Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1302 insertions, 0 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
new file mode 100644
index 00000000000..43763a0bd09
--- /dev/null
+++ b/drivers/md/dm-mpath.c
@@ -0,0 +1,1302 @@
+/*
+ * Copyright (C) 2003 Sistina Software Limited.
+ * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include "dm-path-selector.h"
+#include "dm-hw-handler.h"
+#include "dm-bio-list.h"
+#include "dm-bio-record.h"
+
+#include <linux/ctype.h>
+#include <linux/init.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/time.h>
+#include <linux/workqueue.h>
+#include <asm/atomic.h>
+
+#define MESG_STR(x) x, sizeof(x)
+
+/* Path properties */
+struct pgpath {
+	struct list_head list;
+
+	struct priority_group *pg;	/* Owning PG */
+	unsigned fail_count;		/* Cumulative failure count */
+
+	struct path path;
+};
+
+#define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
+
+/*
+ * Paths are grouped into Priority Groups and numbered from 1 upwards.
+ * Each has a path selector which controls which path gets used.
+ */
+struct priority_group {
+	struct list_head list;
+
+	struct multipath *m;		/* Owning multipath instance */
+	struct path_selector ps;
+
+	unsigned pg_num;		/* Reference number */
+	unsigned bypassed;		/* Temporarily bypass this PG? */
+
+	unsigned nr_pgpaths;		/* Number of paths in PG */
+	struct list_head pgpaths;
+};
+
+/* Multipath context */
+struct multipath {
+	struct list_head list;
+	struct dm_target *ti;
+
+	spinlock_t lock;
+
+	struct hw_handler hw_handler;
+	unsigned nr_priority_groups;
+	struct list_head priority_groups;
+	unsigned pg_init_required;	/* pg_init needs calling? */
+
+	unsigned nr_valid_paths;	/* Total number of usable paths */
+	struct pgpath *current_pgpath;
+	struct priority_group *current_pg;
+	struct priority_group *next_pg;	/* Switch to this PG if set */
+	unsigned repeat_count;		/* I/Os left before calling PS again */
+
+	unsigned queue_io;		/* Must we queue all I/O? */
+	unsigned queue_if_no_path;	/* Queue I/O if last path fails? */
+	unsigned suspended;		/* Has dm core suspended our I/O? */
+
+	struct work_struct process_queued_ios;
+	struct bio_list queued_ios;
+	unsigned queue_size;
+
+	struct work_struct trigger_event;
+
+	/*
+	 * We must use a mempool of mpath_io structs so that we
+	 * can resubmit bios on error.
+	 */
+	mempool_t *mpio_pool;
+};
+
+/*
+ * Context information attached to each bio we process.
+ */
+struct mpath_io {
+	struct pgpath *pgpath;
+	struct dm_bio_details details;
+};
+
+typedef int (*action_fn) (struct pgpath *pgpath);
+
+#define MIN_IOS 256	/* Mempool size */
+
+static kmem_cache_t *_mpio_cache;
+
+static void process_queued_ios(void *data);
+static void trigger_event(void *data);
+
+
+/*-----------------------------------------------
+ * Allocation routines
+ *-----------------------------------------------*/
+
+static struct pgpath *alloc_pgpath(void)
+{
+	struct pgpath *pgpath = kmalloc(sizeof(*pgpath), GFP_KERNEL);
+
+	if (pgpath) {
+		memset(pgpath, 0, sizeof(*pgpath));
+		pgpath->path.is_active = 1;
+	}
+
+	return pgpath;
+}
+
+static inline void free_pgpath(struct pgpath *pgpath)
+{
+	kfree(pgpath);
+}
+
+static struct priority_group *alloc_priority_group(void)
+{
+	struct priority_group *pg;
+
+	pg = kmalloc(sizeof(*pg), GFP_KERNEL);
+	if (!pg)
+		return NULL;
+
+	memset(pg, 0, sizeof(*pg));
+	INIT_LIST_HEAD(&pg->pgpaths);
+
+	return pg;
+}
+
+static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
+{
+	struct pgpath *pgpath, *tmp;
+
+	list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
+		list_del(&pgpath->list);
+		dm_put_device(ti, pgpath->path.dev);
+		free_pgpath(pgpath);
+	}
+}
+
+static void free_priority_group(struct priority_group *pg,
+				struct dm_target *ti)
+{
+	struct path_selector *ps = &pg->ps;
