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Subject[PATCH 08/14] blk-mq: separate number of hardware queues from nr_cpu_ids
Date
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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-mq.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0fab36372ace..60a951c4934c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2663,6 +2663,19 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
mutex_unlock(&q->sysfs_lock);
}

+/*
+ * Maximum number of 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)
{
@@ -2682,7 +2695,8 @@ 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;
@@ -2694,7 +2708,6 @@ 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;
@@ -2884,12 +2897,13 @@ 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;
@@ -2932,7 +2946,7 @@ 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++) {
@@ -3064,7 +3078,7 @@ 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;
--
2.17.1
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