linux-kernel - Re: [PATCH v1 1/3] mm/memory-failure: Use a mutex to avoid memory

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Message-ID: <20210421005659.GA24391@hori.linux.bs1.fc.nec.co.jp>
Date:   Wed, 21 Apr 2021 00:57:01 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     Naoya Horiguchi <nao.horiguchi@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Tony Luck <tony.luck@...el.com>,
        Aili Yao <yaoaili@...gsoft.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/3] mm/memory-failure: Use a mutex to avoid
 memory_failure() races

On Tue, Apr 20, 2021 at 12:16:57PM +0200, Borislav Petkov wrote:
> On Tue, Apr 20, 2021 at 07:46:26AM +0000, HORIGUCHI NAOYA(堀口 直也) wrote:
> > If you have any other suggestion, please let me know.
> 
> Looks almost ok...
> 
> > From: Tony Luck <tony.luck@...el.com>
> > Date: Tue, 20 Apr 2021 16:42:01 +0900
> > Subject: [PATCH 1/3] mm/memory-failure: Use a mutex to avoid memory_failure()
> >  races
> > 
> > There can be races when multiple CPUs consume poison from the same
> > page. The first into memory_failure() atomically sets the HWPoison
> > page flag and begins hunting for tasks that map this page. Eventually
> > it invalidates those mappings and may send a SIGBUS to the affected
> > tasks.
> > 
> > But while all that work is going on, other CPUs see a "success"
> > return code from memory_failure() and so they believe the error
> > has been handled and continue executing.
> > 
> > Fix by wrapping most of the internal parts of memory_failure() in
> > a mutex.
> > 
> > Along with introducing an additional goto label, this patch also
> 
> ... avoid having "This patch" or "This commit" in the commit message.
> It is tautologically useless. Also, you don't have to explain what the
> patch does - that's visible hopefully. :-)

OK, I'll drop this paragraph from next version.

Thanks,
Naoya Horiguchi