+
+	if (ps->type) {
+		ps->type->destroy(ps);
+		dm_put_path_selector(ps->type);
+	}
+
+	free_pgpaths(&pg->pgpaths, ti);
+	kfree(pg);
+}
+
+static struct multipath *alloc_multipath(void)
+{
+	struct multipath *m;
+
+	m = kmalloc(sizeof(*m), GFP_KERNEL);
+	if (m) {
+		memset(m, 0, sizeof(*m));
+		INIT_LIST_HEAD(&m->priority_groups);
+		spin_lock_init(&m->lock);
+		m->queue_io = 1;
+		INIT_WORK(&m->process_queued_ios, process_queued_ios, m);
+		INIT_WORK(&m->trigger_event, trigger_event, m);
+		m->mpio_pool = mempool_create(MIN_IOS, mempool_alloc_slab,
+					      mempool_free_slab, _mpio_cache);
+		if (!m->mpio_pool) {
+			kfree(m);
+			return NULL;
+		}
+	}
+
+	return m;
+}
+
+static void free_multipath(struct multipath *m)
+{
+	struct priority_group *pg, *tmp;
+	struct hw_handler *hwh = &m->hw_handler;
+
+	list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
+		list_del(&pg->list);
+		free_priority_group(pg, m->ti);
+	}
+
+	if (hwh->type) {
+		hwh->type->destroy(hwh);
+		dm_put_hw_handler(hwh->type);
+	}
+
+	mempool_destroy(m->mpio_pool);
+	kfree(m);
+}
+
+
+/*-----------------------------------------------
+ * Path selection
+ *-----------------------------------------------*/
+
+static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
+{
+	struct hw_handler *hwh = &m->hw_handler;
+
+	m->current_pg = pgpath->pg;
+
+	/* Must we initialise the PG first, and queue I/O till it's ready? */
+	if (hwh->type && hwh->type->pg_init) {
+		m->pg_init_required = 1;
+		m->queue_io = 1;
+	} else {
+		m->pg_init_required = 0;
+		m->queue_io = 0;
+	}
+}
+
+static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
+{
+	struct path *path;
+
+	path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
+	if (!path)
+		return -ENXIO;
+
+	m->current_pgpath = path_to_pgpath(path);
+
+	if (m->current_pg != pg)
+		__switch_pg(m, m->current_pgpath);
+
+	return 0;
+}
+
+static void __choose_pgpath(struct multipath *m)
+{
+	struct priority_group *pg;
+	unsigned bypassed = 1;
+
+	if (!m->nr_valid_paths)
+		goto failed;
+
+	/* Were we instructed to switch PG? */
+	if (m->next_pg) {
+		pg = m->next_pg;
+		m->next_pg = NULL;
+		if (!__choose_path_in_pg(m, pg))
+			return;
+	}
+
+	/* Don't change PG until it has no remaining paths */
+	if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
+		return;
+
+	/*
+	 * Loop through priority groups until we find a valid path.
+	 * First time we skip PGs marked 'bypassed'.
+	 * Second time we only try the ones we skipped.
+	 */
+	do {
+		list_for_each_entry(pg, &m->priority_groups, list) {
+			if (pg->bypassed == bypassed)
+				continue;
+			if (!__choose_path_in_pg(m, pg))
+				return;
+		}
+	} while (bypassed--);
+
+failed:
+	m->current_pgpath = NULL;
+	m->current_pg = NULL;
+}
+
+static int map_io(struct multipath *m, struct bio *bio, struct mpath_io *mpio,
+		  unsigned was_queued)
+{
+	int r = 1;
+	unsigned long flags;
+	struct pgpath *pgpath;
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	/* Do we need to select a new pgpath? */
+	if (!m->current_pgpath ||
+	    (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
+		__choose_pgpath(m);
+
+	pgpath = m->current_pgpath;
+
+	if (was_queued)
+		m->queue_size--;
+
+	if ((pgpath && m->queue_io) ||
+	    (!pgpath && m->queue_if_no_path && !m->suspended)) {
+		/* Queue for the daemon to resubmit */
+		bio_list_add(&m->queued_ios, bio);
+		m->queue_size++;
+		if (m->pg_init_required || !m->queue_io)
+			schedule_work(&m->process_queued_ios);
+		pgpath = NULL;
+		r = 0;
+	} else if (!pgpath)
+		r = -EIO;		/* Failed */
+	else
+		bio->bi_bdev = pgpath->path.dev->bdev;
+
+	mpio->pgpath = pgpath;
+
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	return r;
+}
+
+/*
+ * If we run out of usable paths, should we queue I/O or error it?
