Re: [PATCH 2.6.27.y 1/3] ext4: Use our own write_cache_pages()

[tytso@mit.edu]

On Fri, May 28, 2010 at 02:26:25PM -0500, Jayson R. King wrote:
> From: Theodore Ts'o <tytso@mit.edu>
> Date: Sun May 16 18:00:00 2010 -0400
> Subject: ext4: Use our own write_cache_pages()
> 
> commit 8e48dcfbd7c0892b4cfd064d682cc4c95a29df32 upstream.
> 
> Make a copy of write_cache_pages() for the benefit of
> ext4_da_writepages().  This allows us to simplify the code some, and
> will allow us to further customize the code in future patches.
> 
> There are some nasty hacks in write_cache_pages(), which Linus has
> (correctly) characterized as vile.  I've just copied it into
> write_cache_pages_da(), without trying to clean those bits up lest I
> break something in the ext4's delalloc implementation, which is a bit
> fragile right now.  This will allow Dave Chinner to clean up
> write_cache_pages() in mm/page-writeback.c, without worrying about
> breaking ext4.  Eventually write_cache_pages_da() will go away when I
> rewrite ext4's delayed allocation and create a general
> ext4_writepages() which is used for all of ext4's writeback.  Until
> now this is the lowest risk way to clean up the core
> write_cache_pages() function.
> 
> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

This doesn't fix a bug; it's to make it easy for Dave Chinner to make
some changes to fix XFS's performance and to undo some ext4-specific
changes to write_cache_pages().  I'm not sure there's a good reason to
backport this to 2.6.27.y....

					- Ted