4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 only,
8 * as published by the Free Software Foundation.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License version 2 for more details (a copy is included
14 * in the LICENSE file that accompanied this code).
16 * You should have received a copy of the GNU General Public License
17 * version 2 along with this program; If not, see
18 * http://www.gnu.org/licenses/gpl-2.0.html
24 * struct dynlock is lockspace
25 * one may request lock (exclusive or shared) for some value
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/sched.h>
34 #include <libcfs/libcfs.h>
36 #include <obd_support.h>
37 #include "osd_dynlocks.h"
38 #include "osd_internal.h"
40 #define DYNLOCK_HANDLE_MAGIC 0xd19a10c
41 #define DYNLOCK_HANDLE_DEAD 0xd1956ee
42 #define DYNLOCK_LIST_MAGIC 0x11ee91e6
47 * initialize lockspace
50 void dynlock_init(struct dynlock *dl)
52 spin_lock_init(&dl->dl_list_lock);
53 INIT_LIST_HEAD(&dl->dl_list);
54 dl->dl_magic = DYNLOCK_LIST_MAGIC;
60 * acquires lock (exclusive or shared) in specified lockspace
61 * each lock in lockspace is allocated separately, so user have
62 * to specify GFP flags.
63 * routine returns pointer to lock. this pointer is intended to
64 * be passed to dynlock_unlock
67 struct dynlock_handle *dynlock_lock(struct dynlock *dl, unsigned long value,
68 enum dynlock_type lt, gfp_t gfp)
70 struct dynlock_handle *nhl = NULL;
71 struct dynlock_handle *hl;
74 BUG_ON(dl->dl_magic != DYNLOCK_LIST_MAGIC);
77 /* find requested lock in lockspace */
78 spin_lock(&dl->dl_list_lock);
79 BUG_ON(dl->dl_list.next == NULL);
80 BUG_ON(dl->dl_list.prev == NULL);
81 list_for_each_entry(hl, &dl->dl_list, dh_list) {
82 BUG_ON(hl->dh_list.next == NULL);
83 BUG_ON(hl->dh_list.prev == NULL);
84 BUG_ON(hl->dh_magic != DYNLOCK_HANDLE_MAGIC);
85 if (hl->dh_value == value) {
88 /* someone else just allocated
89 * lock we didn't find and just created
90 * so, we drop our lock
92 OBD_SLAB_FREE(nhl, dynlock_cachep, sizeof(*nhl));
100 /* we already have allocated lock. use it */
103 list_add(&hl->dh_list, &dl->dl_list);
106 spin_unlock(&dl->dl_list_lock);
108 /* lock not found and we haven't allocated lock yet. allocate it */
109 OBD_SLAB_ALLOC_GFP(nhl, dynlock_cachep, sizeof(*nhl), gfp);
112 nhl->dh_refcount = 1;
113 nhl->dh_value = value;
116 nhl->dh_magic = DYNLOCK_HANDLE_MAGIC;
117 init_waitqueue_head(&nhl->dh_wait);
119 /* while lock is being allocated, someone else may allocate it
120 * and put onto to list. check this situation
125 if (lt == DLT_WRITE) {
126 /* exclusive lock: user don't want to share lock at all
127 * NOTE: one process may take the same lock several times
128 * this functionaly is useful for rename operations */
129 while ((hl->dh_writers && hl->dh_pid != current->pid) ||
131 spin_unlock(&dl->dl_list_lock);
132 wait_event(hl->dh_wait,
133 hl->dh_writers == 0 && hl->dh_readers == 0);
134 spin_lock(&dl->dl_list_lock);
138 /* shared lock: user do not want to share lock with writer */
139 while (hl->dh_writers) {
140 spin_unlock(&dl->dl_list_lock);
141 wait_event(hl->dh_wait, hl->dh_writers == 0);
142 spin_lock(&dl->dl_list_lock);
146 hl->dh_pid = current->pid;
147 spin_unlock(&dl->dl_list_lock);
155 * user have to specify lockspace (dl) and pointer to lock structure
156 * returned by dynlock_lock()
159 void dynlock_unlock(struct dynlock *dl, struct dynlock_handle *hl)
165 BUG_ON(dl->dl_magic != DYNLOCK_LIST_MAGIC);
167 if (hl->dh_magic != DYNLOCK_HANDLE_MAGIC)
168 printk(KERN_EMERG "wrong lock magic: %#x\n", hl->dh_magic);
170 BUG_ON(hl->dh_magic != DYNLOCK_HANDLE_MAGIC);
171 BUG_ON(hl->dh_writers != 0 && current->pid != hl->dh_pid);
173 spin_lock(&dl->dl_list_lock);
174 if (hl->dh_writers) {
175 BUG_ON(hl->dh_readers != 0);
177 if (hl->dh_writers == 0)
179 } else if (hl->dh_readers) {
181 if (hl->dh_readers == 0)
188 wake_up(&hl->dh_wait);
190 if (--(hl->dh_refcount) == 0) {
191 hl->dh_magic = DYNLOCK_HANDLE_DEAD;
192 list_del(&hl->dh_list);
193 OBD_SLAB_FREE(hl, dynlock_cachep, sizeof(*hl));
195 spin_unlock(&dl->dl_list_lock);
198 int dynlock_is_locked(struct dynlock *dl, unsigned long value)
200 struct dynlock_handle *hl;
203 /* find requested lock in lockspace */
204 spin_lock(&dl->dl_list_lock);
205 BUG_ON(dl->dl_list.next == NULL);
206 BUG_ON(dl->dl_list.prev == NULL);
207 list_for_each_entry(hl, &dl->dl_list, dh_list) {
208 BUG_ON(hl->dh_list.next == NULL);
209 BUG_ON(hl->dh_list.prev == NULL);
210 BUG_ON(hl->dh_magic != DYNLOCK_HANDLE_MAGIC);
211 if (hl->dh_value == value && hl->dh_pid == current->pid) {
217 spin_unlock(&dl->dl_list_lock);