+ */
+static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	m->queue_if_no_path = queue_if_no_path;
+	if (!m->queue_if_no_path)
+		schedule_work(&m->process_queued_ios);
+
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	return 0;
+}
+
+/*-----------------------------------------------------------------
+ * The multipath daemon is responsible for resubmitting queued ios.
+ *---------------------------------------------------------------*/
+
+static void dispatch_queued_ios(struct multipath *m)
+{
+	int r;
+	unsigned long flags;
+	struct bio *bio = NULL, *next;
+	struct mpath_io *mpio;
+	union map_info *info;
+
+	spin_lock_irqsave(&m->lock, flags);
+	bio = bio_list_get(&m->queued_ios);
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	while (bio) {
+		next = bio->bi_next;
+		bio->bi_next = NULL;
+
+		info = dm_get_mapinfo(bio);
+		mpio = info->ptr;
+
+		r = map_io(m, bio, mpio, 1);
+		if (r < 0)
+			bio_endio(bio, bio->bi_size, r);
+		else if (r == 1)
+			generic_make_request(bio);
+
+		bio = next;
+	}
+}
+
+static void process_queued_ios(void *data)
+{
+	struct multipath *m = (struct multipath *) data;
+	struct hw_handler *hwh = &m->hw_handler;
+	struct pgpath *pgpath;
+	unsigned init_required, must_queue = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	if (!m->current_pgpath)
+		__choose_pgpath(m);
+
+	pgpath = m->current_pgpath;
+
+	if ((pgpath && m->queue_io) ||
+	    (!pgpath && m->queue_if_no_path && !m->suspended))
+		must_queue = 1;
+
+	init_required = m->pg_init_required;
+	if (init_required)
+		m->pg_init_required = 0;
+
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	if (init_required)
+		hwh->type->pg_init(hwh, pgpath->pg->bypassed, &pgpath->path);
+
+	if (!must_queue)
+		dispatch_queued_ios(m);
+}
+
+/*
+ * An event is triggered whenever a path is taken out of use.
+ * Includes path failure and PG bypass.
+ */
+static void trigger_event(void *data)
+{
+	struct multipath *m = (struct multipath *) data;
+
+	dm_table_event(m->ti->table);
+}
+
+/*-----------------------------------------------------------------
+ * Constructor/argument parsing:
+ * <#multipath feature args> [<arg>]*
+ * <#hw_handler args> [hw_handler [<arg>]*]
+ * <#priority groups>
+ * <initial priority group>
+ *     [<selector> <#selector args> [<arg>]*
+ *      <#paths> <#per-path selector args>
+ *         [<path> [<arg>]* ]+ ]+
+ *---------------------------------------------------------------*/
+struct param {
+	unsigned min;
+	unsigned max;
+	char *error;
+};
+
+#define ESTR(s) ("dm-multipath: " s)
+
+static int read_param(struct param *param, char *str, unsigned *v, char **error)
+{
+	if (!str ||
+	    (sscanf(str, "%u", v) != 1) ||
+	    (*v < param->min) ||
+	    (*v > param->max)) {
+		*error = param->error;
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+struct arg_set {
+	unsigned argc;
+	char **argv;
+};
+
+static char *shift(struct arg_set *as)
+{
+	char *r;
+
+	if (as->argc) {
+		as->argc--;
+		r = *as->argv;
+		as->argv++;
+		return r;
+	}
+
+	return NULL;
+}
+
+static void consume(struct arg_set *as, unsigned n)
+{
+	BUG_ON (as->argc < n);
+	as->argc -= n;
+	as->argv += n;
+}
+
+static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
+			       struct dm_target *ti)
+{
+	int r;
+	struct path_selector_type *pst;
+	unsigned ps_argc;
+
+	static struct param _params[] = {
+		{0, 1024, ESTR("invalid number of path selector args")},
+	};
+
+	pst = dm_get_path_selector(shift(as));
+	if (!pst) {
+		ti->error = ESTR("unknown path selector type");
+		return -EINVAL;
+	}
+
