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236 lines
5.0 KiB
236 lines
5.0 KiB
/* |
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* Copyright (C) 2003 Sistina Software. |
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* Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved. |
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* |
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* Module Author: Heinz Mauelshagen |
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* |
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* This file is released under the GPL. |
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* |
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* Round-robin path selector. |
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*/ |
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#include <linux/device-mapper.h> |
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#include "dm-path-selector.h" |
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#include <linux/slab.h> |
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#include <linux/module.h> |
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#define DM_MSG_PREFIX "multipath round-robin" |
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#define RR_MIN_IO 1 |
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#define RR_VERSION "1.2.0" |
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/*----------------------------------------------------------------- |
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* Path-handling code, paths are held in lists |
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*---------------------------------------------------------------*/ |
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struct path_info { |
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struct list_head list; |
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struct dm_path *path; |
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unsigned repeat_count; |
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}; |
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static void free_paths(struct list_head *paths) |
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{ |
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struct path_info *pi, *next; |
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list_for_each_entry_safe(pi, next, paths, list) { |
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list_del(&pi->list); |
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kfree(pi); |
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} |
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} |
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/*----------------------------------------------------------------- |
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* Round-robin selector |
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*---------------------------------------------------------------*/ |
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struct selector { |
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struct list_head valid_paths; |
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struct list_head invalid_paths; |
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spinlock_t lock; |
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}; |
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static struct selector *alloc_selector(void) |
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{ |
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struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL); |
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if (s) { |
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INIT_LIST_HEAD(&s->valid_paths); |
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INIT_LIST_HEAD(&s->invalid_paths); |
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spin_lock_init(&s->lock); |
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} |
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return s; |
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} |
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static int rr_create(struct path_selector *ps, unsigned argc, char **argv) |
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{ |
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struct selector *s; |
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s = alloc_selector(); |
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if (!s) |
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return -ENOMEM; |
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ps->context = s; |
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return 0; |
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} |
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static void rr_destroy(struct path_selector *ps) |
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{ |
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struct selector *s = ps->context; |
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free_paths(&s->valid_paths); |
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free_paths(&s->invalid_paths); |
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kfree(s); |
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ps->context = NULL; |
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} |
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static int rr_status(struct path_selector *ps, struct dm_path *path, |
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status_type_t type, char *result, unsigned int maxlen) |
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{ |
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struct path_info *pi; |
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int sz = 0; |
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if (!path) |
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DMEMIT("0 "); |
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else { |
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switch(type) { |
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case STATUSTYPE_INFO: |
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break; |
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case STATUSTYPE_TABLE: |
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pi = path->pscontext; |
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DMEMIT("%u ", pi->repeat_count); |
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break; |
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} |
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} |
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return sz; |
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} |
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/* |
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* Called during initialisation to register each path with an |
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* optional repeat_count. |
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*/ |
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static int rr_add_path(struct path_selector *ps, struct dm_path *path, |
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int argc, char **argv, char **error) |
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{ |
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struct selector *s = ps->context; |
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struct path_info *pi; |
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unsigned repeat_count = RR_MIN_IO; |
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char dummy; |
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unsigned long flags; |
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if (argc > 1) { |
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*error = "round-robin ps: incorrect number of arguments"; |
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return -EINVAL; |
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} |
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/* First path argument is number of I/Os before switching path */ |
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if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) { |
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*error = "round-robin ps: invalid repeat count"; |
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return -EINVAL; |
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} |
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if (repeat_count > 1) { |
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DMWARN_LIMIT("repeat_count > 1 is deprecated, using 1 instead"); |
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repeat_count = 1; |
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} |
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/* allocate the path */ |
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pi = kmalloc(sizeof(*pi), GFP_KERNEL); |
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if (!pi) { |
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*error = "round-robin ps: Error allocating path context"; |
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return -ENOMEM; |
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} |
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pi->path = path; |
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pi->repeat_count = repeat_count; |
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path->pscontext = pi; |
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spin_lock_irqsave(&s->lock, flags); |
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list_add_tail(&pi->list, &s->valid_paths); |
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spin_unlock_irqrestore(&s->lock, flags); |
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return 0; |
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} |
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static void rr_fail_path(struct path_selector *ps, struct dm_path *p) |
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{ |
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unsigned long flags; |
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struct selector *s = ps->context; |
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struct path_info *pi = p->pscontext; |
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spin_lock_irqsave(&s->lock, flags); |
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list_move(&pi->list, &s->invalid_paths); |
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spin_unlock_irqrestore(&s->lock, flags); |
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} |
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static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p) |
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{ |
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unsigned long flags; |
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struct selector *s = ps->context; |
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struct path_info *pi = p->pscontext; |
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spin_lock_irqsave(&s->lock, flags); |
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list_move(&pi->list, &s->valid_paths); |
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spin_unlock_irqrestore(&s->lock, flags); |
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return 0; |
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} |
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static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes) |
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{ |
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unsigned long flags; |
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struct selector *s = ps->context; |
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struct path_info *pi = NULL; |
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spin_lock_irqsave(&s->lock, flags); |
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if (!list_empty(&s->valid_paths)) { |
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pi = list_entry(s->valid_paths.next, struct path_info, list); |
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list_move_tail(&pi->list, &s->valid_paths); |
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} |
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spin_unlock_irqrestore(&s->lock, flags); |
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return pi ? pi->path : NULL; |
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} |
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static struct path_selector_type rr_ps = { |
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.name = "round-robin", |
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.module = THIS_MODULE, |
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.table_args = 1, |
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.info_args = 0, |
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.create = rr_create, |
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.destroy = rr_destroy, |
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.status = rr_status, |
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.add_path = rr_add_path, |
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.fail_path = rr_fail_path, |
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.reinstate_path = rr_reinstate_path, |
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.select_path = rr_select_path, |
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}; |
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static int __init dm_rr_init(void) |
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{ |
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int r = dm_register_path_selector(&rr_ps); |
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if (r < 0) |
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DMERR("register failed %d", r); |
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DMINFO("version " RR_VERSION " loaded"); |
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return r; |
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} |
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static void __exit dm_rr_exit(void) |
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{ |
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int r = dm_unregister_path_selector(&rr_ps); |
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if (r < 0) |
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DMERR("unregister failed %d", r); |
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} |
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module_init(dm_rr_init); |
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module_exit(dm_rr_exit); |
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MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector"); |
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MODULE_AUTHOR("Sistina Software <[email protected]>"); |
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MODULE_LICENSE("GPL");
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