Date: Tue, 2 Dec 2014 10:18:29 -0500
From: Johannes Weiner <hannes@cmpxchg.org>
To: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>, Tejun Heo <tj@kernel.org>,
        Hugh Dickins <hughd@google.com>, Michel Lespinasse <walken@google.com>,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [patch 2/3] mm: memory: remove ->vm_file check on shared
 writable vmas
Message-ID: <20141202151829.GC8401@phnom.home.cmpxchg.org>
References: <1417474682-29326-1-git-send-email-hannes@cmpxchg.org>
 <1417474682-29326-2-git-send-email-hannes@cmpxchg.org>
 <20141202085825.GA9092@quack.suse.cz>
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On Tue, Dec 02, 2014 at 09:58:25AM +0100, Jan Kara wrote:
> On Mon 01-12-14 17:58:01, Johannes Weiner wrote:
> > The only way a VMA can have shared and writable semantics is with a
> > backing file.
>   OK, one always learns :) After some digging I found that MAP_SHARED |
> MAP_ANONYMOUS mappings are in fact mappings of a temporary file in tmpfs.
> It would be worth to mention this in the changelog I believe. Otherwise
> feel free to add:
>   Reviewed-by: Jan Kara <jack@suse.cz>

Thanks, Jan.  I updated the changelog to read:

Shared anonymous mmaps are implemented with shmem files, so all VMAs
with shared writable semantics also have an underlying backing file.
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