ioctl.c 47.1 KB
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/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/file.h>
#include <linux/fs.h>
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#include <linux/fsnotify.h>
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#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
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#include <linux/mount.h>
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#include <linux/mpage.h>
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#include <linux/namei.h>
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#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
#include <linux/bit_spinlock.h>
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#include <linux/security.h>
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#include <linux/xattr.h>
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#include <linux/vmalloc.h>
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#include "compat.h"
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#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "ioctl.h"
#include "print-tree.h"
#include "volumes.h"
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#include "locking.h"
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#include "ctree.h"
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/* Mask out flags that are inappropriate for the given type of inode. */
static inline __u32 btrfs_mask_flags(umode_t mode, __u32 flags)
{
	if (S_ISDIR(mode))
		return flags;
	else if (S_ISREG(mode))
		return flags & ~FS_DIRSYNC_FL;
	else
		return flags & (FS_NODUMP_FL | FS_NOATIME_FL);
}

/*
 * Export inode flags to the format expected by the FS_IOC_GETFLAGS ioctl.
 */
static unsigned int btrfs_flags_to_ioctl(unsigned int flags)
{
	unsigned int iflags = 0;

	if (flags & BTRFS_INODE_SYNC)
		iflags |= FS_SYNC_FL;
	if (flags & BTRFS_INODE_IMMUTABLE)
		iflags |= FS_IMMUTABLE_FL;
	if (flags & BTRFS_INODE_APPEND)
		iflags |= FS_APPEND_FL;
	if (flags & BTRFS_INODE_NODUMP)
		iflags |= FS_NODUMP_FL;
	if (flags & BTRFS_INODE_NOATIME)
		iflags |= FS_NOATIME_FL;
	if (flags & BTRFS_INODE_DIRSYNC)
		iflags |= FS_DIRSYNC_FL;

	return iflags;
}

/*
 * Update inode->i_flags based on the btrfs internal flags.
 */
void btrfs_update_iflags(struct inode *inode)
{
	struct btrfs_inode *ip = BTRFS_I(inode);

	inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);

	if (ip->flags & BTRFS_INODE_SYNC)
		inode->i_flags |= S_SYNC;
	if (ip->flags & BTRFS_INODE_IMMUTABLE)
		inode->i_flags |= S_IMMUTABLE;
	if (ip->flags & BTRFS_INODE_APPEND)
		inode->i_flags |= S_APPEND;
	if (ip->flags & BTRFS_INODE_NOATIME)
		inode->i_flags |= S_NOATIME;
	if (ip->flags & BTRFS_INODE_DIRSYNC)
		inode->i_flags |= S_DIRSYNC;
}

/*
 * Inherit flags from the parent inode.
 *
 * Unlike extN we don't have any flags we don't want to inherit currently.
 */
void btrfs_inherit_iflags(struct inode *inode, struct inode *dir)
{
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	unsigned int flags;

	if (!dir)
		return;

	flags = BTRFS_I(dir)->flags;
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	if (S_ISREG(inode->i_mode))
		flags &= ~BTRFS_INODE_DIRSYNC;
	else if (!S_ISDIR(inode->i_mode))
		flags &= (BTRFS_INODE_NODUMP | BTRFS_INODE_NOATIME);

	BTRFS_I(inode)->flags = flags;
	btrfs_update_iflags(inode);
}

static int btrfs_ioctl_getflags(struct file *file, void __user *arg)
{
	struct btrfs_inode *ip = BTRFS_I(file->f_path.dentry->d_inode);
	unsigned int flags = btrfs_flags_to_ioctl(ip->flags);

	if (copy_to_user(arg, &flags, sizeof(flags)))
		return -EFAULT;
	return 0;
}

static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
{
	struct inode *inode = file->f_path.dentry->d_inode;
	struct btrfs_inode *ip = BTRFS_I(inode);
	struct btrfs_root *root = ip->root;
	struct btrfs_trans_handle *trans;
	unsigned int flags, oldflags;
	int ret;

