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TOMOYO Linux Cross Reference
Linux/fs/dlm/plock.c

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  1 /*
  2  * Copyright (C) 2005-2008 Red Hat, Inc.  All rights reserved.
  3  *
  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 version 2.
  7  */
  8 
  9 #include <linux/fs.h>
 10 #include <linux/miscdevice.h>
 11 #include <linux/poll.h>
 12 #include <linux/dlm.h>
 13 #include <linux/dlm_plock.h>
 14 #include <linux/slab.h>
 15 
 16 #include "dlm_internal.h"
 17 #include "lockspace.h"
 18 
 19 static spinlock_t ops_lock;
 20 static struct list_head send_list;
 21 static struct list_head recv_list;
 22 static wait_queue_head_t send_wq;
 23 static wait_queue_head_t recv_wq;
 24 
 25 struct plock_op {
 26         struct list_head list;
 27         int done;
 28         struct dlm_plock_info info;
 29 };
 30 
 31 struct plock_xop {
 32         struct plock_op xop;
 33         int (*callback)(struct file_lock *fl, int result);
 34         void *fl;
 35         void *file;
 36         struct file_lock flc;
 37 };
 38 
 39 
 40 static inline void set_version(struct dlm_plock_info *info)
 41 {
 42         info->version[0] = DLM_PLOCK_VERSION_MAJOR;
 43         info->version[1] = DLM_PLOCK_VERSION_MINOR;
 44         info->version[2] = DLM_PLOCK_VERSION_PATCH;
 45 }
 46 
 47 static int check_version(struct dlm_plock_info *info)
 48 {
 49         if ((DLM_PLOCK_VERSION_MAJOR != info->version[0]) ||
 50             (DLM_PLOCK_VERSION_MINOR < info->version[1])) {
 51                 log_print("plock device version mismatch: "
 52                           "kernel (%u.%u.%u), user (%u.%u.%u)",
 53                           DLM_PLOCK_VERSION_MAJOR,
 54                           DLM_PLOCK_VERSION_MINOR,
 55                           DLM_PLOCK_VERSION_PATCH,
 56                           info->version[0],
 57                           info->version[1],
 58                           info->version[2]);
 59                 return -EINVAL;
 60         }
 61         return 0;
 62 }
 63 
 64 static void send_op(struct plock_op *op)
 65 {
 66         set_version(&op->info);
 67         INIT_LIST_HEAD(&op->list);
 68         spin_lock(&ops_lock);
 69         list_add_tail(&op->list, &send_list);
 70         spin_unlock(&ops_lock);
 71         wake_up(&send_wq);
 72 }
 73 
 74 /* If a process was killed while waiting for the only plock on a file,
 75    locks_remove_posix will not see any lock on the file so it won't
 76    send an unlock-close to us to pass on to userspace to clean up the
 77    abandoned waiter.  So, we have to insert the unlock-close when the
 78    lock call is interrupted. */
 79 
 80 static void do_unlock_close(struct dlm_ls *ls, u64 number,
 81                             struct file *file, struct file_lock *fl)
 82 {
 83         struct plock_op *op;
 84 
 85         op = kzalloc(sizeof(*op), GFP_NOFS);
 86         if (!op)
 87                 return;
 88 
 89         op->info.optype         = DLM_PLOCK_OP_UNLOCK;
 90         op->info.pid            = fl->fl_pid;
 91         op->info.fsid           = ls->ls_global_id;
 92         op->info.number         = number;
 93         op->info.start          = 0;
 94         op->info.end            = OFFSET_MAX;
 95         if (fl->fl_lmops && fl->fl_lmops->lm_grant)
 96                 op->info.owner  = (__u64) fl->fl_pid;
 97         else
 98                 op->info.owner  = (__u64)(long) fl->fl_owner;
 99 
100         op->info.flags |= DLM_PLOCK_FL_CLOSE;
101         send_op(op);
102 }
103 
104 int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
105                    int cmd, struct file_lock *fl)
106 {
107         struct dlm_ls *ls;
108         struct plock_op *op;
109         struct plock_xop *xop;
110         int rv;
111 
112         ls = dlm_find_lockspace_local(lockspace);
113         if (!ls)
114                 return -EINVAL;
115 
116         xop = kzalloc(sizeof(*xop), GFP_NOFS);
117         if (!xop) {
118                 rv = -ENOMEM;
119                 goto out;
120         }
121 
122         op = &xop->xop;
123         op->info.optype         = DLM_PLOCK_OP_LOCK;
