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

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Message-ID: <YJz16WxZH3sVMatV@kroah.com>
Date:   Thu, 13 May 2021 11:48:25 +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 11:47:15AM +0200, Greg Kroah-Hartman wrote:
> 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...

Yup, it's a bug in quilt, the header is just dropped for some reason.
Will dig further, thanks for pointing this out.

greg k-h