scsi: scsi-mq: Always unprepare before requeuing a request

One of the two scsi-mq functions that requeue a request unprepares a
request before requeueing (scsi_io_completion()) but the other function
not (__scsi_queue_insert()). Make sure that a request is unprepared
before requeuing it.

Fixes: commit d285203cf647 ("scsi: add support for a blk-mq based I/O path.")
Signed-off-by: Bart Van Assche <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Hannes Reinecke <[e-mail]>
Cc: Damien Le Moal <[e-mail]>
Cc: Johannes Thumshirn <[e-mail]>
Reviewed-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/scsi_lib.c

···
 static struct kmem_cache *scsi_sense_isadma_cache;
 static DEFINE_MUTEX(scsi_sense_cache_mutex);
 
+static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd);
+
 static inline struct kmem_cache *
 scsi_select_sense_cache(bool unchecked_isa_dma)
 {
···
 {
 	struct scsi_device *sdev = cmd->device;
 
+	if (cmd->request->rq_flags & RQF_DONTPREP) {
+		cmd->request->rq_flags &= ~RQF_DONTPREP;
+		scsi_mq_uninit_cmd(cmd);
+	} else {
+		WARN_ON_ONCE(true);
+	}
 	blk_mq_requeue_request(cmd->request, true);
 	put_device(&sdev->sdev_gendev);
 }
···
 		 * A new command will be prepared and issued.
 		 */
 		if (q->mq_ops) {
-			cmd->request->rq_flags &= ~RQF_DONTPREP;
-			scsi_mq_uninit_cmd(cmd);
 			scsi_mq_requeue_cmd(cmd);
 		} else {
 			scsi_release_buffers(cmd);