diff options
Diffstat (limited to 'drivers/md/dm-round-robin.c')
| -rw-r--r-- | drivers/md/dm-round-robin.c | 214 |
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"); |