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blk-throttle: make tg_dispatch_one_bio() ready for hierarchy

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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: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
This commit is contained in:
Tejun Heo 2013-05-14 13:52:38 -07:00
parent 9e660acffc
commit 6bc9c2b464
1 changed files with 21 additions and 7 deletions
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28
block/blk-throttle.c
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@ -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));
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);
/*
* 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_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;