btrfs: do commit in sync_fs if there are pending changes

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>

1 files changed, 11 insertions, 3 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 54bd91ece35b..1da16d59e115 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);
+                } else {
+                        return PTR_ERR(trans);
+                }
         }
         return btrfs_commit_transaction(trans, root);
 }