In data=journal mode, reiserfs writepage needs to make sure not to trigger
transactions while being run under PF_MEMALLOC.  This patch makes sure to
redirty the page instead of forcing a transaction start in this case.

Also, calling filemap_fdata* in order to trigger io on the block device can
cause lock inversions on the page lock.  Instead, do simple batching from
flush_commit_list.
Signed-off-by: Chris Mason <mason@suse.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>