	if (copy_from_user(&flags, arg, sizeof(flags)))
		return -EFAULT;

	if (flags & ~(FS_IMMUTABLE_FL | FS_APPEND_FL | \
		      FS_NOATIME_FL | FS_NODUMP_FL | \
		      FS_SYNC_FL | FS_DIRSYNC_FL))
		return -EOPNOTSUPP;
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	if (!is_owner_or_cap(inode))
		return -EACCES;

	mutex_lock(&inode->i_mutex);

	flags = btrfs_mask_flags(inode->i_mode, flags);
	oldflags = btrfs_flags_to_ioctl(ip->flags);
	if ((flags ^ oldflags) & (FS_APPEND_FL | FS_IMMUTABLE_FL)) {
		if (!capable(CAP_LINUX_IMMUTABLE)) {
			ret = -EPERM;
			goto out_unlock;
		}
	}

	ret = mnt_want_write(file->f_path.mnt);
	if (ret)
		goto out_unlock;

	if (flags & FS_SYNC_FL)
		ip->flags |= BTRFS_INODE_SYNC;
	else
		ip->flags &= ~BTRFS_INODE_SYNC;
	if (flags & FS_IMMUTABLE_FL)
		ip->flags |= BTRFS_INODE_IMMUTABLE;
	else
		ip->flags &= ~BTRFS_INODE_IMMUTABLE;
	if (flags & FS_APPEND_FL)
		ip->flags |= BTRFS_INODE_APPEND;
	else
		ip->flags &= ~BTRFS_INODE_APPEND;
	if (flags & FS_NODUMP_FL)
		ip->flags |= BTRFS_INODE_NODUMP;
	else
		ip->flags &= ~BTRFS_INODE_NODUMP;
	if (flags & FS_NOATIME_FL)
		ip->flags |= BTRFS_INODE_NOATIME;
	else
		ip->flags &= ~BTRFS_INODE_NOATIME;
	if (flags & FS_DIRSYNC_FL)
		ip->flags |= BTRFS_INODE_DIRSYNC;
	else
		ip->flags &= ~BTRFS_INODE_DIRSYNC;


	trans = btrfs_join_transaction(root, 1);
	BUG_ON(!trans);

	ret = btrfs_update_inode(trans, root, inode);
	BUG_ON(ret);

	btrfs_update_iflags(inode);
	inode->i_ctime = CURRENT_TIME;
	btrfs_end_transaction(trans, root);

	mnt_drop_write(file->f_path.mnt);
 out_unlock:
	mutex_unlock(&inode->i_mutex);
	return 0;
}

static int btrfs_ioctl_getversion(struct file *file, int __user *arg)
{
	struct inode *inode = file->f_path.dentry->d_inode;

	return put_user(inode->i_generation, arg);
}
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static noinline int create_subvol(struct btrfs_root *root,
				  struct dentry *dentry,
				  char *name, int namelen)
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{
	struct btrfs_trans_handle *trans;
	struct btrfs_key key;
	struct btrfs_root_item root_item;
	struct btrfs_inode_item *inode_item;
	struct extent_buffer *leaf;
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	struct btrfs_root *new_root;
	struct inode *dir = dentry->d_parent->d_inode;
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	int ret;
	int err;
	u64 objectid;
	u64 new_dirid = BTRFS_FIRST_FREE_OBJECTID;
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	u64 index = 0;
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	/*
	 * 1 - inode item
	 * 2 - refs
	 * 1 - root item
	 * 2 - dir items
	 */
	ret = btrfs_reserve_metadata_space(root, 6);
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	if (ret)
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		return ret;
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	trans = btrfs_start_transaction(root, 1);
	BUG_ON(!trans);

	ret = btrfs_find_free_objectid(trans, root->fs_info->tree_root,
				       0, &objectid);
	if (ret)
		goto fail;

