From: Rik van Riel <riel@redhat.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>, Hugh Dickins <hughd@google.com>,
Linux-MM <linux-mm@kvack.org>,
David Gibson <david@gibson.dropbear.id.au>,
Ken Chen <kenchen@google.com>,
Cong Wang <xiyou.wangcong@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Larry Woodman <lwoodman@redhat.com>
Subject: Re: [PATCH -mm] mm: hugetlbfs: Correctly populate shared pmd
Date: Thu, 02 Aug 2012 10:40:36 -0400 [thread overview]
Message-ID: <501A9164.5040304@redhat.com> (raw)
In-Reply-To: <20120802141656.GB18084@dhcp22.suse.cz>
On 08/02/2012 10:16 AM, Michal Hocko wrote:
> Hi Andrew,
> the following patch fixes yet-another race in the hugetlb pte sharing
> code reported by Larry. It is based on top of the current -mm tree but
> it cleanly applies to linus tree as well. It should go to stable as
> well. The bug is there for ages but this fix is possible only since 3.0
> because i_mmap_lock used to be a spinlock until 3d48ae45 which turned it
> into mutex and so we can call pmd_alloc.
> This patch addresses the issue by moving pmd_alloc into huge_pmd_share
> which guarantees that the shared pud is populated in the same
> critical section as pmd. This also means that huge_pte_offset test in
> huge_pmd_share is serialized correctly now which in turn means that
> the success of the sharing will be higher as the racing tasks see the
> pud and pmd populated together.
>
> Race identified and changelog written mostly by Mel Gorman
> Reported-and-tested-by: Larry Woodman <lwoodman@redhat.com>
> Reviewed-by: Mel Gorman <mgorman@suse.de>
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Rik van Riel <riel@redhat.com>
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next prev parent reply other threads:[~2012-08-02 14:42 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-02 14:16 [PATCH -mm] mm: hugetlbfs: Correctly populate shared pmd Michal Hocko
2012-08-02 14:40 ` Rik van Riel [this message]
2012-08-03 14:16 ` Hillf Danton
2012-08-03 14:37 ` Michal Hocko
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