2 * Copyright (C) 2006-2010 Red Hat, Inc. All rights reserved.
4 * This copyrighted material is made available to anyone wishing to use,
5 * modify, copy, or redistribute it subject to the terms and conditions
6 * of the GNU General Public License v.2.
9 #include <linux/miscdevice.h>
10 #include <linux/init.h>
11 #include <linux/wait.h>
12 #include <linux/module.h>
13 #include <linux/file.h>
15 #include <linux/poll.h>
16 #include <linux/signal.h>
17 #include <linux/spinlock.h>
18 #include <linux/dlm.h>
19 #include <linux/dlm_device.h>
20 #include <linux/slab.h>
22 #include "dlm_internal.h"
23 #include "lockspace.h"
25 #include "lvb_table.h"
29 static const char name_prefix[] = "dlm";
30 static const struct file_operations device_fops;
31 static atomic_t dlm_monitor_opened;
32 static int dlm_monitor_unused = 1;
36 struct dlm_lock_params32 {
50 char lvb[DLM_USER_LVB_LEN];
54 struct dlm_write_request32 {
61 struct dlm_lock_params32 lock;
62 struct dlm_lspace_params lspace;
63 struct dlm_purge_params purge;
74 struct dlm_lock_result32 {
80 struct dlm_lksb32 lksb;
83 /* Offsets may be zero if no data is present */
87 static void compat_input(struct dlm_write_request *kb,
88 struct dlm_write_request32 *kb32,
91 kb->version[0] = kb32->version[0];
92 kb->version[1] = kb32->version[1];
93 kb->version[2] = kb32->version[2];
96 kb->is64bit = kb32->is64bit;
97 if (kb->cmd == DLM_USER_CREATE_LOCKSPACE ||
98 kb->cmd == DLM_USER_REMOVE_LOCKSPACE) {
99 kb->i.lspace.flags = kb32->i.lspace.flags;
100 kb->i.lspace.minor = kb32->i.lspace.minor;
101 memcpy(kb->i.lspace.name, kb32->i.lspace.name, namelen);
102 } else if (kb->cmd == DLM_USER_PURGE) {
103 kb->i.purge.nodeid = kb32->i.purge.nodeid;
104 kb->i.purge.pid = kb32->i.purge.pid;
106 kb->i.lock.mode = kb32->i.lock.mode;
107 kb->i.lock.namelen = kb32->i.lock.namelen;
108 kb->i.lock.flags = kb32->i.lock.flags;
109 kb->i.lock.lkid = kb32->i.lock.lkid;
110 kb->i.lock.parent = kb32->i.lock.parent;
111 kb->i.lock.xid = kb32->i.lock.xid;
112 kb->i.lock.timeout = kb32->i.lock.timeout;
113 kb->i.lock.castparam = (void *)(long)kb32->i.lock.castparam;
114 kb->i.lock.castaddr = (void *)(long)kb32->i.lock.castaddr;
115 kb->i.lock.bastparam = (void *)(long)kb32->i.lock.bastparam;
116 kb->i.lock.bastaddr = (void *)(long)kb32->i.lock.bastaddr;
117 kb->i.lock.lksb = (void *)(long)kb32->i.lock.lksb;
118 memcpy(kb->i.lock.lvb, kb32->i.lock.lvb, DLM_USER_LVB_LEN);
119 memcpy(kb->i.lock.name, kb32->i.lock.name, namelen);
123 static void compat_output(struct dlm_lock_result *res,
124 struct dlm_lock_result32 *res32)
126 res32->version[0] = res->version[0];
127 res32->version[1] = res->version[1];
128 res32->version[2] = res->version[2];
130 res32->user_astaddr = (__u32)(long)res->user_astaddr;
131 res32->user_astparam = (__u32)(long)res->user_astparam;
132 res32->user_lksb = (__u32)(long)res->user_lksb;
133 res32->bast_mode = res->bast_mode;
135 res32->lvb_offset = res->lvb_offset;
136 res32->length = res->length;
138 res32->lksb.sb_status = res->lksb.sb_status;
139 res32->lksb.sb_flags = res->lksb.sb_flags;
140 res32->lksb.sb_lkid = res->lksb.sb_lkid;
141 res32->lksb.sb_lvbptr = (__u32)(long)res->lksb.sb_lvbptr;
145 /* Figure out if this lock is at the end of its life and no longer
146 available for the application to use. The lkb still exists until
147 the final ast is read. A lock becomes EOL in three situations:
