From: Mel Gorman <mgorman@suse.de>
To: jglisse@redhat.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Hugh Dickins <hughd@google.com>,
Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH] mm/numa/thp: fix assumptions of migrate_misplaced_transhuge_page()
Date: Thu, 5 May 2016 10:53:56 +0100 [thread overview]
Message-ID: <20160505095356.GD2765@suse.de> (raw)
In-Reply-To: <1462278831-1959-1-git-send-email-jglisse@redhat.com>
On Tue, May 03, 2016 at 02:33:51PM +0200, jglisse@redhat.com wrote:
> From: Jerome Glisse <jglisse@redhat.com>
>
> Fix assumptions in migrate_misplaced_transhuge_page() which is only
> call by do_huge_pmd_numa_page() itself only call by __handle_mm_fault()
> for pmd with PROT_NONE. This means that if the pmd stays the same
> then there can be no concurrent get_user_pages / get_user_pages_fast
> (GUP/GUP_fast). More over because migrate_misplaced_transhuge_page()
> abort if page is mapped more than once then there can be no GUP from
> a different process. Finaly, holding the pmd lock assure us that no
> other part of the kernel can take an extra reference on the page.
>
> In the end this means that the failure code path should never be
> taken unless something is horribly wrong, so convert it to BUG_ON().
>
> Signed-off-by: Jerome Glisse <jglisse@redhat.com>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
--
Mel Gorman
SUSE Labs
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prev parent reply other threads:[~2016-05-05 9:54 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-03 12:33 [PATCH] mm/numa/thp: fix assumptions of migrate_misplaced_transhuge_page() jglisse
2016-05-05 9:53 ` Mel Gorman [this message]
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