Re: [PATCH] HP storage works support take 2

[Mike Christie <michaelc@cs.wisc.edu>]

christophe varoqui wrote:
> I told you I tried this simple fix, without success.

That fix is necessary. If the context does not get set then we will hit 
a null pointer reference like in your oops you reported.

In the mail you sent you said it hung on module load. I verified that 
and it worked here.

> 
> It is not enough, as it still hangs the kernel upon first io submited to
> the map.
> 

this is news to me. I will test out your table when I get a chance.


> I verified this even without any hardware, with ram disks.
> Here is a sample table :
> 
> [root@s64p17bibrn mce-dm-sstart]# dmsetup table toto: 0 1000 multipath 1
> queue_if_no_path 1 hp_sw 2 1 round-robin 0 1 1 1:2 1000 round-robin 0 1
> 1 1:2 1000
> [root@s64p17bibrn mce-dm-sstart]# dd if=/dev/mapper/toto of=/dev/null
> bs=512 count=1
> 
> <HANG>
> 
> Regards,
> cvaroqui
> 
> On sam, 2005-06-11 at 18:33 -0700, Mike Christie wrote:
> 
>>This should fix some bugs.
>>
>>
>>
>>diff -Naurp linux-2.6.12-rc5.orig/drivers/md/dm-hp-sw.c linux-2.6.12-rc5/drivers/md/dm-hp-sw.c
>>--- linux-2.6.12-rc5.orig/drivers/md/dm-hp-sw.c	1969-12-31 16:00:00.000000000 -0800
>>+++ linux-2.6.12-rc5/drivers/md/dm-hp-sw.c	2005-06-10 23:25:01.000000000 -0700
>>@@ -0,0 +1,160 @@
>>+/*
>>+ * Copyright (C) 2005 Mike Christie, All rights reserved.
>>+ *
>>+ * This file is released under the GPL.
>>+ *
>>+ * Basic, very basic, support for HP StorageWorks and FSC FibreCat
>>+ */
>>+#include <scsi/scsi.h>
>>+#include <scsi/scsi_cmnd.h>
>>+
>>+#include "dm.h"
>>+#include "dm-hw-handler.h"
>>+
>>+struct hp_sw_handler {
>>+	unsigned char sense[SCSI_SENSE_BUFFERSIZE];
>>+};
>>+
>>+static void hp_sw_endio(struct request *rq)
>>+{
>>+	struct path *path = rq->end_io_data;
>>+
>>+	/*
>>+	 * TODO: something.. we have the sense and scsi bytes
>>+	 */
>>+	if (rq->errors) {
>>+		DMINFO("hp_sw: START_STOP completed %d", rq->errors);
>>+		dm_pg_init_complete(path, MP_FAIL_PATH);
>>+	} else
>>+		dm_pg_init_complete(path, 0);
>>+
>>+	blk_put_request(rq);
>>+}
>>+
>>+static struct request *hp_sw_get_request(struct hp_sw_handler *h,
>>+					struct path *path)
>>+{
>>+	struct request *rq;
>>+	struct block_device *bdev = path->dev->bdev;
>>+	struct request_queue *q = bdev_get_queue(bdev);
>>+
>>+	rq = blk_get_request(q, READ, __GFP_WAIT);
>>+	if (!rq)
>>+		return NULL;
>>+
>>+	rq->end_io = hp_sw_endio;
>>+	rq->end_io_data = path;
>>+	rq->rq_disk = bdev->bd_contains->bd_disk;
>>+	rq->sense = h->sense;
>>+	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
>>+	rq->sense_len = 0;
>>+	/*
>>+	 * TODO: make me configurable
>>+	 */
>>+	rq->timeout = 30;
>>+	rq->flags |= (REQ_BLOCK_PC | REQ_FAILFAST | REQ_NOMERGE);
>>+
>>+	memset(&rq->cmd, 0, BLK_MAX_CDB);
>>+	rq->cmd[0] = START_STOP;
>>+	/* Start spin cycle */
>>+	rq->cmd[4] = 1;
>>+	rq->cmd_len = COMMAND_SIZE(rq->cmd[0]);
>>+
>>+	return rq;
>>+}
>>+
>>+static void hp_sw_pg_init(struct hw_handler *hwh, unsigned bypassed,
>>+			   struct path *path)
>>+{
>>+	struct request *rq;
>>+	struct request_queue *q = bdev_get_queue(path->dev->bdev);
>>+
>>+	/*
>>+	 * We can either blindly init the pg (then look at the sense),
>>+	 * or we can send some commands to get the state here (then
