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SubjectRe: [PATCH -next 1/8] md/raid10: prevent soft lockup while flush writes
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Hi,

在 2023/04/25 14:39, Song Liu 写道:
> On Mon, Apr 24, 2023 at 11:16 PM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>>
>> Hi,
>>
>> 在 2023/04/25 8:23, Song Liu 写道:
>>> On Thu, Apr 20, 2023 at 4:31 AM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>>>>
>>>> From: Yu Kuai <yukuai3@huawei.com>
>>>>
>>>> Currently, there is no limit for raid1/raid10 plugged bio. While flushing
>>>> writes, raid1 has cond_resched() while raid10 doesn't, and too many
>>>> writes can cause soft lockup.
>>>>
>>>> Follow up soft lockup can be triggered easily with writeback test for
>>>> raid10 with ramdisks:
>>>>
>>>> watchdog: BUG: soft lockup - CPU#10 stuck for 27s! [md0_raid10:1293]
>>>> Call Trace:
>>>> <TASK>
>>>> call_rcu+0x16/0x20
>>>> put_object+0x41/0x80
>>>> __delete_object+0x50/0x90
>>>> delete_object_full+0x2b/0x40
>>>> kmemleak_free+0x46/0xa0
>>>> slab_free_freelist_hook.constprop.0+0xed/0x1a0
>>>> kmem_cache_free+0xfd/0x300
>>>> mempool_free_slab+0x1f/0x30
>>>> mempool_free+0x3a/0x100
>>>> bio_free+0x59/0x80
>>>> bio_put+0xcf/0x2c0
>>>> free_r10bio+0xbf/0xf0
>>>> raid_end_bio_io+0x78/0xb0
>>>> one_write_done+0x8a/0xa0
>>>> raid10_end_write_request+0x1b4/0x430
>>>> bio_endio+0x175/0x320
>>>> brd_submit_bio+0x3b9/0x9b7 [brd]
>>>> __submit_bio+0x69/0xe0
>>>> submit_bio_noacct_nocheck+0x1e6/0x5a0
>>>> submit_bio_noacct+0x38c/0x7e0
>>>> flush_pending_writes+0xf0/0x240
>>>> raid10d+0xac/0x1ed0
>>>
>>> Is it possible to trigger this with a mdadm test?
>>>
>>
>> The test I mentioned in patch 8 can trigger this problem reliablity, so
>> I this add a new test can achieve this.
>
> To be clear, by "mdadm test" I mean the tests included in mdadm:
>
> https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/tree/tests
>
> Could you please try to add a test? If it works, we should add it to
> mdadm.

Yes, of course. However, I'm not familiar how mdadm tests works yet, it
might take some time. By the way, I'll be good if I can add the test to
blktests if possible.

Thanks,
Kuai
>
> Thanks,
> Song
> .
>

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