blk-throttle: Use blk_plug in throttle code (Was: Re: [PATCH 05/10]block: remove per-queue plugging)

[Vivek Goyal]

On Tue, Mar 08, 2011 at 01:24:01PM +0100, Jens Axboe wrote:
> On 2011-03-04 05:00, Vivek Goyal wrote:
> > On Sat, Jan 22, 2011 at 01:17:24AM +0000, Jens Axboe wrote:
> > 
> > [..]
> >>  mm/page-writeback.c                |    2 +-
> >>  mm/readahead.c                     |   12 ---
> >>  mm/shmem.c                         |    1 -
> >>  mm/swap_state.c                    |    5 +-
> >>  mm/swapfile.c                      |   37 --------
> >>  mm/vmscan.c                        |    2 +-
> >>  118 files changed, 153 insertions(+), 1248 deletions(-)
> > 
> > block/blk-throttle.c also uses blk_unplug(). We need to get rid of that
> > also.
> 
> Done.

Thanks Jens. Looking at the usage of blk_plug, i think it makes sense to
make use of it in throttle dispatch also. Here is the patch.

blk-throttle: Use blk_plug in throttle dispatch

Use plug in throttle dispatch also as we are dispatching a bunch of
bios in throttle context and some of them might merge.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
 block/blk-throttle.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-2.6-block/block/blk-throttle.c
===================================================================
--- linux-2.6-block.orig/block/blk-throttle.c	2011-03-08 16:43:14.000000000 -0500
+++ linux-2.6-block/block/blk-throttle.c	2011-03-08 16:59:44.359620804 -0500
@@ -770,6 +770,7 @@ static int throtl_dispatch(struct reques
 	unsigned int nr_disp = 0;
 	struct bio_list bio_list_on_stack;
 	struct bio *bio;
+	struct blk_plug plug;
 
 	spin_lock_irq(q->queue_lock);
 
@@ -798,8 +799,10 @@ out:
 	 * immediate dispatch
 	 */
 	if (nr_disp) {
+		blk_start_plug(&plug);
 		while((bio = bio_list_pop(&bio_list_on_stack)))
 			generic_make_request(bio);
+		blk_finish_plug(&plug);
 	}
 	return nr_disp;
 }
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