In order for filesystems to detect asynchronous ordered write failures for
buffers sent via submit_bh, they need a bit they can test for in the buffer
head.  This adds BH_Eopnotsupp and the related buffer operations

end_buffer_write_sync is changed to avoid a printk for BH_Eoptnotsupp
related failures, since the FS is responsible for a retry.

sync_dirty_buffer is changed to test for BH_Eopnotsupp and return
-EOPNOTSUPP to the caller

Some of this came from Jens Axboe
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>