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authorTejun Heo <tj@kernel.org>2013-05-14 13:52:38 -0700
committerTejun Heo <tj@kernel.org>2013-05-14 13:52:38 -0700
commit6bc9c2b464fb89eab705da87aa4284171d942369 (patch)
tree9b302b4d3f036f28ee2c0198148a3bf7d8bceadf
parent9e660acffcd1b5adc4ec1ffba0cbb584f86b8907 (diff)
downloadlinux-linaro-stable-6bc9c2b464fb89eab705da87aa4284171d942369.tar.gz
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: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com>
-rw-r--r--block/blk-throttle.c28
1 files changed, 21 insertions, 7 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 52321a42cd78..04202617fda5 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -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;