+	r = read_param(_params, shift(as), &ps_argc, &ti->error);
+	if (r)
+		return -EINVAL;
+
+	r = pst->create(&pg->ps, ps_argc, as->argv);
+	if (r) {
+		dm_put_path_selector(pst);
+		ti->error = ESTR("path selector constructor failed");
+		return r;
+	}
+
+	pg->ps.type = pst;
+	consume(as, ps_argc);
+
+	return 0;
+}
+
+static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
+			       struct dm_target *ti)
+{
+	int r;
+	struct pgpath *p;
+
+	/* we need at least a path arg */
+	if (as->argc < 1) {
+		ti->error = ESTR("no device given");
+		return NULL;
+	}
+
+	p = alloc_pgpath();
+	if (!p)
+		return NULL;
+
+	r = dm_get_device(ti, shift(as), ti->begin, ti->len,
+			  dm_table_get_mode(ti->table), &p->path.dev);
+	if (r) {
+		ti->error = ESTR("error getting device");
+		goto bad;
+	}
+
+	r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
+	if (r) {
+		dm_put_device(ti, p->path.dev);
+		goto bad;
+	}
+
+	return p;
+
+ bad:
+	free_pgpath(p);
+	return NULL;
+}
+
+static struct priority_group *parse_priority_group(struct arg_set *as,
+						   struct multipath *m,
+						   struct dm_target *ti)
+{
+	static struct param _params[] = {
+		{1, 1024, ESTR("invalid number of paths")},
+		{0, 1024, ESTR("invalid number of selector args")}
+	};
+
+	int r;
+	unsigned i, nr_selector_args, nr_params;
+	struct priority_group *pg;
+
+	if (as->argc < 2) {
+		as->argc = 0;
+		ti->error = ESTR("not enough priority group aruments");
+		return NULL;
+	}
+
+	pg = alloc_priority_group();
+	if (!pg) {
+		ti->error = ESTR("couldn't allocate priority group");
+		return NULL;
+	}
+	pg->m = m;
+
+	r = parse_path_selector(as, pg, ti);
+	if (r)
+		goto bad;
+
+	/*
+	 * read the paths
+	 */
+	r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
+	if (r)
+		goto bad;
+
+	r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
+	if (r)
+		goto bad;
+
+	nr_params = 1 + nr_selector_args;
+	for (i = 0; i < pg->nr_pgpaths; i++) {
+		struct pgpath *pgpath;
+		struct arg_set path_args;
+
+		if (as->argc < nr_params)
+			goto bad;
+
+		path_args.argc = nr_params;
+		path_args.argv = as->argv;
+
+		pgpath = parse_path(&path_args, &pg->ps, ti);
+		if (!pgpath)
+			goto bad;
+
+		pgpath->pg = pg;
+		list_add_tail(&pgpath->list, &pg->pgpaths);
+		consume(as, nr_params);
+	}
+
+	return pg;
+
+ bad:
+	free_priority_group(pg, ti);
+	return NULL;
+}
+
+static int parse_hw_handler(struct arg_set *as, struct multipath *m,
+			    struct dm_target *ti)
+{
+	int r;
+	struct hw_handler_type *hwht;
+	unsigned hw_argc;
+
+	static struct param _params[] = {
+		{0, 1024, ESTR("invalid number of hardware handler args")},
+	};
+
+	r = read_param(_params, shift(as), &hw_argc, &ti->error);
+	if (r)
+		return -EINVAL;
+
+	if (!hw_argc)
+		return 0;
+
+	hwht = dm_get_hw_handler(shift(as));
+	if (!hwht) {
+		ti->error = ESTR("unknown hardware handler type");
+		return -EINVAL;
+	}
+
+	r = hwht->create(&m->hw_handler, hw_argc - 1, as->argv);
+	if (r) {
+		dm_put_hw_handler(hwht);
+		ti->error = ESTR("hardware handler constructor failed");
+		return r;
+	}
+
+	m->hw_handler.type = hwht;
+	consume(as, hw_argc - 1);
+
+	return 0;
+}
+
+static int parse_features(struct arg_set *as, struct multipath *m,
+			  struct dm_target *ti)
+{
+	int r;
+	unsigned argc;
+
+	static struct param _params[] = {
+		{0, 1, ESTR("invalid number of feature args")},
+	};
+
+	r = read_param(_params, shift(as), &argc, &ti->error);
+	if (r)
+		return -EINVAL;
+
+	if (!argc)
+		return 0;
+
+	if (!strnicmp(shift(as), MESG_STR("queue_if_no_path")))
+		return queue_if_no_path(m, 1);
+	else {
+		ti->error = "Unrecognised multipath feature request";