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	leaf = btrfs_alloc_free_block(trans, root, root->leafsize,
				      0, objectid, NULL, 0, 0, 0);
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	if (IS_ERR(leaf)) {
		ret = PTR_ERR(leaf);
		goto fail;
	}
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	memset_extent_buffer(leaf, 0, 0, sizeof(struct btrfs_header));
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	btrfs_set_header_bytenr(leaf, leaf->start);
	btrfs_set_header_generation(leaf, trans->transid);
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	btrfs_set_header_backref_rev(leaf, BTRFS_MIXED_BACKREF_REV);
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	btrfs_set_header_owner(leaf, objectid);

	write_extent_buffer(leaf, root->fs_info->fsid,
			    (unsigned long)btrfs_header_fsid(leaf),
			    BTRFS_FSID_SIZE);
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	write_extent_buffer(leaf, root->fs_info->chunk_tree_uuid,
			    (unsigned long)btrfs_header_chunk_tree_uuid(leaf),
			    BTRFS_UUID_SIZE);
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	btrfs_mark_buffer_dirty(leaf);

	inode_item = &root_item.inode;
	memset(inode_item, 0, sizeof(*inode_item));
	inode_item->generation = cpu_to_le64(1);
	inode_item->size = cpu_to_le64(3);
	inode_item->nlink = cpu_to_le32(1);
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	inode_item->nbytes = cpu_to_le64(root->leafsize);
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	inode_item->mode = cpu_to_le32(S_IFDIR | 0755);

	btrfs_set_root_bytenr(&root_item, leaf->start);
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	btrfs_set_root_generation(&root_item, trans->transid);
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	btrfs_set_root_level(&root_item, 0);
	btrfs_set_root_refs(&root_item, 1);
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	btrfs_set_root_used(&root_item, leaf->len);
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	btrfs_set_root_last_snapshot(&root_item, 0);
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	memset(&root_item.drop_progress, 0, sizeof(root_item.drop_progress));
	root_item.drop_level = 0;

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	btrfs_tree_unlock(leaf);
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	free_extent_buffer(leaf);
	leaf = NULL;

	btrfs_set_root_dirid(&root_item, new_dirid);

	key.objectid = objectid;
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	key.offset = 0;
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	btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
	ret = btrfs_insert_root(trans, root->fs_info->tree_root, &key,
				&root_item);
	if (ret)
		goto fail;

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	key.offset = (u64)-1;
	new_root = btrfs_read_fs_root_no_name(root->fs_info, &key);
	BUG_ON(IS_ERR(new_root));

	btrfs_record_root_in_trans(trans, new_root);

	ret = btrfs_create_subvol_root(trans, new_root, new_dirid,
				       BTRFS_I(dir)->block_group);
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	/*
	 * insert the directory item
	 */
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	ret = btrfs_set_inode_index(dir, &index);
	BUG_ON(ret);

	ret = btrfs_insert_dir_item(trans, root,
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				    name, namelen, dir->i_ino, &key,
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				    BTRFS_FT_DIR, index);
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	if (ret)
		goto fail;
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	btrfs_i_size_write(dir, dir->i_size + namelen * 2);
	ret = btrfs_update_inode(trans, root, dir);
	BUG_ON(ret);

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	ret = btrfs_add_root_ref(trans, root->fs_info->tree_root,
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				 objectid, root->root_key.objectid,
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				 dir->i_ino, index, name, namelen);

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	BUG_ON(ret);
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	d_instantiate(dentry, btrfs_lookup_dentry(dir, dentry));
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fail:
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	err = btrfs_commit_transaction(trans, root);
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	if (err && !ret)
		ret = err;
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	btrfs_unreserve_metadata_space(root, 6);
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	return ret;
}

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static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,
			   char *name, int namelen)
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{
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	struct inode *inode;
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	struct btrfs_pending_snapshot *pending_snapshot;
	struct btrfs_trans_handle *trans;
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	int ret;
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	if (!root->ref_cows)
		return -EINVAL;

