btrfs: fix return value check of btrfs_start_transaction()

The error check of btrfs_start_transaction() is added, and the mistake
of the error check on several places is corrected.

Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 9de4ff03882a..f07ba21cbf06 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -6271,6 +6271,8 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
         BUG_ON(!wc);
 
         trans = btrfs_start_transaction(tree_root, 0);
+        BUG_ON(IS_ERR(trans));
+
         if (block_rsv)
                 trans->block_rsv = block_rsv;
 
@@ -6368,6 +6370,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
 
                         btrfs_end_transaction_throttle(trans, tree_root);
                         trans = btrfs_start_transaction(tree_root, 0);
+                        BUG_ON(IS_ERR(trans));
                         if (block_rsv)
                                 trans->block_rsv = block_rsv;
                 }
@@ -7587,7 +7590,7 @@ int btrfs_cleanup_reloc_trees(struct btrfs_root *root)
 
         if (found) {
                 trans = btrfs_start_transaction(root, 1);
-                BUG_ON(!trans);
+                BUG_ON(IS_ERR(trans));
                 ret = btrfs_commit_transaction(trans, root);
                 BUG_ON(ret);
         }
@@ -7831,7 +7834,7 @@ static noinline int relocate_one_extent(struct btrfs_root *extent_root,
 
 
         trans = btrfs_start_transaction(extent_root, 1);
-        BUG_ON(!trans);
+        BUG_ON(IS_ERR(trans));
 
         if (extent_key->objectid == 0) {
                 ret = del_extent_zero(trans, extent_root, path, extent_key);