[dm-devel] [PATCH RFC 7/5] add support for manual failover devices

[Mike Christie <michaelc cs wisc edu>]

rdac-test-support.patch - this is just an example of what needs to
be done by the ps to send a failover command to the device. This
example is just sending a TUR, and I just bascially ripped off the
rr ps's other functions.

diff -Naurp linux-2.6.5-rc1-udm1-orig/drivers/md/Kconfig linux-2.6.5-rc1-udm1-work/drivers/md/Kconfig
--- linux-2.6.5-rc1-udm1-orig/drivers/md/Kconfig	2004-04-02 01:24:19.000000000 -0800
+++ linux-2.6.5-rc1-udm1-work/drivers/md/Kconfig	2004-04-04 12:23:56.607842249 -0700
@@ -186,6 +186,12 @@ config DM_MULTIPATH
        ---help---
          Allow volume managers to support multipath hardware.
 
+config DM_RDAC
+       tristate "IBM FAStT RDAC/AVT (EXPERIMENTAL)"
+       depends on BLK_DEV_DM && DM_MULTIPATH && EXPERIMENTAL
+       ---help---
+         IBM FAStT RDAC/AVT support for DM Multipath.
+
 config DM_SNAPSHOT
        tristate "Snapshot target (EXPERIMENTAL)"
        depends on BLK_DEV_DM && EXPERIMENTAL
diff -Naurp linux-2.6.5-rc1-udm1-orig/drivers/md/Makefile linux-2.6.5-rc1-udm1-work/drivers/md/Makefile
--- linux-2.6.5-rc1-udm1-orig/drivers/md/Makefile	2004-04-02 01:24:19.000000000 -0800
+++ linux-2.6.5-rc1-udm1-work/drivers/md/Makefile	2004-04-04 12:23:51.382707192 -0700
@@ -28,6 +28,7 @@ obj-$(CONFIG_BLK_DEV_MD)	+= md.o
 obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o
 obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
 obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o
+obj-$(CONFIG_DM_RDAC)		+= rdac.o
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
 obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
diff -Naurp linux-2.6.5-rc1-udm1-orig/drivers/md/rdac.c linux-2.6.5-rc1-udm1-work/drivers/md/rdac.c
--- linux-2.6.5-rc1-udm1-orig/drivers/md/rdac.c	1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.5-rc1-udm1-work/drivers/md/rdac.c	2004-04-04 12:23:43.496010731 -0700
@@ -0,0 +1,292 @@
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+
+#include "dm.h"
+#include "dm-path-selector.h"
+
+struct path_info {
+	struct list_head list;
+	struct path *path;
+
+	unsigned fail_count;
+};
+
+static struct path_info *path_lookup(struct list_head *head, struct path *p)
+{
+	struct path_info *pi;
+
+	list_for_each_entry (pi, head, list)
+		if (pi->path == p)
+			return pi;
+
+	return NULL;
+}
+
+/* FIXME: get rid of this */
+#define MPATH_FAIL_COUNT	1
+
+/* Failover modes */
+enum {
+	NONE,
+	AVT,
+	RDAC,
+};
+
+struct selector {
+	spinlock_t path_lock;
+	
+	struct list_head active_paths;
+	struct list_head failed_paths;
+
+	int failover;
+};
+
+static struct selector *alloc_selector(void)
+{
+	struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
+
+	if (s) {
+		INIT_LIST_HEAD(&s->active_paths);
+		INIT_LIST_HEAD(&s->failed_paths);
+		s->path_lock = SPIN_LOCK_UNLOCKED;
+		/*
+		 * TODO modify arg passing.
+		 */
+		s->failover = RDAC;
+	}
+
+	return s;
+}
+
+static int rdac_ctr(struct path_selector *ps)
+{
+	struct selector *s;
+
+	s = alloc_selector();
+	if (!s)
+		return -ENOMEM;
+
+	ps->context = s;
+	return 0;
+}
+
+static void free_paths(struct list_head *paths)
+{
+	struct path_info *pi, *next;
+
+	list_for_each_entry_safe (pi, next, paths, list) {
+		list_del(&pi->list);
+		kfree(pi);
+	}
+}
+
+static void rdac_dtr(struct path_selector *ps)
+{
+	struct selector *s = (struct selector *) ps->context;
+	free_paths(&s->active_paths);
+	free_paths(&s->failed_paths);
+	kfree(s);
+}
+
+static int send_failover_cmd(struct block_device *bdev)
+{
+	struct request *rq;
+	request_queue_t *q = bdev_get_queue(bdev);
+	struct gendisk *bd_disk = bdev->bd_contains->bd_disk;
+	int err;
+	/* tmp test */
+	char sense[SCSI_SENSE_BUFFERSIZE];
+	static unsigned char tur_command[6] = {TEST_UNIT_READY, 0, 0, 0, 0, 0};
+
+	printk (KERN_ERR "get_request\n");
+
+	if (!q)
+		return -EPERM;
+
+	rq = blk_get_request(q, READ, __GFP_WAIT);
+
+	printk (KERN_ERR "got it\n");
+
+
+	memcpy(rq->cmd, tur_command, sizeof(tur_command));
+	rq->cmd_len = COMMAND_SIZE(rq->cmd[0]);
