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[dm-devel] [PATCH 1/4] scsi_dh: Change the scsidh_activate interface to be asynchronous



Make scsi_dh_activate() function asynchronous, by taking in two additional 
parameters, one is the callback function and the other is the data to call
the callback function with.

Signed-off-by: Chandra Seetharaman <sekharan us ibm com>

--------------
 drivers/md/dm-mpath.c                       |    8 ++++----
 drivers/scsi/device_handler/scsi_dh.c       |   17 ++++++++++++-----
 drivers/scsi/device_handler/scsi_dh_alua.c  |    6 ++++--
 drivers/scsi/device_handler/scsi_dh_emc.c   |    6 ++++--
 drivers/scsi/device_handler/scsi_dh_hp_sw.c |    6 ++++--
 drivers/scsi/device_handler/scsi_dh_rdac.c  |    6 ++++--
 include/scsi/scsi_device.h                  |    3 ++-
 include/scsi/scsi_dh.h                      |    7 +++++--
 8 files changed, 39 insertions(+), 20 deletions(-)

Index: linux-2.6.31/include/scsi/scsi_dh.h
===================================================================
--- linux-2.6.31.orig/include/scsi/scsi_dh.h
+++ linux-2.6.31/include/scsi/scsi_dh.h
@@ -55,14 +55,17 @@ enum {
 	SCSI_DH_NOSYS,
 	SCSI_DH_DRIVER_MAX,
 };
+
 #if defined(CONFIG_SCSI_DH) || defined(CONFIG_SCSI_DH_MODULE)
-extern int scsi_dh_activate(struct request_queue *);
+extern int scsi_dh_activate(struct request_queue *, activate_complete, void *);
 extern int scsi_dh_handler_exist(const char *);
 extern int scsi_dh_attach(struct request_queue *, const char *);
 extern void scsi_dh_detach(struct request_queue *);
 #else
-static inline int scsi_dh_activate(struct request_queue *req)
+static inline int scsi_dh_activate(struct request_queue *req,
+					activate_complete fn, void *data)
 {
+	fn(data, 0);
 	return 0;
 }
 static inline int scsi_dh_handler_exist(const char *name)
Index: linux-2.6.31/drivers/scsi/device_handler/scsi_dh.c
===================================================================
--- linux-2.6.31.orig/drivers/scsi/device_handler/scsi_dh.c
+++ linux-2.6.31/drivers/scsi/device_handler/scsi_dh.c
@@ -214,7 +214,7 @@ store_dh_state(struct device *dev, struc
 			 * Activate a device handler
 			 */
 			if (scsi_dh->activate)
-				err = scsi_dh->activate(sdev);
+				err = scsi_dh->activate(sdev, NULL, NULL);
 			else
 				err = 0;
 		}
@@ -411,10 +411,17 @@ EXPORT_SYMBOL_GPL(scsi_unregister_device
 /*
  * scsi_dh_activate - activate the path associated with the scsi_device
  *      corresponding to the given request queue.
- * @q - Request queue that is associated with the scsi_device to be
- *      activated.
+ *     Returns immediately without waiting for activation to be completed.
+ * @q    - Request queue that is associated with the scsi_device to be
+ *         activated.
+ * @fn   - Function to be called upon completion of the activation.
+ *         Function fn is called with data (below) and the error code.
+ *         Function fn may be called from the same calling context. So,
+ *         do not hold the lock in the caller which may be needed in fn.
+ * @data - data passed to the function fn upon completion.
+ *
  */
-int scsi_dh_activate(struct request_queue *q)
+int scsi_dh_activate(struct request_queue *q, activate_complete fn, void *data)
 {
 	int err = 0;
 	unsigned long flags;
@@ -433,7 +440,7 @@ int scsi_dh_activate(struct request_queu
 		return err;
 
 	if (scsi_dh->activate)
-		err = scsi_dh->activate(sdev);
+		err = scsi_dh->activate(sdev, fn, data);
 	put_device(&sdev->sdev_gendev);
 	return err;
 }
Index: linux-2.6.31/drivers/scsi/device_handler/scsi_dh_rdac.c
===================================================================
--- linux-2.6.31.orig/drivers/scsi/device_handler/scsi_dh_rdac.c
+++ linux-2.6.31/drivers/scsi/device_handler/scsi_dh_rdac.c
@@ -516,7 +516,7 @@ done:
 	return err;
 }
 
