scsi: target: pscsi: Clean up after failure in pscsi_map_sg()

If pscsi_map_sg() fails, make sure to drop references to already allocated
bios.

Link: https://lore.kernel.org/r/20210323212431.15306-2-mwilck@suse.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_pscsi.c

@@ -938,6 +938,14 @@ pscsi_map_sg(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 
 	return 0;
 fail:
+	if (bio)
+		bio_put(bio);
+	while (req->bio) {
+		bio = req->bio;
+		req->bio = bio->bi_next;
+		bio_put(bio);
+	}
+	req->biotail = NULL;
 	return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 }