148 1. a noqueue request fails with EAGAIN
149 2. an unlock completes with EUNLOCK
150 3. a cancel of a waiting request completes with ECANCEL/EDEADLK
151 An EOL lock needs to be removed from the process's list of locks.
152 And we can't allow any new operation on an EOL lock. This is
153 not related to the lifetime of the lkb struct which is managed
154 entirely by refcount. */
156 static int lkb_is_endoflife(int mode, int status)
165 if (mode == DLM_LOCK_IV)
172 /* we could possibly check if the cancel of an orphan has resulted in the lkb
173 being removed and then remove that lkb from the orphans list and free it */
175 void dlm_user_add_ast(struct dlm_lkb *lkb, uint32_t flags, int mode,
176 int status, uint32_t sbflags, uint64_t seq)
179 struct dlm_user_args *ua;
180 struct dlm_user_proc *proc;
183 if (lkb->lkb_flags & (DLM_IFL_ORPHAN | DLM_IFL_DEAD))
186 ls = lkb->lkb_resource->res_ls;
187 mutex_lock(&ls->ls_clear_proc_locks);
189 /* If ORPHAN/DEAD flag is set, it means the process is dead so an ast
190 can't be delivered. For ORPHAN's, dlm_clear_proc_locks() freed
191 lkb->ua so we can't try to use it. This second check is necessary
192 for cases where a completion ast is received for an operation that
193 began before clear_proc_locks did its cancel/unlock. */
195 if (lkb->lkb_flags & (DLM_IFL_ORPHAN | DLM_IFL_DEAD))
198 DLM_ASSERT(lkb->lkb_ua, dlm_print_lkb(lkb););
202 if ((flags & DLM_CB_BAST) && ua->bastaddr == NULL)
205 if ((flags & DLM_CB_CAST) && lkb_is_endoflife(mode, status))
206 lkb->lkb_flags |= DLM_IFL_ENDOFLIFE;
208 spin_lock(&proc->asts_spin);
210 rv = dlm_add_lkb_callback(lkb, flags, mode, status, sbflags, seq);
212 spin_unlock(&proc->asts_spin);
216 if (list_empty(&lkb->lkb_cb_list)) {
217 kref_get(&lkb->lkb_ref);
218 list_add_tail(&lkb->lkb_cb_list, &proc->asts);
219 wake_up_interruptible(&proc->wait);
221 spin_unlock(&proc->asts_spin);
223 if (lkb->lkb_flags & DLM_IFL_ENDOFLIFE) {
224 /* N.B. spin_lock locks_spin, not asts_spin */
225 spin_lock(&proc->locks_spin);
226 if (!list_empty(&lkb->lkb_ownqueue)) {
227 list_del_init(&lkb->lkb_ownqueue);
230 spin_unlock(&proc->locks_spin);
233 mutex_unlock(&ls->ls_clear_proc_locks);
236 static int device_user_lock(struct dlm_user_proc *proc,
237 struct dlm_lock_params *params)
240 struct dlm_user_args *ua;
243 ls = dlm_find_lockspace_local(proc->lockspace);
247 if (!params->castaddr || !params->lksb) {
252 ua = kzalloc(sizeof(struct dlm_user_args), GFP_NOFS);
256 ua->user_lksb = params->lksb;
257 ua->castparam = params->castparam;
258 ua->castaddr = params->castaddr;
259 ua->bastparam = params->bastparam;
260 ua->bastaddr = params->bastaddr;
261 ua->xid = params->xid;
263 if (params->flags & DLM_LKF_CONVERT)
264 error = dlm_user_convert(ls, ua,
265 params->mode, params->flags,
266 params->lkid, params->lvb,
267 (unsigned long) params->timeout);
269 error = dlm_user_request(ls, ua,
270 params->mode, params->flags,
271 params->name, params->namelen,
272 (unsigned long) params->timeout);
274 error = ua->lksb.sb_lkid;
277 dlm_put_lockspace(ls);
281 static int device_user_unlock(struct dlm_user_proc *proc,
282 struct dlm_lock_params *params)
285 struct dlm_user_args *ua;
288 ls = dlm_find_lockspace_local(proc->lockspace);
292 ua = kzalloc(sizeof(struct dlm_user_args), GFP_NOFS);
296 ua->user_lksb = params->lksb;
297 ua->castparam = params->castparam;
298 ua->castaddr = params->castaddr;
300 if (params->flags & DLM_LKF_CANCEL)
301 error = dlm_user_cancel(ls, ua, params->flags, params->lkid);
