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

[Chandra Seetharaman]

Hi Dave,

some coding style related comments (below).

On Thu, 2007-07-26 at 00:44 -0400, dwysocha at 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 at 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
> 
-- 

----------------------------------------------------------------------
    Chandra Seetharaman               | Be careful what you choose....
              - sekharan at us.ibm.com   |      .......you may get it.
----------------------------------------------------------------------