block: introduce blk_mq_tagset_iter

Iterator helper to apply a function on all the
tags in a given tagset. export it as it will be used
outside the block layer later on.
Reviewed-by: NBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: NJens Axboe <axboe@kernel.dk>
Reviewed-by: NMax Gurtovoy <maxg@mellanox.com>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NSagi Grimberg <sagi@grimberg.me>
Signed-off-by: NChristoph Hellwig <hch@lst.de>

block/blk-mq-tag.c

@@ -298,12 +298,12 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 }
 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
 
-int blk_mq_reinit_tagset(struct blk_mq_tag_set *set,
-			 int (reinit_request)(void *, struct request *))
+int blk_mq_tagset_iter(struct blk_mq_tag_set *set, void *data,
+			 int (fn)(void *, struct request *))
 {
 	int i, j, ret = 0;
 
-	if (WARN_ON_ONCE(!reinit_request))
+	if (WARN_ON_ONCE(!fn))
 		goto out;
 
 	for (i = 0; i < set->nr_hw_queues; i++) {
@@ -316,8 +316,7 @@ int blk_mq_reinit_tagset(struct blk_mq_tag_set *set,
 			if (!tags->static_rqs[j])
 				continue;
 
-			ret = reinit_request(set->driver_data,
-					     tags->static_rqs[j]);
+			ret = fn(data, tags->static_rqs[j]);
 			if (ret)
 				goto out;
 		}
@@ -326,6 +325,13 @@ int blk_mq_reinit_tagset(struct blk_mq_tag_set *set,
 out:
 	return ret;
 }
+EXPORT_SYMBOL_GPL(blk_mq_tagset_iter);
+
+int blk_mq_reinit_tagset(struct blk_mq_tag_set *set,
+			 int (reinit_request)(void *, struct request *))
+{
+	return blk_mq_tagset_iter(set, set->driver_data, reinit_request);
+}
 EXPORT_SYMBOL_GPL(blk_mq_reinit_tagset);
 
 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,

include/linux/blk-mq.h

@@ -259,6 +259,8 @@ void blk_freeze_queue_start(struct request_queue *q);
 void blk_mq_freeze_queue_wait(struct request_queue *q);
 int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
 				     unsigned long timeout);
+int blk_mq_tagset_iter(struct blk_mq_tag_set *set, void *data,
+		int (reinit_request)(void *, struct request *));
 int blk_mq_reinit_tagset(struct blk_mq_tag_set *set,
 			 int (reinit_request)(void *, struct request *));