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, 53 insertions, 12 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5681a91ed400..7cb9d734f6e5 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4560,19 +4560,60 @@ void btrfs_orphan_release_metadata(struct inode *inode)
 	btrfs_block_rsv_release(root, root->orphan_block_rsv, num_bytes);
 }
 
-int btrfs_snap_reserve_metadata(struct btrfs_trans_handle *trans,
-				struct btrfs_pending_snapshot *pending)
+/*
+ * btrfs_subvolume_reserve_metadata() - reserve space for subvolume operation
+ * root: the root of the parent directory
+ * rsv: block reservation
+ * items: the number of items that we need do reservation
+ * qgroup_reserved: used to return the reserved size in qgroup
+ *
+ * This function is used to reserve the space for snapshot/subvolume
+ * creation and deletion. Those operations are different with the
+ * common file/directory operations, they change two fs/file trees
+ * and root tree, the number of items that the qgroup reserves is
+ * different with the free space reservation. So we can not use
+ * the space reseravtion mechanism in start_transaction().
+ */
+int btrfs_subvolume_reserve_metadata(struct btrfs_root *root,
+				     struct btrfs_block_rsv *rsv,
+				     int items,
+				     u64 *qgroup_reserved)
 {
-	struct btrfs_root *root = pending->root;
-	struct btrfs_block_rsv *src_rsv = get_block_rsv(trans, root);
-	struct btrfs_block_rsv *dst_rsv = &pending->block_rsv;
-	/*
-	 * two for root back/forward refs, two for directory entries,
-	 * one for root of the snapshot and one for parent inode.
-	 */
-	u64 num_bytes = btrfs_calc_trans_metadata_size(root, 6);
-	dst_rsv->space_info = src_rsv->space_info;
-	return block_rsv_migrate_bytes(src_rsv, dst_rsv, num_bytes);
+	u64 num_bytes;
+	int ret;
+
+	if (root->fs_info->quota_enabled) {
+		/* One for parent inode, two for dir entries */
+		num_bytes = 3 * root->leafsize;
+		ret = btrfs_qgroup_reserve(root, num_bytes);
+		if (ret)
+			return ret;
+	} else {
+		num_bytes = 0;
+	}
+
+	*qgroup_reserved = num_bytes;
+
+	num_bytes = btrfs_calc_trans_metadata_size(root, items);
+	rsv->space_info = __find_space_info(root->fs_info,
+					    BTRFS_BLOCK_GROUP_METADATA);
+	ret = btrfs_block_rsv_add(root, rsv, num_bytes,
+				  BTRFS_RESERVE_FLUSH_ALL);
+	if (ret) {
+		if (*qgroup_reserved)
+			btrfs_qgroup_free(root, *qgroup_reserved);
+	}
+
+	return ret;
+}
+
+void btrfs_subvolume_release_metadata(struct btrfs_root *root,
+				      struct btrfs_block_rsv *rsv,
+				      u64 qgroup_reserved)
+{
+	btrfs_block_rsv_release(root, rsv, (u64)-1);
+	if (qgroup_reserved)
+		btrfs_qgroup_free(root, qgroup_reserved);
 }
 
 /**