fs/dlm/plock.c

   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_interruptible(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 (locks_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 = locks_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 __poll_t dev_poll(struct file *file, poll_table *wait)
 467 {
 468         __poll_t mask = 0;
 469
 470         poll_wait(file, &send_wq, wait);
 471
 472         spin_lock(&ops_lock);
 473         if (!list_empty(&send_list))
 474                 mask = EPOLLIN | EPOLLRDNORM;
 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         misc_deregister(&plock_dev_misc);
 513 }
 514