Btrfs: fix mount failure when qgroup rescan is in progress

If a power failure happens while the qgroup rescan kthread is running,
the next mount operation will always fail. This is because of a recent
regression that makes qgroup_rescan_init() incorrectly return -EINVAL
when we are mounting the filesystem (through btrfs_read_qgroup_config()).
This causes the -EINVAL error to be returned regardless of any qgroup
flags being set instead of returning the error only when neither of
the flags BTRFS_QGROUP_STATUS_FLAG_RESCAN nor BTRFS_QGROUP_STATUS_FLAG_ON
are set.

A test case for fstests follows up soon.

Fixes: 9593bf49675e ("btrfs: qgroup: show more meaningful qgroup_rescan_init error message")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 99f2b9ce0f15..c25dc47210a3 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2786,13 +2786,20 @@ qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
 
         if (!init_flags) {
                 /* we're resuming qgroup rescan at mount time */
-                if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN))
+                if (!(fs_info->qgroup_flags &
+                      BTRFS_QGROUP_STATUS_FLAG_RESCAN)) {
                         btrfs_warn(fs_info,
                         "qgroup rescan init failed, qgroup is not enabled");
-                else if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
+                        ret = -EINVAL;
+                } else if (!(fs_info->qgroup_flags &
+                             BTRFS_QGROUP_STATUS_FLAG_ON)) {
                         btrfs_warn(fs_info,
                         "qgroup rescan init failed, qgroup rescan is not queued");
-                return -EINVAL;
+                        ret = -EINVAL;
+                }
+
+                if (ret)
+                        return ret;
         }
 
         mutex_lock(&fs_info->qgroup_rescan_lock);