
 			parent = dget_parent(next);

 			type = ovl_path_type(parent);
 			if (OVL_TYPE_UPPER(type))
 				break;

 			dput(next);
 			next = parent;
 		}

 		ovl_path_lower(next, &lowerpath);
 		err = vfs_getattr(&lowerpath, &stat,
 				  STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
 		/* maybe truncate regular file. this has no effect on dirs */
 		if (flags & O_TRUNC)
 			stat.size = 0;
 		if (!err)
 			err = ovl_copy_up_one(parent, next, &lowerpath, &stat);

 		dput(parent);
 		dput(next);
 	}
 	revert_creds(old_cred);

 	return err;
 }

 int ovl_copy_up(struct dentry *dentry)
 {
 	return ovl_copy_up_flags(dentry, 0);
 }
	/*
	*
	* Copyright (C) 2011 Novell Inc.
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 as published by
	* the Free Software Foundation.
	*/

	#include <linux/module.h>
	#include <linux/fs.h>
	#include <linux/slab.h>
	#include <linux/file.h>
	#include <linux/splice.h>
	#include <linux/xattr.h>
	#include <linux/security.h>
	#include <linux/uaccess.h>
	#include <linux/sched/signal.h>
	#include <linux/cred.h>
	#include <linux/namei.h>
	#include <linux/fdtable.h>
	#include <linux/ratelimit.h>
	#include <linux/exportfs.h>
	#include "overlayfs.h"
	#include "ovl_entry.h"

	#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)

	static bool __read_mostly ovl_check_copy_up;
	module_param_named(check_copy_up, ovl_check_copy_up, bool,
	S_IWUSR \| S_IRUGO);
	MODULE_PARM_DESC(ovl_check_copy_up,
	"Warn on copy-up when causing process also has a R/O fd open");

	static int ovl_check_fd(const void data, struct file f, unsigned int fd)
	{
	const struct dentry *dentry = data;

	if (file_inode(f) == d_inode(dentry))
	pr_warn_ratelimited("overlayfs: Warning: Copying up %pD, but open R/O on fd %u which will cease to be coherent [pid=%d %s]\n",
	f, fd, current->pid, current->comm);
	return 0;
	}

	/*
	* Check the fds open by this process and warn if something like the following
	* scenario is about to occur:
	*
	* fd1 = open("foo", O_RDONLY);
	* fd2 = open("foo", O_RDWR);
	*/
	static void ovl_do_check_copy_up(struct dentry *dentry)
	{
	if (ovl_check_copy_up)
	iterate_fd(current->files, 0, ovl_check_fd, dentry);
	}

	int ovl_copy_xattr(struct dentry old, struct dentry new)
	{
	ssize_t list_size, size, value_size = 0;
	char buf, name, *value = NULL;
	int uninitialized_var(error);
	size_t slen;

	if (!(old->d_inode->i_opflags & IOP_XATTR) \|\|
	!(new->d_inode->i_opflags & IOP_XATTR))
	return 0;

	list_size = vfs_listxattr(old, NULL, 0);
	if (list_size <= 0) {
	if (list_size == -EOPNOTSUPP)
	return 0;
	return list_size;
	}

	buf = kzalloc(list_size, GFP_KERNEL);
	if (!buf)
	return -ENOMEM;

	list_size = vfs_listxattr(old, buf, list_size);
	if (list_size <= 0) {
	error = list_size;
	goto out;
	}

	for (name = buf; list_size; name += slen) {
	slen = strnlen(name, list_size) + 1;

	/* underlying fs providing us with an broken xattr list? */
	if (WARN_ON(slen > list_size)) {
	error = -EIO;
	break;
	}
	list_size -= slen;

	if (ovl_is_private_xattr(name))
	continue;
	retry:
	size = vfs_getxattr(old, name, value, value_size);
	if (size == -ERANGE)
	size = vfs_getxattr(old, name, NULL, 0);

	if (size < 0) {
	error = size;
	break;
	}

	if (size > value_size) {
	void *new;

	new = krealloc(value, size, GFP_KERNEL);
	if (!new) {
	error = -ENOMEM;
	break;
	}
	value = new;
	value_size = size;
	goto retry;
	}

	error = security_inode_copy_up_xattr(name);
	if (error < 0 && error != -EOPNOTSUPP)
	break;
	if (error == 1) {
	error = 0;
	continue; /* Discard */
	}
	error = vfs_setxattr(new, name, value, size, 0);
	if (error)
	break;
	}
	kfree(value);
	out:
	kfree(buf);
	return error;
	}

