linux-kernel - Re: [patch 00/14] Page cache cleanup in anticipation of Large Blocksize support

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Message-ID: <20070614235450.GH86004887@sgi.com>
Date:	Fri, 15 Jun 2007 09:54:50 +1000
From:	David Chinner <dgc@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	clameter@....com, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [patch 00/14] Page cache cleanup in anticipation of Large Blocksize support

On Thu, Jun 14, 2007 at 01:06:45PM -0700, Andrew Morton wrote:
> On Thu, 14 Jun 2007 12:38:39 -0700
> clameter@....com wrote:
> 
> > This patchset cleans up the page cache handling by replacing
> > open coded shifts and adds through inline function calls.
> 
> If we never inflict variable PAGE_CACHE_SIZE upon the kernel, these changes
> become pointless obfuscation.

The open coding of shifts, masks, and other associated cruft is a real
problem. It leads to ugly and hard to understand code when you have to do
anything complex. That means when you come back to that code 6 months later,
you've got to take to the time to understand exactly what all that logic is
doing again.

IMO, xfs_page_state_convert() is a great example of where open coding
of PAGE_CACHE_SIZE manipulations lead to eye-bleeding code. This
patch set would go a long way to help clean up that mess.

IOWs, like hch, I think this patch set stands on it's own merit
regardless of concerns over variable page cache page sizes....

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group
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