blk-throttle: move bio_lists[] and friends to throtl_service_queue

throtl_service_queues will eventually form a tree which is anchored at
throtl_data->service_queue and queue bios will climb the tree to the
top service_queue to be executed.

This patch moves bio_lists[] and nr_queued[] from throtl_grp to its
service_queue to prepare for that.  As currently only the
throtl_data->service_queue is in use, this patch just ends up moving
throtl_grp->bio_lists[] and ->nr_queued[] to
throtl_grp->service_queue.bio_lists[] and ->nr_queued[] without making
any functional differences.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

1 files changed, 39 insertions, 24 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 7340440ccfb5..6f57f94c3c57 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -27,6 +27,17 @@ static struct blkcg_policy blkcg_policy_throtl;
 static struct workqueue_struct *kthrotld_workqueue;
 
 struct throtl_service_queue {
+        /*
+         * Bios queued directly to this service_queue or dispatched from
+         * children throtl_grp's.
+         */
+        struct bio_list         bio_lists[2];   /* queued bios [READ/WRITE] */
+        unsigned int            nr_queued[2];   /* number of queued bios */
+
+        /*
+         * RB tree of active children throtl_grp's, which are sorted by
+         * their ->disptime.
+         */
         struct rb_root          pending_tree;   /* RB tree of active tgs */
         struct rb_node          *first_pending; /* first node in the tree */
         unsigned int            nr_pending;     /* # queued in the tree */
@@ -69,12 +80,6 @@ struct throtl_grp {
 
         unsigned int flags;
 
-        /* Two lists for READ and WRITE */
-        struct bio_list bio_lists[2];
-
-        /* Number of queued bios on READ and WRITE lists */
-        unsigned int nr_queued[2];
-
         /* bytes per second rate limits */
         uint64_t bps[2];
 
@@ -193,6 +198,8 @@ alloc_stats:
 /* init a service_queue, assumes the caller zeroed it */
 static void throtl_service_queue_init(struct throtl_service_queue *sq)
 {
+        bio_list_init(&sq->bio_lists[0]);
+        bio_list_init(&sq->bio_lists[1]);
         sq->pending_tree = RB_ROOT;
 }
 
@@ -204,8 +211,6 @@ static void throtl_pd_init(struct blkcg_gq *blkg)
         throtl_service_queue_init(&tg->service_queue);
         RB_CLEAR_NODE(&tg->rb_node);
         tg->td = blkg->q->td;
-        bio_list_init(&tg->bio_lists[0]);
-        bio_list_init(&tg->bio_lists[1]);
 
         tg->bps[READ] = -1;
         tg->bps[WRITE] = -1;
@@ -624,7 +629,8 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
          * this function with a different bio if there are other bios
          * queued.
          */
-        BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
+        BUG_ON(tg->service_queue.nr_queued[rw] &&
+               bio != bio_list_peek(&tg->service_queue.bio_lists[rw]));
 
         /* If tg->bps = -1, then BW is unlimited */
         if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
@@ -703,12 +709,13 @@ static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
 static void throtl_add_bio_tg(struct bio *bio, struct throtl_grp *tg,
                               struct throtl_service_queue *parent_sq)
 {
+        struct throtl_service_queue *sq = &tg->service_queue;
         bool rw = bio_data_dir(bio);
 
-        bio_list_add(&tg->bio_lists[rw], bio);
+        bio_list_add(&sq->bio_lists[rw], bio);
         /* Take a bio reference on tg */
         blkg_get(tg_to_blkg(tg));
-        tg->nr_queued[rw]++;
+        sq->nr_queued[rw]++;
         tg->td->nr_queued[rw]++;
         throtl_enqueue_tg(tg, parent_sq);
 }
@@ -716,13 +723,14 @@ static void throtl_add_bio_tg(struct bio *bio, struct throtl_grp *tg,
 static void tg_update_disptime(struct throtl_grp *tg,
                                struct throtl_service_queue *parent_sq)
 {
+        struct throtl_service_queue *sq = &tg->service_queue;
         unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
         struct bio *bio;
 
-        if ((bio = bio_list_peek(&tg->bio_lists[READ])))
+        if ((bio = bio_list_peek(&sq->bio_lists[READ])))
                 tg_may_dispatch(tg, bio, &read_wait);
 
-        if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
+        if ((bio = bio_list_peek(&sq->bio_lists[WRITE])))
                 tg_may_dispatch(tg, bio, &write_wait);
 
         min_wait = min(read_wait, write_wait);
@@ -737,10 +745,11 @@ static void tg_update_disptime(struct throtl_grp *tg,
 static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw,
                                 struct bio_list *bl)
 {
+        struct throtl_service_queue *sq = &tg->service_queue;
         struct bio *bio;
 
