[PATCH] xfs/837: set rtinherit on the root directory programmatically

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

I patched mkfs to enable metadir by default, but then this test
regressed on the "-m metadir=0 -d rtinherit=1..." configuration.  Upon
digging into the test results, I observed that the scratch filesystem
actually had metadir enabled despite the intended configuration.  That
in turn revealed that _scratch_mkfs was failing because -d rtinherit was
being respecified, so it did that obnoxious thing it does and reformats
with only the caller's mkfs options.

As a result, the scratch filesystem is configured incorrectly -- metadir
is enabled when we don't want it to be, so we pick the wrong output file
and fail.

Instead of passing -drtinherit and potentially conflicting with the test
configuration options, let's use _xfs_force_bdev to set rtinherit
programmatically.

Cc: <Hans.Holmberg@wdc.com>
Cc: <fstests@vger.kernel.org> # v2025.06.22
Fixes: e225772353e212 ("xfs: add mount test for read only rt devices")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 tests/xfs/837 |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tests/xfs/837 b/tests/xfs/837
index 2fe195a009f10f..33ec37ae3dbde3 100755
--- a/tests/xfs/837
+++ b/tests/xfs/837
@@ -35,7 +35,11 @@ fi
 
 _register_cleanup "_cleanup_setrw"
 
-_scratch_mkfs "-d rtinherit" > /dev/null 2>&1
+_scratch_mkfs > /dev/null 2>&1
+
+_scratch_mount
+_xfs_force_bdev realtime $SCRATCH_MNT
+_scratch_unmount
 
 # Select appropriate output file
 features=""