On 5/2/23 11:00, Luis Chamberlain wrote:
When using direct IO of say 4k on a 32k physical block size device
we crash. The amount of data requested must match the minimum IO supported
by the device but instead we take it for a ride right now and try to fail
later after checking alignments.
Use the logical block size to ensure the data passed on matches our minimum
supported.
Without this we end up in a crash below:
kernel BUG at lib/iov_iter.c:999!
invalid opcode: 0000 [#1] PREEMPT SMP PTI
CPU: 4 PID: 949 Comm: fio Not tainted 6.3.0-large-block-20230426-dirty #28
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-debian-1.16.0-5 04/01/2014 [ 43.513057] RIP: 0010:iov_iter_revert.part.0+0x16e/0x170
Code: f9 40 a2 63 af 74 07 03 56 08 89 d8 29 d0 89 45 08 44 89 6d 20 <etc>
RSP: 0018:ffffaa52006cfc60 EFLAGS: 00010246
RAX: 0000000000000016 RBX: 0000000000000016 RCX: 0000000000000000
RDX: 0000000000000004 RSI: 0000000000000006 RDI: ffffaa52006cfd08
RBP: ffffaa52006cfd08 R08: 0000000000000000 R09: ffffaa52006cfb40
R10: 0000000000000003 R11: ffffffffafcc21e8 R12: 0000000000004000
R13: 0000000000003fea R14: ffff9de3d7565e00 R15: ffff9de3c1f68600
FS: 00007f8bfe726c40(0000) GS:ffff9de43bd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8bf5eadd68 CR3: 0000000102c76001 CR4: 0000000000770ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<TASK>
blkdev_direct_write+0xf0/0x160
blkdev_write_iter+0x11b/0x230
io_write+0x10c/0x420
? kmem_cache_alloc_bulk+0x2a1/0x410
? fget+0x79/0xb0
io_issue_sqe+0x60/0x3b0
? io_prep_rw+0x5a/0x190
io_submit_sqes+0x1e6/0x640
__do_sys_io_uring_enter+0x54c/0xb90
? handle_mm_fault+0x9a/0x340
? preempt_count_add+0x47/0xa0
? up_read+0x37/0x70
? do_user_addr_fault+0x27c/0x780
do_syscall_64+0x37/0x90
entry_SYSCALL_64_after_hw
The issue is we end up calling iov_iter_revert() at the end of
blkdev_direct_write() due to the writes not being valid and
being unaligned. We can fail twice, for on __blkdev_direct_IO_simple()
and later on __blkdev_direct_IO_async().
Something is askew with that reasoning.
If the above were true, we would also crash if we were attempting a 512
byte direct I/O write on a 4k drive.
And I'm reasonably sure that we don't.
So where's the difference?
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions Germany GmbH, Frankenstr. 146, 90461 Nürnberg
Managing Directors: I. Totev, A. Myers, A. McDonald, M. B. Moerman
(HRB 36809, AG Nürnberg)
