Btrfs: fix wrong reserved space when deleting a snapshot/subvolume

When deleting a snapshot/subvolume, we need remove root ref/backref,
dir entries and update the dir inode, so we must reserve free space
for those operations.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 56d92549389c..b908960c9746 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2064,6 +2064,8 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
         struct btrfs_root *dest = NULL;
         struct btrfs_ioctl_vol_args *vol_args;
         struct btrfs_trans_handle *trans;
+        struct btrfs_block_rsv block_rsv;
+        u64 qgroup_reserved;
         int namelen;
         int ret;
         int err = 0;
@@ -2153,12 +2155,23 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
         if (err)
                 goto out_up_write;
 
+        btrfs_init_block_rsv(&block_rsv, BTRFS_BLOCK_RSV_TEMP);
+        /*
+         * One for dir inode, two for dir entries, two for root
+         * ref/backref.
+         */
+        err = btrfs_subvolume_reserve_metadata(root, &block_rsv,
+                                               5, &qgroup_reserved);
+        if (err)
+                goto out_up_write;
+
         trans = btrfs_start_transaction(root, 0);
         if (IS_ERR(trans)) {
                 err = PTR_ERR(trans);
-                goto out_up_write;
+                goto out_release;
         }
-        trans->block_rsv = &root->fs_info->global_block_rsv;
+        trans->block_rsv = &block_rsv;
+        trans->bytes_reserved = block_rsv.size;
 
         ret = btrfs_unlink_subvol(trans, root, dir,
                                 dest->root_key.objectid,
@@ -2188,10 +2201,14 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
                 }
         }
 out_end_trans:
+        trans->block_rsv = NULL;
+        trans->bytes_reserved = 0;
         ret = btrfs_end_transaction(trans, root);
         if (ret && !err)
                 err = ret;
         inode->i_flags |= S_DEAD;
+out_release:
+        btrfs_subvolume_release_metadata(root, &block_rsv, qgroup_reserved);
 out_up_write:
         up_write(&root->fs_info->subvol_sem);
 out_unlock: