[PATCH 3/4] generic/570: fix regression when SCRATCH_DEV is still formatted

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

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

Newer versions of mkswap (or at least the one in util-linux 2.34)
complain to stderr when they're formatting over a device that seems to
contain existing data:

    mkswap: /dev/sdf: warning: wiping old btrfs signature.

This is harmless (since the swap image does get written!) but the extra
golden output is flagged as a regression.  Update the mkswap usage in
this test to dump the stderr output to $seqres.full, and complain if the
exit code is nonzero.

This fixes a regression that the author noticed when testing btrfs and
generic/507 and generic/570 run sequentially.  generic/507 calls
_require_scratch_shutdown to see if the shutdown call is supported.
btrfs does not support that, so the test is _notrun.  This leaves the
scratch filesystem mounted, causing the _try_wipe_scratch_devs between
tests to fail.  When g/570 starts up, the scratch device still contains
leftovers from the failed attempt to run g/507, which is why the mkswap
command outputs the above warning.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 tests/generic/570 |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


diff --git a/tests/generic/570 b/tests/generic/570
index 7d03acfe..02c1d333 100755
--- a/tests/generic/570
+++ b/tests/generic/570
@@ -27,7 +27,7 @@ _require_scratch_nocheck
 _require_block_device $SCRATCH_DEV
 test -e /dev/snapshot && _notrun "userspace hibernation to swap is enabled"
 
-$MKSWAP_PROG "$SCRATCH_DEV" >> $seqres.full
+$MKSWAP_PROG -f "$SCRATCH_DEV" &>> $seqres.full || echo "mkswap failed?"
 
 # Can you modify the swap dev via previously open file descriptors?
 for verb in 1 2 3 4; do