124         op->info.pid            = fl->fl_pid;
125         op->info.ex             = (fl->fl_type == F_WRLCK);
126         op->info.wait           = IS_SETLKW(cmd);
127         op->info.fsid           = ls->ls_global_id;
128         op->info.number         = number;
129         op->info.start          = fl->fl_start;
130         op->info.end            = fl->fl_end;
131         if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
132                 /* fl_owner is lockd which doesn't distinguish
133                    processes on the nfs client */
134                 op->info.owner  = (__u64) fl->fl_pid;
135                 xop->callback   = fl->fl_lmops->lm_grant;
136                 locks_init_lock(&xop->flc);
137                 locks_copy_lock(&xop->flc, fl);
138                 xop->fl         = fl;
139                 xop->file       = file;
140         } else {
141                 op->info.owner  = (__u64)(long) fl->fl_owner;
142                 xop->callback   = NULL;
143         }
144 
145         send_op(op);
146 
147         if (xop->callback == NULL) {
148                 rv = wait_event_killable(recv_wq, (op->done != 0));
149                 if (rv == -ERESTARTSYS) {
150                         log_debug(ls, "dlm_posix_lock: wait killed %llx",
151                                   (unsigned long long)number);
152                         spin_lock(&ops_lock);
153                         list_del(&op->list);
154                         spin_unlock(&ops_lock);
155                         kfree(xop);
156                         do_unlock_close(ls, number, file, fl);
157                         goto out;
158                 }
159         } else {
160                 rv = FILE_LOCK_DEFERRED;
161                 goto out;
162         }
163 
164         spin_lock(&ops_lock);
165         if (!list_empty(&op->list)) {
166                 log_error(ls, "dlm_posix_lock: op on list %llx",
167                           (unsigned long long)number);
168                 list_del(&op->list);
169         }
170         spin_unlock(&ops_lock);
171 
172         rv = op->info.rv;
173 
174         if (!rv) {
175                 if (posix_lock_file_wait(file, fl) < 0)
176                         log_error(ls, "dlm_posix_lock: vfs lock error %llx",
177                                   (unsigned long long)number);
178         }
179 
180         kfree(xop);
181 out:
182         dlm_put_lockspace(ls);
183         return rv;
184 }
185 EXPORT_SYMBOL_GPL(dlm_posix_lock);
186 
187 /* Returns failure iff a successful lock operation should be canceled */
188 static int dlm_plock_callback(struct plock_op *op)
189 {
190         struct file *file;
191         struct file_lock *fl;
192         struct file_lock *flc;
193         int (*notify)(struct file_lock *fl, int result) = NULL;
194         struct plock_xop *xop = (struct plock_xop *)op;
195         int rv = 0;
196 
197         spin_lock(&ops_lock);
198         if (!list_empty(&op->list)) {
199                 log_print("dlm_plock_callback: op on list %llx",
200                           (unsigned long long)op->info.number);
201                 list_del(&op->list);
202         }
203         spin_unlock(&ops_lock);
204 
205         /* check if the following 2 are still valid or make a copy */
206         file = xop->file;
207         flc = &xop->flc;
208         fl = xop->fl;
209         notify = xop->callback;
210 
211         if (op->info.rv) {
212                 notify(fl, op->info.rv);
213                 goto out;
214         }
215 
216         /* got fs lock; bookkeep locally as well: */
217         flc->fl_flags &= ~FL_SLEEP;
218         if (posix_lock_file(file, flc, NULL)) {
219                 /*
220                  * This can only happen in the case of kmalloc() failure.
221                  * The filesystem's own lock is the authoritative lock,
222                  * so a failure to get the lock locally is not a disaster.
223                  * As long as the fs cannot reliably cancel locks (especially
224                  * in a low-memory situation), we're better off ignoring
225                  * this failure than trying to recover.
