[PATCH] fstests: generic/228: do not rely on the bash core dump output

[Qu Wenruo <wqu@suse.com>]

[BUG]
With bash 5.3.x, the test case generic/228 will always fail with the
following golden output mismatch:

FSTYP         -- btrfs
PLATFORM      -- Linux/x86_64 btrfs-vm 6.17.0-rc3-custom+ #281 SMP PREEMPT_DYNAMIC Thu Aug 28 11:15:21 ACST 2025
MKFS_OPTIONS  -- /dev/mapper/test-scratch1
MOUNT_OPTIONS -- /dev/mapper/test-scratch1 /mnt/scratch

generic/228 1s ... - output mismatch (see /home/adam/xfstests/results//generic/228.out.bad)
    --- tests/generic/228.out	2025-09-04 15:15:08.965000000 +0930
    +++ /home/adam/xfstests/results//generic/228.out.bad	2025-09-04 15:16:05.627457599 +0930
    @@ -1,6 +1,6 @@
     QA output created by 228
     File size limit is now set to 100 MB.
     Let us try to preallocate 101 MB. This should fail.
    -File size limit exceeded
    +File size limit exceeded   $XFS_IO_PROG -f -c 'falloc 0 101m' $TEST_DIR/ouch
     Let us now try to preallocate 50 MB. This should succeed.
     Test over.
    ...
    (Run 'diff -u /home/adam/xfstests/tests/generic/228.out /home/adam/xfstests/results//generic/228.out.bad'  to see the entire diff)
Ran: generic/228
Failures: generic/228
Failed 1 of 1 tests

[CAUSE]
The "File size limit exceeded" line is never from xfs_io, but the
coredump from bash itself.

And with latest 5.3.x bash, it added extra dump during such core dump
handling (even if we have explicitly skipped the coredump).

[FIX]
Instead of relying on bash to do the coredump, which is unreliable
between different bash versions as I have shown above, ignore the
SIGXFSZ signal so that xfs_io will do the error output, which is more
reliable than bash.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 tests/generic/228     | 6 +++++-
 tests/generic/228.out | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/tests/generic/228 b/tests/generic/228
index f1881f84..defa1e9f 100755
--- a/tests/generic/228
+++ b/tests/generic/228
@@ -50,7 +50,11 @@ flim=`ulimit -f`
 
 echo "File size limit is now set to 100 MB."
 echo "Let us try to preallocate 101 MB. This should fail."
-$XFS_IO_PROG -f -c 'falloc 0 101m' $TEST_DIR/ouch
+# xfs_io will fail with SIGXFSZ signal, if not handled it will trigger a coredump.
+# And in bash 5.3.x, bash will always output the command/script triggering the
+# coredump
+# Work around the new behavior by catcing the signal.
+bash -c "trap '' SIGXFSZ; $XFS_IO_PROG -f -c 'falloc 0 101m' $TEST_DIR/ouch"
 rm -f $TEST_DIR/ouch
 
 echo "Let us now try to preallocate 50 MB. This should succeed."
diff --git a/tests/generic/228.out b/tests/generic/228.out
index 842d4bb7..00d041f6 100644
--- a/tests/generic/228.out
+++ b/tests/generic/228.out
@@ -1,6 +1,6 @@
 QA output created by 228
 File size limit is now set to 100 MB.
 Let us try to preallocate 101 MB. This should fail.
-File size limit exceeded
+fallocate: File too large
 Let us now try to preallocate 50 MB. This should succeed.
 Test over.
-- 
2.51.0