+		return -EINVAL;
+	}
+}
+
+static int multipath_ctr(struct dm_target *ti, unsigned int argc,
+			 char **argv)
+{
+	/* target parameters */
+	static struct param _params[] = {
+		{1, 1024, ESTR("invalid number of priority groups")},
+		{1, 1024, ESTR("invalid initial priority group number")},
+	};
+
+	int r;
+	struct multipath *m;
+	struct arg_set as;
+	unsigned pg_count = 0;
+	unsigned next_pg_num;
+
+	as.argc = argc;
+	as.argv = argv;
+
+	m = alloc_multipath();
+	if (!m) {
+		ti->error = ESTR("can't allocate multipath");
+		return -EINVAL;
+	}
+
+	r = parse_features(&as, m, ti);
+	if (r)
+		goto bad;
+
+	r = parse_hw_handler(&as, m, ti);
+	if (r)
+		goto bad;
+
+	r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
+	if (r)
+		goto bad;
+
+	r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
+	if (r)
+		goto bad;
+
+	/* parse the priority groups */
+	while (as.argc) {
+		struct priority_group *pg;
+
+		pg = parse_priority_group(&as, m, ti);
+		if (!pg) {
+			r = -EINVAL;
+			goto bad;
+		}
+
+		m->nr_valid_paths += pg->nr_pgpaths;
+		list_add_tail(&pg->list, &m->priority_groups);
+		pg_count++;
+		pg->pg_num = pg_count;
+		if (!--next_pg_num)
+			m->next_pg = pg;
+	}
+
+	if (pg_count != m->nr_priority_groups) {
+		ti->error = ESTR("priority group count mismatch");
+		r = -EINVAL;
+		goto bad;
+	}
+
+	ti->private = m;
+	m->ti = ti;
+
+	return 0;
+
+ bad:
+	free_multipath(m);
+	return r;
+}
+
+static void multipath_dtr(struct dm_target *ti)
+{
+	struct multipath *m = (struct multipath *) ti->private;
+	free_multipath(m);
+}
+
+/*
+ * Map bios, recording original fields for later in case we have to resubmit
+ */
+static int multipath_map(struct dm_target *ti, struct bio *bio,
+			 union map_info *map_context)
+{
+	int r;
+	struct mpath_io *mpio;
+	struct multipath *m = (struct multipath *) ti->private;
+
+	mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
+	dm_bio_record(&mpio->details, bio);
+
+	map_context->ptr = mpio;
+	bio->bi_rw |= (1 << BIO_RW_FAILFAST);
+	r = map_io(m, bio, mpio, 0);
+	if (r < 0)
+		mempool_free(mpio, m->mpio_pool);
+
+	return r;
+}
+
+/*
+ * Take a path out of use.
+ */
+static int fail_path(struct pgpath *pgpath)
+{
+	unsigned long flags;
+	struct multipath *m = pgpath->pg->m;
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	if (!pgpath->path.is_active)
+		goto out;
+
+	DMWARN("dm-multipath: Failing path %s.", pgpath->path.dev->name);
+
+	pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
+	pgpath->path.is_active = 0;
+	pgpath->fail_count++;
+
+	m->nr_valid_paths--;
+
+	if (pgpath == m->current_pgpath)
+		m->current_pgpath = NULL;
+
+	schedule_work(&m->trigger_event);
+
+out:
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	return 0;
+}
+
+/*
+ * Reinstate a previously-failed path
+ */
+static int reinstate_path(struct pgpath *pgpath)
+{
+	int r = 0;
+	unsigned long flags;
+	struct multipath *m = pgpath->pg->m;
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	if (pgpath->path.is_active)
+		goto out;
+
+	if (!pgpath->pg->ps.type) {
+		DMWARN("Reinstate path not supported by path selector %s",
+		       pgpath->pg->ps.type->name);
+		r = -EINVAL;
+		goto out;
+	}
+
+	r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
+	if (r)
+		goto out;
+
+	pgpath->path.is_active = 1;
+
+	m->current_pgpath = NULL;
+	if (!m->nr_valid_paths++)
+		schedule_work(&m->process_queued_ios);
+
+	schedule_work(&m->trigger_event);
+
+out:
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	return r;
+}
+
+/*
+ * Fail or reinstate all paths that match the provided struct dm_dev.