303 error = dlm_user_unlock(ls, ua, params->flags, params->lkid,
306 dlm_put_lockspace(ls);
310 static int device_user_deadlock(struct dlm_user_proc *proc,
311 struct dlm_lock_params *params)
316 ls = dlm_find_lockspace_local(proc->lockspace);
320 error = dlm_user_deadlock(ls, params->flags, params->lkid);
322 dlm_put_lockspace(ls);
326 static int dlm_device_register(struct dlm_ls *ls, char *name)
330 /* The device is already registered. This happens when the
331 lockspace is created multiple times from userspace. */
332 if (ls->ls_device.name)
336 len = strlen(name) + strlen(name_prefix) + 2;
337 ls->ls_device.name = kzalloc(len, GFP_NOFS);
338 if (!ls->ls_device.name)
341 snprintf((char *)ls->ls_device.name, len, "%s_%s", name_prefix,
343 ls->ls_device.fops = &device_fops;
344 ls->ls_device.minor = MISC_DYNAMIC_MINOR;
346 error = misc_register(&ls->ls_device);
348 kfree(ls->ls_device.name);
354 int dlm_device_deregister(struct dlm_ls *ls)
358 /* The device is not registered. This happens when the lockspace
359 was never used from userspace, or when device_create_lockspace()
360 calls dlm_release_lockspace() after the register fails. */
361 if (!ls->ls_device.name)
364 error = misc_deregister(&ls->ls_device);
366 kfree(ls->ls_device.name);
370 static int device_user_purge(struct dlm_user_proc *proc,
371 struct dlm_purge_params *params)
376 ls = dlm_find_lockspace_local(proc->lockspace);
380 error = dlm_user_purge(ls, proc, params->nodeid, params->pid);
382 dlm_put_lockspace(ls);
386 static int device_create_lockspace(struct dlm_lspace_params *params)
388 dlm_lockspace_t *lockspace;
392 if (!capable(CAP_SYS_ADMIN))
395 error = dlm_new_lockspace(params->name, NULL, params->flags,
396 DLM_USER_LVB_LEN, NULL, NULL, NULL,
401 ls = dlm_find_lockspace_local(lockspace);
405 error = dlm_device_register(ls, params->name);
406 dlm_put_lockspace(ls);
409 dlm_release_lockspace(lockspace, 0);
411 error = ls->ls_device.minor;
416 static int device_remove_lockspace(struct dlm_lspace_params *params)
418 dlm_lockspace_t *lockspace;
420 int error, force = 0;
422 if (!capable(CAP_SYS_ADMIN))
425 ls = dlm_find_lockspace_device(params->minor);
429 if (params->flags & DLM_USER_LSFLG_FORCEFREE)
432 lockspace = ls->ls_local_handle;
433 dlm_put_lockspace(ls);
435 /* The final dlm_release_lockspace waits for references to go to
436 zero, so all processes will need to close their device for the
437 ls before the release will proceed. release also calls the
438 device_deregister above. Converting a positive return value
439 from release to zero means that userspace won't know when its
440 release was the final one, but it shouldn't need to know. */
442 error = dlm_release_lockspace(lockspace, force);
448 /* Check the user's version matches ours */
449 static int check_version(struct dlm_write_request *req)
451 if (req->version[0] != DLM_DEVICE_VERSION_MAJOR ||
452 (req->version[0] == DLM_DEVICE_VERSION_MAJOR &&
453 req->version[1] > DLM_DEVICE_VERSION_MINOR)) {
455 printk(KERN_DEBUG "dlm: process %s (%d) version mismatch "
456 "user (%d.%d.%d) kernel (%d.%d.%d)\n",
458 task_pid_nr(current),
462 DLM_DEVICE_VERSION_MAJOR,
463 DLM_DEVICE_VERSION_MINOR,
464 DLM_DEVICE_VERSION_PATCH);
474 * dlm_user_request -> request_lock
475 * dlm_user_convert -> convert_lock
478 * dlm_user_unlock -> unlock_lock
479 * dlm_user_cancel -> cancel_lock
481 * device_create_lockspace
484 * device_remove_lockspace
485 * dlm_release_lockspace
488 /* a write to a lockspace device is a lock or unlock request, a write
