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Message-ID: <1273280081.2444.5.camel@faldara>
Date:	Fri, 07 May 2010 20:54:41 -0400
From:	Phillip Susi <psusi@....rr.com>
To:	tytso@....edu
Cc:	Matthew Wilcox <matthew@....cx>, linux-fsdevel@...r.kernel.org,
	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: unified page and buffer cache?

Would it be possible to somehow keep the current buffer heads, but
associate them with the inode such that readahead() on the directory
would work?

On Fri, 2010-05-07 at 20:46 -0400, tytso@....edu wrote:
> Ext2 does use the page cache for directories.  Ext3 and Ext4 access
> directories via buffer heads because of the journaling requirement.
> 
> In *theory* they could be modified to use the page cache, given that
> we can do data journaling for files, and files live in the page cache
> --- however, for cases where the PAGE_SIZE > FS_BLOCKSIZE, which will
> happen if you are using 1k or 2k block filesystems, or on the Power
> Architecture or on the Itanic where the page size is 16k, updates to
> the directory will be much less efficient, since we journal changes to
> data files on page granularity and not buffer granuality.
> 
> Furthermore, someone would have to supply me with the patches; it's
> pretty low on my priority list.  And people on the Power and ia64
> platforms won't be happy....
> 
> 						- Ted


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