-static int rdac_activate(struct scsi_device *sdev)
+static int rdac_activate(struct scsi_device *sdev, activate_complete fn, void *data)
 {
 	struct rdac_dh_data *h = get_rdac_data(sdev);
 	int err = SCSI_DH_OK;
@@ -539,7 +539,9 @@ static int rdac_activate(struct scsi_dev
 	if (h->lun_state == RDAC_LUN_UNOWNED)
 		err = send_mode_select(sdev, h);
 done:
-	return err;
+	if (fn)
+		fn(data, err);
+	return 0;
 }
 
 static int rdac_prep_fn(struct scsi_device *sdev, struct request *req)
Index: linux-2.6.31/drivers/scsi/device_handler/scsi_dh_alua.c
===================================================================
--- linux-2.6.31.orig/drivers/scsi/device_handler/scsi_dh_alua.c
+++ linux-2.6.31/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -652,7 +652,7 @@ out:
  * based on a certain policy. But until we actually encounter them it
  * should be okay.
  */
-static int alua_activate(struct scsi_device *sdev)
+static int alua_activate(struct scsi_device *sdev, activate_complete fn, void *data)
 {
 	struct alua_dh_data *h = get_alua_data(sdev);
 	int err = SCSI_DH_OK;
@@ -667,7 +667,9 @@ static int alua_activate(struct scsi_dev
 		err = alua_stpg(sdev, TPGS_STATE_OPTIMIZED, h);
 
 out:
-	return err;
+	if (fn)
+		fn(data, err);
+	return 0;
 }
 
 /*
Index: linux-2.6.31/drivers/scsi/device_handler/scsi_dh_emc.c
===================================================================
--- linux-2.6.31.orig/drivers/scsi/device_handler/scsi_dh_emc.c
+++ linux-2.6.31/drivers/scsi/device_handler/scsi_dh_emc.c
@@ -528,7 +528,7 @@ retry:
 	return err;
 }
 
-static int clariion_activate(struct scsi_device *sdev)
+static int clariion_activate(struct scsi_device *sdev, activate_complete fn, void *data)
 {
 	struct clariion_dh_data *csdev = get_clariion_data(sdev);
 	int result;
@@ -559,7 +559,9 @@ done:
 		    csdev->port, lun_state[csdev->lun_state],
 		    csdev->default_sp + 'A');
 
-	return result;
+	if (fn)
+		fn(data, result);
+	return 0;
 }
 
 static const struct scsi_dh_devlist clariion_dev_list[] = {
Index: linux-2.6.31/drivers/scsi/device_handler/scsi_dh_hp_sw.c
===================================================================
--- linux-2.6.31.orig/drivers/scsi/device_handler/scsi_dh_hp_sw.c
+++ linux-2.6.31/drivers/scsi/device_handler/scsi_dh_hp_sw.c
@@ -268,7 +268,7 @@ static int hp_sw_prep_fn(struct scsi_dev
  * activate the passive path (and deactivate the
  * previously active one).
  */
-static int hp_sw_activate(struct scsi_device *sdev)
+static int hp_sw_activate(struct scsi_device *sdev, activate_complete fn, void *data)
 {
 	int ret = SCSI_DH_OK;
 	struct hp_sw_dh_data *h = get_hp_sw_data(sdev);
@@ -283,7 +283,9 @@ static int hp_sw_activate(struct scsi_de
 				    HP_SW_NAME);
 	}
 
-	return ret;
+	if (fn)
+		fn(data, ret);
+	return 0;
 }
 
 static const struct scsi_dh_devlist hp_sw_dh_data_list[] = {
Index: linux-2.6.31/include/scsi/scsi_device.h
===================================================================
--- linux-2.6.31.orig/include/scsi/scsi_device.h
+++ linux-2.6.31/include/scsi/scsi_device.h
@@ -174,6 +174,7 @@ struct scsi_dh_devlist {
 	char *model;
 };
 
+typedef void (*activate_complete)(void *, int);
 struct scsi_device_handler {
 	/* Used by the infrastructure */
 	struct list_head list; /* list of scsi_device_handlers */
@@ -185,7 +186,7 @@ struct scsi_device_handler {
 	int (*check_sense)(struct scsi_device *, struct scsi_sense_hdr *);
 	int (*attach)(struct scsi_device *);
 	void (*detach)(struct scsi_device *);
-	int (*activate)(struct scsi_device *);
+	int (*activate)(struct scsi_device *, activate_complete, void *);
 	int (*prep_fn)(struct scsi_device *, struct request *);
 };
 
Index: linux-2.6.31/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.31.orig/drivers/md/dm-mpath.c
+++ linux-2.6.31/drivers/md/dm-mpath.c
@@ -1086,8 +1086,9 @@ static int pg_init_limit_reached(struct 
 	return limit_reached;
 }
 
-static void pg_init_done(struct dm_path *path, int errors)
+static void pg_init_done(void *data, int errors)
 {
+	struct dm_path *path = data;
 	struct pgpath *pgpath = path_to_pgpath(path);
 	struct priority_group *pg = pgpath->pg;
 	struct multipath *m = pg->m;
@@ -1153,12 +1154,11 @@ static void pg_init_done(struct dm_path 
 
 static void activate_path(struct work_struct *work)
 {
-	int ret;
 	struct pgpath *pgpath =
 		container_of(work, struct pgpath, activate_path);
 
-	ret = scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev));
-	pg_init_done(&pgpath->path, ret);
+	scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
+				pg_init_done, &pgpath->path);
 }
 
 /*


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