Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / drivers / md / dm-round-robin.c

diff --git a/kernel/drivers/md/dm-round-robin.c b/kernel/drivers/md/dm-round-robin.c
new file mode 100644 (file)
index 0000000..6ab1192
--- /dev/null
+++ b/kernel/drivers/md/dm-round-robin.c
@@ -0,0 +1,219 @@
+/*
+ * 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 <linux/device-mapper.h>
+
+#include "dm-path-selector.h"
+
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#define DM_MSG_PREFIX "multipath round-robin"
+
+/*-----------------------------------------------------------------
+ * Path-handling code, paths are held in lists
+ *---------------------------------------------------------------*/
+struct path_info {
+       struct list_head list;
+       struct dm_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 dm_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 dm_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;
+       char dummy;
+
+       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%c", &repeat_count, &dummy) != 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_tail(&pi->list, &s->valid_paths);
+
+       return 0;
+}
+
+static void rr_fail_path(struct path_selector *ps, struct dm_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 dm_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 dm_path *rr_select_path(struct path_selector *ps,
+                                     unsigned *repeat_count, size_t nr_bytes)
+{
+       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("register failed %d", r);
+
+       DMINFO("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("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");