linux-kernel - Re: [patch] mm, writeback: prevent race when calculating dirty limits

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Message-ID: <20140717035740.GE29639@cmpxchg.org>
Date:	Wed, 16 Jul 2014 23:57:40 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>, Rik van Riel <riel@...hat.com>,
	stable@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [patch] mm, writeback: prevent race when calculating dirty limits

On Wed, Jul 16, 2014 at 05:36:49PM -0700, David Rientjes wrote:
> Setting vm_dirty_bytes and dirty_background_bytes is not protected by any 
> serialization.
> 
> Therefore, it's possible for either variable to change value after the 
> test in global_dirty_limits() to determine whether available_memory needs 
> to be initialized or not.
> 
> Always ensure that available_memory is properly initialized.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: David Rientjes <rientjes@...gle.com>

Any such race should be barely noticable to the user, so I assume you
realized this while looking at the code?  The patch looks good, but I
don't see that it's stable material.

Acked-by: Johannes Weiner <hannes@...xchg.org>
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