[xfstests generic/617] fsx io_uring dio starts to fail on overlayfs since v6.6-rc1

[Zorro Lang <zlang@redhat.com>]

Hi,

The generic/617 of fstests is a test case does IO_URING soak direct-IO
fsx test, but recently (about from v6.6-rc1 to now) it always fails on
overlayfs as [1], no matter the underlying fs is ext4 or xfs. But it
never failed on overlay before, likes [2].

So I thought it might be a regression of overlay or io-uring on current v6.6.
Please help to review, it's easy to reproduce. My system is Fedora-rawhide/RHEL-9,
with upstream mainline linux HEAD=dc912ba91b7e2fa74650a0fc22cccf0e0d50f371.
The generic/617.full output as [3].

Thanks,
Zorro

[1]
FSTYP         -- overlay
PLATFORM      -- Linux/x86_64 dell-xxxx-xxx 6.6.0-rc2+ #1 SMP PREEMPT_DYNAMIC Fri Sep 22 15:41:10 EDT 2023
MKFS_OPTIONS  -- -m crc=1,finobt=1,rmapbt=0,reflink=1,inobtcount=1,bigtime=1 /mnt/xfstests/scratch
MOUNT_OPTIONS -- -o context=system_u:object_r:root_t:s0 /mnt/xfstests/scratch /mnt/xfstests/scratch/ovl-mnt

generic/617       - output mismatch (see /var/lib/xfstests/results//generic/617.out.bad)
    --- tests/generic/617.out	2023-09-22 16:08:35.444572181 -0400
    +++ /var/lib/xfstests/results//generic/617.out.bad	2023-09-22 19:33:29.240901008 -0400
    @@ -1,2 +1,54 @@
     QA output created by 617
    +uring write bad io length: 0 instead of 8192
    +short write: 0x0 bytes instead of 0x2000
    +LOG DUMP (46 total operations):
    +1(  1 mod 256): FALLOC   0x28c0d thru 0x2953a	(0x92d bytes) EXTENDING
    +2(  2 mod 256): TRUNCATE UP	from 0x2953a to 0x81000
    +3(  3 mod 256): ZERO     0x6f07 thru 0x14790	(0xd88a bytes)
    ...
    (Run 'diff -u /var/lib/xfstests/tests/generic/617.out /var/lib/xfstests/results//generic/617.out.bad'  to see the entire diff)
Ran: generic/617
Failures: generic/617
Failed 1 of 1 tests

[2]
FSTYP         -- overlay
PLATFORM      -- Linux/x86_64 hp-xxxxxx-xx 6.5.0-rc6+ #1 SMP PREEMPT_DYNAMIC Mon Aug 14 12:45:06 UTC 2023
MKFS_OPTIONS  -- /mnt/scratch
MOUNT_OPTIONS -- -o context=system_u:object_r:root_t:s0 /mnt/scratch /mnt/scratch/ovl-mnt

