[PATCH 2/6 v2] btrfs: do commit in sync_fs if there are pending changes

[David Sterba <dsterba@suse.cz>]

If a pending change is requested, it's not processed unless there is a
transaction commit about to happen, not even after sync or SYNC_FS
ioctl. For example a remount that toggles the inode_cache option will
not take effect after sync on a quiescent filesystem.

Signed-off-by: David Sterba <dsterba@suse.cz>
---

v2: catch error from btrfs_start_transaction

 fs/btrfs/super.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 54bd91ece35b..0cf589402d8d 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -993,9 +993,17 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
 	trans = btrfs_attach_transaction_barrier(root);
 	if (IS_ERR(trans)) {
 		/* no transaction, don't bother */
-		if (PTR_ERR(trans) == -ENOENT)
-			return 0;
-		return PTR_ERR(trans);
+		if (PTR_ERR(trans) == -ENOENT) {
+			/*
+			 * Exit unless we have some pending changes
+			 * that need to go through commit
+			 */
+			if (fs_info->pending_changes == 0)
+				return 0;
+			trans = btrfs_start_transaction(root, 0);
+		}
+		if (IS_ERR(trans))
+			return PTR_ERR(trans);
 	}
 	return btrfs_commit_transaction(trans, root);
 }
-- 
2.1.3