Re: [dm-devel] [patch 1/3] Extremely basic hp hardware handler (no retries, no error handling, etc).

[Dave Wysochanski <dwysocha redhat com>]

On Thu, 2007-07-26 at 12:09 -0700, Chandra Seetharaman wrote:
> Hi Dave,
> 
> some coding style related comments (below).
> 
> On Thu, 2007-07-26 at 00:44 -0400, dwysocha redhat com wrote:
> > plain text document attachment (dm-hp-sw-v0.0.2.patch)
> > This patch adds the most basic dm-multipath hardware support for the 
> > HP active/passive arrays.
> > 
> > 
> > Index: linux-2.6.23-rc1/drivers/md/Makefile
> > ===================================================================
> > --- linux-2.6.23-rc1.orig/drivers/md/Makefile
> > +++ linux-2.6.23-rc1/drivers/md/Makefile
> > @@ -35,6 +35,7 @@ obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
> >  obj-$(CONFIG_DM_DELAY)		+= dm-delay.o
> >  obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
> >  obj-$(CONFIG_DM_MULTIPATH_EMC)	+= dm-emc.o
> > +obj-$(CONFIG_DM_MULTIPATH_HP)	+= dm-hp-sw.o
> >  obj-$(CONFIG_DM_MULTIPATH_RDAC)	+= dm-rdac.o
> >  obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
> >  obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
> > Index: linux-2.6.23-rc1/drivers/md/dm-hp-sw.c
> > ===================================================================
> > --- /dev/null
> > +++ linux-2.6.23-rc1/drivers/md/dm-hp-sw.c
> > @@ -0,0 +1,203 @@
> > +/*
> > + * Copyright (C) 2005 Mike Christie, All rights reserved.
> > + * Copyright (C) 2007 Red Hat, Inc. All rights reserved.
> > + * Authors: Mike Christie
> > + *          Dave Wysochanski
> > + *
> > + * This file is released under the GPL.
> > + *
> > + * This module implements the specific path activation code for
> > + * HP StorageWorks and FSC FibreCat Asymmetric (Active/Passive)
> > + * storage arrays.
> > + * These storage arrays have controller-based failover, not
> > + * LUN-based failover.  However, LUN-based failover is the design
> > + * of dm-multipath. Thus, this module is written for LUN-based failover.
> > + */
> > +#include <linux/blkdev.h>
> > +#include <linux/list.h>
> > +#include <linux/types.h>
> > +#include <scsi/scsi.h>
> > +#include <scsi/scsi_cmnd.h>
> > +
> > +#include "dm.h"
> > +#include "dm-hw-handler.h"
> > +
> > +#define DM_MSG_PREFIX "multipath hp_sw"
> > +
> > +struct hp_sw_context {
> > +	unsigned char sense[SCSI_SENSE_BUFFERSIZE];
> > +};
> > +
> > +
> > +/**
> > + * hp_sw_end_io - Completion handler for HP path activation.
> > + * @req: path activation request
> > + * @error: scsi-ml error
> > + *
> > + *  Check sense data, free request structure, and notify dm that
> > + *  pg initialization has completed.
> > + *
> > + * 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;
> > +	unsigned err_flags;
> > +
> > +	if (!error) {
> > +		err_flags = 0;
> > +		DMDEBUG("%s path activation command - success",
> > +		       	path->dev->name);
> 
> Mixed use of space and tab for indentation (many other places too).
> 
> > +	} else {
> > +		DMWARN("path activation command on %s - error=0x%x",
> 
> Could use the same format like "%s: path activation command - status",
> you made changes towards that in the next patch. Could make is
> consistent.
> 
> > +		       path->dev->name, error);
> > +		err_flags = MP_FAIL_PATH;
> > +	}
> > +
> > +	req->end_io_data = NULL;
> > +	__blk_put_request(req->q, req);
> > +	dm_pg_init_complete(path, err_flags);
> > +}
> > +
> > +/**
> > + * hp_sw_get_request - Allocate an HP specific path activation request
> > + * @path: path on which request will be sent (needed for request queue)
> > + *
> > + * The START command is used for path activation request.
> > + * These arrays are controller-based failover, not LUN based.
> > + * One START command issued to a single path will fail over all
> > + * LUNs for the same controller.
> > + *
> > + * Possible optimizations
> > + * 1. Make timeout configurable
> > + * 2. Preallocate request
> > + */
> > +static struct request *hp_sw_get_request(struct dm_path *path)
> > +{
> > +	struct request *req;
> > +	struct block_device *bdev = path->dev->bdev;
> > +	struct request_queue *q = bdev_get_queue(bdev);
> > +	struct hp_sw_context *h = path->hwhcontext;
> > +