+ */
+static int action_dev(struct multipath *m, struct dm_dev *dev,
+		      action_fn action)
+{
+	int r = 0;
+	struct pgpath *pgpath;
+	struct priority_group *pg;
+
+	list_for_each_entry(pg, &m->priority_groups, list) {
+		list_for_each_entry(pgpath, &pg->pgpaths, list) {
+			if (pgpath->path.dev == dev)
+				r = action(pgpath);
+		}
+	}
+
+	return r;
+}
+
+/*
+ * Temporarily try to avoid having to use the specified PG
+ */
+static void bypass_pg(struct multipath *m, struct priority_group *pg,
+		      int bypassed)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	pg->bypassed = bypassed;
+	m->current_pgpath = NULL;
+	m->current_pg = NULL;
+
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	schedule_work(&m->trigger_event);
+}
+
+/*
+ * Switch to using the specified PG from the next I/O that gets mapped
+ */
+static int switch_pg_num(struct multipath *m, const char *pgstr)
+{
+	struct priority_group *pg;
+	unsigned pgnum;
+	unsigned long flags;
+
+	if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
+	    (pgnum > m->nr_priority_groups)) {
+		DMWARN("invalid PG number supplied to switch_pg_num");
+		return -EINVAL;
+	}
+
+	spin_lock_irqsave(&m->lock, flags);
+	list_for_each_entry(pg, &m->priority_groups, list) {
+		pg->bypassed = 0;
+		if (--pgnum)
+			continue;
+
+		m->current_pgpath = NULL;
+		m->current_pg = NULL;
+		m->next_pg = pg;
+	}
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	schedule_work(&m->trigger_event);
+	return 0;
+}
+
+/*
+ * Set/clear bypassed status of a PG.
+ * PGs are numbered upwards from 1 in the order they were declared.
+ */
+static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
+{
+	struct priority_group *pg;
+	unsigned pgnum;
+
+	if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
+	    (pgnum > m->nr_priority_groups)) {
+		DMWARN("invalid PG number supplied to bypass_pg");
+		return -EINVAL;
+	}
+
+	list_for_each_entry(pg, &m->priority_groups, list) {
+		if (!--pgnum)
+			break;
+	}
+
+	bypass_pg(m, pg, bypassed);
+	return 0;
+}
+
+/*
+ * pg_init must call this when it has completed its initialisation
+ */
+void dm_pg_init_complete(struct path *path, unsigned err_flags)
+{
+	struct pgpath *pgpath = path_to_pgpath(path);
+	struct priority_group *pg = pgpath->pg;
+	struct multipath *m = pg->m;
+	unsigned long flags;
+
+	/* We insist on failing the path if the PG is already bypassed. */
+	if (err_flags && pg->bypassed)
+		err_flags |= MP_FAIL_PATH;
+
+	if (err_flags & MP_FAIL_PATH)
+		fail_path(pgpath);
+
+	if (err_flags & MP_BYPASS_PG)
+		bypass_pg(m, pg, 1);
+
+	spin_lock_irqsave(&m->lock, flags);
+	if (!err_flags)
+		m->queue_io = 0;
+	else {
+		m->current_pgpath = NULL;
+		m->current_pg = NULL;
+	}
+	schedule_work(&m->process_queued_ios);
+	spin_unlock_irqrestore(&m->lock, flags);
+}
+
+/*
+ * end_io handling
+ */
+static int do_end_io(struct multipath *m, struct bio *bio,
+		     int error, struct mpath_io *mpio)
+{
+	struct hw_handler *hwh = &m->hw_handler;
+	unsigned err_flags = MP_FAIL_PATH;	/* Default behavior */
+
+	if (!error)
+		return 0;	/* I/O complete */
+
+	spin_lock(&m->lock);
+	if (!m->nr_valid_paths) {
+		if (!m->queue_if_no_path || m->suspended) {
+			spin_unlock(&m->lock);
+			return -EIO;
+		} else {
+			spin_unlock(&m->lock);
+			goto requeue;
+		}
+	}
+	spin_unlock(&m->lock);
+
+	if (hwh->type && hwh->type->error)
+		err_flags = hwh->type->error(hwh, bio);
+
+	if (mpio->pgpath) {
+		if (err_flags & MP_FAIL_PATH)
+			fail_path(mpio->pgpath);
+
+		if (err_flags & MP_BYPASS_PG)
+			bypass_pg(m, mpio->pgpath->pg, 1);
+	}
+
+	if (err_flags & MP_ERROR_IO)
+		return -EIO;
+
+      requeue:
+	dm_bio_restore(&mpio->details, bio);
+
+	/* queue for the daemon to resubmit or fail */
+	spin_lock(&m->lock);
+	bio_list_add(&m->queued_ios, bio);
+	m->queue_size++;
+	if (!m->queue_io)
+		schedule_work(&m->process_queued_ios);
+	spin_unlock(&m->lock);
+
+	return 1;	/* io not complete */
+}
+
+static int multipath_end_io(struct dm_target *ti, struct bio *bio,
+			    int error, union map_info *map_context)
+{
+	struct multipath *m = (struct multipath *) ti->private;
+	struct mpath_io *mpio = (struct mpath_io *) map_context->ptr;
+	struct pgpath *pgpath = mpio->pgpath;
+	struct path_selector *ps;
+	int r;
+
+	r  = do_end_io(m, bio, error, mpio);
+	if (pgpath) {
+		ps = &pgpath->pg->ps;
+		if (ps->type->end_io)
+			ps->type->end_io(ps, &pgpath->path);
+	}
+	if (r <= 0)
+		mempool_free(mpio, m->mpio_pool);
+
+	return r;
+}
+
+/*
+ * Suspend can't complete until all the I/O is processed so if
+ * the last path failed we will now error any queued I/O.
