linux-kernel - Re: [PATCH 5/5] Mark page cache pages as __GFP_PAGECACHE instead of __GFP

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Date:	Fri, 18 May 2007 10:23:05 +0100 (IST)
From:	Mel Gorman <mel@....ul.ie>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 5/5] Mark page cache pages as __GFP_PAGECACHE instead of
 __GFP_MOVABLE

On Thu, 17 May 2007, Andrew Morton wrote:

> On Thu, 17 May 2007 11:12:03 +0100 (IST)
> Mel Gorman <mel@....ul.ie> wrote:
>
>> --- linux-2.6.22-rc1-mm1-025_gfphighuser/fs/buffer.c	2007-05-16 22:55:50.000000000 +0100
>> +++ linux-2.6.22-rc1-mm1-030_pagecache_mark/fs/buffer.c	2007-05-16 23:07:30.000000000 +0100
>> @@ -1009,7 +1009,7 @@ grow_dev_page(struct block_device *bdev,
>>  	struct buffer_head *bh;
>>
>>  	page = find_or_create_page(inode->i_mapping, index,
>> -					GFP_NOFS|__GFP_RECLAIMABLE);
>> +					GFP_NOFS_PAGECACHE);
>>  	if (!page)
>>  		return NULL;
>>
>
> I ended up with
>
>        page = find_or_create_page(inode->i_mapping, index,
>                (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
>
> here.
>

That looks like it'll work fine with respects to grouping by mobility but 
there is a slight functional difference worth noting. Specifically, the 
old code did not obey cpuset limits because __GFP_HARDWALL was not set. 
This change gets it's GFP mask from bdget() calling mapping_set_gfp_mask() 
which is GFP_USER and so will obey CPUSET limits. This new version looks 
more correct.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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