[XFS] Check that a page has dirty buffers before finding it acceptable for
rewrite clustering.  This prevents writing excessive amounts of clean data
when doing random rewrites of a cached file.
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>