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: Jens Axboe <axboe@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 55369a65dea2a82e58396f68e74bc58868b434c5..9cf0537593630f51423c30777e40b2927d628981 100644 (file)
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -836,6 +836,18 @@ void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
 }
 EXPORT_SYMBOL_GPL(blk_queue_flush_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;
+}
+EXPORT_SYMBOL(blk_set_queue_depth);
+
 /**
  * blk_queue_write_cache - configure queue's write cache
  * @q:         the request queue for the device

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 1deb6adc411f795833a444a84b1e80e9f9629c4d..75455d4dab68b5cd49378635d2848da8340b7ff3 100644 (file)
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -621,6 +621,9 @@ int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
                wmb();
        }
 
+       if (sdev->request_queue)
+               blk_set_queue_depth(sdev->request_queue, depth);
+
        return sdev->queue_depth;
 }
 EXPORT_SYMBOL(scsi_change_queue_depth);

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9189a2d5c392a804a69c04be5d7303c3cb650541..d364be6e695983fde62dd943018cc4dd451e2ab7 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -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,