Add HP hardware handler support to dm-mp

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Index: linux-2.6.22-rc1/drivers/md/dm-hw-handler.h
===================================================================
@@ -58,5 +58,6 @@ unsigned dm_scsi_err_handler(struct hw_h
 #define MP_FAIL_PATH 1
 #define MP_BYPASS_PG 2
 #define MP_ERROR_IO  4	/* Don't retry this I/O */
+#define MP_RETRY_PG_INIT 8
 
 #endif

Index: linux-2.6.22-rc1/drivers/md/dm-mpath.c
===================================================================
@@ -999,7 +999,9 @@ void dm_pg_init_complete(struct dm_path 
 		bypass_pg(m, pg, 1);
 
 	spin_lock_irqsave(&m->lock, flags);
-	if (err_flags) {
+	if (err_flags & MP_RETRY_PG_INIT)
+		m->pg_init_required = 1;
+	else if (err_flags) {
 		m->current_pgpath = NULL;
 		m->current_pg = NULL;
 	} else if (!m->pg_init_required)

Index: linux-2.6.22-rc1/drivers/md/dm-hp-sw.c
===================================================================
@@ -17,20 +17,58 @@
 #include <linux/types.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_dbg.h>
 
 #include "dm.h"
 #include "dm-hw-handler.h"
 
 #define DM_MSG_PREFIX "multipath hp"
 
+#define HP_SW_PG_INIT_RETRIES 5
+
 struct hp_sw_context {
 	unsigned char sense[SCSI_SENSE_BUFFERSIZE];
+	unsigned pg_init_count;
 };
 
+/**
+ * hp_sw_error_is_retryable - Is an HP-specific check condition retryable?
+ * @req: path activation request
+ *
+ * Examine error codes of request and determine whether the error is retryable.
+ * Some error codes are already retried by scsi-ml (see
+ * scsi_decide_disposition), but some HP specific codes are not.
+ * The intent of this routine is to supply the logic for the HP specific
+ * check conditions.
+ *
+ * Returns:
+ *  1 - command completed with retryable error
+ *  0 - command completed with non-retryable error
+ *
+ * Possible optimizations
+ * 1. More hardware-specific error codes
+ */
+static int hp_sw_error_is_retryable(struct request *req)
+{
+	/*
+	 * NOT_READY is known to be retryable
+	 * For now we just dump out the sense data and call it retryable
+	 */
+	if ((status_byte(req->errors) == CHECK_CONDITION) &&
+	    (driver_byte(req->errors) & DRIVER_SENSE))
+		__scsi_print_sense("hp_sw", req->sense, req->sense_len);
+
+	/*
+	 * At this point we don't have complete information about all the error
+	 * codes from this hardware, so we are just conservative and retry
+	 * when in doubt.
+	 */
+	return 1;
+}
 
 /**
  * hp_sw_end_io - Completion handler for HP path activation.
- * @req: failover request
+ * @req: path activation request
  * @error: scsi-ml error
  *
  *  Check sense data, free request structure, and notify dm that

@@ -38,24 +76,38 @@ struct hp_sw_context {
  *
  * Context: scsi-ml softirq
  *
- * Possible optimizations
- * 1. Actually check sense data for retryable error (e.g. NOT_READY)
  */
 static void hp_sw_end_io(struct request *req, int error)
 {
 	struct dm_path *path = req->end_io_data;
+	struct hp_sw_context *h = path->hwhcontext;
 	unsigned err_flags;
 
 	if (!error) {
+		h->pg_init_count = 0;
 		err_flags = 0;
-		DMDEBUG("hp_sw: path activation command on %s - success",
+		DMDEBUG("hp_sw: %s path activation command - success",
 		       	path->dev->name);
 	} else {
-		DMWARN("hp_sw: path activation command on %s - error=0x%x",
+		DMWARN("hp_sw: %s path activation command - error=0x%x",
 		       path->dev->name, error);
+		if (hp_sw_error_is_retryable(req)) {
+			if (h->pg_init_count <= HP_SW_PG_INIT_RETRIES) {
+				DMWARN("hp_sw: %s path activation command "
+				       "count=%d",
+				       path->dev->name, h->pg_init_count);
+				err_flags = MP_RETRY_PG_INIT;
+				goto exit;
+			} else
+				DMWARN("hp_sw: %s path activation command "
+				       "out of retries",
+				       path->dev->name);
+		}
+		DMWARN("hp_sw: %s path activation fail", path->dev->name);
+		h->pg_init_count = 0;
 		err_flags = MP_FAIL_PATH;
 	}
-
+ exit:
 	req->end_io_data = NULL;
 	__blk_put_request(req->q, req);
 	dm_pg_init_complete(path, err_flags);

@@ -126,25 +178,31 @@ static void hp_sw_pg_init(struct hw_hand
 {
 	struct request *req;
 	struct hp_sw_context *h;
+	unsigned err_flags;
 
 	path->hwhcontext = hwh->context;
 	h = (struct hp_sw_context *) hwh->context;
+	h->pg_init_count++;
 
 	req = hp_sw_get_request(path);
 	if (!req) {
-		DMERR("hp_sw: path activation command allocation fail on %s ",
+		DMERR("hp_sw: %s path activation command allocation fail ",
 		      path->dev->name);
 		goto fail;
 	}
 
-	DMDEBUG("hp_sw: path activation command sent on %s",
-		path->dev->name);
+	DMDEBUG("hp_sw: %s path activation command sent, pg_init_count=%d",
+		path->dev->name, h->pg_init_count);
 
 	elv_add_request(req->q, req, ELEVATOR_INSERT_FRONT, 1);
 	return;
 
  fail:
-	dm_pg_init_complete(path, MP_FAIL_PATH);
+	if (h->pg_init_count <= HP_SW_PG_INIT_RETRIES)
+		err_flags = MP_RETRY_PG_INIT;
+	else
+		err_flags = MP_FAIL_PATH;
+	dm_pg_init_complete(path, err_flags);
 }
 
 static int hp_sw_create(struct hw_handler *hwh, unsigned argc, char **argv)

@@ -155,6 +213,7 @@ static int hp_sw_create(struct hw_handle
 	if (!h)
 		return -ENOMEM;
 	hwh->context = h;
+	h->pg_init_count = 0;
 	return 0;
 }
 

@@ -182,7 +241,7 @@ static int __init hp_sw_init(void)
 	if (r < 0)
 		DMERR("hp_sw: register failed %d", r);
 
-	DMINFO("hp_sw version 0.0.2 loaded");
+	DMINFO("hp_sw version 0.0.3 loaded");
 
 	return r;
 }