Re: [PATCH Linux 2.6.12-rc5-mm1 04/06] blk: reimplement QUEUE_OREDERED_FLUSH

[Tejun Heo <htejun@gmail.com>]

On Sun, May 29, 2005 at 01:23:38PM +0900, Tejun Heo wrote:
> 04_blk_flush_reimplementation.patch
> 
> 	Reimplement QUEUE_ORDERED_FLUSH.
> 
> 	* Implementation is contained inside blk layer.  Only
> 	  prepare_flush_fn() is needed from individual drivers.
> 	* Tagged queues which don't support ordered tag can use
>           flushing.
> 	* Multi-bio barrier requests supported.
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>
> 
>  drivers/block/elevator.c   |   52 ++++----
>  drivers/block/ll_rw_blk.c  |  279 +++++++++++++++++++++++++++------------------
>  drivers/ide/ide-disk.c     |   39 ------
>  drivers/ide/ide-io.c       |    5 
>  drivers/scsi/scsi_lib.c    |   21 ---
>  drivers/scsi/sd.c          |   25 ----
>  include/linux/blkdev.h     |   29 ++--
>  include/scsi/scsi_driver.h |    1 
>  8 files changed, 210 insertions(+), 241 deletions(-)

 In blk_do_barrier() above patch implements, when a barrier request is
terminated w/ -EOPNOTSUPP, the request is not dequeued.  The following
patch fixes this.  The fixed path is a very rare error path, so, for
reviewing, this patch doesn't make much difference.  I'll use properly
regenerated patch on the next posting of this patchset.

diff -u blk-fixes/drivers/block/ll_rw_blk.c blk-fixes/drivers/block/ll_rw_blk.c
--- blk-fixes/drivers/block/ll_rw_blk.c	2005-05-29 13:20:31.000000000 +0900
+++ blk-fixes/drivers/block/ll_rw_blk.c	2005-05-29 18:23:05.000000000 +0900
@@ -352,6 +352,8 @@
 	struct request *rq = q->bar_rq;
 	struct bio *bio = q->bar_bio;
 
+	BUG_ON(!list_empty(&rq->queuelist));
+
 	q->flush_seq = QUEUE_FLUSH_NONE;
 	q->bar_rq = NULL;
 	q->bar_bio = NULL;
@@ -457,6 +459,7 @@
 			 * This can happen when the queue switches to
 			 * ORDERED_NONE while this request is on it.
 			 */
+			blkdev_dequeue_request(rq);
 			end_that_request_first(rq, -EOPNOTSUPP,
 					       rq->hard_nr_sectors);
 			end_that_request_last(rq, -EOPNOTSUPP);