+
+	memset(sense, 0, sizeof(sense));
+	rq->sense = sense;
+	rq->sense_len = 0;
+
+	rq->data = NULL;
+	rq->data_len = 0;
+
+//	rq->data = buffer;
+//	rq->data_len = bytes;
+	rq->flags |= REQ_BLOCK_PC;
+
+	printk (KERN_ERR "sending\n");
+
+	err = blk_execute_rq(q, bd_disk, rq);
+	if (rq->errors)
+		printk(KERN_ERR "send_failover_cmd failed\n");
+	else
+		printk(KERN_ERR "send_failover_cmd succeeded\n");
+	blk_put_request(rq);
+
+	return err;
+}
+
+static int rdac_init(struct path_selector *ps)
+{
+	struct selector *s = (struct selector *) ps->context;
+	struct path_info *pi;
+
+	if (s->failover != RDAC)
+		return 0;
+
+	/*
+	 * This is called before any IO has been sent to
+	 * these paths and after all paths have been added,
+	 * so we do not need to hold the path lock.
+	 */
+	while (!list_empty(&s->active_paths)) {
+		pi = list_entry(s->active_paths.next, struct path_info, list);
+		
+		if (!send_failover_cmd(dm_path_to_bdev(pi->path)))
+			return 0;
+		else
+			list_move(&pi->list, &s->failed_paths);
+	}
+
+	return -EPERM;
+}
+
+static int rdac_add_path(struct path_selector *ps, struct path *path,
+			 int argc, char **argv, char **error)
+{
+	struct selector *s = (struct selector *) ps->context;
+	struct path_info *pi;
+
+	/* parse the path arguments */
+	if (argc != 0) {
+		*error = "rdac ps: incorrect number of arguments";
+		return -EINVAL;
+	}
+
+	/* allocate the path */
+	pi = kmalloc(sizeof(*pi), GFP_KERNEL);
+	if (!pi) {
+		*error = "rdac ps: Error allocating path context";
+		return -ENOMEM;
+	}
+
+	pi->fail_count = MPATH_FAIL_COUNT;
+	pi->path = path;
+
+	spin_lock(&s->path_lock);
+	list_add(&pi->list, &s->active_paths);
+	spin_unlock(&s->path_lock);
+
+	return 0;
+}
+
+static void rdac_update_path(struct path_selector *ps, struct path *p,
+			     int error)
+{
+	unsigned long flags;
+	struct selector *s = (struct selector *) ps->context;
+	struct path_info *pi;
+
+	/*
+	 * This function will be called infrequently so we don't
+	 * mind the expense of these searches.
+	 */
+	spin_lock_irqsave(&s->path_lock, flags);
+
+	pi = path_lookup(&s->active_paths, p);
+	if (pi && !--pi->fail_count)
+		list_move(&pi->list, &s->failed_paths);
+
+	spin_unlock_irqrestore(&s->path_lock, flags);
+}
+
+static struct path *rdac_select_path(struct path_selector *ps)
+{
+	unsigned long flags;
+	struct selector *s = (struct selector *) ps->context;
+	struct path_info *pi = NULL;
+
+	spin_lock_irqsave(&s->path_lock, flags);
+	if (!list_empty(&s->active_paths)) {
+		pi = list_entry(s->active_paths.next, struct path_info, list);
+		list_move_tail(&pi->list, &s->active_paths);
+	}
+	spin_unlock_irqrestore(&s->path_lock, flags);
+
+	return pi ? pi->path : NULL;
+}
+
+static int rdac_status(struct path_selector *ps, struct path *path,
+		       status_type_t type, char *result, unsigned int maxlen)
+{
+	unsigned long flags;
+	struct path_info *pi;
+	int failed = 0;
+	struct selector *s = (struct selector *) ps->context;
+	int sz = 0;
+
+	if (type == STATUSTYPE_TABLE)
+		return 0;
+
+	spin_lock_irqsave(&s->path_lock, flags);
+
+	/*
+	 * Is status called often for testing or something?
+	 * If so maybe a ps's info should be allocated w/ path
+	 * so a simple container_of can be used.
+	 */
+	pi = path_lookup(&s->active_paths, path);
+	if (!pi) {
+		failed = 1;
+		pi = path_lookup(&s->failed_paths, path);
+	}
+
+	sz = scnprintf(result, maxlen, "%s %u ", failed ? "F" : "A",
+		       pi->fail_count);
+
+	spin_unlock_irqrestore(&s->path_lock, flags);
+
+	return sz;
+}
+
+static struct path_selector_type rdac_ps = {
+	.name = "rdac",
+	.ctr = rdac_ctr,
+	.init = rdac_init,
+	.dtr = rdac_dtr,
+	.add_path = rdac_add_path,
+	.update_path = rdac_update_path,
+	.select_path = rdac_select_path,
+	.status = rdac_status,
+};
+
+int __init init_rdac(void)
+{
+	return dm_register_path_selector(&rdac_ps);
+}
+
+void __exit exit_rdac(void)
+{
+	dm_unregister_path_selector(&rdac_ps);
+}
+
+module_init(init_rdac);
+module_exit(exit_rdac);
+
+MODULE_DESCRIPTION("RDAC/AVT Path Selector");
+MODULE_AUTHOR("Mike Christie");
+MODULE_LICENSE("GPL");