From: "Hillf Danton" <hillf.zj@alibaba-inc.com>
To: Michal Hocko <mhocko@suse.com>
Cc: 'zhongjiang' <zhongjiang@huawei.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: + mm-hugetlb-fix-race-when-migrate-pages.patch added to -mm tree
Date: Thu, 21 Jul 2016 16:19:42 +0800 [thread overview]
Message-ID: <003801d1e328$a24c2030$e6e46090$@alibaba-inc.com> (raw)
In-Reply-To: <003701d1e328$202ca9d0$6085fd70$@alibaba-inc.com>
>
> From b1e9b3214f1859fdf7d134cdcb56f5871933539c Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@suse.com>
> Date: Thu, 21 Jul 2016 09:28:13 +0200
> Subject: [PATCH] mm, hugetlb: fix huge_pte_alloc BUG_ON
>
> Zhong Jiang has reported a BUG_ON from huge_pte_alloc hitting when he
> runs his database load with memory online and offline running in
> parallel. The reason is that huge_pmd_share might detect a shared pmd
> which is currently migrated and so it has migration pte which is
> !pte_huge.
>
> There doesn't seem to be any easy way to prevent from the race and in
> fact seeing the migration swap entry is not harmful. Both callers of
> huge_pte_alloc are prepared to handle them. copy_hugetlb_page_range
> will copy the swap entry and make it COW if needed. hugetlb_fault will
> back off and so the page fault is retries if the page is still under
> migration and waits for its completion in hugetlb_fault.
>
> That means that the BUG_ON is wrong and we should update it. Let's
> simply check that all present ptes are pte_huge instead.
>
> Reported-by: zhongjiang <zhongjiang@huawei.com>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
> mm/hugetlb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 34379d653aa3..31dd2b8b86b3 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4303,7 +4303,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
> pte = (pte_t *)pmd_alloc(mm, pud, addr);
> }
> }
> - BUG_ON(pte && !pte_none(*pte) && !pte_huge(*pte));
> + BUG_ON(pte && pte_present(*pte) && !pte_huge(*pte));
>
> return pte;
> }
> --
> 2.8.1
>
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next parent reply other threads:[~2016-07-21 8:19 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <003701d1e328$202ca9d0$6085fd70$@alibaba-inc.com>
2016-07-21 8:19 ` Hillf Danton [this message]
[not found] <578eb28b.YbRUDGz5RloTVlrE%akpm@linux-foundation.org>
2016-07-21 7:43 ` + mm-hugetlb-fix-race-when-migrate-pages.patch added to -mm tree Michal Hocko
2016-07-21 8:13 ` Naoya Horiguchi
2016-07-21 10:29 ` Michal Hocko
2016-07-21 10:54 ` zhong jiang
2016-07-21 11:27 ` Michal Hocko
2016-07-21 12:14 ` zhong jiang
2016-07-21 12:30 ` Michal Hocko
2016-07-21 12:45 ` zhong jiang
2016-07-21 12:55 ` Michal Hocko
2016-07-21 13:25 ` zhong jiang
2016-07-21 13:40 ` Michal Hocko
2016-07-21 13:58 ` zhong jiang
2016-07-21 14:01 ` Michal Hocko
2016-07-21 14:13 ` zhong jiang
2016-07-21 14:27 ` Michal Hocko
2016-07-21 14:33 ` zhong jiang
2016-07-22 7:17 ` Naoya Horiguchi
2016-07-26 7:58 ` Michal Hocko
2016-07-26 14:04 ` zhong jiang
2016-07-27 14:44 ` Michal Hocko
2016-07-29 11:27 ` Michal Hocko
2016-07-30 6:33 ` zhong jiang
2016-08-01 11:02 ` Michal Hocko
2016-08-01 15:04 ` zhong jiang
2016-08-01 15:31 ` Michal Hocko
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