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	/*
	 * 1 - inode item
	 * 2 - refs
	 * 1 - root item
	 * 2 - dir items
	 */
	ret = btrfs_reserve_metadata_space(root, 6);
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	if (ret)
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		goto fail;
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	pending_snapshot = kzalloc(sizeof(*pending_snapshot), GFP_NOFS);
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	if (!pending_snapshot) {
		ret = -ENOMEM;
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		btrfs_unreserve_metadata_space(root, 6);
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		goto fail;
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	}
	pending_snapshot->name = kmalloc(namelen + 1, GFP_NOFS);
	if (!pending_snapshot->name) {
		ret = -ENOMEM;
		kfree(pending_snapshot);
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		btrfs_unreserve_metadata_space(root, 6);
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		goto fail;
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	}
	memcpy(pending_snapshot->name, name, namelen);
	pending_snapshot->name[namelen] = '\0';
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	pending_snapshot->dentry = dentry;
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	trans = btrfs_start_transaction(root, 1);
	BUG_ON(!trans);
	pending_snapshot->root = root;
	list_add(&pending_snapshot->list,
		 &trans->transaction->pending_snapshots);
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	ret = btrfs_commit_transaction(trans, root);
	BUG_ON(ret);
	btrfs_unreserve_metadata_space(root, 6);
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	inode = btrfs_lookup_dentry(dentry->d_parent->d_inode, dentry);
	if (IS_ERR(inode)) {
		ret = PTR_ERR(inode);
		goto fail;
	}
	BUG_ON(!inode);
	d_instantiate(dentry, inode);
	ret = 0;
fail:
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	return ret;
}

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/* copy of may_create in fs/namei.c() */
static inline int btrfs_may_create(struct inode *dir, struct dentry *child)
{
	if (child->d_inode)
		return -EEXIST;
	if (IS_DEADDIR(dir))
		return -ENOENT;
	return inode_permission(dir, MAY_WRITE | MAY_EXEC);
}

/*
 * Create a new subvolume below @parent.  This is largely modeled after
 * sys_mkdirat and vfs_mkdir, but we only do a single component lookup
 * inside this filesystem so it's quite a bit simpler.
 */
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static noinline int btrfs_mksubvol(struct path *parent,
				   char *name, int namelen,
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				   struct btrfs_root *snap_src)
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{
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	struct inode *dir  = parent->dentry->d_inode;
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	struct dentry *dentry;
	int error;

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	mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
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	dentry = lookup_one_len(name, parent->dentry, namelen);
	error = PTR_ERR(dentry);
	if (IS_ERR(dentry))
		goto out_unlock;

	error = -EEXIST;
	if (dentry->d_inode)
		goto out_dput;

	error = mnt_want_write(parent->mnt);
	if (error)
		goto out_dput;

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	error = btrfs_may_create(dir, dentry);
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	if (error)
		goto out_drop_write;

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	down_read(&BTRFS_I(dir)->root->fs_info->subvol_sem);

	if (btrfs_root_refs(&BTRFS_I(dir)->root->root_item) == 0)
		goto out_up_read;

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	if (snap_src) {
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		error = create_snapshot(snap_src, dentry,
					name, namelen);
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	} else {
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		error = create_subvol(BTRFS_I(dir)->root, dentry,
				      name, namelen);
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	}
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	if (!error)
		fsnotify_mkdir(dir, dentry);
out_up_read:
	up_read(&BTRFS_I(dir)->root->fs_info->subvol_sem);
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out_drop_write:
	mnt_drop_write(parent->mnt);
out_dput:
	dput(dentry);
out_unlock:
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	mutex_unlock(&dir->i_mutex);
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	return error;
}

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static int should_defrag_range(struct inode *inode, u64 start, u64 len,
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			       int thresh, u64 *last_len, u64 *skip,
			       u64 *defrag_end)
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{
	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
	struct extent_map *em = NULL;
	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
	int ret = 1;