> > +	req = blk_get_request(q, WRITE, GFP_NOIO);
> > +	if (!req)
> > +		goto out;
> > +
> > +	req->timeout = 60*HZ;
> > +
> > +	req->errors = 0;
> > +	req->cmd_type = REQ_TYPE_BLOCK_PC;
> > +	req->cmd_flags |= REQ_FAILFAST | REQ_NOMERGE;
> > +	req->end_io_data = path;
> > +	req->sense = h->sense;
> > +	memset(req->sense, 0, SCSI_SENSE_BUFFERSIZE);
> > +
> > +	memset(&req->cmd, 0, BLK_MAX_CDB);
> > +	req->cmd[0] = START_STOP;
> > +	req->cmd[4] = 1;
> > +	req->cmd_len = COMMAND_SIZE(req->cmd[0]);
> > + out:
> 
> I think there will be no space before the label (one more below).
> 
> > +	return req;
> > +}
> > +
> > +/**
> > + * hp_sw_pg_init - HP path activation implementation.
> > + * @hwh: hardware handler specific data
> > + * @bypassed: unused; is the path group bypassed? (see dm-mpath.c)
> > + * @path: path to send initialization command
> > + *
> > + * Send an HP-specific path activation command on 'path'.
> > + * Do not try to optimize in any way, just send the activation command.
> > + * More than one path activation command may be sent to the same controller.
> > + * This seems to work fine for basic failover support.
> > + *
> > + * Possible optimizations
> > + * 1. Detect an in-progress activation request and avoid submitting another one
> > + * 2. Model the controller and only send a single activation request at a time
> > + * 3. Determine the state of a path before sending an activation request
> > + *
> > + * Context: kmpathd (see process_queued_ios() in dm-mpath.c)
> > + */
> > +static void hp_sw_pg_init(struct hw_handler *hwh, unsigned bypassed,
> > +			  struct dm_path *path)
> > +{
> > +	struct request *req;
> > +	struct hp_sw_context *h;
> > +
> > +	path->hwhcontext = hwh->context;
> > +	h = hwh->context;
> > +
> > +	req = hp_sw_get_request(path);
> > +	if (!req) {
> > +		DMERR("%s path activation command allocation fail ",
> > +		      path->dev->name);
> > +		goto fail;
> > +	}
> > +
> > +	DMDEBUG("path activation command sent on %s",
> > +		path->dev->name);
> > +
> > +	blk_execute_rq_nowait(req->q, NULL, req, 1, hp_sw_end_io);
> > +	return;
> > +
> > + fail:
> > +	dm_pg_init_complete(path, MP_FAIL_PATH);
> > +}
> > +
> > +static int hp_sw_create(struct hw_handler *hwh, unsigned argc, char **argv)
> > +{
> > +	struct hp_sw_context *h;
> > +
> > +	h = kmalloc(sizeof(*h), GFP_KERNEL);
> > +	if (!h)
> > +		return -ENOMEM;
> > +	hwh->context = h;
> > +	return 0;
> > +}
> > +
> > +static void hp_sw_destroy(struct hw_handler *hwh)
> > +{
> > +	struct hp_sw_context *h = hwh->context;
> > +
> > +	kfree(h);
> > +}
> > +
> > +static struct hw_handler_type hp_sw_hwh = {
> > +	.name = "hp_sw",
> > +	.module = THIS_MODULE,
> > +	.create = hp_sw_create,
> > +	.destroy = hp_sw_destroy,
> > +	.pg_init = hp_sw_pg_init,
> > +};
> > +
> > +static int __init hp_sw_init(void)
> > +{
> > +	int r;
> > +
> > +	r = dm_register_hw_handler(&hp_sw_hwh);
> > +	if (r < 0)
> > +		DMERR("register failed %d", r);
> > +	else
> > +		DMINFO("version 0.0.2 loaded");
> > +
> > +	return r;
> > +}
> > +
> > +static void __exit hp_sw_exit(void)
> > +{
> > +	int r;
> > +
> > +	r = dm_unregister_hw_handler(&hp_sw_hwh);
> > +	if (r < 0)
> > +		DMERR("unregister failed %d", r);
> > +}
> > +
> > +module_init(hp_sw_init);
> > +module_exit(hp_sw_exit);
> > +
> > +MODULE_DESCRIPTION("HP StorageWorks and FSC FibreCat (A/P) support for dm-multipath");
> > +MODULE_AUTHOR("Mike Christie <michaelc cs wisc edu>");
> > +MODULE_LICENSE("GPL");
> > Index: linux-2.6.23-rc1/drivers/md/Kconfig
> > ===================================================================
> > --- linux-2.6.23-rc1.orig/drivers/md/Kconfig
> > +++ linux-2.6.23-rc1/drivers/md/Kconfig
> > @@ -267,6 +267,12 @@ config DM_MULTIPATH_RDAC
> >  	---help---
> >  	  Multipath support for LSI/Engenio RDAC.
> > 
> > +config DM_MULTIPATH_HP
> > +        tristate "HP MSA multipath support (EXPERIMENTAL)"
> > +        depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
> > +        ---help---
> > +          Multipath support for HP MSA (Active/Passive) series hardware.
> > +
> >  config DM_DELAY
> >  	tristate "I/O delaying target (EXPERIMENTAL)"
> >  	depends on BLK_DEV_DM && EXPERIMENTAL
> > 
> -- 
> 

