sd/skd: stuff discard page in request->completion_data

Store the pointer to the page there, so we can always safely
reference it from end_io context where ->bio may have been
cleared.
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/block/skd_main.c

@@ -743,6 +743,7 @@ static void skd_request_fn(struct request_queue *q)
 				break;
 			}
 			skreq->discard_page = 1;
+			req->completion_data = page;
 			skd_prep_discard_cdb(scsi_req, skreq, page, lba, count);
 
 		} else if (flush == SKD_FLUSH_ZERO_SIZE_FIRST) {
@@ -855,10 +856,9 @@ static void skd_end_request(struct skd_device *skdev,
 
 	if ((io_flags & REQ_DISCARD) &&
 		(skreq->discard_page == 1)) {
-		struct bio *bio = req->bio;
 		pr_debug("%s:%s:%d, free the page!",
 			 skdev->name, __func__, __LINE__);
-		__free_page(bio->bi_io_vec->bv_page);
+		__free_page(req->completion_data);
 	}
 
 	if (unlikely(error)) {

drivers/scsi/sd.c

@@ -737,6 +737,7 @@ static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
 		goto out;
 	}
 
+	rq->completion_data = page;
 	blk_add_request_payload(rq, page, len);
 	ret = scsi_setup_blk_pc_cmnd(sdp, rq);
 	rq->__data_len = nr_bytes;
@@ -839,11 +840,9 @@ static void sd_unprep_fn(struct request_queue *q, struct request *rq)
 {
 	struct scsi_cmnd *SCpnt = rq->special;
 
-	if (rq->cmd_flags & REQ_DISCARD) {
-		struct bio *bio = rq->bio;
+	if (rq->cmd_flags & REQ_DISCARD)
+		__free_page(rq->completion_data);
 
-		__free_page(bio->bi_io_vec->bv_page);
-	}
 	if (SCpnt->cmnd != rq->cmd) {
 		mempool_free(SCpnt->cmnd, sd_cdb_pool);
 		SCpnt->cmnd = NULL;