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	if (thresh == 0)
		thresh = 256 * 1024;

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	/*
	 * make sure that once we start defragging and extent, we keep on
	 * defragging it
	 */
	if (start < *defrag_end)
		return 1;

	*skip = 0;

	/*
	 * hopefully we have this extent in the tree already, try without
	 * the full extent lock
	 */
	read_lock(&em_tree->lock);
	em = lookup_extent_mapping(em_tree, start, len);
	read_unlock(&em_tree->lock);

	if (!em) {
		/* get the big lock and read metadata off disk */
		lock_extent(io_tree, start, start + len - 1, GFP_NOFS);
		em = btrfs_get_extent(inode, NULL, 0, start, len, 0);
		unlock_extent(io_tree, start, start + len - 1, GFP_NOFS);

		if (!em)
			return 0;
	}

	/* this will cover holes, and inline extents */
	if (em->block_start >= EXTENT_MAP_LAST_BYTE)
		ret = 0;

	/*
	 * we hit a real extent, if it is big don't bother defragging it again
	 */
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	if ((*last_len == 0 || *last_len >= thresh) && em->len >= thresh)
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		ret = 0;

	/*
	 * last_len ends up being a counter of how many bytes we've defragged.
	 * every time we choose not to defrag an extent, we reset *last_len
	 * so that the next tiny extent will force a defrag.
	 *
	 * The end result of this is that tiny extents before a single big
	 * extent will force at least part of that big extent to be defragged.
	 */
	if (ret) {
		*last_len += len;
		*defrag_end = extent_map_end(em);
	} else {
		*last_len = 0;
		*skip = extent_map_end(em);
		*defrag_end = 0;
	}

	free_extent_map(em);
	return ret;
}

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static int btrfs_defrag_file(struct file *file,
			     struct btrfs_ioctl_defrag_range_args *range)
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{
	struct inode *inode = fdentry(file)->d_inode;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
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	struct btrfs_ordered_extent *ordered;
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	struct page *page;
	unsigned long last_index;
	unsigned long ra_pages = root->fs_info->bdi.ra_pages;
	unsigned long total_read = 0;
	u64 page_start;
	u64 page_end;
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	u64 last_len = 0;
	u64 skip = 0;
	u64 defrag_end = 0;
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	unsigned long i;
	int ret;

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	if (inode->i_size == 0)
		return 0;

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	if (range->start + range->len > range->start) {
		last_index = min_t(u64, inode->i_size - 1,
			 range->start + range->len - 1) >> PAGE_CACHE_SHIFT;
	} else {
		last_index = (inode->i_size - 1) >> PAGE_CACHE_SHIFT;
	}

	i = range->start >> PAGE_CACHE_SHIFT;
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	while (i <= last_index) {
		if (!should_defrag_range(inode, (u64)i << PAGE_CACHE_SHIFT,
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					PAGE_CACHE_SIZE,
					range->extent_thresh,
					&last_len, &skip,
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					&defrag_end)) {
			unsigned long next;
			/*
			 * the should_defrag function tells us how much to skip
			 * bump our counter by the suggested amount
			 */
			next = (skip + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
			i = max(i + 1, next);
			continue;
		}
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		if (total_read % ra_pages == 0) {
			btrfs_force_ra(inode->i_mapping, &file->f_ra, file, i,
				       min(last_index, i + ra_pages - 1));
		}
		total_read++;
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		mutex_lock(&inode->i_mutex);
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		if (range->flags & BTRFS_DEFRAG_RANGE_COMPRESS)
			BTRFS_I(inode)->force_compress = 1;
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		ret = btrfs_check_data_free_space(root, inode, PAGE_CACHE_SIZE);
		if (ret) {
			ret = -ENOSPC;
			break;
		}

		ret = btrfs_reserve_metadata_for_delalloc(root, inode, 1);
		if (ret) {
			btrfs_free_reserved_data_space(root, inode,
						       PAGE_CACHE_SIZE);
			ret = -ENOSPC;
			break;
		}
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		if (inode->i_size == 0 ||
		    i > ((inode->i_size - 1) >> PAGE_CACHE_SHIFT)) {
			ret = 0;
			goto err_reservations;
		}

