On 05/28/2010 07:49 PM, tytso@xxxxxxx wrote: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....
The difference is that, 2.6.27's write_cache_pages() in page-writeback.c
still updates wbc->nr_to_write, since the patch which changed that
behavior was dropped from .27-rc2 due to the XFS regression it causes on
mainline.
ext4 appears to want the behavior of write_cache_pages which--
does not update wbc->nr_to_write. This write_cache_pages_da() does what
ext4 wants, without introducing the XFS regression. So I believe it is
needed.
Did I mis-judge?
Rgds,
Jayson