	static int ovl_copy_up_data(struct path old, struct path new, loff_t len)
	{
	struct file *old_file;
	struct file *new_file;
	loff_t old_pos = 0;
	loff_t new_pos = 0;
	int error = 0;

	if (len == 0)
	return 0;

	old_file = ovl_path_open(old, O_LARGEFILE \| O_RDONLY);
	if (IS_ERR(old_file))
	return PTR_ERR(old_file);

	new_file = ovl_path_open(new, O_LARGEFILE \| O_WRONLY);
	if (IS_ERR(new_file)) {
	error = PTR_ERR(new_file);
	goto out_fput;
	}

	/* Try to use clone_file_range to clone up within the same fs */
	error = vfs_clone_file_range(old_file, 0, new_file, 0, len);
	if (!error)
	goto out;
	/* Couldn't clone, so now we try to copy the data */
	error = 0;

	/* FIXME: copy up sparse files efficiently */
	while (len) {
	size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
	long bytes;

	if (len < this_len)
	this_len = len;

	if (signal_pending_state(TASK_KILLABLE, current)) {
	error = -EINTR;
	break;
	}

	bytes = do_splice_direct(old_file, &old_pos,
	new_file, &new_pos,
	this_len, SPLICE_F_MOVE);
	if (bytes <= 0) {
	error = bytes;
	break;
	}
	WARN_ON(old_pos != new_pos);

	len -= bytes;
	}
	out:
	if (!error)
	error = vfs_fsync(new_file, 0);
	fput(new_file);
	out_fput:
	fput(old_file);
	return error;
	}

	static int ovl_set_timestamps(struct dentry upperdentry, struct kstat stat)
	{
	struct iattr attr = {
	.ia_valid =
	ATTR_ATIME \| ATTR_MTIME \| ATTR_ATIME_SET \| ATTR_MTIME_SET,
	.ia_atime = stat->atime,
	.ia_mtime = stat->mtime,
	};

	return notify_change(upperdentry, &attr, NULL);
	}

	int ovl_set_attr(struct dentry upperdentry, struct kstat stat)
	{
	int err = 0;

	if (!S_ISLNK(stat->mode)) {
	struct iattr attr = {
	.ia_valid = ATTR_MODE,
	.ia_mode = stat->mode,
	};
	err = notify_change(upperdentry, &attr, NULL);
	}
	if (!err) {
	struct iattr attr = {
	.ia_valid = ATTR_UID \| ATTR_GID,
	.ia_uid = stat->uid,
	.ia_gid = stat->gid,
	};
	err = notify_change(upperdentry, &attr, NULL);
	}
	if (!err)
	ovl_set_timestamps(upperdentry, stat);

	return err;
	}

	static struct ovl_fh ovl_encode_fh(struct dentry lower, uuid_t *uuid)
	{
	struct ovl_fh *fh;
	int fh_type, fh_len, dwords;
	void *buf;
	int buflen = MAX_HANDLE_SZ;

	buf = kmalloc(buflen, GFP_TEMPORARY);
	if (!buf)
	return ERR_PTR(-ENOMEM);

	/*
	* We encode a non-connectable file handle for non-dir, because we
	* only need to find the lower inode number and we don't want to pay
	* the price or reconnecting the dentry.
	*/
	dwords = buflen >> 2;
	fh_type = exportfs_encode_fh(lower, buf, &dwords, 0);
	buflen = (dwords << 2);

	fh = ERR_PTR(-EIO);
	if (WARN_ON(fh_type < 0) \|\|
	WARN_ON(buflen > MAX_HANDLE_SZ) \|\|
	WARN_ON(fh_type == FILEID_INVALID))
	goto out;

	BUILD_BUG_ON(MAX_HANDLE_SZ + offsetof(struct ovl_fh, fid) > 255);
	fh_len = offsetof(struct ovl_fh, fid) + buflen;
	fh = kmalloc(fh_len, GFP_KERNEL);
	if (!fh) {
	fh = ERR_PTR(-ENOMEM);
	goto out;
	}

	fh->version = OVL_FH_VERSION;
	fh->magic = OVL_FH_MAGIC;
	fh->type = fh_type;
	fh->flags = OVL_FH_FLAG_CPU_ENDIAN;
	fh->len = fh_len;
	fh->uuid = *uuid;
	memcpy(fh->fid, buf, buflen);

	out:
	kfree(buf);
	return fh;
	}

	static int ovl_set_origin(struct dentry dentry, struct dentry lower,
	struct dentry *upper)
	{
	struct super_block *sb = lower->d_sb;
	const struct ovl_fh *fh = NULL;
	int err;

