fio verify breaks in the presence of short writes not aligned with blocksize

[koverstreet]

To reproduce: run xfstests generic/299 on bcachefs; optionally change verify method to meta

It will fail like so: fio is complaining about a bad magic header at an offset not aligned to fio's blocksize, and it never wrote a verify_header there.

changing the blocksize for the verify jobs to 512 (matching filesystem blocksize) causes the test to pass.

• output mismatch (see /ktest-out/xfstests/generic/299.out.bad)
  mv: failed to preserve ownership for '/ktest-out/xfstests/generic/299.out.bad': Operation not permitted
  --- tests/generic/299.out 2017-03-18 04:22:34.053459304 +0000
  +++ /ktest-out/xfstests/generic/299.out.bad 2024-10-17 05:12:45.000000000 +0000
  @@ -3,3 +3,41 @@
  Run fio with random aio-dio pattern

  Start fallocate/truncate loop
  +verify: bad magic header e1a3, wanted acca at file /mnt/scratch/buffered-aio-verifier offset 6782324224, length 4096 (requested block: offset=6782324224, length=4096)

  •   hdr_fail data dumped as buffered-aio-verifier.6782324224.hdr_fail                                                                                                                                                                                                                                                     
    

  +verify: bad magic header c2f2, wanted acca at file /mnt/scratch/buffered-aio-verifier offset 693197312, length 4096 (requested block: offset=693197312, length=4096)

  •   hdr_fail data dumped as buffered-aio-verifier.693197312.hdr_fail                                                                                                                                                                                                                                                      
    

  ...
  (Run 'diff -u /host/home/kent/ktest/tests/fs/xfstests/tests/generic/299.out /ktest-out/xfstests/generic/299.out.bad' to see the entire diff)
  /ktest-out/xfstests/generic/299.full:
  fio --ioengine=libaio --bs=128k --directory=/mnt/scratch --filesize=25769803776 --size=999G --iodepth=1281 --continue_on_error=write --ignore_error=,ENOSPC --error_dump=0 --create_on_open=1 --fallocate=none --exitall=1 --name=direct_aio --direct=1 --buffered=0 --numjobs=4 --rw=randwrite --runtime=1001 --time_based --na
  me=aio-dio-verifier Option verifysort is deprecated
  --numjobs=1 --verify=meta --verify_fatal=1 --verify_dump=1 --verify_backlog=1024 --verify_async=4 --verifysort=1 --direct=1 --bs=4k --rw=randrw --filename=aio-dio-verifier --name=buffered-aio-verifier Option verifysort is deprecated
  --numjobs=1 --verify=meta --verify_fatal=1 --verify_dump=1 --verify_backlog=1024 --verify_async=4 --verifysort=1 --direct=0 --buffered=1 --bs=4k --rw=randrw --filename=buffered-aio-verifier
  ###########

299 test fio activity

Filenames derived from jobsname and jobid like follows:

..

[global]
ioengine=libaio
bs=128k
directory=/mnt/scratch
filesize=25769803776
size=999G
iodepth=128*1
continue_on_error=write
ignore_error=,ENOSPC
error_dump=0
create_on_open=1
fallocate=none
exitall=1

Perform direct aio, to files which may be truncated

by external task

[direct_aio]
direct=1
buffered=0
numjobs=4
rw=randwrite
runtime=100*1
time_based

Perform direct aio and verify data

This test case should check use-after-free issues

[aio-dio-verifier]
numjobs=1
verify=meta
verify_fatal=1
verify_dump=1
verify_backlog=1024
verify_async=4
verifysort=1
direct=1
bs=4k
rw=randrw
filename=aio-dio-verifier

Perform buffered aio and verify data

This test case should check use-after-free issues

[buffered-aio-verifier]
numjobs=1
verify=meta
verify_fatal=1
verify_dump=1
verify_backlog=1024
verify_async=4
verifysort=1
direct=0
buffered=1
bs=4k
rw=randrw