linux-kernel - Re: [PATCH v1] mm: soft-offline: check return value in second __get_any

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Date:	Fri, 8 Jan 2016 15:36:26 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH v1] mm: soft-offline: check return value in second
 __get_any_page() call

On Fri, 8 Jan 2016 07:51:59 +0000 Naoya Horiguchi <n-horiguchi@...jp.nec.com> wrote:

> >   [   52.600579]  [<ffffffff811bd18c>] SyS_madvise+0x6bc/0x6f0
> >   [   52.600579]  [<ffffffff8104d0ac>] ? fpu__restore_sig+0xcc/0x320
> >   [   52.600579]  [<ffffffff810a0003>] ? do_sigaction+0x73/0x1b0
> >   [   52.600579]  [<ffffffff8109ceb2>] ? __set_task_blocked+0x32/0x70
> >   [   52.600579]  [<ffffffff81652757>] entry_SYSCALL_64_fastpath+0x12/0x6a
> >   [   52.600579] Code: 8b fc ff ff 5b 5d c3 48 89 df e8 b0 fa ff ff 48 89 df 31 f6 e8 c6 7d ff ff 5b 5d c3 48 c7 c6 08 54 a2 81 48 89 df e8 a4 c5 01 00 <0f> 0b 66 90 66 66 66 66 90 55 48 89 e5 41 55 41 54 53 48 8b 47
> >   [   52.600579] RIP  [<ffffffff8118998c>] put_page+0x5c/0x60
> >   [   52.600579]  RSP <ffff88007c213e00>
> > 
> > The root cause resides in get_any_page() which retries to get a refcount of
> > the page to be soft-offlined. This function calls put_hwpoison_page(), expecting
> > that the target page is putback to LRU list. But it can be also freed to buddy.
> > So the second check need to care about such case.
> > 
> > Fixes: af8fae7c0886 ("mm/memory-failure.c: clean up soft_offline_page()")
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> > Cc: stable@...r.kernel.org # v3.9+

Please don't top-post.  I manually fixed it here.

> Sorry, I forgot to notice that this specific problem is already fixed in
> mmotm with patch "mm: hwpoison: adjust for new thp refcounting", but
> considering backporting to -stable, it's easier to handle this separately.
> 
> So Andrew, could you separate out the code of this patch from
> "mm: hwpoison: adjust for new thp refcounting"?

I don't understand what you're asking for.  Please be very
specific and carefully identify patches by filename or Subject:.