	/*
	* When lower layer doesn't support export operations store a 'null' fh,
	* so we can use the overlay.origin xattr to distignuish between a copy
	* up and a pure upper inode.
	*/
	if (sb->s_export_op && sb->s_export_op->fh_to_dentry &&
	!uuid_is_null(&sb->s_uuid)) {
	fh = ovl_encode_fh(lower, &sb->s_uuid);
	if (IS_ERR(fh))
	return PTR_ERR(fh);
	}

	/*
	* Do not fail when upper doesn't support xattrs.
	*/
	err = ovl_check_setxattr(dentry, upper, OVL_XATTR_ORIGIN, fh,
	fh ? fh->len : 0, 0);
	kfree(fh);

	return err;
	}

	static int ovl_copy_up_locked(struct dentry workdir, struct dentry upperdir,
	struct dentry dentry, struct path lowerpath,
	struct kstat stat, const char link,
	struct kstat *pstat, bool tmpfile)
	{
	struct inode *wdir = workdir->d_inode;
	struct inode *udir = upperdir->d_inode;
	struct dentry *newdentry = NULL;
	struct dentry *upper = NULL;
	struct dentry *temp = NULL;
	int err;
	const struct cred *old_creds = NULL;
	struct cred *new_creds = NULL;
	struct cattr cattr = {
	/* Can't properly set mode on creation because of the umask */
	.mode = stat->mode & S_IFMT,
	.rdev = stat->rdev,
	.link = link
	};

	err = security_inode_copy_up(dentry, &new_creds);
	if (err < 0)
	goto out;

	if (new_creds)
	old_creds = override_creds(new_creds);

	if (tmpfile)
	temp = ovl_do_tmpfile(upperdir, stat->mode);
	else
	temp = ovl_lookup_temp(workdir);
	err = 0;
	if (IS_ERR(temp)) {
	err = PTR_ERR(temp);
	temp = NULL;
	}

	if (!err && !tmpfile)
	err = ovl_create_real(wdir, temp, &cattr, NULL, true);

	if (new_creds) {
	revert_creds(old_creds);
	put_cred(new_creds);
	}

	if (err)
	goto out;

	if (S_ISREG(stat->mode)) {
	struct path upperpath;

	ovl_path_upper(dentry, &upperpath);
	BUG_ON(upperpath.dentry != NULL);
	upperpath.dentry = temp;

	if (tmpfile) {
	inode_unlock(udir);
	err = ovl_copy_up_data(lowerpath, &upperpath,
	stat->size);
	inode_lock_nested(udir, I_MUTEX_PARENT);
	} else {
	err = ovl_copy_up_data(lowerpath, &upperpath,
	stat->size);
	}

	if (err)
	goto out_cleanup;
	}

	err = ovl_copy_xattr(lowerpath->dentry, temp);
	if (err)
	goto out_cleanup;

	inode_lock(temp->d_inode);
	err = ovl_set_attr(temp, stat);
	inode_unlock(temp->d_inode);
	if (err)
	goto out_cleanup;

	/*
	* Store identifier of lower inode in upper inode xattr to
	* allow lookup of the copy up origin inode.
	*
	* Don't set origin when we are breaking the association with a lower
	* hard link.
	*/
	if (S_ISDIR(stat->mode) \|\| stat->nlink == 1) {
	err = ovl_set_origin(dentry, lowerpath->dentry, temp);
	if (err)
	goto out_cleanup;
	}

	upper = lookup_one_len(dentry->d_name.name, upperdir,
	dentry->d_name.len);
	if (IS_ERR(upper)) {
	err = PTR_ERR(upper);
	upper = NULL;
	goto out_cleanup;
	}

	if (tmpfile)
	err = ovl_do_link(temp, udir, upper, true);
	else
	err = ovl_do_rename(wdir, temp, udir, upper, 0);
	if (err)
	goto out_cleanup;

	newdentry = dget(tmpfile ? upper : temp);
	ovl_dentry_update(dentry, newdentry);
	ovl_inode_update(d_inode(dentry), d_inode(newdentry));

