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Date:   Tue, 20 Nov 2018 17:07:15 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Michal Hocko <mhocko@kernel.org>
Cc:     linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Oscar Salvador <OSalvador@suse.com>,
        Pavel Tatashin <pasha.tatashin@oracle.com>,
        David Hildenbrand <david@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Michal Hocko <mhocko@suse.com>
Subject: Re: [RFC PATCH 3/3] mm, fault_around: do not take a reference to a
 locked page
Message-ID: <20181120140715.mouc7okin3ht5krr@kshutemo-mobl1>
References: <20181120134323.13007-1-mhocko@kernel.org>
 <20181120134323.13007-4-mhocko@kernel.org>
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On Tue, Nov 20, 2018 at 02:43:23PM +0100, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> filemap_map_pages takes a speculative reference to each page in the
> range before it tries to lock that page. While this is correct it
> also can influence page migration which will bail out when seeing
> an elevated reference count. The faultaround code would bail on
> seeing a locked page so we can pro-actively check the PageLocked
> bit before page_cache_get_speculative and prevent from pointless
> reference count churn.

Looks fine to me.

But please drop a line of comment in the code. As is it might be confusing
for a reader.

-- 
 Kirill A. Shutemov