226                  */
227                 log_print("dlm_plock_callback: vfs lock error %llx file %p fl %p",
228                           (unsigned long long)op->info.number, file, fl);
229         }
230 
231         rv = notify(fl, 0);
232         if (rv) {
233                 /* XXX: We need to cancel the fs lock here: */
234                 log_print("dlm_plock_callback: lock granted after lock request "
235                           "failed; dangling lock!\n");
236                 goto out;
237         }
238 
239 out:
240         kfree(xop);
241         return rv;
242 }
243 
244 int dlm_posix_unlock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
245                      struct file_lock *fl)
246 {
247         struct dlm_ls *ls;
248         struct plock_op *op;
249         int rv;
250         unsigned char fl_flags = fl->fl_flags;
251 
252         ls = dlm_find_lockspace_local(lockspace);
253         if (!ls)
254                 return -EINVAL;
255 
256         op = kzalloc(sizeof(*op), GFP_NOFS);
257         if (!op) {
258                 rv = -ENOMEM;
259                 goto out;
260         }
261 
262         /* cause the vfs unlock to return ENOENT if lock is not found */
263         fl->fl_flags |= FL_EXISTS;
264 
265         rv = posix_lock_file_wait(file, fl);
266         if (rv == -ENOENT) {
267                 rv = 0;
268                 goto out_free;
269         }
270         if (rv < 0) {
271                 log_error(ls, "dlm_posix_unlock: vfs unlock error %d %llx",
272                           rv, (unsigned long long)number);
273         }
274 
275         op->info.optype         = DLM_PLOCK_OP_UNLOCK;
276         op->info.pid            = fl->fl_pid;
277         op->info.fsid           = ls->ls_global_id;
278         op->info.number         = number;
279         op->info.start          = fl->fl_start;
280         op->info.end            = fl->fl_end;
281         if (fl->fl_lmops && fl->fl_lmops->lm_grant)
282                 op->info.owner  = (__u64) fl->fl_pid;
283         else
284                 op->info.owner  = (__u64)(long) fl->fl_owner;
285 
286         if (fl->fl_flags & FL_CLOSE) {
287                 op->info.flags |= DLM_PLOCK_FL_CLOSE;
288                 send_op(op);
289                 rv = 0;
290                 goto out;
291         }
292 
293         send_op(op);
294         wait_event(recv_wq, (op->done != 0));
295 
296         spin_lock(&ops_lock);
297         if (!list_empty(&op->list)) {
298                 log_error(ls, "dlm_posix_unlock: op on list %llx",
299                           (unsigned long long)number);
300                 list_del(&op->list);
301         }
302         spin_unlock(&ops_lock);
303 
304         rv = op->info.rv;
305 
306         if (rv == -ENOENT)
307                 rv = 0;
308 
309 out_free:
310         kfree(op);
311 out:
312         dlm_put_lockspace(ls);
313         fl->fl_flags = fl_flags;
314         return rv;
315 }
316 EXPORT_SYMBOL_GPL(dlm_posix_unlock);
317 
318 int dlm_posix_get(dlm_lockspace_t *lockspace, u64 number, struct file *file,
319                   struct file_lock *fl)
320 {
321         struct dlm_ls *ls;
322         struct plock_op *op;
323         int rv;
324 
325         ls = dlm_find_lockspace_local(lockspace);
326         if (!ls)
327                 return -EINVAL;
328 
329         op = kzalloc(sizeof(*op), GFP_NOFS);
330         if (!op) {
331                 rv = -ENOMEM;
332                 goto out;
333         }
334 
335         op->info.optype         = DLM_PLOCK_OP_GET;
336         op->info.pid            = fl->fl_pid;
337         op->info.ex             = (fl->fl_type == F_WRLCK);
338         op->info.fsid           = ls->ls_global_id;
339         op->info.number         = number;
340         op->info.start          = fl->fl_start;
341         op->info.end            = fl->fl_end;
342         if (fl->fl_lmops && fl->fl_lmops->lm_grant)
343                 op->info.owner  = (__u64) fl->fl_pid;
344         else
345                 op->info.owner  = (__u64)(long) fl->fl_owner;
346 
347         send_op(op);
348         wait_event(recv_wq, (op->done != 0));
349 
350         spin_lock(&ops_lock);
351         if (!list_empty(&op->list)) {
352                 log_error(ls, "dlm_posix_get: op on list %llx",
353                           (unsigned long long)number);
354                 list_del(&op->list);
355         }
356         spin_unlock(&ops_lock);
357 
358         /* info.rv from userspace is 1 for conflict, 0 for no-conflict,
359            -ENOENT if there are no locks on the file */
360 
361         rv = op->info.rv;
362 
363         fl->fl_type = F_UNLCK;
364         if (rv == -ENOENT)
365                 rv = 0;
366         else if (rv > 0) {
367                 locks_init_lock(fl);
368                 fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
