[PATCH 4.9 011/165] btrfs: log message when rw remount is attempted with unclean tree-log

[Greg Kroah-Hartman]

From: David Sterba <dsterba@xxxxxxxx>

commit 10a3a3edc5b89a8cd095bc63495fb1e0f42047d9 upstream.

A remount to a read-write filesystem is not safe when there's tree-log
to be replayed. Files that could be opened until now might be affected
by the changes in the tree-log.

A regular mount is needed to replay the log so the filesystem presents
the consistent view with the pending changes included.

CC: stable@xxxxxxxxxxxxxxx # 4.4+
Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/btrfs/super.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1809,6 +1809,8 @@ static int btrfs_remount(struct super_bl
 		}
 
 		if (btrfs_super_log_root(fs_info->super_copy) != 0) {
+			btrfs_warn(fs_info,
+		"mount required to replay tree-log, cannot remount read-write");
 			ret = -EINVAL;
 			goto restore;
 		}