linux-kernel - Re: [PATCH v3] mm/hwpoison: do not lock page again when me_huge

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Message-Id: <20210614193528.c2cc50d92eb76c4bea1b40e8@linux-foundation.org>
Date:   Mon, 14 Jun 2021 19:35:28 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     HORIGUCHI NAOYA (堀口　直也) 
        <naoya.horiguchi@....com>
Cc:     Naoya Horiguchi <nao.horiguchi@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        Tony Luck <tony.luck@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] mm/hwpoison: do not lock page again when
 me_huge_page() successfully recovers

On Fri, 11 Jun 2021 00:23:29 +0000 HORIGUCHI NAOYA(堀口　直也) <naoya.horiguchi@....com> wrote:

> > 
> > --- mm/memory-failure.c
> > +++ mm/memory-failure.c
> > @@ -1782,6 +1796,8 @@ int memory_failure(unsigned long pfn, int flags)
> >  
> >  identify_page_state:
> >  	res = identify_page_state(pfn, p, page_flags);
> > +	mutex_unlock(&mf_mutex);
> > +	return res;
> >  unlock_page:
> >  	unlock_page(p);
> >  unlock_mutex:
> > 
> > and...  That mutex_unlock() looks odd.  The patch adds no matching
> > mutex_lock?
> 
> Yes, memory_failure() already has one mutex_lock (introduced by
> mm-memory-failure-use-a-mutex-to-avoid-memory_failure-races.patch,
> sorry for not clarifying that), and the change introduces a separate
> return path.  But I now think that I should have used "goto unlock_mutex"
> to use existing return path.

But mm-memory-failure-use-a-mutex-to-avoid-memory_failure-races.patch
is part of Tony's three patch series which is not marked for -stable. 
So it isn't appropriate that this patch be based on top of that three
patch series.

Should Tony's patchset also be targeted to -stable?  If so then OK.

If not then please let's prepare your -stable patch against current
mainline, as it is higher priority than the 5.14-rc1 material in
linux-next.