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Subject[PATCH 07/14] blk-mq: support multiple hctx maps
Date
Add support for the tag set carrying multiple queue maps, and
for the driver to inform blk-mq how many it wishes to support
through setting set->nr_maps.

This adds an mq_ops helper for drivers that support more than 1
map, mq_ops->flags_to_type(). The function takes request/bio flags
and CPU, and returns a queue map index for that. We then use the
type information in blk_mq_map_queue() to index the map set.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-mq.c | 85 ++++++++++++++++++++++++++++--------------
block/blk-mq.h | 19 ++++++----
include/linux/blk-mq.h | 7 ++++
3 files changed, 76 insertions(+), 35 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index fab84c6bda18..0fab36372ace 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2257,7 +2257,8 @@ static int blk_mq_init_hctx(struct request_queue *q,
static void blk_mq_init_cpu_queues(struct request_queue *q,
unsigned int nr_hw_queues)
{
- unsigned int i;
+ struct blk_mq_tag_set *set = q->tag_set;
+ unsigned int i, j;

for_each_possible_cpu(i) {
struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
@@ -2272,9 +2273,11 @@ static void blk_mq_init_cpu_queues(struct request_queue *q,
* Set local node, IFF we have more than one hw queue. If
* not, we remain on the home node of the device
*/
- hctx = blk_mq_map_queue_type(q, 0, i);
- if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
- hctx->numa_node = local_memory_node(cpu_to_node(i));
+ for (j = 0; j < set->nr_maps; j++) {
+ hctx = blk_mq_map_queue_type(q, j, i);
+ if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
+ hctx->numa_node = local_memory_node(cpu_to_node(i));
+ }
}
}

@@ -2309,7 +2312,7 @@ static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,

static void blk_mq_map_swqueue(struct request_queue *q)
{
- unsigned int i, hctx_idx;
+ unsigned int i, j, hctx_idx;
struct blk_mq_hw_ctx *hctx;
struct blk_mq_ctx *ctx;
struct blk_mq_tag_set *set = q->tag_set;
@@ -2345,13 +2348,23 @@ static void blk_mq_map_swqueue(struct request_queue *q)
}

ctx = per_cpu_ptr(q->queue_ctx, i);
- hctx = blk_mq_map_queue_type(q, 0, i);
- hctx->type = 0;
- cpumask_set_cpu(i, hctx->cpumask);
- ctx->index_hw[hctx->type] = hctx->nr_ctx;
- hctx->ctxs[hctx->nr_ctx++] = ctx;
- /* wrap */
- BUG_ON(!hctx->nr_ctx);
+ for (j = 0; j < set->nr_maps; j++) {
+ hctx = blk_mq_map_queue_type(q, j, i);
+ hctx->type = j;
+
+ /*
+ * If the CPU is already set in the mask, then we've
+ * mapped this one already. This can happen if
+ * devices share queues across queue maps.
+ */
+ if (cpumask_test_cpu(i, hctx->cpumask))
+ continue;
+ cpumask_set_cpu(i, hctx->cpumask);
+ ctx->index_hw[hctx->type] = hctx->nr_ctx;
+ hctx->ctxs[hctx->nr_ctx++] = ctx;
+ /* wrap */
+ BUG_ON(!hctx->nr_ctx);
+ }
}

mutex_unlock(&q->sysfs_lock);
@@ -2519,6 +2532,7 @@ struct request_queue *blk_mq_init_sq_queue(struct blk_mq_tag_set *set,
memset(set, 0, sizeof(*set));
set->ops = ops;
set->nr_hw_queues = 1;
+ set->nr_maps = 1;
set->queue_depth = queue_depth;
set->numa_node = NUMA_NO_NODE;
set->flags = set_flags;
@@ -2798,6 +2812,8 @@ static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
{
if (set->ops->map_queues) {
+ int i;
+
/*
* transport .map_queues is usually done in the following
* way:
@@ -2805,18 +2821,21 @@ static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
* for (queue = 0; queue < set->nr_hw_queues; queue++) {
* mask = get_cpu_mask(queue)
* for_each_cpu(cpu, mask)
- * set->map.mq_map[cpu] = queue;
+ * set->map[x].mq_map[cpu] = queue;
* }
*
* When we need to remap, the table has to be cleared for
* killing stale mapping since one CPU may not be mapped
* to any hw queue.
*/
- blk_mq_clear_mq_map(&set->map[0]);
+ for (i = 0; i < set->nr_maps; i++)
+ blk_mq_clear_mq_map(&set->map[i]);

return set->ops->map_queues(set);
- } else
+ } else {
+ BUG_ON(set->nr_maps > 1);
return blk_mq_map_queues(&set->map[0]);
+ }
}

