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         void *callback;
  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->fl_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->fl_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->fl_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)(void *, void *, int) = 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, NULL, 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, NULL, 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
 251         ls = dlm_find_lockspace_local(lockspace);
 252         if (!ls)
 253                 return -EINVAL;
 254
 255         op = kzalloc(sizeof(*op), GFP_NOFS);
 256         if (!op) {
 257                 rv = -ENOMEM;
 258                 goto out;
 259         }
 260
 261         if (posix_lock_file_wait(file, fl) < 0)
 262                 log_error(ls, "dlm_posix_unlock: vfs unlock error %llx",
 263                           (unsigned long long)number);
 264
 265         op->info.optype         = DLM_PLOCK_OP_UNLOCK;
 266         op->info.pid            = fl->fl_pid;
 267         op->info.fsid           = ls->ls_global_id;
 268         op->info.number         = number;
 269         op->info.start          = fl->fl_start;
 270         op->info.end            = fl->fl_end;
 271         if (fl->fl_lmops && fl->fl_lmops->fl_grant)
 272                 op->info.owner  = (__u64) fl->fl_pid;
 273         else
 274                 op->info.owner  = (__u64)(long) fl->fl_owner;
 275
 276         if (fl->fl_flags & FL_CLOSE) {
 277                 op->info.flags |= DLM_PLOCK_FL_CLOSE;
 278                 send_op(op);
 279                 rv = 0;
 280                 goto out;
 281         }
 282
 283         send_op(op);
 284         wait_event(recv_wq, (op->done != 0));
 285
 286         spin_lock(&ops_lock);
 287         if (!list_empty(&op->list)) {
 288                 log_error(ls, "dlm_posix_unlock: op on list %llx",
 289                           (unsigned long long)number);
 290                 list_del(&op->list);
 291         }
 292         spin_unlock(&ops_lock);
 293
 294         rv = op->info.rv;
 295
 296         if (rv == -ENOENT)
 297                 rv = 0;
 298
 299         kfree(op);
 300 out:
 301         dlm_put_lockspace(ls);
 302         return rv;
 303 }
 304 EXPORT_SYMBOL_GPL(dlm_posix_unlock);
 305
 306 int dlm_posix_get(dlm_lockspace_t *lockspace, u64 number, struct file *file,
 307                   struct file_lock *fl)
 308 {
 309         struct dlm_ls *ls;
 310         struct plock_op *op;
 311         int rv;
 312
 313         ls = dlm_find_lockspace_local(lockspace);
 314         if (!ls)
 315                 return -EINVAL;
 316
 317         op = kzalloc(sizeof(*op), GFP_NOFS);
 318         if (!op) {
 319                 rv = -ENOMEM;
 320                 goto out;
 321         }
 322
 323         op->info.optype         = DLM_PLOCK_OP_GET;
 324         op->info.pid            = fl->fl_pid;
 325         op->info.ex             = (fl->fl_type == F_WRLCK);
 326         op->info.fsid           = ls->ls_global_id;
 327         op->info.number         = number;
 328         op->info.start          = fl->fl_start;
 329         op->info.end            = fl->fl_end;
 330         if (fl->fl_lmops && fl->fl_lmops->fl_grant)
 331                 op->info.owner  = (__u64) fl->fl_pid;
 332         else
 333                 op->info.owner  = (__u64)(long) fl->fl_owner;
 334
 335         send_op(op);
 336         wait_event(recv_wq, (op->done != 0));
 337
 338         spin_lock(&ops_lock);
 339         if (!list_empty(&op->list)) {
 340                 log_error(ls, "dlm_posix_get: op on list %llx",
 341                           (unsigned long long)number);
 342                 list_del(&op->list);
 343         }
 344         spin_unlock(&ops_lock);
 345
 346         /* info.rv from userspace is 1 for conflict, 0 for no-conflict,
 347            -ENOENT if there are no locks on the file */
 348
 349         rv = op->info.rv;
 350
 351         fl->fl_type = F_UNLCK;
 352         if (rv == -ENOENT)
 353                 rv = 0;
 354         else if (rv > 0) {
 355                 locks_init_lock(fl);
 356                 fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
 357                 fl->fl_flags = FL_POSIX;