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		page = grab_cache_page(inode->i_mapping, i);
		if (!page)
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			goto err_reservations;

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		if (!PageUptodate(page)) {
			btrfs_readpage(NULL, page);
			lock_page(page);
			if (!PageUptodate(page)) {
				unlock_page(page);
				page_cache_release(page);
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				goto err_reservations;
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			}
		}

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		if (page->mapping != inode->i_mapping) {
			unlock_page(page);
			page_cache_release(page);
			goto again;
		}

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		wait_on_page_writeback(page);

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		if (PageDirty(page)) {
			btrfs_free_reserved_data_space(root, inode,
						       PAGE_CACHE_SIZE);
			goto loop_unlock;
		}

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		page_start = (u64)page->index << PAGE_CACHE_SHIFT;
		page_end = page_start + PAGE_CACHE_SIZE - 1;
		lock_extent(io_tree, page_start, page_end, GFP_NOFS);
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		ordered = btrfs_lookup_ordered_extent(inode, page_start);
		if (ordered) {
			unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
			unlock_page(page);
			page_cache_release(page);
			btrfs_start_ordered_extent(inode, ordered, 1);
			btrfs_put_ordered_extent(ordered);
			goto again;
		}
		set_page_extent_mapped(page);

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		/*
		 * this makes sure page_mkwrite is called on the
		 * page if it is dirtied again later
		 */
		clear_page_dirty_for_io(page);
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		clear_extent_bits(&BTRFS_I(inode)->io_tree, page_start,
				  page_end, EXTENT_DIRTY | EXTENT_DELALLOC |
				  EXTENT_DO_ACCOUNTING, GFP_NOFS);
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		btrfs_set_extent_delalloc(inode, page_start, page_end, NULL);
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		ClearPageChecked(page);
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		set_page_dirty(page);
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		unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
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loop_unlock:
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		unlock_page(page);
		page_cache_release(page);
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		mutex_unlock(&inode->i_mutex);

		btrfs_unreserve_metadata_for_delalloc(root, inode, 1);
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		balance_dirty_pages_ratelimited_nr(inode->i_mapping, 1);
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		i++;
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	}

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	if ((range->flags & BTRFS_DEFRAG_RANGE_START_IO))
		filemap_flush(inode->i_mapping);

	if ((range->flags & BTRFS_DEFRAG_RANGE_COMPRESS)) {
		/* the filemap_flush will queue IO into the worker threads, but
		 * we have to make sure the IO is actually started and that
		 * ordered extents get created before we return
		 */
		atomic_inc(&root->fs_info->async_submit_draining);
		while (atomic_read(&root->fs_info->nr_async_submits) ||
		      atomic_read(&root->fs_info->async_delalloc_pages)) {
			wait_event(root->fs_info->async_submit_wait,
			   (atomic_read(&root->fs_info->nr_async_submits) == 0 &&
			    atomic_read(&root->fs_info->async_delalloc_pages) == 0));
		}
		atomic_dec(&root->fs_info->async_submit_draining);

		mutex_lock(&inode->i_mutex);
		BTRFS_I(inode)->force_compress = 0;
		mutex_unlock(&inode->i_mutex);
	}

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	return 0;
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err_reservations:
	mutex_unlock(&inode->i_mutex);
	btrfs_free_reserved_data_space(root, inode, PAGE_CACHE_SIZE);
	btrfs_unreserve_metadata_for_delalloc(root, inode, 1);
	return ret;
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}