generic/617        5s
Ran: generic/617
Passed all 1 tests

[3]
/var/lib/xfstests/ltp/fsx -S 0 -U -q -N 20000 -p 200 -o 128000 -l 600000 -r 4096 -t 4096 -w 4096 -Z /mnt/xfstests/test/ovl-mnt/junk
uring write bad io length: 0 instead of 8192
short write: 0x0 bytes instead of 0x2000
LOG DUMP (46 total operations):
1(  1 mod 256): FALLOC   0x28c0d thru 0x2953a	(0x92d bytes) EXTENDING
2(  2 mod 256): TRUNCATE UP	from 0x2953a to 0x81000
3(  3 mod 256): ZERO     0x6f07 thru 0x14790	(0xd88a bytes)
4(  4 mod 256): ZERO     0x4a097 thru 0x5dfc8	(0x13f32 bytes)
5(  5 mod 256): TRUNCATE DOWN	from 0x81000 to 0x10000
6(  6 mod 256): MAPWRITE 0x74000 thru 0x78de7	(0x4de8 bytes)
7(  7 mod 256): SKIPPED (no operation)
8(  8 mod 256): MAPWRITE 0x52000 thru 0x57bf5	(0x5bf6 bytes)
9(  9 mod 256): DEDUPE 0x19000 thru 0x20fff	(0x8000 bytes) to 0x57000 thru 0x5efff
10( 10 mod 256): COPY 0x64000 thru 0x6bfff	(0x8000 bytes) to 0x1c000 thru 0x23fff
11( 11 mod 256): INSERT 0x38000 thru 0x46fff	(0xf000 bytes)
12( 12 mod 256): WRITE    0x16000 thru 0x1cfff	(0x7000 bytes)
13( 13 mod 256): MAPWRITE 0x3f000 thru 0x444d5	(0x54d6 bytes)
14( 14 mod 256): INSERT 0x83000 thru 0x8cfff	(0xa000 bytes)
15( 15 mod 256): COPY 0x54000 thru 0x5dfff	(0xa000 bytes) to 0x6d000 thru 0x76fff
16( 16 mod 256): PUNCH    0x34f3d thru 0x48c45	(0x13d09 bytes)
17( 17 mod 256): FALLOC   0x47bd5 thru 0x5a950	(0x12d7b bytes) INTERIOR
18( 18 mod 256): READ     0x20000 thru 0x3cfff	(0x1d000 bytes)
19( 19 mod 256): READ     0xe000 thru 0x1cfff	(0xf000 bytes)
20( 20 mod 256): MAPREAD  0x70000 thru 0x8d512	(0x1d513 bytes)
21( 21 mod 256): PUNCH    0x12773 thru 0x1f5b1	(0xce3f bytes)
22( 22 mod 256): DEDUPE 0x81000 thru 0x8ffff	(0xf000 bytes) to 0x3b000 thru 0x49fff
23( 23 mod 256): CLONE 0x78000 thru 0x7efff	(0x7000 bytes) to 0x1e000 thru 0x24fff
24( 24 mod 256): MAPREAD  0x1000 thru 0x1b6c1	(0x1a6c2 bytes)
25( 25 mod 256): SKIPPED (no operation)
26( 26 mod 256): FALLOC   0x43b4c thru 0x5ecb7	(0x1b16b bytes) INTERIOR
27( 27 mod 256): SKIPPED (no operation)
28( 28 mod 256): WRITE    0x3000 thru 0x8fff	(0x6000 bytes)
29( 29 mod 256): COPY 0x19000 thru 0x20fff	(0x8000 bytes) to 0x79000 thru 0x80fff
30( 30 mod 256): WRITE    0x19000 thru 0x28fff	(0x10000 bytes)
31( 31 mod 256): DEDUPE 0x3a000 thru 0x3dfff	(0x4000 bytes) to 0x49000 thru 0x4cfff
32( 32 mod 256): ZERO     0x8f290 thru 0x927bf	(0x3530 bytes)
33( 33 mod 256): PUNCH    0x45aec thru 0x58137	(0x1264c bytes)
34( 34 mod 256): SKIPPED (no operation)
35( 35 mod 256): FALLOC   0x5b567 thru 0x613ab	(0x5e44 bytes) INTERIOR
36( 36 mod 256): ZERO     0x1abc7 thru 0x1bbd6	(0x1010 bytes)
37( 37 mod 256): MAPWRITE 0x44000 thru 0x45411	(0x1412 bytes)
38( 38 mod 256): FALLOC   0x3b222 thru 0x4de57	(0x12c35 bytes) INTERIOR
39( 39 mod 256): COLLAPSE 0x1e000 thru 0x20fff	(0x3000 bytes)
40( 40 mod 256): INSERT 0x62000 thru 0x64fff	(0x3000 bytes)
41( 41 mod 256): DEDUPE 0xf000 thru 0x16fff	(0x8000 bytes) to 0x78000 thru 0x7ffff
42( 42 mod 256): WRITE    0x4000 thru 0x12fff	(0xf000 bytes)
43( 43 mod 256): COPY 0x62000 thru 0x79fff	(0x18000 bytes) to 0x2000 thru 0x19fff
44( 44 mod 256): SKIPPED (no operation)
45( 45 mod 256): MAPWRITE 0x22000 thru 0x297c9	(0x77ca bytes)
46( 46 mod 256): WRITE    0x41000 thru 0x42fff	(0x2000 bytes)
Log of operations saved to "/mnt/xfstests/test/ovl-mnt/junk.fsxops"; replay with --replay-ops
Correct content saved for comparison
(maybe hexdump "/mnt/xfstests/test/ovl-mnt/junk" vs "/mnt/xfstests/test/ovl-mnt/junk.fsxgood")