From: Mikulas Patocka Set the bit that prevents queue plugging --- so that the request goes immediately to the device. This makes dm-delay more precise, without the patch, there could be additional 3ms delay. Signed-off-by: Mikulas Patocka --- drivers/md/dm-delay.c | 1 + 1 file changed, 1 insertion(+) Index: linux-2.6.28-rc5-devel/drivers/md/dm-delay.c =================================================================== --- linux-2.6.28-rc5-devel.orig/drivers/md/dm-delay.c 2008-11-18 14:55:15.000000000 +0100 +++ linux-2.6.28-rc5-devel/drivers/md/dm-delay.c 2008-11-18 14:57:33.000000000 +0100 @@ -74,6 +74,7 @@ static void flush_bios(struct bio *bio) while (bio) { n = bio->bi_next; bio->bi_next = NULL; + bio->bi_flags |= (1 << BIO_RW_SYNC); generic_make_request(bio); bio = n; }