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static noinline int btrfs_ioctl_resize(struct btrfs_root *root,
					void __user *arg)
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{
	u64 new_size;
	u64 old_size;
	u64 devid = 1;
	struct btrfs_ioctl_vol_args *vol_args;
	struct btrfs_trans_handle *trans;
	struct btrfs_device *device = NULL;
	char *sizestr;
	char *devstr = NULL;
	int ret = 0;
	int namelen;
	int mod = 0;

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	if (root->fs_info->sb->s_flags & MS_RDONLY)
		return -EROFS;

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	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

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	vol_args = memdup_user(arg, sizeof(*vol_args));
	if (IS_ERR(vol_args))
		return PTR_ERR(vol_args);
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	vol_args->name[BTRFS_PATH_NAME_MAX] = '\0';
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	namelen = strlen(vol_args->name);

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	mutex_lock(&root->fs_info->volume_mutex);
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	sizestr = vol_args->name;
	devstr = strchr(sizestr, ':');
	if (devstr) {
		char *end;
		sizestr = devstr + 1;
		*devstr = '\0';
		devstr = vol_args->name;
		devid = simple_strtoull(devstr, &end, 10);
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		printk(KERN_INFO "resizing devid %llu\n",
		       (unsigned long long)devid);
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	}
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	device = btrfs_find_device(root, devid, NULL, NULL);
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	if (!device) {
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		printk(KERN_INFO "resizer unable to find device %llu\n",
		       (unsigned long long)devid);
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		ret = -EINVAL;
		goto out_unlock;
	}
	if (!strcmp(sizestr, "max"))
		new_size = device->bdev->bd_inode->i_size;
	else {
		if (sizestr[0] == '-') {
			mod = -1;
			sizestr++;
		} else if (sizestr[0] == '+') {
			mod = 1;
			sizestr++;
		}
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		new_size = memparse(sizestr, NULL);
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		if (new_size == 0) {
			ret = -EINVAL;
			goto out_unlock;
		}
	}

	old_size = device->total_bytes;

	if (mod < 0) {
		if (new_size > old_size) {
			ret = -EINVAL;
			goto out_unlock;
		}
		new_size = old_size - new_size;
	} else if (mod > 0) {
		new_size = old_size + new_size;
	}

	if (new_size < 256 * 1024 * 1024) {
		ret = -EINVAL;
		goto out_unlock;
	}
	if (new_size > device->bdev->bd_inode->i_size) {
		ret = -EFBIG;
		goto out_unlock;
	}

	do_div(new_size, root->sectorsize);
	new_size *= root->sectorsize;

	printk(KERN_INFO "new size for %s is %llu\n",
		device->name, (unsigned long long)new_size);

	if (new_size > old_size) {
		trans = btrfs_start_transaction(root, 1);
		ret = btrfs_grow_device(trans, device, new_size);
		btrfs_commit_transaction(trans, root);
	} else {
		ret = btrfs_shrink_device(device, new_size);
	}

out_unlock:
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	mutex_unlock(&root->fs_info->volume_mutex);
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	kfree(vol_args);
	return ret;
}

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static noinline int btrfs_ioctl_snap_create(struct file *file,
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					    void __user *arg, int subvol)
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{
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	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
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	struct btrfs_ioctl_vol_args *vol_args;
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	struct file *src_file;
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	int namelen;
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	int ret = 0;
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	if (root->fs_info->sb->s_flags & MS_RDONLY)
		return -EROFS;

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	vol_args = memdup_user(arg, sizeof(*vol_args));
	if (IS_ERR(vol_args))
		return PTR_ERR(vol_args);
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	vol_args->name[BTRFS_PATH_NAME_MAX] = '\0';
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	namelen = strlen(vol_args->name);
	if (strchr(vol_args->name, '/')) {
		ret = -EINVAL;
		goto out;
	}

