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Date: Thu, 14 Aug 2014 11:32:36 -0400
Message-ID: <CAFdhcLQ11MnF7Py+X1wrJMiu0L15-JrV883oYGopdz1oag0njQ@mail.gmail.com>
Subject: Re: [PATCH 3/3] zram: add mem_used_max via sysfs
From: David Horner <ds2horner@gmail.com>
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To: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Linux-MM <linux-mm@kvack.org>, linux-kernel <linux-kernel@vger.kernel.org>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Jerome Marchand <jmarchan@redhat.com>, juno.choi@lge.com, seungho1.park@lge.com, Luigi Semenzato <semenzato@google.com>, Nitin Gupta <ngupta@vflare.org>, Seth Jennings <sjennings@variantweb.net>

On Thu, Aug 14, 2014 at 11:09 AM, Dan Streetman <ddstreet@ieee.org> wrote:
> On Wed, Aug 13, 2014 at 9:12 PM, Minchan Kim <minchan@kernel.org> wrote:
>> -       if (zram->limit_bytes &&
>> -               zs_get_total_size_bytes(meta->mem_pool) > zram->limit_bytes) {
>> +       total_bytes = zs_get_total_size_bytes(meta->mem_pool);
>> +       if (zram->limit_bytes && total_bytes > zram->limit_bytes) {
>
> do you need to take the init_lock to read limit_bytes here?  It could
> be getting changed between these checks...

There is no real danger in freeing with an error.
It is more timing than a race.

The max calculation is still ok because committed allocations are
added atomically.

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