489 to the control device is to create/remove a lockspace */
491 static ssize_t device_write(struct file *file, const char __user *buf,
492 size_t count, loff_t *ppos)
494 struct dlm_user_proc *proc = file->private_data;
495 struct dlm_write_request *kbuf;
499 if (count < sizeof(struct dlm_write_request32))
501 if (count < sizeof(struct dlm_write_request))
506 * can't compare against COMPAT/dlm_write_request32 because
507 * we don't yet know if is64bit is zero
509 if (count > sizeof(struct dlm_write_request) + DLM_RESNAME_MAXLEN)
512 kbuf = kzalloc(count + 1, GFP_NOFS);
516 if (copy_from_user(kbuf, buf, count)) {
521 if (check_version(kbuf)) {
527 if (!kbuf->is64bit) {
528 struct dlm_write_request32 *k32buf;
531 if (count > sizeof(struct dlm_write_request32))
532 namelen = count - sizeof(struct dlm_write_request32);
534 k32buf = (struct dlm_write_request32 *)kbuf;
536 /* add 1 after namelen so that the name string is terminated */
537 kbuf = kzalloc(sizeof(struct dlm_write_request) + namelen + 1,
545 set_bit(DLM_PROC_FLAGS_COMPAT, &proc->flags);
547 compat_input(kbuf, k32buf, namelen);
552 /* do we really need this? can a write happen after a close? */
553 if ((kbuf->cmd == DLM_USER_LOCK || kbuf->cmd == DLM_USER_UNLOCK) &&
554 (proc && test_bit(DLM_PROC_FLAGS_CLOSING, &proc->flags))) {
565 log_print("no locking on control device");
568 error = device_user_lock(proc, &kbuf->i.lock);
571 case DLM_USER_UNLOCK:
573 log_print("no locking on control device");
576 error = device_user_unlock(proc, &kbuf->i.lock);
579 case DLM_USER_DEADLOCK:
581 log_print("no locking on control device");
584 error = device_user_deadlock(proc, &kbuf->i.lock);
587 case DLM_USER_CREATE_LOCKSPACE:
589 log_print("create/remove only on control device");
592 error = device_create_lockspace(&kbuf->i.lspace);
595 case DLM_USER_REMOVE_LOCKSPACE:
597 log_print("create/remove only on control device");
600 error = device_remove_lockspace(&kbuf->i.lspace);
605 log_print("no locking on control device");
608 error = device_user_purge(proc, &kbuf->i.purge);
612 log_print("Unknown command passed to DLM device : %d\n",
621 /* Every process that opens the lockspace device has its own "proc" structure
622 hanging off the open file that's used to keep track of locks owned by the
623 process and asts that need to be delivered to the process. */
625 static int device_open(struct inode *inode, struct file *file)
627 struct dlm_user_proc *proc;
630 ls = dlm_find_lockspace_device(iminor(inode));
634 proc = kzalloc(sizeof(struct dlm_user_proc), GFP_NOFS);
636 dlm_put_lockspace(ls);
640 proc->lockspace = ls->ls_local_handle;
641 INIT_LIST_HEAD(&proc->asts);
642 INIT_LIST_HEAD(&proc->locks);
643 INIT_LIST_HEAD(&proc->unlocking);
644 spin_lock_init(&proc->asts_spin);
645 spin_lock_init(&proc->locks_spin);
646 init_waitqueue_head(&proc->wait);
647 file->private_data = proc;
652 static int device_close(struct inode *inode, struct file *file)
654 struct dlm_user_proc *proc = file->private_data;
657 ls = dlm_find_lockspace_local(proc->lockspace);
661 set_bit(DLM_PROC_FLAGS_CLOSING, &proc->flags);
663 dlm_clear_proc_locks(ls, proc);
665 /* at this point no more lkb's should exist for this lockspace,
666 so there's no chance of dlm_user_add_ast() being called and
667 looking for lkb->ua->proc */
670 file->private_data = NULL;
672 dlm_put_lockspace(ls);
673 dlm_put_lockspace(ls); /* for the find in device_open() */
675 /* FIXME: AUTOFREE: if this ls is no longer used do
676 device_remove_lockspace() */
681 static int copy_result_to_user(struct dlm_user_args *ua, int compat,
