1 files changed, 214 insertions, 0 deletions

diff --git a/drivers/md/dm-round-robin.c b/drivers/md/dm-round-robin.c
new file mode 100644
index 000000000000..d0024865a789
--- /dev/null
+++ b/drivers/md/dm-round-robin.c
@@ -0,0 +1,214 @@
+/*
+ * Copyright (C) 2003 Sistina Software.
+ * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
+ *
+ * Module Author: Heinz Mauelshagen
+ *
+ * This file is released under the GPL.
+ *
+ * Round-robin path selector.
+ */
+
+#include "dm.h"
+#include "dm-path-selector.h"
+
+#include <linux/slab.h>
+
+/*-----------------------------------------------------------------
+ * Path-handling code, paths are held in lists
+ *---------------------------------------------------------------*/
+struct path_info {
+        struct list_head list;
+        struct path *path;
+        unsigned repeat_count;
+};
+
+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);
+        }
+}
+
+/*-----------------------------------------------------------------
+ * Round-robin selector
+ *---------------------------------------------------------------*/
+
+#define RR_MIN_IO               1000
+
+struct selector {
+        struct list_head valid_paths;
+        struct list_head invalid_paths;
+};
+
+static struct selector *alloc_selector(void)
+{
+        struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
+
+        if (s) {
+                INIT_LIST_HEAD(&s->valid_paths);
+                INIT_LIST_HEAD(&s->invalid_paths);
+        }
+
+        return s;
+}
+
+static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
+{
+        struct selector *s;
+
+        s = alloc_selector();
+        if (!s)
+                return -ENOMEM;
+
+        ps->context = s;
+        return 0;
+}
+
+static void rr_destroy(struct path_selector *ps)
+{
+        struct selector *s = (struct selector *) ps->context;
+
+        free_paths(&s->valid_paths);
+        free_paths(&s->invalid_paths);
+        kfree(s);
+        ps->context = NULL;
+}
+
+static int rr_status(struct path_selector *ps, struct path *path,
+                     status_type_t type, char *result, unsigned int maxlen)
+{
+        struct path_info *pi;
+        int sz = 0;
+
+        if (!path)
+                DMEMIT("0 ");
+        else {
+                switch(type) {
+                case STATUSTYPE_INFO:
+                        break;
+                case STATUSTYPE_TABLE:
+                        pi = path->pscontext;
+                        DMEMIT("%u ", pi->repeat_count);
+                        break;
+                }
+        }
+
+        return sz;
+}
+
+/*
+ * Called during initialisation to register each path with an
+ * optional repeat_count.
+ */
+static int rr_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;
+        unsigned repeat_count = RR_MIN_IO;
+
+        if (argc > 1) {
+                *error = "round-robin ps: incorrect number of arguments";
+                return -EINVAL;
+        }
+
+        /* First path argument is number of I/Os before switching path */
+        if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
+                *error = "round-robin ps: invalid repeat count";
+                return -EINVAL;
+        }
+
+        /* allocate the path */
+        pi = kmalloc(sizeof(*pi), GFP_KERNEL);
+        if (!pi) {
+                *error = "round-robin ps: Error allocating path context";
+                return -ENOMEM;
+        }
+
+        pi->path = path;
+        pi->repeat_count = repeat_count;
+
+        path->pscontext = pi;
+
+        list_add(&pi->list, &s->valid_paths);
+
+        return 0;
+}
+
+static void rr_fail_path(struct path_selector *ps, struct path *p)
+{
+        struct selector *s = (struct selector *) ps->context;
+        struct path_info *pi = p->pscontext;
+
+        list_move(&pi->list, &s->invalid_paths);
+}
+
+static int rr_reinstate_path(struct path_selector *ps, struct path *p)
+{
+        struct selector *s = (struct selector *) ps->context;
+        struct path_info *pi = p->pscontext;
+
+        list_move(&pi->list, &s->valid_paths);
+
+        return 0;
+}
+
+static struct path *rr_select_path(struct path_selector *ps,
+                                   unsigned *repeat_count)
+{
+        struct selector *s = (struct selector *) ps->context;
+        struct path_info *pi = NULL;
+
+        if (!list_empty(&s->valid_paths)) {
+                pi = list_entry(s->valid_paths.next, struct path_info, list);
+                list_move_tail(&pi->list, &s->valid_paths);
+                *repeat_count = pi->repeat_count;
+        }
+
+        return pi ? pi->path : NULL;
+}
+
+static struct path_selector_type rr_ps = {
+        .name = "round-robin",
+        .module = THIS_MODULE,
+        .table_args = 1,
+        .info_args = 0,
+        .create = rr_create,
+        .destroy = rr_destroy,
+        .status = rr_status,
+        .add_path = rr_add_path,
+        .fail_path = rr_fail_path,
+        .reinstate_path = rr_reinstate_path,
+        .select_path = rr_select_path,
+};
+
+static int __init dm_rr_init(void)
+{
+        int r = dm_register_path_selector(&rr_ps);
+
+        if (r < 0)
+                DMERR("round-robin: register failed %d", r);
+
+        DMINFO("dm-round-robin version 1.0.0 loaded");
+
+        return r;
+}
+
+static void __exit dm_rr_exit(void)
+{
+        int r = dm_unregister_path_selector(&rr_ps);
+
+        if (r < 0)
+                DMERR("round-robin: unregister failed %d", r);
+}
+
+module_init(dm_rr_init);
+module_exit(dm_rr_exit);
+
+MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
+MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");