linux-kernel - Re: [PATCH 1/2] [PATCH] Fix a hugepage reservation check for MAP

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Date:	Thu, 10 Jul 2008 14:01:59 -0500
From:	Adam Litke <agl@...ibm.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, apw@...dowen.org
Subject: Re: [PATCH 1/2] [PATCH] Fix a hugepage reservation check for
	MAP_SHARED

On Thu, 2008-07-10 at 18:30 +0100, Mel Gorman wrote:
> When removing a huge page from the hugepage pool for a fault the system
> checks to see if the mapping requires additional pages to be reserved, and
> if it does whether there are any unreserved pages remaining.  If not, the
> allocation fails without even attempting to get a page. In order to determine
> whether to apply this check we call vma_has_private_reserves() which tells us
> if this vma is MAP_PRIVATE and is the owner.  This incorrectly triggers the
> remaining reservation test for MAP_SHARED mappings which prevents allocation
> of the final page in the pool even though it is reserved for this mapping.
> 
> In reality we only want to check this for MAP_PRIVATE mappings where the
> process is not the original mapper.  Replace vma_has_private_reserves() with
> vma_has_reserves() which indicates whether further reserves are required,
> and update the caller.
> 
> Signed-off-by: Mel Gorman <mel@....ul.ie>

Acked-by: Adam Litke <agl@...ibm.com>

Tested and confirmed.

-- 
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center

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