From: Jens Axboe <[email protected]>
To: Fabian Ebner <[email protected]>, [email protected]
Cc: [email protected]
Subject: Re: [PATCH 2/2] io_uring: don't block level reissue off completion path
Date: Wed, 28 Jul 2021 07:23:07 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 7/28/21 3:26 AM, Fabian Ebner wrote:
> Am 27.07.21 um 18:58 schrieb Jens Axboe:
>> Some setups, like SCSI, can throw spurious -EAGAIN off the softirq
>> completion path. Normally we expect this to happen inline as part
>> of submission, but apparently SCSI has a weird corner case where it
>> can happen as part of normal completions.
>>
>> This should be solved by having the -EAGAIN bubble back up the stack
>> as part of submission, but previous attempts at this failed and we're
>> not just quite there yet. Instead we currently use REQ_F_REISSUE to
>> handle this case.
>>
>> For now, catch it in io_rw_should_reissue() and prevent a reissue
>> from a bogus path.
>>
>> Cc: [email protected]
>> Reported-by: Fabian Ebner <[email protected]>
>> Signed-off-by: Jens Axboe <[email protected]>
>> ---
>> fs/io_uring.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 6ba101cd4661..83f67d33bf67 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -2447,6 +2447,12 @@ static bool io_rw_should_reissue(struct io_kiocb *req)
>> */
>> if (percpu_ref_is_dying(&ctx->refs))
>> return false;
>> + /*
>> + * Play it safe and assume not safe to re-import and reissue if we're
>> + * not in the original thread group (or in task context).
>> + */
>> + if (!same_thread_group(req->task, current) || !in_task())
>> + return false;
>> return true;
>> }
>> #else
>>
>
> Hi,
>
> thank you for the fix! This does indeed prevent the panic (with 5.11.22)
> and hang (with 5.13.3) with my problematic workload.
Perfect, thanks for re-testing! Can I add your Tested-by to the patch?
--
Jens Axboe
next prev parent reply other threads:[~2021-07-28 13:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-27 16:58 [PATCH 0/2] Further async re-queue tightening/fix Jens Axboe
2021-07-27 16:58 ` [PATCH 1/2] io_uring: always reissue from task_work context Jens Axboe
2021-07-27 16:58 ` [PATCH 2/2] io_uring: don't block level reissue off completion path Jens Axboe
2021-07-28 9:26 ` Fabian Ebner
2021-07-28 13:23 ` Jens Axboe [this message]
2021-07-29 6:50 ` Fabian Ebner
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