/*
@@ -2827,7 +2846,7 @@ static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
*/
int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
{
- int ret;
+ int i, ret;

BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);

@@ -2850,6 +2869,11 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
set->queue_depth = BLK_MQ_MAX_DEPTH;
}

+ if (!set->nr_maps)
+ set->nr_maps = 1;
+ else if (set->nr_maps > HCTX_MAX_TYPES)
+ return -EINVAL;
+
/*
* If a crashdump is active, then we are potentially in a very
* memory constrained environment. Limit us to 1 queue and
@@ -2871,12 +2895,14 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
return -ENOMEM;

ret = -ENOMEM;
- set->map[0].mq_map = kcalloc_node(nr_cpu_ids,
- sizeof(*set->map[0].mq_map),
- GFP_KERNEL, set->numa_node);
- if (!set->map[0].mq_map)
- goto out_free_tags;
- set->map[0].nr_queues = set->nr_hw_queues;
+ for (i = 0; i < set->nr_maps; i++) {
+ set->map[i].mq_map = kcalloc_node(nr_cpu_ids,
+ sizeof(struct blk_mq_queue_map),
+ GFP_KERNEL, set->numa_node);
+ if (!set->map[i].mq_map)
+ goto out_free_mq_map;
+ set->map[i].nr_queues = set->nr_hw_queues;
+ }

ret = blk_mq_update_queue_map(set);
if (ret)
@@ -2892,9 +2918,10 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
return 0;

out_free_mq_map:
- kfree(set->map[0].mq_map);
- set->map[0].mq_map = NULL;
-out_free_tags:
+ for (i = 0; i < set->nr_maps; i++) {
+ kfree(set->map[i].mq_map);
+ set->map[i].mq_map = NULL;
+ }
kfree(set->tags);
set->tags = NULL;
return ret;
@@ -2903,13 +2930,15 @@ EXPORT_SYMBOL(blk_mq_alloc_tag_set);

void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
{
- int i;
+ int i, j;

for (i = 0; i < nr_cpu_ids; i++)
blk_mq_free_map_and_requests(set, i);

- kfree(set->map[0].mq_map);
- set->map[0].mq_map = NULL;
+ for (j = 0; j < set->nr_maps; j++) {
+ kfree(set->map[j].mq_map);
+ set->map[j].mq_map = NULL;
+ }

kfree(set->tags);
set->tags = NULL;
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 7b5a790acdbf..e27c6f8dc86c 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -72,19 +72,24 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
*/
extern int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int);

-static inline struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q,
- unsigned int flags,
- int cpu)
+static inline struct blk_mq_hw_ctx *blk_mq_map_queue_type(struct request_queue *q,
+ int type, int cpu)
{
struct blk_mq_tag_set *set = q->tag_set;

- return q->queue_hw_ctx[set->map[0].mq_map[cpu]];
+ return q->queue_hw_ctx[set->map[type].mq_map[cpu]];
}

-static inline struct blk_mq_hw_ctx *blk_mq_map_queue_type(struct request_queue *q,
- int type, int cpu)
+static inline struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q,
+ unsigned int flags,
+ int cpu)
{
- return blk_mq_map_queue(q, type, cpu);
+ int type = 0;
+
+ if (q->mq_ops->flags_to_type)
+ type = q->mq_ops->flags_to_type(q, flags);
+
+ return blk_mq_map_queue_type(q, type, cpu);
}

/*
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index f9e19962a22f..837087cf07cc 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -86,6 +86,7 @@ enum {

struct blk_mq_tag_set {
struct blk_mq_queue_map map[HCTX_MAX_TYPES];
+ unsigned int nr_maps;
const struct blk_mq_ops *ops;
unsigned int nr_hw_queues;
unsigned int queue_depth; /* max hw supported */
@@ -109,6 +110,7 @@ struct blk_mq_queue_data {

typedef blk_status_t (queue_rq_fn)(struct blk_mq_hw_ctx *,
const struct blk_mq_queue_data *);
+typedef int (flags_to_type_fn)(struct request_queue *, unsigned int);
typedef bool (get_budget_fn)(struct blk_mq_hw_ctx *);
typedef void (put_budget_fn)(struct blk_mq_hw_ctx *);
typedef enum blk_eh_timer_return (timeout_fn)(struct request *, bool);
@@ -133,6 +135,11 @@ struct blk_mq_ops {
*/
queue_rq_fn *queue_rq;

+ /*
+ * Return a queue map type for the given request/bio flags
+ */
+ flags_to_type_fn *flags_to_type;
+
/*
* Reserve budget before queue request, once .queue_rq is
* run, it is driver's responsibility to release the
--
2.17.1
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