linux-kernel - Re: [PATCH -next 2/3] md/raid10: convert resync

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Date:   Fri, 2 Sep 2022 08:49:37 +0800
From:   Guoqing Jiang <guoqing.jiang@...ux.dev>
To:     Logan Gunthorpe <logang@...tatee.com>,
        Yu Kuai <yukuai1@...weicloud.com>, song@...nel.org
Cc:     linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH -next 2/3] md/raid10: convert resync_lock to use seqlock



On 9/2/22 2:41 AM, Logan Gunthorpe wrote:
> Hi,
>
> On 2022-08-29 07:15, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@...wei.com>
>>
>> Currently, wait_barrier() will hold 'resync_lock' to read 'conf->barrier',
>> and io can't be dispatched until 'barrier' is dropped.
>>
>> Since holding the 'barrier' is not common, convert 'resync_lock' to use
>> seqlock so that holding lock can be avoided in fast path.
>>
>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> I've found some lockdep issues starting with this patch in md-next while
> running mdadm tests (specifically 00raid10 when run about 10 times in a
> row).
>
> I've seen a couple different lock dep errors. The first seems to be
> reproducible on this patch, then it possibly changes to the second on
> subsequent patches. Not sure exactly.

That's why I said "try mdadm test suites too to avoid regression." ...

Guoqing