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 000000000000..43763a0bd096
--- /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");