On 6/2/25 05:58, Qu Wenruo wrote:
[BUG]
With recent kernel patch "btrfs: always fallback to buffered write if the
inode requires checksum", the test case btrfs/226 will fail with the
following error:
FSTYP -- btrfs
PLATFORM -- Linux/x86_64 btrfs-vm 6.13.0-rc6-custom+ #209 SMP PREEMPT_DYNAMIC Fri Jan 24 17:23:03 ACDT 2025
MKFS_OPTIONS -- /dev/mapper/test-scratch1
MOUNT_OPTIONS -- /dev/mapper/test-scratch1 /mnt/scratch
btrfs/226 1s ... - output mismatch (see /home/adam/xfstests/results//btrfs/226.out.bad)
--- tests/btrfs/226.out 2024-04-12 14:04:03.080000035 +0930
+++ /home/adam/xfstests/results//btrfs/226.out.bad 2025-02-06 08:23:42.564298585 +1030
@@ -39,14 +39,11 @@
Testing write against prealloc extent at eof
wrote 65536/65536 bytes at offset 0
XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-wrote 65536/65536 bytes at offset 65536
-XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+pwrite: Resource temporarily unavailable
File after write:
...
(Run 'diff -u /home/adam/xfstests/tests/btrfs/226.out /home/adam/xfstests/results//btrfs/226.out.bad' to see the entire diff)
Ran: btrfs/226
Failures: btrfs/226
Failed 1 of 1 tests
[CAUSE]
That kernel patch makes btrfs to always fallback to buffered IO if the
target inode requires data checksum.
This is to avoid more deadly problems of mismatched data checksum.
But this also means, for inodes with data checksum, RWF_NOWAIT will
always fail, because we will wait writing back the page cache, thus
breaking the RWF_NOWAIT requirement.
[FIX]
Update the test case to utilize nodatasum mount option, so that the
direct-IO will not fallback to buffered ones unconditionally.
Reported-by: Filipe Manana <fdmanana@xxxxxxxxxx>
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
tests/btrfs/226 | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/tests/btrfs/226 b/tests/btrfs/226
index 70275d0aa2d8..359813c4f394 100755
--- a/tests/btrfs/226
+++ b/tests/btrfs/226
@@ -21,7 +21,12 @@ _require_xfs_io_command falloc -k
_require_xfs_io_command fpunch
_scratch_mkfs >>$seqres.full 2>&1
-_scratch_mount
+
+# This test involves RWF_NOWAIT direct IOs, but for inodes with data checksum,
+# btrfs will fall back to buffered IO unconditionally to prevent data checksum
+# mimsatch, and that will break RWF_NOWAIT with -EAGAIN.
+# So here we have to go with nodatasum mount option.
+_scratch_mount -o nodatasum
Looks good.
Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx>
Thx.
# Test a write against COW file/extent - should fail with -EAGAIN. Disable the
# NOCOW attribute of the file just in case MOUNT_OPTIONS has "-o nodatacow".