+ */
+static void multipath_presuspend(struct dm_target *ti)
+{
+	struct multipath *m = (struct multipath *) ti->private;
+	unsigned long flags;
+
+	spin_lock_irqsave(&m->lock, flags);
+	m->suspended = 1;
+	if (m->queue_if_no_path)
+		schedule_work(&m->process_queued_ios);
+	spin_unlock_irqrestore(&m->lock, flags);
+}
+
+static void multipath_resume(struct dm_target *ti)
+{
+	struct multipath *m = (struct multipath *) ti->private;
+	unsigned long flags;
+
+	spin_lock_irqsave(&m->lock, flags);
+	m->suspended = 0;
+	spin_unlock_irqrestore(&m->lock, flags);
+}
+
+/*
+ * Info output has the following format:
+ * num_multipath_feature_args [multipath_feature_args]*
+ * num_handler_status_args [handler_status_args]*
+ * num_groups init_group_number
+ *            [A|D|E num_ps_status_args [ps_status_args]*
+ *             num_paths num_selector_args
+ *             [path_dev A|F fail_count [selector_args]* ]+ ]+
+ *
+ * Table output has the following format (identical to the constructor string):
+ * num_feature_args [features_args]*
+ * num_handler_args hw_handler [hw_handler_args]*
+ * num_groups init_group_number
+ *     [priority selector-name num_ps_args [ps_args]*
+ *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
+ */
+static int multipath_status(struct dm_target *ti, status_type_t type,
+			    char *result, unsigned int maxlen)
+{
+	int sz = 0;
+	unsigned long flags;
+	struct multipath *m = (struct multipath *) ti->private;
+	struct hw_handler *hwh = &m->hw_handler;
+	struct priority_group *pg;
+	struct pgpath *p;
+	unsigned pg_num;
+	char state;
+
+	spin_lock_irqsave(&m->lock, flags);
+
+	/* Features */
+	if (type == STATUSTYPE_INFO)
+		DMEMIT("1 %u ", m->queue_size);
+	else if (m->queue_if_no_path)
+		DMEMIT("1 queue_if_no_path ");
+	else
+		DMEMIT("0 ");
+
+	if (hwh->type && hwh->type->status)
+		sz += hwh->type->status(hwh, type, result + sz, maxlen - sz);
+	else if (!hwh->type || type == STATUSTYPE_INFO)
+		DMEMIT("0 ");
+	else
+		DMEMIT("1 %s ", hwh->type->name);
+
+	DMEMIT("%u ", m->nr_priority_groups);
+
+	if (m->next_pg)
+		pg_num = m->next_pg->pg_num;
+	else if (m->current_pg)
+		pg_num = m->current_pg->pg_num;
+	else
+			pg_num = 1;
+
+	DMEMIT("%u ", pg_num);
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		list_for_each_entry(pg, &m->priority_groups, list) {
+			if (pg->bypassed)
+				state = 'D';	/* Disabled */
+			else if (pg == m->current_pg)
+				state = 'A';	/* Currently Active */
+			else
+				state = 'E';	/* Enabled */
+
+			DMEMIT("%c ", state);
+
+			if (pg->ps.type->status)
+				sz += pg->ps.type->status(&pg->ps, NULL, type,
+							  result + sz,
+							  maxlen - sz);
+			else
+				DMEMIT("0 ");
+
+			DMEMIT("%u %u ", pg->nr_pgpaths,
+			       pg->ps.type->info_args);
+
+			list_for_each_entry(p, &pg->pgpaths, list) {
+				DMEMIT("%s %s %u ", p->path.dev->name,
+				       p->path.is_active ? "A" : "F",
+				       p->fail_count);
+				if (pg->ps.type->status)
+					sz += pg->ps.type->status(&pg->ps,
+					      &p->path, type, result + sz,
+					      maxlen - sz);
+			}
+		}
+		break;
+
+	case STATUSTYPE_TABLE:
+		list_for_each_entry(pg, &m->priority_groups, list) {
+			DMEMIT("%s ", pg->ps.type->name);
+
+			if (pg->ps.type->status)
+				sz += pg->ps.type->status(&pg->ps, NULL, type,