-        bio = bio_list_pop(&tg->bio_lists[rw]);
-        tg->nr_queued[rw]--;
+        bio = bio_list_pop(&sq->bio_lists[rw]);
+        sq->nr_queued[rw]--;
         /* Drop bio reference on blkg */
         blkg_put(tg_to_blkg(tg));
 
@@ -756,6 +765,7 @@ static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw,
 
 static int throtl_dispatch_tg(struct throtl_grp *tg, struct bio_list *bl)
 {
+        struct throtl_service_queue *sq = &tg->service_queue;
         unsigned int nr_reads = 0, nr_writes = 0;
         unsigned int max_nr_reads = throtl_grp_quantum*3/4;
         unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
@@ -763,7 +773,7 @@ static int throtl_dispatch_tg(struct throtl_grp *tg, struct bio_list *bl)
 
         /* Try to dispatch 75% READS and 25% WRITES */
 
-        while ((bio = bio_list_peek(&tg->bio_lists[READ])) &&
+        while ((bio = bio_list_peek(&sq->bio_lists[READ])) &&
                tg_may_dispatch(tg, bio, NULL)) {
 
                 tg_dispatch_one_bio(tg, bio_data_dir(bio), bl);
@@ -773,7 +783,7 @@ static int throtl_dispatch_tg(struct throtl_grp *tg, struct bio_list *bl)
                         break;
         }
 
-        while ((bio = bio_list_peek(&tg->bio_lists[WRITE])) &&
+        while ((bio = bio_list_peek(&sq->bio_lists[WRITE])) &&
                tg_may_dispatch(tg, bio, NULL)) {
 
                 tg_dispatch_one_bio(tg, bio_data_dir(bio), bl);
@@ -790,10 +800,10 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq,
                                   struct bio_list *bl)
 {
         unsigned int nr_disp = 0;
-        struct throtl_grp *tg;
 
         while (1) {
-                tg = throtl_rb_first(parent_sq);
+                struct throtl_grp *tg = throtl_rb_first(parent_sq);
+                struct throtl_service_queue *sq = &tg->service_queue;
 
                 if (!tg)
                         break;
@@ -805,7 +815,7 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq,
 
                 nr_disp += throtl_dispatch_tg(tg, bl);
 
-                if (tg->nr_queued[0] || tg->nr_queued[1])
+                if (sq->nr_queued[0] || sq->nr_queued[1])
                         tg_update_disptime(tg, parent_sq);
 
                 if (nr_disp >= throtl_quantum)
@@ -1043,6 +1053,7 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
 {
         struct throtl_data *td = q->td;
         struct throtl_grp *tg;
+        struct throtl_service_queue *sq;
         bool rw = bio_data_dir(bio), update_disptime = true;
         struct blkcg *blkcg;
         bool throttled = false;
@@ -1077,7 +1088,9 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
         if (unlikely(!tg))
                 goto out_unlock;
 
-        if (tg->nr_queued[rw]) {
+        sq = &tg->service_queue;
+
+        if (sq->nr_queued[rw]) {
                 /*
                  * There is already another bio queued in same dir. No
                  * need to update dispatch time.
@@ -1112,7 +1125,7 @@ queue_bio:
                         rw == READ ? 'R' : 'W',
                         tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
                         tg->io_disp[rw], tg->iops[rw],
-                        tg->nr_queued[READ], tg->nr_queued[WRITE]);
+                        sq->nr_queued[READ], sq->nr_queued[WRITE]);
 
         bio_associate_current(bio);
         throtl_add_bio_tg(bio, tg, &q->td->service_queue);
@@ -1151,11 +1164,13 @@ void blk_throtl_drain(struct request_queue *q)
         bio_list_init(&bl);
 
         while ((tg = throtl_rb_first(parent_sq))) {
+                struct throtl_service_queue *sq = &tg->service_queue;
+
                 throtl_dequeue_tg(tg, parent_sq);
 
-                while ((bio = bio_list_peek(&tg->bio_lists[READ])))
+                while ((bio = bio_list_peek(&sq->bio_lists[READ])))
                         tg_dispatch_one_bio(tg, bio_data_dir(bio), &bl);
-                while ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
+                while ((bio = bio_list_peek(&sq->bio_lists[WRITE])))
                         tg_dispatch_one_bio(tg, bio_data_dir(bio), &bl);
         }
         spin_unlock_irq(q->queue_lock);