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Date: Wed, 15 Jul 2015 15:20:53 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound
 pages
In-Reply-To: <1426784902-125149-5-git-send-email-kirill.shutemov@linux.intel.com>
Message-ID: <alpine.DEB.2.11.1507151520040.30883@east.gentwo.org>
References: <1426784902-125149-1-git-send-email-kirill.shutemov@linux.intel.com> <1426784902-125149-5-git-send-email-kirill.shutemov@linux.intel.com>
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Sender: owner-linux-mm@kvack.org
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To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Dave Hansen <dave.hansen@intel.com>, Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>, Vlastimil Babka <vbabka@suse.cz>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, Steve Capper <steve.capper@linaro.org>, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>, Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>, Jerome Marchand <jmarchan@redhat.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org

On Thu, 19 Mar 2015, Kirill A. Shutemov wrote:

> SLUB uses PG_locked as a bit spin locked. IIUC, tail pages should never
> appear there. VM_BUG_ON() is added to make sure that this assumption is
> correct.

Its really not worth checking that AFAICT. Tail page pointers are not
used.

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