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From: Nadav Amit <nadav.amit@gmail.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Pavel Begunkov <asml.silence@gmail.com>,
	io-uring@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: io-uring: KASAN failure, presumably
Date: Sun, 12 Sep 2021 11:21:55 -0700	[thread overview]
Message-ID: <C5C0EB71-B05E-4FE6-871D-900231F8454B@gmail.com> (raw)
In-Reply-To: <859829f3-ecd0-0c01-21d4-28c17382aa52@kernel.dk>



> On Sep 12, 2021, at 11:15 AM, Jens Axboe <axboe@kernel.dk> wrote:
> 
> On 9/11/21 8:34 PM, Nadav Amit wrote:
>> Hello Jens (& Pavel),
>> 
>> I hope you are having a nice weekend. I ran into a KASAN failure in io-uring
>> which I think is not "my fault".
>> 
>> The failure does not happen very infrequently, so my analysis is based on
>> reading the code. IIUC the failure, then I do not understand the code well
>> enough, as to say I do not understand how it was supposed to work. I would
>> appreciate your feedback.
>> 
>> The failure happens on my own custom kernel (do not try to correlate the line
>> numbers). The gist of the splat is:
> 
> I think this is specific to your use case, but I also think that we
> should narrow the scope for this type of REQ_F_REISSUE trigger. It
> really should only happen on bdev backed regular files, where we cannot
> easily pass back congestion. For that case, the completion for this is
> called while we're in ->write_iter() for example, and hence there is no
> race here.
> 
> I'll ponder this a bit…

I see what you are saying. The assumption is that write_iter() is setting
REQ_F_REISSUE, which is not the case in my use-case. Perhaps EAGAIN is
anyhow not the right return value (in my case). I am not sure any other
“invalid" use-case exists, but some documentation/assertion(?) can help.

I changed the return error-codes and check that the issue is not
triggered again.

Thanks, as usual, for the quick response.

  reply	other threads:[~2021-09-12 18:22 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-12  2:34 io-uring: KASAN failure, presumably Nadav Amit
2021-09-12  4:43 ` io-uring: KASAN failure, presumably REQ_F_REISSUE issue Nadav Amit
2021-09-12 13:00 ` io-uring: KASAN failure, presumably Jens Axboe
2021-09-12 18:15 ` Jens Axboe
2021-09-12 18:21   ` Nadav Amit [this message]
2021-09-12 18:24     ` Jens Axboe

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