[PATCH] btrfs: fix leaking BTRFS_FS_STATE_REMOUNTING flag

[BUG]
The following script can lead to unexpected qgroup rescan failure:

 # mkfs.btrfs -f -O quota $dev
 # mount $dev $mnt
 # mount -o remount,rescue=ibadroots $mnt
   ^^^^^ This above command is expected to fail

 # btrfs quota rescan -w $mnt
   ^^^^^ The above qgroup rescan is not expected to fail

 # btrfs qgroup show $mnt
 WARNING: qgroup data inconsistent, rescan recommended
 Qgroupid    Referenced    Exclusive   Path
 --------    ----------    ---------   ----
 0/5           16.00KiB     16.00KiB   <toplevel>

The above short script will be converted to a proper fstests case.

[CAUSE]
Inside btrfs_reconfigure(), if either btrfs_check_options() or
btrfs_check_features() failed, we will always have
BTRFS_FS_STATE_REMOUNTING set for the fs until the next successful
remount.

That BTRFS_FS_STATE_REMOUNTING flag will interrupt several operations,
including:

- Qgroup rescan
- Auto defrag
- Space reclaim

[FIX]
Change the error handling of btrfs_check_options() and
btrfs_check_features() to goto restore label.

Fixes: eddb1a433f26 ("btrfs: add reconfigure callback for fs_context")
Signed-off-by: Qu Wenruo <[email protected]>
---
 fs/btrfs/super.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a8c55f7571d0..5843254e3aaf 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1510,12 +1510,14 @@ static int btrfs_reconfigure(struct fs_context *fc)
 	sync_filesystem(sb);
 	set_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);
 
-	if (!btrfs_check_options(fs_info, &ctx->mount_opt, fc->sb_flags))
-		return -EINVAL;
+	if (!btrfs_check_options(fs_info, &ctx->mount_opt, fc->sb_flags)) {
+		ret = -EINVAL;
+		goto restore;
+	}
 
 	ret = btrfs_check_features(fs_info, !(fc->sb_flags & SB_RDONLY));
 	if (ret < 0)
-		return ret;
+		goto restore;
 
 	btrfs_ctx_to_info(fs_info, ctx);
 	btrfs_remount_begin(fs_info, old_ctx.mount_opt, fc->sb_flags);
-- 
2.54.0