[PATCH] btrfs: Move error handling of btrfs_start_dirty_block_groups closer to call site

[PATCH] btrfs: Move error handling of btrfs_start_dirty_block_groups closer to call site

[Nikolay Borisov]

Even though btrfs_start_dirty_block_groups fairly in the beginning of
btrfs_commit_transaction outside of the critical section defined by the
transaction states it can only be run by a single comitter. In other
words it defines its own critical section thanks to the
BTRFS_TRANS_DIRTY_BG run flag and ro_block_group_mutex. However, its
error handling is outside of this critical section which is a bit
counter-intuitive. So move the error handling righ after the function
is executed and let the sole runner of dirty block groups handle the
return value. no functional changes

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/transaction.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index a57065f022ff..2cdf7be02f41 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -2012,12 +2012,13 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 			run_it = 1;
 		mutex_unlock(&fs_info->ro_block_group_mutex);
 
-		if (run_it)
+		if (run_it) {
 			ret = btrfs_start_dirty_block_groups(trans);
-	}
-	if (ret) {
-		btrfs_end_transaction(trans);
-		return ret;
+			if (ret) {
+				btrfs_end_transaction(trans);
+				return ret;
+			}
+		}
 	}
 
 	spin_lock(&fs_info->trans_lock);
-- 
2.7.4

Re: [PATCH] btrfs: Move error handling of btrfs_start_dirty_block_groups closer to call site

[David Sterba]

On Fri, Feb 09, 2018 at 11:30:18AM +0200, Nikolay Borisov wrote:
> Even though btrfs_start_dirty_block_groups fairly in the beginning of
> btrfs_commit_transaction outside of the critical section defined by the
> transaction states it can only be run by a single comitter. In other
> words it defines its own critical section thanks to the
> BTRFS_TRANS_DIRTY_BG run flag and ro_block_group_mutex. However, its
> error handling is outside of this critical section which is a bit
> counter-intuitive. So move the error handling righ after the function
> is executed and let the sole runner of dirty block groups handle the
> return value. no functional changes
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>

Reviewed-by: David Sterba <dsterba@suse.com>