682 uint32_t flags, int mode, int copy_lvb,
683 char __user *buf, size_t count)
686 struct dlm_lock_result32 result32;
688 struct dlm_lock_result result;
694 memset(&result, 0, sizeof(struct dlm_lock_result));
695 result.version[0] = DLM_DEVICE_VERSION_MAJOR;
696 result.version[1] = DLM_DEVICE_VERSION_MINOR;
697 result.version[2] = DLM_DEVICE_VERSION_PATCH;
698 memcpy(&result.lksb, &ua->lksb, sizeof(struct dlm_lksb));
699 result.user_lksb = ua->user_lksb;
701 /* FIXME: dlm1 provides for the user's bastparam/addr to not be updated
702 in a conversion unless the conversion is successful. See code
703 in dlm_user_convert() for updating ua from ua_tmp. OpenVMS, though,
704 notes that a new blocking AST address and parameter are set even if
705 the conversion fails, so maybe we should just do that. */
707 if (flags & DLM_CB_BAST) {
708 result.user_astaddr = ua->bastaddr;
709 result.user_astparam = ua->bastparam;
710 result.bast_mode = mode;
712 result.user_astaddr = ua->castaddr;
713 result.user_astparam = ua->castparam;
718 len = sizeof(struct dlm_lock_result32);
721 len = sizeof(struct dlm_lock_result);
724 /* copy lvb to userspace if there is one, it's been updated, and
725 the user buffer has space for it */
727 if (copy_lvb && ua->lksb.sb_lvbptr && count >= len + DLM_USER_LVB_LEN) {
728 if (copy_to_user(buf+len, ua->lksb.sb_lvbptr,
734 result.lvb_offset = len;
735 len += DLM_USER_LVB_LEN;
742 compat_output(&result, &result32);
743 resultptr = &result32;
747 if (copy_to_user(buf, resultptr, struct_len))
755 static int copy_version_to_user(char __user *buf, size_t count)
757 struct dlm_device_version ver;
759 memset(&ver, 0, sizeof(struct dlm_device_version));
760 ver.version[0] = DLM_DEVICE_VERSION_MAJOR;
761 ver.version[1] = DLM_DEVICE_VERSION_MINOR;
762 ver.version[2] = DLM_DEVICE_VERSION_PATCH;
764 if (copy_to_user(buf, &ver, sizeof(struct dlm_device_version)))
766 return sizeof(struct dlm_device_version);
769 /* a read returns a single ast described in a struct dlm_lock_result */
771 static ssize_t device_read(struct file *file, char __user *buf, size_t count,
774 struct dlm_user_proc *proc = file->private_data;
776 DECLARE_WAITQUEUE(wait, current);
777 struct dlm_callback cb;
778 int rv, resid, copy_lvb = 0;
780 if (count == sizeof(struct dlm_device_version)) {
781 rv = copy_version_to_user(buf, count);
786 log_print("non-version read from control device %zu", count);
791 if (count < sizeof(struct dlm_lock_result32))
793 if (count < sizeof(struct dlm_lock_result))
799 /* do we really need this? can a read happen after a close? */
800 if (test_bit(DLM_PROC_FLAGS_CLOSING, &proc->flags))
803 spin_lock(&proc->asts_spin);
804 if (list_empty(&proc->asts)) {
805 if (file->f_flags & O_NONBLOCK) {
806 spin_unlock(&proc->asts_spin);
810 add_wait_queue(&proc->wait, &wait);
813 set_current_state(TASK_INTERRUPTIBLE);
814 if (list_empty(&proc->asts) && !signal_pending(current)) {
815 spin_unlock(&proc->asts_spin);
817 spin_lock(&proc->asts_spin);
820 set_current_state(TASK_RUNNING);
821 remove_wait_queue(&proc->wait, &wait);
823 if (signal_pending(current)) {
824 spin_unlock(&proc->asts_spin);
829 /* if we empty lkb_callbacks, we don't want to unlock the spinlock
830 without removing lkb_cb_list; so empty lkb_cb_list is always
831 consistent with empty lkb_callbacks */
833 lkb = list_entry(proc->asts.next, struct dlm_lkb, lkb_cb_list);
835 rv = dlm_rem_lkb_callback(lkb->lkb_resource->res_ls, lkb, &cb, &resid);
837 /* this shouldn't happen; lkb should have been removed from
