linux-kernel - Re: [PATCH 1/5] md: Flush workqueue md_rdev_misc_wq in md

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Message-ID: <CAPhsuW66hmkAE=iWHt=F8PfFus_Q5_zB_nqPdZMKr=N2Ddfesg@mail.gmail.com>
Date:   Thu, 11 Aug 2022 10:46:22 -0700
From:   Song Liu <song@...nel.org>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     open list <linux-kernel@...r.kernel.org>,
        linux-raid <linux-raid@...r.kernel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Guoqing Jiang <guoqing.jiang@...ux.dev>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <Martin.Oliveira@...eticom.com>,
        David Sloan <David.Sloan@...eticom.com>
Subject: Re: [PATCH 1/5] md: Flush workqueue md_rdev_misc_wq in md_alloc()

On Thu, Aug 11, 2022 at 10:14 AM Logan Gunthorpe <logang@...tatee.com> wrote:
>
> From: David Sloan <david.sloan@...eticom.com>
>
> A race condition still exists when removing and re-creating md devices
> in test cases. However, it is only seen on some setups.
>
> The race condition was tracked down to a reference still being held
> to the kobject by the rdev in the md_rdev_misc_wq which will be released
> in rdev_delayed_delete().
>
> md_alloc() waits for previous deletions by waiting on the md_misc_wq,
> but the md_rdev_misc_wq may still be holding a reference to a recently
> removed device.
>
> To fix this, also flush the md_rdev_misc_wq in md_alloc().
>
> Signed-off-by: David Sloan <david.sloan@...eticom.com>
> [logang@...tatee.com: rewrote commit message]
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>

Applied 1/5 to md-fixes.

Thanks!
Song