linux-kernel - Re: [PATCH v2 3/9] block: WARN if bdev inflight counter is negative

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Message-ID: <c2c95790-32ad-4de2-bfd6-344b189f1ca1@oracle.com>
Date: Tue, 29 Apr 2025 09:53:53 +0100
From: John Garry <john.g.garry@...cle.com>
To: Yu Kuai <yukuai1@...weicloud.com>, hch@...radead.org, axboe@...nel.dk,
        xni@...hat.com, agk@...hat.com, snitzer@...nel.org,
        mpatocka@...hat.com, song@...nel.org, cl@...ux.com,
        nadav.amit@...il.com, ubizjak@...il.com, akpm@...ux-foundation.org
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        dm-devel@...ts.linux.dev, linux-raid@...r.kernel.org,
        yi.zhang@...wei.com, yangerkun@...wei.com, johnny.chenyi@...wei.com,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2 3/9] block: WARN if bdev inflight counter is negative

On 29/04/2025 02:43, Yu Kuai wrote:
> accounting, IO done is more than IO start, and this is a bug.
>>
>>> for related bio-based disk driver, or blk-mq
>>> for rq-based disk, it's better not to hide the BUG.
>>
>> AFICS, this check was not present for mq, so is it really required 
>> now? I suppose that the code is simpler to always have the check. I 
>> find it an odd check to begin with...
> 
> This check do present for mq, for example, diskstats_show() and
> update_io_ticks().

ok, I just noticed this in part_inflight_show() -> 
blk_mq_in_flight_rw(), which didn't have such a check. I think that is 
because we expect the tagset iter to provide a sane count value.

Thanks,
John