/* * 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> #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; 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_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) { 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");