block: add block polling support
Add basic support for polling for specific IO to complete. This uses
the cookie that blk-mq passes back, which enables the block layer
to pass this cookie to the driver to spin for a specific request.
This will be combined with request latency tracking, so we can make
qualified decisions about when to poll and when not to. For now, for
benchmark purposes, we add a sysfs file that controls whether polling
is enabled or not.
Signed-off-by: Jens Axboe <axboe@fb.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Keith Busch <keith.busch@intel.com>
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 83cc9d4..daf17d7 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -59,6 +59,9 @@
struct blk_mq_cpu_notifier cpu_notifier;
struct kobject kobj;
+
+ unsigned long poll_invoked;
+ unsigned long poll_success;
};
struct blk_mq_tag_set {
@@ -97,6 +100,8 @@
typedef void (busy_iter_fn)(struct blk_mq_hw_ctx *, struct request *, void *,
bool);
typedef void (busy_tag_iter_fn)(struct request *, void *, bool);
+typedef int (poll_fn)(struct blk_mq_hw_ctx *, unsigned int);
+
struct blk_mq_ops {
/*
@@ -114,6 +119,11 @@
*/
timeout_fn *timeout;
+ /*
+ * Called to poll for completion of a specific tag.
+ */
+ poll_fn *poll;
+
softirq_done_fn *complete;
/*
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 5ee0f52..3fe27f8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -487,6 +487,7 @@
#define QUEUE_FLAG_DEAD 19 /* queue tear-down finished */
#define QUEUE_FLAG_INIT_DONE 20 /* queue is initialized */
#define QUEUE_FLAG_NO_SG_MERGE 21 /* don't attempt to merge SG segments*/
+#define QUEUE_FLAG_POLL 22 /* IO polling enabled if set */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -814,6 +815,8 @@
extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,
struct request *, int, rq_end_io_fn *);
+bool blk_poll(struct request_queue *q, blk_qc_t cookie);
+
static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
{
return bdev->bd_disk->queue; /* this is never NULL */