linux-kernel - Re: [PATCH md-6.13 5/5] md/md-bitmap: move bitmap

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Message-ID: <CALTww28kr5TzWoeMrS-W_etfhwQGQHDQ-DeakTEALUGDE9FNVA@mail.gmail.com>
Date: Sat, 23 Nov 2024 11:55:26 +0800
From: Xiao Ni <xni@...hat.com>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: song@...nel.org, linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org, 
	yi.zhang@...wei.com, yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH md-6.13 5/5] md/md-bitmap: move bitmap_{start, end}write
 to md upper layer

On Fri, Nov 22, 2024 at 4:32 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> Hi,
>
> 在 2024/11/22 11:14, Xiao Ni 写道:
> >> Ok, one place that I found is that raid5 can do extra end write while
> >> stripe->dev[].towrite is NULL, the null checking is missing. I'll
> >> mention that in the next version.
> > Does this can cause the deadlock?
>
> Not deadlock, the bit counter will underflow and reach COUNTER_MAX, and
> bitmap_startwrite() can wait forever for the counter.

Hi Kuai

For normal io, endwrite is called in function
handle_stripe_clean_event when sh->dev[i].written has value.
For failed io, endwrite is called when bitmap_end has value.
bitmap_end is set when sh->dev[i].to_write is not NULL.
Which place does extra endwrite?

Regards
Xiao
>
> Thanks,
> Kuai
>