block: introduce blk_rq_is_passthrough

This can be used to check for fs vs non-fs requests and basically
removes all knowledge of BLOCK_PC specific from the block layer,
as well as preparing for removing the cmd_type field in struct request.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 4b40f74..b4ce7bb 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1106,7 +1106,7 @@ static int scsi_request_sense(struct scsi_cmnd *scmd)
 
 static int scsi_eh_action(struct scsi_cmnd *scmd, int rtn)
 {
-	if (scmd->request->cmd_type != REQ_TYPE_BLOCK_PC) {
+	if (!blk_rq_is_passthrough(scmd->request)) {
 		struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
 		if (sdrv->eh_action)
 			rtn = sdrv->eh_action(scmd, rtn);
@@ -1746,7 +1746,7 @@ int scsi_noretry_cmd(struct scsi_cmnd *scmd)
 	 * the check condition was retryable.
 	 */
 	if (scmd->request->cmd_flags & REQ_FAILFAST_DEV ||
-	    scmd->request->cmd_type == REQ_TYPE_BLOCK_PC)
+	    blk_rq_is_passthrough(scmd->request))
 		return 1;
 	else
 		return 0;