linux-kernel - Re: [PATCH] VM: kswapd should not do blocking memory allocations

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Date:	Wed, 18 Aug 2010 15:34:40 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-nfs@...r.kernel.org
Subject: Re: [PATCH] VM: kswapd should not do blocking memory allocations

On Wed, Aug 18, 2010 at 03:04:01PM -0400, Trond Myklebust wrote:
> From: Trond Myklebust <Trond.Myklebust@...app.com>
> 
> Allowing kswapd to do GFP_KERNEL memory allocations (or any blocking memory
> allocations) is wrong and can cause deadlocks in try_to_release_page(), as
> the filesystem believes it is safe to allocate new memory and block,
> whereas kswapd is there specifically to clear a low-memory situation...
> 
> Set the gfp_mask to GFP_IOFS instead.

I always thought releasepage was supposed to do almost zero work.  It
could release an instantly freeable page but it wasn't supposed to dive
in and solve world hunger or anything.

I thought the VM would be using writepage for that.

-chris
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