+							  result + sz,
+							  maxlen - sz);
+			else
+				DMEMIT("0 ");
+
+			DMEMIT("%u %u ", pg->nr_pgpaths,
+			       pg->ps.type->table_args);
+
+			list_for_each_entry(p, &pg->pgpaths, list) {
+				DMEMIT("%s ", p->path.dev->name);
+				if (pg->ps.type->status)
+					sz += pg->ps.type->status(&pg->ps,
+					      &p->path, type, result + sz,
+					      maxlen - sz);
+			}
+		}
+		break;
+	}
+
+	spin_unlock_irqrestore(&m->lock, flags);
+
+	return 0;
+}
+
+static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
+{
+	int r;
+	struct dm_dev *dev;
+	struct multipath *m = (struct multipath *) ti->private;
+	action_fn action;
+
+	if (argc == 1) {
+		if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
+			return queue_if_no_path(m, 1);
+		else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
+			return queue_if_no_path(m, 0);
+	}
+
+	if (argc != 2)
+		goto error;
+
+	if (!strnicmp(argv[0], MESG_STR("disable_group")))
+		return bypass_pg_num(m, argv[1], 1);
+	else if (!strnicmp(argv[0], MESG_STR("enable_group")))
+		return bypass_pg_num(m, argv[1], 0);
+	else if (!strnicmp(argv[0], MESG_STR("switch_group")))
+		return switch_pg_num(m, argv[1]);
+	else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
+		action = reinstate_path;
+	else if (!strnicmp(argv[0], MESG_STR("fail_path")))
+		action = fail_path;
+	else
+		goto error;
+
+	r = dm_get_device(ti, argv[1], ti->begin, ti->len,
+			  dm_table_get_mode(ti->table), &dev);
+	if (r) {
+		DMWARN("dm-multipath message: error getting device %s",
+		       argv[1]);
+		return -EINVAL;
+	}
+
+	r = action_dev(m, dev, action);
+
+	dm_put_device(ti, dev);
+
+	return r;
+
+error:
+	DMWARN("Unrecognised multipath message received.");
+	return -EINVAL;
+}
+
+/*-----------------------------------------------------------------
+ * Module setup
+ *---------------------------------------------------------------*/
+static struct target_type multipath_target = {
+	.name = "multipath",
+	.version = {1, 0, 4},
+	.module = THIS_MODULE,
+	.ctr = multipath_ctr,
+	.dtr = multipath_dtr,
+	.map = multipath_map,
+	.end_io = multipath_end_io,
+	.presuspend = multipath_presuspend,
+	.resume = multipath_resume,
+	.status = multipath_status,
+	.message = multipath_message,
+};
+
+static int __init dm_multipath_init(void)
+{
+	int r;
+
+	/* allocate a slab for the dm_ios */
+	_mpio_cache = kmem_cache_create("dm_mpath", sizeof(struct mpath_io),
+					0, 0, NULL, NULL);
+	if (!_mpio_cache)
+		return -ENOMEM;
+
+	r = dm_register_target(&multipath_target);
+	if (r < 0) {
+		DMERR("%s: register failed %d", multipath_target.name, r);
+		kmem_cache_destroy(_mpio_cache);
+		return -EINVAL;
+	}
+
+	DMINFO("dm-multipath version %u.%u.%u loaded",
+	       multipath_target.version[0], multipath_target.version[1],
+	       multipath_target.version[2]);
+
+	return r;
+}
+
+static void __exit dm_multipath_exit(void)
+{
+	int r;
+
+	r = dm_unregister_target(&multipath_target);
+	if (r < 0)
+		DMERR("%s: target unregister failed %d",
+		      multipath_target.name, r);
+	kmem_cache_destroy(_mpio_cache);
+}
+
+EXPORT_SYMBOL_GPL(dm_pg_init_complete);
+
+module_init(dm_multipath_init);
+module_exit(dm_multipath_exit);
+
+MODULE_DESCRIPTION(DM_NAME " multipath target");
+MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");