	/* Restore timestamps on parent (best effort) */
	ovl_set_timestamps(upperdir, pstat);
	out:
	dput(temp);
	dput(upper);
	return err;

	out_cleanup:
	if (!tmpfile)
	ovl_cleanup(wdir, temp);
	goto out;
	}

	/*
	* Copy up a single dentry
	*
	* All renames start with copy up of source if necessary. The actual
	* rename will only proceed once the copy up was successful. Copy up uses
	* upper parent i_mutex for exclusion. Since rename can change d_parent it
	* is possible that the copy up will lock the old parent. At that point
	* the file will have already been copied up anyway.
	*/
	static int ovl_copy_up_one(struct dentry parent, struct dentry dentry,
	struct path lowerpath, struct kstat stat)
	{
	DEFINE_DELAYED_CALL(done);
	struct dentry *workdir = ovl_workdir(dentry);
	int err;
	struct kstat pstat;
	struct path parentpath;
	struct dentry *lowerdentry = lowerpath->dentry;
	struct dentry *upperdir;
	const char *link = NULL;
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;

	if (WARN_ON(!workdir))
	return -EROFS;

	ovl_do_check_copy_up(lowerdentry);

	ovl_path_upper(parent, &parentpath);
	upperdir = parentpath.dentry;

	/* Mark parent "impure" because it may now contain non-pure upper */
	err = ovl_set_impure(parent, upperdir);
	if (err)
	return err;

	err = vfs_getattr(&parentpath, &pstat,
	STATX_ATIME \| STATX_MTIME, AT_STATX_SYNC_AS_STAT);
	if (err)
	return err;

	if (S_ISLNK(stat->mode)) {
	link = vfs_get_link(lowerdentry, &done);
	if (IS_ERR(link))
	return PTR_ERR(link);
	}

	/* Should we copyup with O_TMPFILE or with workdir? */
	if (S_ISREG(stat->mode) && ofs->tmpfile) {
	err = ovl_copy_up_start(dentry);
	/* err < 0: interrupted, err > 0: raced with another copy-up */
	if (unlikely(err)) {
	pr_debug("ovl_copy_up_start(%pd2) = %i\n", dentry, err);
	if (err > 0)
	err = 0;
	goto out_done;
	}

	inode_lock_nested(upperdir->d_inode, I_MUTEX_PARENT);
	err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
	stat, link, &pstat, true);
	inode_unlock(upperdir->d_inode);
	ovl_copy_up_end(dentry);
	goto out_done;
	}

	err = -EIO;
	if (lock_rename(workdir, upperdir) != NULL) {
	pr_err("overlayfs: failed to lock workdir+upperdir\n");
	goto out_unlock;
	}
	if (ovl_dentry_upper(dentry)) {
	/* Raced with another copy-up? Nothing to do, then... */
	err = 0;
	goto out_unlock;
	}

	err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
	stat, link, &pstat, false);
	out_unlock:
	unlock_rename(workdir, upperdir);
	out_done:
	do_delayed_call(&done);

	return err;
	}

	int ovl_copy_up_flags(struct dentry *dentry, int flags)
	{
	int err = 0;
	const struct cred *old_cred = ovl_override_creds(dentry->d_sb);

	while (!err) {
	struct dentry *next;
	struct dentry *parent;
	struct path lowerpath;
	struct kstat stat;
	enum ovl_path_type type = ovl_path_type(dentry);

	if (OVL_TYPE_UPPER(type))
	break;

	next = dget(dentry);
	/* find the topmost dentry not yet copied up */
	for (;;) {
	parent = dget_parent(next);

	type = ovl_path_type(parent);
	if (OVL_TYPE_UPPER(type))
	break;

	dput(next);
	next = parent;
	}

	ovl_path_lower(next, &lowerpath);
	err = vfs_getattr(&lowerpath, &stat,
	STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
	/* maybe truncate regular file. this has no effect on dirs */
	if (flags & O_TRUNC)
	stat.size = 0;
	if (!err)
	err = ovl_copy_up_one(parent, next, &lowerpath, &stat);

	dput(parent);
	dput(next);
	}
	revert_creds(old_cred);

	return err;
	}

	int ovl_copy_up(struct dentry *dentry)
	{
	return ovl_copy_up_flags(dentry, 0);
	}