I think the attached patch addresses all of your comments.


Extremely basic hp hardware handler (no retries, no error handling, etc).

This patch adds the most basic dm-multipath hardware support for the 
HP active/passive arrays.

Signed-off-by: Dave Wysochanski <dwysocha redhat com>
Signed-off-by: Mike Christie <michaelc cs wisc edu>

---
Index: linux-2.6.23-rc1/drivers/md/Makefile
===================================================================
--- linux-2.6.23-rc1.orig/drivers/md/Makefile
+++ linux-2.6.23-rc1/drivers/md/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
 obj-$(CONFIG_DM_DELAY)		+= dm-delay.o
 obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
 obj-$(CONFIG_DM_MULTIPATH_EMC)	+= dm-emc.o
+obj-$(CONFIG_DM_MULTIPATH_HP)	+= dm-hp-sw.o
 obj-$(CONFIG_DM_MULTIPATH_RDAC)	+= dm-rdac.o
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
Index: linux-2.6.23-rc1/drivers/md/dm-hp-sw.c
===================================================================
--- /dev/null
+++ linux-2.6.23-rc1/drivers/md/dm-hp-sw.c
@@ -0,0 +1,202 @@
+/*
+ * Copyright (C) 2005 Mike Christie, All rights reserved.
+ * Copyright (C) 2007 Red Hat, Inc. All rights reserved.
+ * Authors: Mike Christie
+ *          Dave Wysochanski
+ *
+ * This file is released under the GPL.
+ *
+ * This module implements the specific path activation code for
+ * HP StorageWorks and FSC FibreCat Asymmetric (Active/Passive)
+ * storage arrays.
+ * These storage arrays have controller-based failover, not
+ * LUN-based failover.  However, LUN-based failover is the design
+ * of dm-multipath. Thus, this module is written for LUN-based failover.
+ */
+#include <linux/blkdev.h>
+#include <linux/list.h>
+#include <linux/types.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+
+#include "dm.h"
+#include "dm-hw-handler.h"
+
+#define DM_MSG_PREFIX "multipath hp_sw"
+
+struct hp_sw_context {
+	unsigned char sense[SCSI_SENSE_BUFFERSIZE];
+};
+
+
+/**
+ * hp_sw_end_io - Completion handler for HP path activation.
+ * @req: path activation request
+ * @error: scsi-ml error
+ *
+ *  Check sense data, free request structure, and notify dm that
+ *  pg initialization has completed.
+ *
+ * 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;
+	unsigned err_flags;
+
+	if (!error) {
+		err_flags = 0;
+		DMDEBUG("%s path activation command - success",
+			path->dev->name);
+	} else {
+		DMWARN("%s path activation command - error=0x%x",
+			path->dev->name, error);
+		err_flags = MP_FAIL_PATH;
+	}
+
+	req->end_io_data = NULL;
+	__blk_put_request(req->q, req);
+	dm_pg_init_complete(path, err_flags);
+}
+
+/**
+ * hp_sw_get_request - Allocate an HP specific path activation request
+ * @path: path on which request will be sent (needed for request queue)
+ *
+ * The START command is used for path activation request.
+ * These arrays are controller-based failover, not LUN based.
+ * One START command issued to a single path will fail over all
+ * LUNs for the same controller.
+ *
+ * Possible optimizations
+ * 1. Make timeout configurable
+ * 2. Preallocate request
+ */
+static struct request *hp_sw_get_request(struct dm_path *path)
+{
+	struct request *req;
+	struct block_device *bdev = path->dev->bdev;
+	struct request_queue *q = bdev_get_queue(bdev);
+	struct hp_sw_context *h = path->hwhcontext;
+
+	req = blk_get_request(q, WRITE, GFP_NOIO);
+	if (!req)
+		goto out;
+
+	req->timeout = 60*HZ;
+
+	req->errors = 0;
