linux-kernel - Re: [PATCH v6 12/12] mm,hwpoison: double-check page count in __get_any

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Date:   Mon, 24 Aug 2020 14:21:52 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     nao.horiguchi@...il.com
Cc:     linux-mm@...ck.org, mhocko@...nel.org, akpm@...ux-foundation.org,
        mike.kravetz@...cle.com, tony.luck@...el.com, david@...hat.com,
        aneesh.kumar@...ux.vnet.ibm.com, zeil@...dex-team.ru, cai@....pw,
        naoya.horiguchi@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 12/12] mm,hwpoison: double-check page count in
 __get_any_page()

On Thu, Aug 06, 2020 at 06:49:23PM +0000, nao.horiguchi@...il.com wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> Soft offlining could fail with EIO due to the race condition with
> hugepage migration. This issuse became visible due to the change by
> previous patch that makes soft offline handler take page refcount
> by its own.  We have no way to directly pin zero refcount page, and
> the page considered as a zero refcount page could be allocated just
> after the first check.
> 
> This patch adds the second check to find the race and gives us
> chance to handle it more reliably.
> 
> Reported-by: Qian Cai <cai@....pw>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>

Reviewed-by: Oscar Salvador <osalvador@...e.de>

-- 
Oscar Salvador
SUSE L3