linux-kernel - Re: [PATCH 5.10 050/530] md: md_open returns -EBUSY when entering racing area

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Message-ID: <YJz1o17zGaqfCH0X@kroah.com>
Date:   Thu, 13 May 2021 11:47:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Pavel Machek <pavel@...x.de>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 5.10 050/530] md: md_open returns -EBUSY when entering
 racing area

On Thu, May 13, 2021 at 09:59:41AM +0200, Pavel Machek wrote:
> Hi!
> 
> > commit 6a4db2a60306eb65bfb14ccc9fde035b74a4b4e7 upstream.
> > 
> > commit d3374825ce57 ("md: make devices disappear when they are no longer
> > needed.") introduced protection between mddev creating & removing. The
> > md_open shouldn't create mddev when all_mddevs list doesn't contain
> > mddev. With currently code logic, there will be very easy to trigger
> > soft lockup in non-preempt env.
> > 
> > This patch changes md_open returning from -ERESTARTSYS to -EBUSY, which
> > will break the infinitely retry when md_open enter racing area.
> > 
> > This patch is partly fix soft lockup issue, full fix needs mddev_find
> > is split into two functions: mddev_find & mddev_find_or_alloc. And
> > md_open should call new mddev_find (it only does searching job).
> > 
> > For more detail, please refer with Christoph's "split mddev_find" patch
> > in later commits.
> 
> Something went wrong here; changelog is truncated, in particular it
> does not contain required sign-offs.

That's really odd, let me figure out what went wrong there, might be a
quilt thing...

greg k-hj