369                 fl->fl_flags = FL_POSIX;
370                 fl->fl_pid = op->info.pid;
371                 fl->fl_start = op->info.start;
372                 fl->fl_end = op->info.end;
373                 rv = 0;
374         }
375 
376         kfree(op);
377 out:
378         dlm_put_lockspace(ls);
379         return rv;
380 }
381 EXPORT_SYMBOL_GPL(dlm_posix_get);
382 
383 /* a read copies out one plock request from the send list */
384 static ssize_t dev_read(struct file *file, char __user *u, size_t count,
385                         loff_t *ppos)
386 {
387         struct dlm_plock_info info;
388         struct plock_op *op = NULL;
389 
390         if (count < sizeof(info))
391                 return -EINVAL;
392 
393         spin_lock(&ops_lock);
394         if (!list_empty(&send_list)) {
395                 op = list_entry(send_list.next, struct plock_op, list);
396                 if (op->info.flags & DLM_PLOCK_FL_CLOSE)
397                         list_del(&op->list);
398                 else
399                         list_move(&op->list, &recv_list);
400                 memcpy(&info, &op->info, sizeof(info));
401         }
402         spin_unlock(&ops_lock);
403 
404         if (!op)
405                 return -EAGAIN;
406 
407         /* there is no need to get a reply from userspace for unlocks
408            that were generated by the vfs cleaning up for a close
409            (the process did not make an unlock call). */
410 
411         if (op->info.flags & DLM_PLOCK_FL_CLOSE)
412                 kfree(op);
413 
414         if (copy_to_user(u, &info, sizeof(info)))
415                 return -EFAULT;
416         return sizeof(info);
417 }
418 
419 /* a write copies in one plock result that should match a plock_op
420    on the recv list */
421 static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
422                          loff_t *ppos)
423 {
424         struct dlm_plock_info info;
425         struct plock_op *op;
426         int found = 0, do_callback = 0;
427 
428         if (count != sizeof(info))
429                 return -EINVAL;
430 
431         if (copy_from_user(&info, u, sizeof(info)))
432                 return -EFAULT;
433 
434         if (check_version(&info))
435                 return -EINVAL;
436 
437         spin_lock(&ops_lock);
438         list_for_each_entry(op, &recv_list, list) {
439                 if (op->info.fsid == info.fsid &&
440                     op->info.number == info.number &&
441                     op->info.owner == info.owner) {
442                         struct plock_xop *xop = (struct plock_xop *)op;
443                         list_del_init(&op->list);
444                         memcpy(&op->info, &info, sizeof(info));
445                         if (xop->callback)
446                                 do_callback = 1;
447                         else
448                                 op->done = 1;
449                         found = 1;
450                         break;
451                 }
452         }
453         spin_unlock(&ops_lock);
454 
455         if (found) {
456                 if (do_callback)
457                         dlm_plock_callback(op);
458                 else
459                         wake_up(&recv_wq);
460         } else
461                 log_print("dev_write no op %x %llx", info.fsid,
462                           (unsigned long long)info.number);
463         return count;
464 }
465 
466 static unsigned int dev_poll(struct file *file, poll_table *wait)
467 {
468         unsigned int mask = 0;
469 
470         poll_wait(file, &send_wq, wait);
471 
472         spin_lock(&ops_lock);
473         if (!list_empty(&send_list))
474                 mask = POLLIN | POLLRDNORM;
475         spin_unlock(&ops_lock);
476 
477         return mask;
478 }
479 
480 static const struct file_operations dev_fops = {
481         .read    = dev_read,
482         .write   = dev_write,
483         .poll    = dev_poll,
484         .owner   = THIS_MODULE,
485         .llseek  = noop_llseek,
486 };
487 
488 static struct miscdevice plock_dev_misc = {
489         .minor = MISC_DYNAMIC_MINOR,
490         .name = DLM_PLOCK_MISC_NAME,
491         .fops = &dev_fops
492 };
493 
494 int dlm_plock_init(void)
495 {
496         int rv;
497 
498         spin_lock_init(&ops_lock);
499         INIT_LIST_HEAD(&send_list);
500         INIT_LIST_HEAD(&recv_list);
501         init_waitqueue_head(&send_wq);
502         init_waitqueue_head(&recv_wq);
503 
504         rv = misc_register(&plock_dev_misc);
505         if (rv)
506                 log_print("dlm_plock_init: misc_register failed %d", rv);
507         return rv;
508 }
509 
510 void dlm_plock_exit(void)
511 {
512         if (misc_deregister(&plock_dev_misc) < 0)
513                 log_print("dlm_plock_exit: misc_deregister failed");
514 }
515 
516 

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