Commit d278d4a8 authored by Jens Axboe's avatar Jens Axboe

block: add code to track actual device queue depth

For blk-mq, ->nr_requests does track queue depth, at least at init
time. But for the older queue paths, it's simply a soft setting.
On top of that, it's generally larger than the hardware setting
on purpose, to allow backup of requests for merging.

Fill a hole in struct request with a 'queue_depth' member, that
drivers can call to more closely inform the block layer of the
real queue depth.
Signed-off-by: default avatarJens Axboe <>
Reviewed-by: default avatarJan Kara <>
parent 600271d9
......@@ -836,6 +836,18 @@ void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
* blk_set_queue_depth - tell the block layer about the device queue depth
* @q: the request queue for the device
* @depth: queue depth
void blk_set_queue_depth(struct request_queue *q, unsigned int depth)
q->queue_depth = depth;
* blk_queue_write_cache - configure queue's write cache
* @q: the request queue for the device
......@@ -621,6 +621,9 @@ int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
if (sdev->request_queue)
blk_set_queue_depth(sdev->request_queue, depth);
return sdev->queue_depth;
......@@ -405,6 +405,8 @@ struct request_queue {
struct blk_mq_ctx __percpu *queue_ctx;
unsigned int nr_queues;
unsigned int queue_depth;
/* hw dispatch queues */
struct blk_mq_hw_ctx **queue_hw_ctx;
unsigned int nr_hw_queues;
......@@ -777,6 +779,14 @@ static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
return false;
static inline unsigned int blk_queue_depth(struct request_queue *q)
if (q->queue_depth)
return q->queue_depth;
return q->nr_requests;
* q->prep_rq_fn return values
......@@ -1094,6 +1104,7 @@ extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);
extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
extern void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt);
extern void blk_queue_io_opt(struct request_queue *q, unsigned int opt);
extern void blk_set_queue_depth(struct request_queue *q, unsigned int depth);
extern void blk_set_default_limits(struct queue_limits *lim);
extern void blk_set_stacking_limits(struct queue_limits *lim);
extern int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
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