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286 lines
6.0 KiB
286 lines
6.0 KiB
/* |
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* Copyright (C) 2004-2005 IBM Corp. All Rights Reserved. |
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* Copyright (C) 2006-2009 NEC Corporation. |
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* |
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* dm-queue-length.c |
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* |
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* Module Author: Stefan Bader, IBM |
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* Modified by: Kiyoshi Ueda, NEC |
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* |
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* This file is released under the GPL. |
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* |
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* queue-length path selector - choose a path with the least number of |
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* in-flight I/Os. |
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*/ |
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#include "dm.h" |
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#include "dm-path-selector.h" |
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#include <linux/slab.h> |
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#include <linux/ctype.h> |
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#include <linux/errno.h> |
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#include <linux/module.h> |
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#include <linux/atomic.h> |
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#define DM_MSG_PREFIX "multipath queue-length" |
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#define QL_MIN_IO 1 |
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#define QL_VERSION "0.2.0" |
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struct selector { |
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struct list_head valid_paths; |
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struct list_head failed_paths; |
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spinlock_t lock; |
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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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atomic_t qlen; /* the number of in-flight I/Os */ |
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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->failed_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 ql_create(struct path_selector *ps, unsigned argc, char **argv) |
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{ |
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struct selector *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 ql_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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static void ql_destroy(struct path_selector *ps) |
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{ |
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struct selector *s = ps->context; |
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ql_free_paths(&s->valid_paths); |
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ql_free_paths(&s->failed_paths); |
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kfree(s); |
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ps->context = NULL; |
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} |
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static int ql_status(struct path_selector *ps, struct dm_path *path, |
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status_type_t type, char *result, unsigned maxlen) |
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{ |
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unsigned sz = 0; |
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struct path_info *pi; |
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/* When called with NULL path, return selector status/args. */ |
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if (!path) |
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DMEMIT("0 "); |
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else { |
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pi = path->pscontext; |
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switch (type) { |
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case STATUSTYPE_INFO: |
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DMEMIT("%d ", atomic_read(&pi->qlen)); |
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break; |
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case STATUSTYPE_TABLE: |
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DMEMIT("%u ", pi->repeat_count); |
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break; |
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case STATUSTYPE_IMA: |
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*result = '\0'; |
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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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static int ql_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 = QL_MIN_IO; |
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char dummy; |
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unsigned long flags; |
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/* |
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* Arguments: [<repeat_count>] |
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* <repeat_count>: The number of I/Os before switching path. |
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* If not given, default (QL_MIN_IO) is used. |
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*/ |
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if (argc > 1) { |
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*error = "queue-length ps: incorrect number of arguments"; |
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return -EINVAL; |
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} |
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if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) { |
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*error = "queue-length 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 information structure */ |
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pi = kmalloc(sizeof(*pi), GFP_KERNEL); |
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if (!pi) { |
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*error = "queue-length ps: Error allocating path information"; |
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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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atomic_set(&pi->qlen, 0); |
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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 ql_fail_path(struct path_selector *ps, struct dm_path *path) |
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{ |
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struct selector *s = ps->context; |
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struct path_info *pi = path->pscontext; |
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unsigned long flags; |
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spin_lock_irqsave(&s->lock, flags); |
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list_move(&pi->list, &s->failed_paths); |
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spin_unlock_irqrestore(&s->lock, flags); |
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} |
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static int ql_reinstate_path(struct path_selector *ps, struct dm_path *path) |
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{ |
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struct selector *s = ps->context; |
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struct path_info *pi = path->pscontext; |
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unsigned long flags; |
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spin_lock_irqsave(&s->lock, flags); |
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list_move_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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/* |
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* Select a path having the minimum number of in-flight I/Os |
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*/ |
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static struct dm_path *ql_select_path(struct path_selector *ps, size_t nr_bytes) |
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{ |
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struct selector *s = ps->context; |
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struct path_info *pi = NULL, *best = NULL; |
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struct dm_path *ret = NULL; |
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unsigned long flags; |
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spin_lock_irqsave(&s->lock, flags); |
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if (list_empty(&s->valid_paths)) |
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goto out; |
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list_for_each_entry(pi, &s->valid_paths, list) { |
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if (!best || |
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(atomic_read(&pi->qlen) < atomic_read(&best->qlen))) |
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best = pi; |
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if (!atomic_read(&best->qlen)) |
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break; |
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} |
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if (!best) |
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goto out; |
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/* Move most recently used to least preferred to evenly balance. */ |
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list_move_tail(&best->list, &s->valid_paths); |
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ret = best->path; |
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out: |
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spin_unlock_irqrestore(&s->lock, flags); |
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return ret; |
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} |
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static int ql_start_io(struct path_selector *ps, struct dm_path *path, |
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size_t nr_bytes) |
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{ |
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struct path_info *pi = path->pscontext; |
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atomic_inc(&pi->qlen); |
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return 0; |
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} |
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static int ql_end_io(struct path_selector *ps, struct dm_path *path, |
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size_t nr_bytes, u64 start_time) |
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{ |
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struct path_info *pi = path->pscontext; |
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atomic_dec(&pi->qlen); |
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return 0; |
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} |
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static struct path_selector_type ql_ps = { |
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.name = "queue-length", |
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.module = THIS_MODULE, |
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.table_args = 1, |
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.info_args = 1, |
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.create = ql_create, |
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.destroy = ql_destroy, |
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.status = ql_status, |
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.add_path = ql_add_path, |
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.fail_path = ql_fail_path, |
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.reinstate_path = ql_reinstate_path, |
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.select_path = ql_select_path, |
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.start_io = ql_start_io, |
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.end_io = ql_end_io, |
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}; |
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static int __init dm_ql_init(void) |
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{ |
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int r = dm_register_path_selector(&ql_ps); |
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if (r < 0) |
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DMERR("register failed %d", r); |
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DMINFO("version " QL_VERSION " loaded"); |
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return r; |
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} |
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static void __exit dm_ql_exit(void) |
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{ |
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int r = dm_unregister_path_selector(&ql_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_ql_init); |
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module_exit(dm_ql_exit); |
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MODULE_AUTHOR("Stefan Bader <Stefan.Bader at de.ibm.com>"); |
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MODULE_DESCRIPTION( |
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"(C) Copyright IBM Corp. 2004,2005 All Rights Reserved.\n" |
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DM_NAME " path selector to balance the number of in-flight I/Os" |
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); |
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MODULE_LICENSE("GPL");
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