blk-mq: export blk_mq_tag_busy_iter

Export the blk-mq in-flight tag iterator for driver consumption.
This is particularly useful in exception paths or SRSI where
in-flight IOs need to be cancelled and/or reissued. The NVMe driver
conversion will use this.

Signed-off-by: Sam Bradshaw <sbradshaw@micron.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq-tag.c

@@ -400,6 +400,7 @@ void blk_mq_tag_busy_iter(struct blk_mq_tags *tags,
 	fn(data, tag_map);
 	kfree(tag_map);
 }
+EXPORT_SYMBOL(blk_mq_tag_busy_iter);
 
 static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt)
 {

block/blk-mq-tag.h

@@ -51,7 +51,6 @@ extern void blk_mq_free_tags(struct blk_mq_tags *tags);
 extern unsigned int blk_mq_get_tag(struct blk_mq_hw_ctx *hctx, unsigned int *last_tag, gfp_t gfp, bool reserved);
 extern void blk_mq_wait_for_tags(struct blk_mq_hw_ctx *hctx, bool reserved);
 extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, unsigned int *last_tag);
-extern void blk_mq_tag_busy_iter(struct blk_mq_tags *tags, void (*fn)(void *data, unsigned long *), void *data);
 extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags);
 extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page);
 extern void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *last_tag);

include/linux/blk-mq.h

@@ -181,6 +181,7 @@ void blk_mq_stop_hw_queues(struct request_queue *q);
 void blk_mq_start_hw_queues(struct request_queue *q);
 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async);
 void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs);
+void blk_mq_tag_busy_iter(struct blk_mq_tags *tags, void (*fn)(void *data, unsigned long *), void *data);
 
 /*
  * Driver command data is immediately after the request. So subtract request