dm mpath: add hp handler

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>
Acked-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 206 insertions, 0 deletions

diff --git a/drivers/md/dm-mpath-hp-sw.c b/drivers/md/dm-mpath-hp-sw.c
new file mode 100644
index 000000000000..575317037ce2
--- /dev/null
+++ b/drivers/md/dm-mpath-hp-sw.c
@@ -0,0 +1,206 @@
+/*
+ * 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"
+#define DM_HP_HWH_NAME "hp-sw"
+#define DM_HP_HWH_VER "0.0.3"
+
+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 = 0;
+
+        if (!error)
+                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 = DM_HP_HWH_NAME,
+        .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 " DM_HP_HWH_VER " 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("DM Multipath HP StorageWorks / FSC FibreCat (A/P) support");
+MODULE_AUTHOR("Mike Christie, Dave Wysochanski <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DM_HP_HWH_VER);