>>+	 * possibly send the fo cmnd), or we can also have the
>>+	 * initial state passed into us and then get an update here.
>>+	 */
>>+	if (!q) {
>>+		DMERR("hp_sw: no queue!");
>>+		goto fail_path;
>>+	}
>>+
>>+	if (blk_get_queue(q))
>>+		goto fail_path;
>>+
>>+	rq = hp_sw_get_request(hwh->context, path);
>>+	if (!rq) {
>>+		DMERR("hp_sw: could not allocate request for START_STOP");
>>+		goto rel_queue;
>>+	}
>>+
>>+	DMINFO("hp_sw: queueing START_STOP command");
>>+	elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 1);
>>+	blk_put_queue(q);
>>+	return;
>>+
>>+rel_queue:
>>+	blk_put_queue(q);
>>+fail_path:
>>+	dm_pg_init_complete(path, MP_FAIL_PATH);
>>+}
>>+
>>+static int hp_sw_create(struct hw_handler *hwh, unsigned argc, char **argv)
>>+{
>>+	struct hp_sw_handler *h;
>>+
>>+	h = kmalloc(sizeof(*h), GFP_KERNEL);
>>+	if (!h) {
>>+		DMERR("hp_sw: could not allocate hw_handler");
>>+		return -ENOMEM;
>>+	}
>>+
>>+	hwh->context = h;
>>+	return 0;
>>+}
>>+
>>+static void hp_sw_destroy(struct hw_handler *hwh)
>>+{
>>+	struct hp_sw_handler *h = hwh->context;
>>+
>>+	kfree(h);
>>+	hwh->context = NULL;
>>+}
>>+
>>+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("hp_sw: register failed %d", r);
>>+
>>+	DMINFO("hp_sw version 0.1 loaded");
>>+
>>+	return r;
>>+}
>>+
>>+static void __exit hp_sw_exit(void)
>>+{
>>+	int r;
>>+
>>+	r = dm_unregister_hw_handler(&hp_sw_hwh);
>>+	if (r < 0)
>>+		DMERR("hp_sw: unregister failed %d", r);
>>+}
>>+
>>+module_init(hp_sw_init);
>>+module_exit(hp_sw_exit);
>>+
>>+MODULE_DESCRIPTION("HP StorageWorks and FSC FibreCat support for dm-multipath");
>>+MODULE_AUTHOR("Mike Christie <michaelc@cs.wisc.edu>");
>>+MODULE_LICENSE("GPL");
>>diff -Naurp linux-2.6.12-rc5.orig/drivers/md/Kconfig linux-2.6.12-rc5/drivers/md/Kconfig
>>--- linux-2.6.12-rc5.orig/drivers/md/Kconfig	2005-06-08 19:30:05.000000000 -0700
>>+++ linux-2.6.12-rc5/drivers/md/Kconfig	2005-06-10 23:23:31.000000000 -0700
>>@@ -236,5 +236,14 @@ config DM_MULTIPATH_EMC
>> 	---help---
>> 	  Multipath support for EMC CX/AX series hardware.
>> 
>>+config DM_MULTIPATH_HP_SW
>>+	tristate "HP StorageWorks and FSC FibreCat (EXPERIMENTAL)"
>>+	depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
>>+	---help---
>>+	  Multipath support for HP StorageWorks and FSC FibreCat.
>>+          This was created with no knowledge of the HW other than
>>+          that it uses a START_STOP command for failover so it
>>+          is marked EXPERIMENTAL.
>>+
>> endmenu
>> 
>>diff -Naurp linux-2.6.12-rc5.orig/drivers/md/Makefile linux-2.6.12-rc5/drivers/md/Makefile
>>--- linux-2.6.12-rc5.orig/drivers/md/Makefile	2005-06-08 19:30:05.000000000 -0700
>>+++ linux-2.6.12-rc5/drivers/md/Makefile	2005-06-10 23:23:31.000000000 -0700
>>@@ -33,6 +33,7 @@ obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o
>> obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
>> obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
>> obj-$(CONFIG_DM_MULTIPATH_EMC)	+= dm-emc.o
>>+obj-$(CONFIG_DM_MULTIPATH_HP_SW) += dm-hp-sw.o
>> obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
>> obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
>> obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
>>
>>
>>--
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