linux-kernel - Re: [PATCH v1] mm, hwpoison: do not lock page again when me_huge

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Date:   Fri, 5 Mar 2021 08:26:58 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Naoya Horiguchi <nao.horiguchi@...il.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] mm, hwpoison: do not lock page again when
 me_huge_page() successfully recovers

On Thu, Mar 04, 2021 at 03:44:37PM +0900, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>

Hi Naoya,

good catch!

> Currently me_huge_page() temporary unlocks page to perform some actions
> then locks it again later. My testcase (which calls hard-offline on some
> tail page in a hugetlb, then accesses the address of the hugetlb range)
> showed that page allocation code detects the page lock on buddy page and
> printed out "BUG: Bad page state" message.  PG_hwpoison does not prevent
> it because PG_hwpoison flag is set on any subpage of the hugetlb page
> but the 2nd page lock is on the head page.

I am having difficulties to parse "PG_hwpoison does not prevent it because
PG_hwpoison flag is set on any subpage of the hugetlb page".

What do you mean by that?

> 
> This patch suggests to drop the 2nd page lock to fix the issue.
> 
> Fixes: commit 78bb920344b8 ("mm: hwpoison: dissolve in-use hugepage in unrecoverable memory error")
> Cc: stable@...r.kernel.org
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>

The fix looks fine to me:

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

 

-- 
Oscar Salvador
SUSE L3