Re: regression: data corruption with ext4 on LUKS on nvme with torvalds master

Alex Xu (Hello71)
2021-05-09T14:47:37Z

Excerpts from Jens Axboe's message of May 8, 2021 11:51 pm:
> On 5/8/21 8:29 PM, Alex Xu (Hello71) wrote:
>> Excerpts from Alex Xu (Hello71)'s message of May 8, 2021 1:54 pm:
>>> Hi all,
>>>
>>> Using torvalds master, I recently encountered data corruption on my ext4
>>> volume on LUKS on NVMe. Specifically, during heavy writes, the system
>>> partially hangs; SysRq-W shows that processes are blocked in the kernel
>>> on I/O. After forcibly rebooting, chunks of files are replaced with
>>> other, unrelated data. I'm not sure exactly what the data is; some of it
>>> is unknown binary data, but in at least one case, a list of file paths
>>> was inserted into a file, indicating that the data is misdirected after
>>> encryption.
>>>
>>> This issue appears to affect files receiving writes in the temporal
>>> vicinity of the hang, but affects both new and old data: for example, my
>>> shell history file was corrupted up to many months before.
>>>
>>> The drive reports no SMART issues.
>>>
>>> I believe this is a regression in the kernel related to something merged
>>> in the last few days, as it consistently occurs with my most recent
>>> kernel versions, but disappears when reverting to an older kernel.
>>>
>>> I haven't investigated further, such as by bisecting. I hope this is
>>> sufficient information to give someone a lead on the issue, and if it is
>>> a bug, nail it down before anybody else loses data.
>>>
>>> Regards,
>>> Alex.
>>>
>>
>> I found the following test to reproduce a hang, which I guess may be the
>> cause:
>>
>> host$ cd /tmp
>> host$ truncate -s 10G drive
>> host$ qemu-system-x86_64 -drive format=raw,file=drive,if=none,id=drive -device nvme,drive=drive,serial=1 [... more VM setup options]
>> guest$ cryptsetup luksFormat /dev/nvme0n1
>> [accept warning, use any password]
>> guest$ cryptsetup open /dev/nvme0n1
>> [enter password]
>> guest$ mkfs.ext4 /dev/mapper/test
>> [normal output...]
>> Creating journal (16384 blocks): [hangs forever]
>>
>> I bisected this issue to:
>>
>> cd2c7545ae1beac3b6aae033c7f31193b3255946 is the first bad commit
>> commit cd2c7545ae1beac3b6aae033c7f31193b3255946
>> Author: Changheun Lee <nanich.lee@samsung.com>
>> Date: Mon May 3 18:52:03 2021 +0900
>>
>> bio: limit bio max size
>>
>> I didn't try reverting this commit or further reducing the test case.
>> Let me know if you need my kernel config or other information.
>
> If you have time, please do test with that reverted. I'd be anxious to
> get this revert queued up for 5.13-rc1.
>
> --
> Jens Axboe
>
>

I tested reverting it on top of b741596468b010af2846b75f5e75a842ce344a6e
("Merge tag 'riscv-for-linus-5.13-mw1' of
git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux"), causing it
to no longer hang. I didn't check if this fixes the data corruption, but
I assume so.

I also tested a 1 GB image (works either way), and a virtio-blk
interface (works either way)

The Show Blocked State from the VM (without revert):

sysrq: Show Blocked State
task:kworker/u2:0 state:D stack: 0 pid: 7 ppid: 2 flags:0x00004000
Workqueue: kcryptd/252:0 kcryptd_crypt
Call Trace:
__schedule+0x1a2/0x4f0
schedule+0x63/0xe0
schedule_timeout+0x6a/0xd0
? lock_timer_base+0x80/0x80
io_schedule_timeout+0x4c/0x70
mempool_alloc+0xfc/0x130
? __wake_up_common_lock+0x90/0x90
kcryptd_crypt+0x291/0x4e0
process_one_work+0x1b1/0x300
worker_thread+0x48/0x3d0
? process_one_work+0x300/0x300
kthread+0x129/0x150
? __kthread_create_worker+0x100/0x100
ret_from_fork+0x22/0x30
task:mkfs.ext4 state:D stack: 0 pid: 979 ppid: 964 flags:0x00004000
Call Trace:
__schedule+0x1a2/0x4f0
? __schedule+0x1aa/0x4f0
schedule+0x63/0xe0
schedule_timeout+0x99/0xd0
io_schedule_timeout+0x4c/0x70
wait_for_completion_io+0x74/0xc0
submit_bio_wait+0x46/0x60
blkdev_issue_zeroout+0x118/0x1f0
blkdev_fallocate+0x125/0x180
vfs_fallocate+0x126/0x2e0
__x64_sys_fallocate+0x37/0x60
do_syscall_64+0x61/0x80
? do_syscall_64+0x6e/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Regards,
Alex.