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Date: Tue, 30 Aug 2016 14:36:44 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: wei.guo.simon@gmail.com
Cc: linux-mm@kvack.org, Alexey Klimov <klimov.linux@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Eric B Munson <emunson@akamai.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
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        Mel Gorman <mgorman@techsingularity.net>,
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        Thierry Reding <treding@nvidia.com>, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH 2/4] mm: mlock: avoid increase mm->locked_vm on mlock()
 when already mlock2(,MLOCK_ONFAULT)
Message-ID: <20160830113644.GB32187@node.shutemov.name>
References: <1472554781-9835-1-git-send-email-wei.guo.simon@gmail.com>
 <1472554781-9835-3-git-send-email-wei.guo.simon@gmail.com>
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On Tue, Aug 30, 2016 at 06:59:39PM +0800, wei.guo.simon@gmail.com wrote:
> From: Simon Guo <wei.guo.simon@gmail.com>
> 
> When one vma was with flag VM_LOCKED|VM_LOCKONFAULT (by invoking
> mlock2(,MLOCK_ONFAULT)), it can again be populated with mlock() with
> VM_LOCKED flag only.
> 
> There is a hole in mlock_fixup() which increase mm->locked_vm twice even
> the two operations are on the same vma and both with VM_LOCKED flags.
> 
> The issue can be reproduced by following code:
> mlock2(p, 1024 * 64, MLOCK_ONFAULT); //VM_LOCKED|VM_LOCKONFAULT
> mlock(p, 1024 * 64);  //VM_LOCKED
> Then check the increase VmLck field in /proc/pid/status(to 128k).
> 
> When vma is set with different vm_flags, and the new vm_flags is with
> VM_LOCKED, it is not necessarily be a "new locked" vma.  This patch
> corrects this bug by prevent mm->locked_vm from increment when old
> vm_flags is already VM_LOCKED.
> 
> Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
 Kirill A. Shutemov