+	req->cmd_type = REQ_TYPE_BLOCK_PC;
+	req->cmd_flags |= REQ_FAILFAST | REQ_NOMERGE;
+	req->end_io_data = path;
+	req->sense = h->sense;
+	memset(req->sense, 0, SCSI_SENSE_BUFFERSIZE);
+
+	memset(&req->cmd, 0, BLK_MAX_CDB);
+	req->cmd[0] = START_STOP;
+	req->cmd[4] = 1;
+	req->cmd_len = COMMAND_SIZE(req->cmd[0]);
+out:
+	return req;
+}
+
+/**
+ * hp_sw_pg_init - HP path activation implementation.
+ * @hwh: hardware handler specific data
+ * @bypassed: unused; is the path group bypassed? (see dm-mpath.c)
+ * @path: path to send initialization command
+ *
+ * Send an HP-specific path activation command on 'path'.
+ * Do not try to optimize in any way, just send the activation command.
+ * More than one path activation command may be sent to the same controller.
+ * This seems to work fine for basic failover support.
+ *
+ * Possible optimizations
+ * 1. Detect an in-progress activation request and avoid submitting another one
+ * 2. Model the controller and only send a single activation request at a time
+ * 3. Determine the state of a path before sending an activation request
+ *
+ * Context: kmpathd (see process_queued_ios() in dm-mpath.c)
+ */
+static void hp_sw_pg_init(struct hw_handler *hwh, unsigned bypassed,
+			struct dm_path *path)
+{
+	struct request *req;
+	struct hp_sw_context *h;
+
+	path->hwhcontext = hwh->context;
+	h = hwh->context;
+
+	req = hp_sw_get_request(path);
+	if (!req) {
+		DMERR("%s path activation command - allocation fail",
+			path->dev->name);
+		goto fail;
+	}
+
+	DMDEBUG("%s path activation command - sent", path->dev->name);
+
+	blk_execute_rq_nowait(req->q, NULL, req, 1, hp_sw_end_io);
+	return;
+
+fail:
+	dm_pg_init_complete(path, MP_FAIL_PATH);
+}
+
+static int hp_sw_create(struct hw_handler *hwh, unsigned argc, char **argv)
+{
+	struct hp_sw_context *h;
+
+	h = kmalloc(sizeof(*h), GFP_KERNEL);
+	if (!h)
+		return -ENOMEM;
+	hwh->context = h;
+	return 0;
+}
+
+static void hp_sw_destroy(struct hw_handler *hwh)
+{
+	struct hp_sw_context *h = hwh->context;
+
+	kfree(h);
+}
+
+static struct hw_handler_type hp_sw_hwh = {
+	.name = "hp_sw",
+	.module = THIS_MODULE,
+	.create = hp_sw_create,
+	.destroy = hp_sw_destroy,
+	.pg_init = hp_sw_pg_init,
+};
+
+static int __init hp_sw_init(void)
+{
+	int r;
+
+	r = dm_register_hw_handler(&hp_sw_hwh);
+	if (r < 0)
+		DMERR("register failed %d", r);
+	else
+		DMINFO("version 0.0.2 loaded");
+
+	return r;
+}
+
+static void __exit hp_sw_exit(void)
+{
+	int r;
+
+	r = dm_unregister_hw_handler(&hp_sw_hwh);
+	if (r < 0)
+		DMERR("unregister failed %d", r);
+}
+
+module_init(hp_sw_init);
+module_exit(hp_sw_exit);
+
+MODULE_DESCRIPTION("HP StorageWorks and FSC FibreCat (A/P) support for dm-multipath");
+MODULE_AUTHOR("Mike Christie <michaelc cs wisc edu>");
+MODULE_LICENSE("GPL");
Index: linux-2.6.23-rc1/drivers/md/Kconfig
===================================================================
--- linux-2.6.23-rc1.orig/drivers/md/Kconfig
+++ linux-2.6.23-rc1/drivers/md/Kconfig
@@ -267,6 +267,12 @@ config DM_MULTIPATH_RDAC
 	---help---
 	  Multipath support for LSI/Engenio RDAC.
 
+config DM_MULTIPATH_HP
+        tristate "HP MSA multipath support (EXPERIMENTAL)"
+        depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
+        ---help---
+          Multipath support for HP MSA (Active/Passive) series hardware.
+
 config DM_DELAY
 	tristate "I/O delaying target (EXPERIMENTAL)"
 	depends on BLK_DEV_DM && EXPERIMENTAL