---
 drivers/md/dm-mpath.c |   66 ++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 59 insertions(+), 7 deletions(-)

Index: linux-2.6/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-mpath.c
+++ linux-2.6/drivers/md/dm-mpath.c
@@ -19,6 +19,7 @@
 #include <linux/time.h>
 #include <linux/workqueue.h>
 #include <scsi/scsi_dh.h>
+#include <scsi/scsi_eh.h>
 #include <asm/atomic.h>
 
 #define DM_MSG_PREFIX "multipath"
@@ -104,6 +105,7 @@ struct multipath {
 struct dm_mpath_io {
 	struct pgpath *pgpath;
 	size_t nr_bytes;
+	char sense[SCSI_SENSE_BUFFERSIZE];
 };
 
 typedef int (*action_fn) (struct pgpath *pgpath);
@@ -960,6 +962,9 @@ static int multipath_map(struct dm_targe
 
 	map_context->ptr = mpio;
 	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
+	/* Always attach a sense buffer */
+	if (!clone->sense)
+		clone->sense = mpio->sense;
 	r = map_io(m, clone, mpio, 0);
 	if (r < 0 || r == DM_MAPIO_REQUEUE)
 		mempool_free(mpio, m->mpio_pool);
@@ -1247,6 +1252,54 @@ static void activate_path(struct work_st
 				pg_init_done, pgpath);
 }
 
+// TODO: move to scsi_error.c
+/*
+ * Evaluate scsi return code to see if ULD retry is worthwhile.
+ */
+static bool scsi_uld_should_retry(struct request *req)
+{
+	struct scsi_sense_hdr sshdr;
+	int result = req->errors;
+	char *sense = req->sense;
+	int sense_len = req->sense_len;
+	int r = 1;
+
+	if (req->cmd_flags & REQ_DISCARD)
+		/*
+		 * Pass all discard request failures up.
+		 * FIXME: only fail_path if the discard failed due to a
+		 * transport problem.  This requires precise understanding
+		 * of the underlying failure (e.g. the SCSI sense).
+		 */
+		return 0;
+
+	if (host_byte(result) != DID_OK)
+		return r;
+
+	if (msg_byte(result) != COMMAND_COMPLETE)
+		return r;
+
+	if (status_byte(result) == RESERVATION_CONFLICT)
+		/* Do not retry here, possible data corruption */
+		return 0;
+
+	if (status_byte(result) == CHECK_CONDITION &&
+	    !scsi_normalize_sense(sense, sense_len, &sshdr)) {
+		switch (sshdr.sense_key) {
+		case MEDIUM_ERROR:
+		case DATA_PROTECT:
+		case BLANK_CHECK:
+		case COPY_ABORTED:
+		case VOLUME_OVERFLOW:
+		case MISCOMPARE:
+			r = 0;
+			break;
+		}
+	}
+
+	return r;
+}
+
 /*
  * end_io handling
  */
@@ -1273,13 +1326,8 @@ static int do_end_io(struct multipath *m
 	if (error == -EOPNOTSUPP)
 		return error;
 
-	if (clone->cmd_flags & REQ_DISCARD)
-		/*
-		 * Pass all discard request failures up.
-		 * FIXME: only fail_path if the discard failed due to a
-		 * transport problem.  This requires precise understanding
-		 * of the underlying failure (e.g. the SCSI sense).
-		 */
+	if ((clone->cmd_flags & REQ_SCSI_ERROR) &&
+	    !scsi_uld_should_retry(clone))
 		return error;
 
 	if (mpio->pgpath)
@@ -1308,6 +1356,10 @@ static int multipath_end_io(struct dm_ta
 		if (ps->type->end_io)
 			ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
 	}
+	if (clone->sense == mpio->sense) {
+		clone->sense = NULL;
+		clone->sense_len = 0;
+	}
 	mempool_free(mpio, m->mpio_pool);
 
 	return r;