linux-kernel - Re: [patch 2/3] mm: memory: remove ->vm

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Message-ID: <20141202151829.GC8401@phnom.home.cmpxchg.org>
Date:	Tue, 2 Dec 2014 10:18:29 -0500
From:	Johannes Weiner <hannes@...xchg.org>
To:	Jan Kara <jack@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Hugh Dickins <hughd@...gle.com>,
	Michel Lespinasse <walken@...gle.com>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 2/3] mm: memory: remove ->vm_file check on shared
 writable vmas

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@...e.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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