838 list when resid was zero */
839 log_print("dlm_rem_lkb_callback empty %x", lkb->lkb_id);
840 list_del_init(&lkb->lkb_cb_list);
841 spin_unlock(&proc->asts_spin);
842 /* removes ref for proc->asts, may cause lkb to be freed */
847 list_del_init(&lkb->lkb_cb_list);
848 spin_unlock(&proc->asts_spin);
850 if (cb.flags & DLM_CB_SKIP) {
851 /* removes ref for proc->asts, may cause lkb to be freed */
857 if (cb.flags & DLM_CB_CAST) {
858 int old_mode, new_mode;
860 old_mode = lkb->lkb_last_cast.mode;
863 if (!cb.sb_status && lkb->lkb_lksb->sb_lvbptr &&
864 dlm_lvb_operations[old_mode + 1][new_mode + 1])
867 lkb->lkb_lksb->sb_status = cb.sb_status;
868 lkb->lkb_lksb->sb_flags = cb.sb_flags;
871 rv = copy_result_to_user(lkb->lkb_ua,
872 test_bit(DLM_PROC_FLAGS_COMPAT, &proc->flags),
873 cb.flags, cb.mode, copy_lvb, buf, count);
875 /* removes ref for proc->asts, may cause lkb to be freed */
882 static unsigned int device_poll(struct file *file, poll_table *wait)
884 struct dlm_user_proc *proc = file->private_data;
886 poll_wait(file, &proc->wait, wait);
888 spin_lock(&proc->asts_spin);
889 if (!list_empty(&proc->asts)) {
890 spin_unlock(&proc->asts_spin);
891 return POLLIN | POLLRDNORM;
893 spin_unlock(&proc->asts_spin);
897 int dlm_user_daemon_available(void)
899 /* dlm_controld hasn't started (or, has started, but not
900 properly populated configfs) */
902 if (!dlm_our_nodeid())
905 /* This is to deal with versions of dlm_controld that don't
906 know about the monitor device. We assume that if the
907 dlm_controld was started (above), but the monitor device
908 was never opened, that it's an old version. dlm_controld
909 should open the monitor device before populating configfs. */
911 if (dlm_monitor_unused)
914 return atomic_read(&dlm_monitor_opened) ? 1 : 0;
917 static int ctl_device_open(struct inode *inode, struct file *file)
919 file->private_data = NULL;
923 static int ctl_device_close(struct inode *inode, struct file *file)
928 static int monitor_device_open(struct inode *inode, struct file *file)
930 atomic_inc(&dlm_monitor_opened);
931 dlm_monitor_unused = 0;
935 static int monitor_device_close(struct inode *inode, struct file *file)
937 if (atomic_dec_and_test(&dlm_monitor_opened))
938 dlm_stop_lockspaces();
942 static const struct file_operations device_fops = {
944 .release = device_close,
946 .write = device_write,
948 .owner = THIS_MODULE,
949 .llseek = noop_llseek,
952 static const struct file_operations ctl_device_fops = {
953 .open = ctl_device_open,
954 .release = ctl_device_close,
956 .write = device_write,
957 .owner = THIS_MODULE,
958 .llseek = noop_llseek,
961 static struct miscdevice ctl_device = {
962 .name = "dlm-control",
963 .fops = &ctl_device_fops,
964 .minor = MISC_DYNAMIC_MINOR,
967 static const struct file_operations monitor_device_fops = {
968 .open = monitor_device_open,
969 .release = monitor_device_close,
970 .owner = THIS_MODULE,
971 .llseek = noop_llseek,
974 static struct miscdevice monitor_device = {
975 .name = "dlm-monitor",
976 .fops = &monitor_device_fops,
977 .minor = MISC_DYNAMIC_MINOR,
980 int __init dlm_user_init(void)
984 atomic_set(&dlm_monitor_opened, 0);
986 error = misc_register(&ctl_device);
988 log_print("misc_register failed for control device");
992 error = misc_register(&monitor_device);
994 log_print("misc_register failed for monitor device");
995 misc_deregister(&ctl_device);
1001 void dlm_user_exit(void)
1003 misc_deregister(&ctl_device);
1004 misc_deregister(&monitor_device);