dm mpath: use blk_mq_alloc_request() and blk_mq_free_request() directly

There isn't any need to support both old .request_fn and blk-mq paths
in the blk-mq specific portion of __multipath_map().  Call
blk_mq_alloc_request() directly rather than use blk_get_request().

Similarly, call blk_mq_free_request(), rather than blk_put_request(), in
multipath_release_clone().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-mpath.c

@@ -23,6 +23,7 @@
 #include <linux/delay.h>
 #include <scsi/scsi_dh.h>
 #include <linux/atomic.h>
+#include <linux/blk-mq.h>
 
 #define DM_MSG_PREFIX "multipath"
 #define DM_PG_INIT_DELAY_MSECS 2000
@@ -452,8 +453,8 @@ static int __multipath_map(struct dm_target *ti, struct request *clone,
 		 * .request_fn stacked on blk-mq path(s) and
 		 * blk-mq stacked on blk-mq path(s).
 		 */
-		*__clone = blk_get_request(bdev_get_queue(bdev),
-					   rq_data_dir(rq), GFP_ATOMIC);
+		*__clone = blk_mq_alloc_request(bdev_get_queue(bdev),
+						rq_data_dir(rq), BLK_MQ_REQ_NOWAIT);
 		if (IS_ERR(*__clone)) {
 			/* ENOMEM, requeue */
 			clear_request_fn_mpio(m, map_context);
@@ -491,7 +492,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 
 static void multipath_release_clone(struct request *clone)
 {
-	blk_put_request(clone);
+	blk_mq_free_request(clone);
 }
 
 /*