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	if (subvol) {
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		ret = btrfs_mksubvol(&file->f_path, vol_args->name, namelen,
				     NULL);
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	} else {
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		struct inode *src_inode;
		src_file = fget(vol_args->fd);
		if (!src_file) {
			ret = -EINVAL;
			goto out;
		}

		src_inode = src_file->f_path.dentry->d_inode;
		if (src_inode->i_sb != file->f_path.dentry->d_inode->i_sb) {
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			printk(KERN_INFO "btrfs: Snapshot src from "
			       "another FS\n");
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			ret = -EINVAL;
			fput(src_file);
			goto out;
		}
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		ret = btrfs_mksubvol(&file->f_path, vol_args->name, namelen,
				     BTRFS_I(src_inode)->root);
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		fput(src_file);
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	}
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out:
	kfree(vol_args);
	return ret;
}

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/*
 * helper to check if the subvolume references other subvolumes
 */
static noinline int may_destroy_subvol(struct btrfs_root *root)
{
	struct btrfs_path *path;
	struct btrfs_key key;
	int ret;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = root->root_key.objectid;
	key.type = BTRFS_ROOT_REF_KEY;
	key.offset = (u64)-1;

	ret = btrfs_search_slot(NULL, root->fs_info->tree_root,
				&key, path, 0, 0);
	if (ret < 0)
		goto out;
	BUG_ON(ret == 0);

	ret = 0;
	if (path->slots[0] > 0) {
		path->slots[0]--;
		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
		if (key.objectid == root->root_key.objectid &&
		    key.type == BTRFS_ROOT_REF_KEY)
			ret = -ENOTEMPTY;
	}
out:
	btrfs_free_path(path);
	return ret;
}

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static noinline int key_in_sk(struct btrfs_key *key,
			      struct btrfs_ioctl_search_key *sk)
{
	if (key->objectid < sk->min_objectid)
		return 0;
	if (key->offset < sk->min_offset)
		return 0;
	if (key->type < sk->min_type)
		return 0;
	if (key->objectid > sk->max_objectid)
		return 0;
	if (key->type > sk->max_type)
		return 0;
	if (key->offset > sk->max_offset)
		return 0;
	return 1;
}

static noinline int copy_to_sk(struct btrfs_root *root,
			       struct btrfs_path *path,
			       struct btrfs_key *key,
			       struct btrfs_ioctl_search_key *sk,
			       char *buf,
			       unsigned long *sk_offset,
			       int *num_found)
{
	u64 found_transid;
	struct extent_buffer *leaf;
	struct btrfs_ioctl_search_header sh;
	unsigned long item_off;
	unsigned long item_len;
	int nritems;
	int i;
	int slot;
	int found = 0;
	int ret = 0;

	leaf = path->nodes[0];
	slot = path->slots[0];
	nritems = btrfs_header_nritems(leaf);

	if (btrfs_header_generation(leaf) > sk->max_transid) {
		i = nritems;
		goto advance_key;
	}
	found_transid = btrfs_header_generation(leaf);

	for (i = slot; i < nritems; i++) {
		item_off = btrfs_item_ptr_offset(leaf, i);
		item_len = btrfs_item_size_nr(leaf, i);

		if (item_len > BTRFS_SEARCH_ARGS_BUFSIZE)
			item_len = 0;

		if (sizeof(sh) + item_len + *sk_offset >
		    BTRFS_SEARCH_ARGS_BUFSIZE) {
			ret = 1;
			goto overflow;
		}

		btrfs_item_key_to_cpu(leaf, key, i);
		if (!key_in_sk(key, sk))
			continue;

		sh.objectid = key->objectid;
		sh.offset = key->offset;
		sh.type = key->type;
		sh.len = item_len;
		sh.transid = found_transid;

		/* copy search result header */
		memcpy(buf + *sk_offset, &sh, sizeof(sh));
		*sk_offset += sizeof(sh);

		if (item_len) {
			char *p = buf + *sk_offset;
			/* copy the item */
			read_extent_buffer(leaf, p,
					   item_off, item_len);
			*sk_offset += item_len;
			found++;
		}

		if (*num_found >= sk->nr_items)
			break;
	}
advance_key: