blk-mq: separate number of hardware queues from nr_cpu_ids

With multiple maps, nr_cpu_ids is no longer the maximum number of
hardware queues we support on a given devices. The initializer of
the tag_set can have set ->nr_hw_queues larger than the available
number of CPUs, since we can exceed that with multiple queue maps.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2e730c95513f2e4f8e76bd0ff06ee9d49cfa87e2..ccf135cf41b0c5498a863beb0606551c2c88a171 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2669,6 +2669,19 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
        mutex_unlock(&q->sysfs_lock);
 }
 
+/*
+ * Maximum number of hardware queues we support. For single sets, we'll never
+ * have more than the CPUs (software queues). For multiple sets, the tag_set
+ * user may have set ->nr_hw_queues larger.
+ */
+static unsigned int nr_hw_queues(struct blk_mq_tag_set *set)
+{
+       if (set->nr_maps == 1)
+               return nr_cpu_ids;
+
+       return max(set->nr_hw_queues, nr_cpu_ids);
+}
+
 struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
                                                  struct request_queue *q)
 {
@@ -2688,7 +2701,8 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
        /* init q->mq_kobj and sw queues' kobjects */
        blk_mq_sysfs_init(q);
 
-       q->queue_hw_ctx = kcalloc_node(nr_cpu_ids, sizeof(*(q->queue_hw_ctx)),
+       q->nr_queues = nr_hw_queues(set);
+       q->queue_hw_ctx = kcalloc_node(q->nr_queues, sizeof(*(q->queue_hw_ctx)),
                                                GFP_KERNEL, set->numa_node);
        if (!q->queue_hw_ctx)
                goto err_percpu;
@@ -2700,7 +2714,6 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
        INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
        blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
 
-       q->nr_queues = nr_cpu_ids;
        q->tag_set = set;
 
        q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
@@ -2887,12 +2900,13 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
                set->queue_depth = min(64U, set->queue_depth);
        }
        /*
-        * There is no use for more h/w queues than cpus.
+        * There is no use for more h/w queues than cpus if we just have
+        * a single map
         */
-       if (set->nr_hw_queues > nr_cpu_ids)
+       if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
                set->nr_hw_queues = nr_cpu_ids;
 
-       set->tags = kcalloc_node(nr_cpu_ids, sizeof(struct blk_mq_tags *),
+       set->tags = kcalloc_node(nr_hw_queues(set), sizeof(struct blk_mq_tags *),
                                 GFP_KERNEL, set->numa_node);
        if (!set->tags)
                return -ENOMEM;
@@ -2935,7 +2949,7 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
 {
        int i, j;
 
-       for (i = 0; i < nr_cpu_ids; i++)
+       for (i = 0; i < nr_hw_queues(set); i++)
                blk_mq_free_map_and_requests(set, i);
 
        for (j = 0; j < set->nr_maps; j++) {
@@ -3067,7 +3081,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 
        lockdep_assert_held(&set->tag_list_lock);
 
-       if (nr_hw_queues > nr_cpu_ids)
+       if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
                nr_hw_queues = nr_cpu_ids;
        if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
                return;