[PATCH] fstests: btrfs: detect regular qgroup for older kernels correctly

[Qu Wenruo <wqu@suse.com>]

[BUG]
When running an older (vendoer v6.4) kernel, some qgroup test cases
would be skipped:

  btrfs/017 1s ... [not run] not running normal qgroups

[CAUSE]
With the introduce of simple quota mode, there is a new sysfs interface,
/sys/fs/btrfs/<uuid>/qgroups/mode to indicate the currently running
qgroup modes.

And _qgroup_mode() from `common/btrfs` is using that new interface to
detect the mode.

Unfortuantely for older kernels without simple quota support,
_qgroup_mode() would return "disabled" directly, causing those test case
to be skipped.

[FIX]
Fallback to regular qgroup if that sysfs interface is not accessible, as
qgroup is introduced from the very beginning of btrfs, thus the regular
qgroup is always supported.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 common/btrfs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/common/btrfs b/common/btrfs
index e1b29c61..0a3f0f0b 100644
--- a/common/btrfs
+++ b/common/btrfs
@@ -728,7 +728,7 @@ _qgroup_mode()
 	if _has_fs_sysfs_attr $dev /qgroups/mode; then
 		_get_fs_sysfs_attr $dev qgroups/mode
 	else
-		echo "disabled"
+		echo "qgroup"
 	fi
 }
 
-- 
2.42.0