Commit 6bc9c2b4 authored by Tejun Heo's avatar Tejun Heo
Browse files

blk-throttle: make tg_dispatch_one_bio() ready for hierarchy 



tg_dispatch_one_bio() currently assumes that the parent_sq is the top
level one and the bio being dispatched is ready to be issued; however,
this assumption will be wrong with proper hierarchy support.  This
patch makes the following changes to make tg_dispatch_on_bio() ready
for hiearchy.

* throtl_data->nr_queued[] is incremented in blk_throtl_bio() instead
  of throtl_add_bio_tg() so that throtl_add_bio_tg() can be used to
  transfer a bio from a child tg to its parent.

* tg_dispatch_one_bio() is updated to distinguish whether its parent
  is another throtl_grp or the throtl_data.  If former, the bio is
  transferred to the parent throtl_grp using throtl_add_bio_tg().  If
  latter, the bio is ready to be issued and put on the top-level
  service_queue's bio_lists[] and throtl_data->nr_queued is
  decremented.

As all throtl_grps currently have the top level service_queue as their
->parent_sq, this patch in itself doesn't make any behavior
difference.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
parent 9e660acf

block/blk-throttle.c

+21 −7
Original line number Diff line number Diff line
@@ -824,7 +824,6 @@ static void throtl_add_bio_tg(struct bio *bio, struct throtl_grp *tg) 
	/* Take a bio reference on tg */

	blkg_get(tg_to_blkg(tg));

	sq->nr_queued[rw]++;

	tg->td->nr_queued[rw]++;

	throtl_enqueue_tg(tg);

}
@@ -855,20 +854,34 @@ static void tg_update_disptime(struct throtl_grp *tg) 
static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)

{

	struct throtl_service_queue *sq = &tg->service_queue;

	struct throtl_service_queue *parent_sq = sq->parent_sq;

	struct throtl_grp *parent_tg = sq_to_tg(parent_sq);

	struct bio *bio;



	bio = bio_list_pop(&sq->bio_lists[rw]);

	sq->nr_queued[rw]--;

	/* Drop bio reference on blkg */

	blkg_put(tg_to_blkg(tg));



	throtl_charge_bio(tg, bio);



	/*

	 * If our parent is another tg, we just need to transfer @bio to

	 * the parent using throtl_add_bio_tg().  If our parent is

	 * @td->service_queue, @bio is ready to be issued.  Put it on its

	 * bio_lists[] and decrease total number queued.  The caller is

	 * responsible for issuing these bios.

	 */

	if (parent_tg) {

		throtl_add_bio_tg(bio, parent_tg);

	} else {

		bio_list_add(&parent_sq->bio_lists[rw], bio);

		BUG_ON(tg->td->nr_queued[rw] <= 0);

		tg->td->nr_queued[rw]--;



	throtl_charge_bio(tg, bio);

	bio_list_add(&sq->parent_sq->bio_lists[rw], bio);

	}



	throtl_trim_slice(tg, rw);



	/* @bio is transferred to parent, drop its blkg reference */

	blkg_put(tg_to_blkg(tg));

}



static int throtl_dispatch_tg(struct throtl_grp *tg)
@@ -1283,6 +1296,7 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio) 
		   sq->nr_queued[READ], sq->nr_queued[WRITE]);



	bio_associate_current(bio);

	tg->td->nr_queued[rw]++;

	throtl_add_bio_tg(bio, tg);

	throttled = true;

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