blk-throttle: delay initialization until configuration

[linux-block.git] / block / blk-throttle.c

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index d907040859f9f2c7b99f1fadef0cc13cda7e6d7f..80aaca18bfb0681f34fe87e11cdfd645c15a19fe 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1211,6 +1211,53 @@ static void tg_conf_updated(struct throtl_grp *tg, bool global)
        }
 }
 
+static int blk_throtl_init(struct gendisk *disk)
+{
+       struct request_queue *q = disk->queue;
+       struct throtl_data *td;
+       int ret;
+
+       td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
+       if (!td)
+               return -ENOMEM;
+
+       INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
+       throtl_service_queue_init(&td->service_queue);
+
+       /*
+        * Freeze queue before activating policy, to synchronize with IO path,
+        * which is protected by 'q_usage_counter'.
+        */
+       blk_mq_freeze_queue(disk->queue);
+       blk_mq_quiesce_queue(disk->queue);
+
+       q->td = td;
+       td->queue = q;
+
+       /* activate policy */
+       ret = blkcg_activate_policy(disk, &blkcg_policy_throtl);
+       if (ret) {
+               q->td = NULL;
+               kfree(td);
+               goto out;
+       }
+
+       if (blk_queue_nonrot(q))
+               td->throtl_slice = DFL_THROTL_SLICE_SSD;
+       else
+               td->throtl_slice = DFL_THROTL_SLICE_HD;
+       td->track_bio_latency = !queue_is_mq(q);
+       if (!td->track_bio_latency)
+               blk_stat_enable_accounting(q);
+
+out:
+       blk_mq_unquiesce_queue(disk->queue);
+       blk_mq_unfreeze_queue(disk->queue);
+
+       return ret;
+}
+
+
 static ssize_t tg_set_conf(struct kernfs_open_file *of,
                           char *buf, size_t nbytes, loff_t off, bool is_u64)
 {
@@ -1222,6 +1269,16 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of,
 
        blkg_conf_init(&ctx, buf);
 
+       ret = blkg_conf_open_bdev(&ctx);
+       if (ret)
+               goto out_finish;
+
+       if (!blk_throtl_activated(ctx.bdev->bd_queue)) {
+               ret = blk_throtl_init(ctx.bdev->bd_disk);
+               if (ret)
+                       goto out_finish;
+       }
+
        ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
        if (ret)
                goto out_finish;
@@ -1396,6 +1453,16 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 
        blkg_conf_init(&ctx, buf);
 
+       ret = blkg_conf_open_bdev(&ctx);
+       if (ret)
+               goto out_finish;
+
+       if (!blk_throtl_activated(ctx.bdev->bd_queue)) {
+               ret = blk_throtl_init(ctx.bdev->bd_disk);
+               if (ret)
+                       goto out_finish;
+       }
+
        ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
        if (ret)
                goto out_finish;
@@ -1488,6 +1555,9 @@ void blk_throtl_cancel_bios(struct gendisk *disk)
        struct cgroup_subsys_state *pos_css;
        struct blkcg_gq *blkg;
 
+       if (!blk_throtl_activated(q))
+               return;
+
        spin_lock_irq(&q->queue_lock);
        /*
         * queue_lock is held, rcu lock is not needed here technically.
@@ -1617,57 +1687,19 @@ out_unlock:
        return throttled;
 }
 
-int blk_throtl_init(struct gendisk *disk)
-{
-       struct request_queue *q = disk->queue;
-       struct throtl_data *td;
-       int ret;
-
-       td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
-       if (!td)
-               return -ENOMEM;
-
-       INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
-       throtl_service_queue_init(&td->service_queue);
-
-       q->td = td;
-       td->queue = q;
-
-       /* activate policy */
-       ret = blkcg_activate_policy(disk, &blkcg_policy_throtl);
-       if (ret)
-               kfree(td);
-       return ret;
-}
-
 void blk_throtl_exit(struct gendisk *disk)
 {
        struct request_queue *q = disk->queue;
 
-       BUG_ON(!q->td);
+       if (!blk_throtl_activated(q))
+               return;
+
        del_timer_sync(&q->td->service_queue.pending_timer);
        throtl_shutdown_wq(q);
        blkcg_deactivate_policy(disk, &blkcg_policy_throtl);
        kfree(q->td);
 }
 
-void blk_throtl_register(struct gendisk *disk)
-{
-       struct request_queue *q = disk->queue;
-       struct throtl_data *td;
-
-       td = q->td;
-       BUG_ON(!td);
-
-       if (blk_queue_nonrot(q))
-               td->throtl_slice = DFL_THROTL_SLICE_SSD;
-       else
-               td->throtl_slice = DFL_THROTL_SLICE_HD;
-       td->track_bio_latency = !queue_is_mq(q);
-       if (!td->track_bio_latency)
-               blk_stat_enable_accounting(q);
-}
-
 static int __init throtl_init(void)
 {
        kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);