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Message-ID: <20251121052901.1341976-5-yukuai@fnnas.com>
Date: Fri, 21 Nov 2025 13:28:51 +0800
From: Yu Kuai <yukuai@...as.com>
To: axboe@...nel.dk,
nilay@...ux.ibm.com,
bvanassche@....org,
linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: yukuai@...as.com
Subject: [PATCH v6 4/8] blk-mq: add a new queue sysfs attribute async_depth
Add a new field async_depth to request_queue and related APIs, this is
currently not used, following patches will convert elevators to use
this instead of internal async_depth.
Signed-off-by: Yu Kuai <yukuai@...as.com>
Reviewed-by: Nilay Shroff <nilay@...ux.ibm.com>
---
block/blk-core.c | 1 +
block/blk-mq.c | 6 ++++++
block/blk-sysfs.c | 42 ++++++++++++++++++++++++++++++++++++++++++
block/elevator.c | 1 +
include/linux/blkdev.h | 1 +
5 files changed, 51 insertions(+)
diff --git a/block/blk-core.c b/block/blk-core.c
index 14ae73eebe0d..cc5c9ced8e6f 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -463,6 +463,7 @@ struct request_queue *blk_alloc_queue(struct queue_limits *lim, int node_id)
fs_reclaim_release(GFP_KERNEL);
q->nr_requests = BLKDEV_DEFAULT_RQ;
+ q->async_depth = BLKDEV_DEFAULT_RQ;
return q;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6c505ebfab65..ae6ce68f4786 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4628,6 +4628,7 @@ int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
spin_lock_init(&q->requeue_lock);
q->nr_requests = set->queue_depth;
+ q->async_depth = set->queue_depth;
blk_mq_init_cpu_queues(q, set->nr_hw_queues);
blk_mq_map_swqueue(q);
@@ -4994,6 +4995,11 @@ struct elevator_tags *blk_mq_update_nr_requests(struct request_queue *q,
q->elevator->et = et;
}
+ /*
+ * Preserve relative value, both nr and async_depth are at most 16 bit
+ * value, no need to worry about overflow.
+ */
+ q->async_depth = max(q->async_depth * nr / q->nr_requests, 1);
q->nr_requests = nr;
if (q->elevator && q->elevator->type->ops.depth_updated)
q->elevator->type->ops.depth_updated(q);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 8684c57498cc..5c2d29ac6570 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -127,6 +127,46 @@ queue_requests_store(struct gendisk *disk, const char *page, size_t count)
return ret;
}
+static ssize_t queue_async_depth_show(struct gendisk *disk, char *page)
+{
+ guard(mutex)(&disk->queue->elevator_lock);
+
+ return queue_var_show(disk->queue->async_depth, page);
+}
+
+static ssize_t
+queue_async_depth_store(struct gendisk *disk, const char *page, size_t count)
+{
+ struct request_queue *q = disk->queue;
+ unsigned int memflags;
+ unsigned long nr;
+ int ret;
+
+ if (!queue_is_mq(q))
+ return -EINVAL;
+
+ ret = queue_var_store(&nr, page, count);
+ if (ret < 0)
+ return ret;
+
+ if (nr == 0)
+ return -EINVAL;
+
+ memflags = blk_mq_freeze_queue(q);
+ scoped_guard(mutex, &q->elevator_lock) {
+ if (q->elevator) {
+ q->async_depth = min(q->nr_requests, nr);
+ if (q->elevator->type->ops.depth_updated)
+ q->elevator->type->ops.depth_updated(q);
+ } else {
+ ret = -EINVAL;
+ }
+ }
+ blk_mq_unfreeze_queue(q, memflags);
+
+ return ret;
+}
+
static ssize_t queue_ra_show(struct gendisk *disk, char *page)
{
ssize_t ret;
@@ -532,6 +572,7 @@ static struct queue_sysfs_entry _prefix##_entry = { \
}
QUEUE_RW_ENTRY(queue_requests, "nr_requests");
+QUEUE_RW_ENTRY(queue_async_depth, "async_depth");
QUEUE_RW_ENTRY(queue_ra, "read_ahead_kb");
QUEUE_LIM_RW_ENTRY(queue_max_sectors, "max_sectors_kb");
QUEUE_LIM_RO_ENTRY(queue_max_hw_sectors, "max_hw_sectors_kb");
@@ -754,6 +795,7 @@ static struct attribute *blk_mq_queue_attrs[] = {
*/
&elv_iosched_entry.attr,
&queue_requests_entry.attr,
+ &queue_async_depth_entry.attr,
#ifdef CONFIG_BLK_WBT
&queue_wb_lat_entry.attr,
#endif
diff --git a/block/elevator.c b/block/elevator.c
index 5b37ef44f52d..5ff21075a84a 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -589,6 +589,7 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
q->elevator = NULL;
q->nr_requests = q->tag_set->queue_depth;
+ q->async_depth = q->tag_set->queue_depth;
}
blk_add_trace_msg(q, "elv switch: %s", ctx->name);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index cdc68c41fa96..edddf17f8304 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -552,6 +552,7 @@ struct request_queue {
* queue settings
*/
unsigned int nr_requests; /* Max # of requests */
+ unsigned int async_depth; /* Max # of async requests */
#ifdef CONFIG_BLK_INLINE_ENCRYPTION
struct blk_crypto_profile *crypto_profile;
--
2.51.0
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