Btrfs: fix wrong reserved space in qgroup during snap/subv creation

There are two problems in the space reservation of the snapshot/
subvolume creation.
- don't reserve the space for the root item insertion
- the space which is reserved in the qgroup is different with
  the free space reservation. we need reserve free space for
  7 items, but in qgroup reservation, we need reserve space only
  for 3 items.

So we implement new metadata reservation functions for the
snapshot/subvolume creation.

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

1 files changed, 43 insertions, 19 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8dcd4ff0c3a5..56d92549389c 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -363,7 +363,7 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg)
         return 0;
 }
 
-static noinline int create_subvol(struct btrfs_root *root,
+static noinline int create_subvol(struct inode *dir,
                                   struct dentry *dentry,
                                   char *name, int namelen,
                                   u64 *async_transid,
@@ -374,32 +374,39 @@ static noinline int create_subvol(struct btrfs_root *root,
         struct btrfs_root_item root_item;
         struct btrfs_inode_item *inode_item;
         struct extent_buffer *leaf;
+        struct btrfs_root *root = BTRFS_I(dir)->root;
         struct btrfs_root *new_root;
-        struct dentry *parent = dentry->d_parent;
-        struct inode *dir;
+        struct btrfs_block_rsv block_rsv;
         struct timespec cur_time = CURRENT_TIME;
         int ret;
         int err;
         u64 objectid;
         u64 new_dirid = BTRFS_FIRST_FREE_OBJECTID;
         u64 index = 0;
+        u64 qgroup_reserved;
         uuid_le new_uuid;
 
         ret = btrfs_find_free_objectid(root->fs_info->tree_root, &objectid);
         if (ret)
                 return ret;
 
-        dir = parent->d_inode;
-
+        btrfs_init_block_rsv(&block_rsv, BTRFS_BLOCK_RSV_TEMP);
         /*
-         * 1 - inode item
-         * 2 - refs
-         * 1 - root item
-         * 2 - dir items
+         * The same as the snapshot creation, please see the comment
+         * of create_snapshot().
          */
-        trans = btrfs_start_transaction(root, 6);
-        if (IS_ERR(trans))
-                return PTR_ERR(trans);
+        ret = btrfs_subvolume_reserve_metadata(root, &block_rsv,
+                                               7, &qgroup_reserved);
+        if (ret)
+                return ret;
+
+        trans = btrfs_start_transaction(root, 0);
+        if (IS_ERR(trans)) {
+                ret = PTR_ERR(trans);
+                goto out;
+        }
+        trans->block_rsv = &block_rsv;
+        trans->bytes_reserved = block_rsv.size;
 
         ret = btrfs_qgroup_inherit(trans, root->fs_info, 0, objectid, inherit);
         if (ret)
@@ -515,6 +522,8 @@ static noinline int create_subvol(struct btrfs_root *root,
         BUG_ON(ret);
 
 fail:
+        trans->block_rsv = NULL;
+        trans->bytes_reserved = 0;
         if (async_transid) {
                 *async_transid = trans->transid;
                 err = btrfs_commit_transaction_async(trans, root, 1);
@@ -526,7 +535,8 @@ fail:
 
         if (!ret)
                 d_instantiate(dentry, btrfs_lookup_dentry(dir, dentry));
-
+out:
+        btrfs_subvolume_release_metadata(root, &block_rsv, qgroup_reserved);
         return ret;
 }
 
@@ -549,21 +559,31 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 
         btrfs_init_block_rsv(&pending_snapshot->block_rsv,
                              BTRFS_BLOCK_RSV_TEMP);
+        /*
+         * 1 - parent dir inode
+         * 2 - dir entries
+         * 1 - root item
+         * 2 - root ref/backref
+         * 1 - root of snapshot
+         */
+        ret = btrfs_subvolume_reserve_metadata(BTRFS_I(dir)->root,
+                                        &pending_snapshot->block_rsv, 7,
+                                        &pending_snapshot->qgroup_reserved);
+        if (ret)
+                goto out;
+
         pending_snapshot->dentry = dentry;
         pending_snapshot->root = root;
         pending_snapshot->readonly = readonly;
         pending_snapshot->dir = dir;
         pending_snapshot->inherit = inherit;
 
-        trans = btrfs_start_transaction(root->fs_info->extent_root, 6);
+        trans = btrfs_start_transaction(root, 0);
         if (IS_ERR(trans)) {
                 ret = PTR_ERR(trans);
                 goto fail;
         }
 
-        ret = btrfs_snap_reserve_metadata(trans, pending_snapshot);
-        BUG_ON(ret);
-
         spin_lock(&root->fs_info->trans_lock);
         list_add(&pending_snapshot->list,
                  &trans->transaction->pending_snapshots);
@@ -600,6 +620,10 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
         d_instantiate(dentry, inode);
         ret = 0;
 fail:
+        btrfs_subvolume_release_metadata(BTRFS_I(dir)->root,
+                                         &pending_snapshot->block_rsv,
+                                         pending_snapshot->qgroup_reserved);
+out:
         kfree(pending_snapshot);
         return ret;
 }
@@ -733,8 +757,8 @@ static noinline int btrfs_mksubvol(struct path *parent,
                 error = create_snapshot(snap_src, dir, dentry, name, namelen,
                                         async_transid, readonly, inherit);
         } else {
-                error = create_subvol(BTRFS_I(dir)->root, dentry,
-                                      name, namelen, async_transid, inherit);
+                error = create_subvol(dir, dentry, name, namelen,
+                                      async_transid, inherit);
         }
         if (!error)
                 fsnotify_mkdir(dir, dentry);