[PATCH 2/2] dont retry st SG_IO and scsi SCSI-ml REQ_BLOCK_PC requests

[Mike Christie <michaelc@cs.wisc.edu>]

sd does not allow scsi_io_completion to retry commands for
SG_IO requests, and it make sense that it should not happen for st
SG_IO commands too. If for st we hit the bottom of scsi_io_completion
we will probably screw things up pretty bad. This patch returns to the
block layer that the whole command completed and relies on the caller to check
the request errors field. For initialization commands like in sd, this adds
the previous behavior where scsi_io_completion did not process the error.

When st is converted to using the REQ_BLOCK_PC requests, allowing
scsi-ml's scsi_io_completion to driver retires also causes a bug
since st normallly wants retries=0 (Bug found from Kai).


Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>


diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index ce9d73a..e75e6c5 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1082,7 +1082,13 @@ static int scsi_issue_flush_fn(request_q
 static void scsi_generic_done(struct scsi_cmnd *cmd)
 {
 	BUG_ON(!blk_pc_request(cmd->request));
-	scsi_io_completion(cmd, cmd->result == 0 ? cmd->bufflen : 0, 0);
+	/*
+	 * This will complete the whole command with uptodate=1 so
+	 * as far as the block layer is concerned the command completed
+	 * successfully. Since this is a REQ_BLOCK_PC command the
+	 * caller should check the request's errors value
+	 */
+	scsi_io_completion(cmd, cmd->bufflen, 0);
 }
 
 static int scsi_prep_fn(struct request_queue *q, struct request *req)
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index 770c432..a2176c2 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -4185,7 +4185,11 @@ static void scsi_tape_release(struct kre
 
 static void st_intr(struct scsi_cmnd *SCpnt)
 {
-	scsi_io_completion(SCpnt, (SCpnt->result ? 0: SCpnt->bufflen), 1);
+	/*
+	 * The caller should be checking the request's errors
+	 * value.
+	 */
+	scsi_io_completion(SCpnt, SCpnt->bufflen, 0);
 }
 
 /*