 358                 fl->fl_pid = op->info.pid;
 359                 fl->fl_start = op->info.start;
 360                 fl->fl_end = op->info.end;
 361                 rv = 0;
 362         }
 363
 364         kfree(op);
 365 out:
 366         dlm_put_lockspace(ls);
 367         return rv;
 368 }
 369 EXPORT_SYMBOL_GPL(dlm_posix_get);
 370
 371 /* a read copies out one plock request from the send list */
 372 static ssize_t dev_read(struct file *file, char __user *u, size_t count,
 373                         loff_t *ppos)
 374 {
 375         struct dlm_plock_info info;
 376         struct plock_op *op = NULL;
 377
 378         if (count < sizeof(info))
 379                 return -EINVAL;
 380
 381         spin_lock(&ops_lock);
 382         if (!list_empty(&send_list)) {
 383                 op = list_entry(send_list.next, struct plock_op, list);
 384                 if (op->info.flags & DLM_PLOCK_FL_CLOSE)
 385                         list_del(&op->list);
 386                 else
 387                         list_move(&op->list, &recv_list);
 388                 memcpy(&info, &op->info, sizeof(info));
 389         }
 390         spin_unlock(&ops_lock);
 391
 392         if (!op)
 393                 return -EAGAIN;
 394
 395         /* there is no need to get a reply from userspace for unlocks
 396            that were generated by the vfs cleaning up for a close
 397            (the process did not make an unlock call). */
 398
 399         if (op->info.flags & DLM_PLOCK_FL_CLOSE)
 400                 kfree(op);
 401
 402         if (copy_to_user(u, &info, sizeof(info)))
 403                 return -EFAULT;
 404         return sizeof(info);
 405 }
 406
 407 /* a write copies in one plock result that should match a plock_op
 408    on the recv list */
 409 static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
 410                          loff_t *ppos)
 411 {
 412         struct dlm_plock_info info;
 413         struct plock_op *op;
 414         int found = 0, do_callback = 0;
 415
 416         if (count != sizeof(info))
 417                 return -EINVAL;
 418
 419         if (copy_from_user(&info, u, sizeof(info)))
 420                 return -EFAULT;
 421
 422         if (check_version(&info))
 423                 return -EINVAL;
 424
 425         spin_lock(&ops_lock);
 426         list_for_each_entry(op, &recv_list, list) {
 427                 if (op->info.fsid == info.fsid &&
 428                     op->info.number == info.number &&
 429                     op->info.owner == info.owner) {
 430                         struct plock_xop *xop = (struct plock_xop *)op;
 431                         list_del_init(&op->list);
 432                         memcpy(&op->info, &info, sizeof(info));
 433                         if (xop->callback)
 434                                 do_callback = 1;
 435                         else
 436                                 op->done = 1;
 437                         found = 1;
 438                         break;
 439                 }
 440         }
 441         spin_unlock(&ops_lock);
 442
 443         if (found) {
 444                 if (do_callback)
 445                         dlm_plock_callback(op);
 446                 else
 447                         wake_up(&recv_wq);
 448         } else
 449                 log_print("dev_write no op %x %llx", info.fsid,
 450                           (unsigned long long)info.number);
 451         return count;
 452 }
 453
 454 static unsigned int dev_poll(struct file *file, poll_table *wait)
 455 {
 456         unsigned int mask = 0;
 457
 458         poll_wait(file, &send_wq, wait);
 459
 460         spin_lock(&ops_lock);
 461         if (!list_empty(&send_list))
 462                 mask = POLLIN | POLLRDNORM;
 463         spin_unlock(&ops_lock);
 464
 465         return mask;
 466 }
 467
 468 static const struct file_operations dev_fops = {
 469         .read    = dev_read,
 470         .write   = dev_write,
 471         .poll    = dev_poll,
 472         .owner   = THIS_MODULE,
 473         .llseek  = noop_llseek,
 474 };
 475
 476 static struct miscdevice plock_dev_misc = {
 477         .minor = MISC_DYNAMIC_MINOR,
 478         .name = DLM_PLOCK_MISC_NAME,
 479         .fops = &dev_fops
 480 };
 481
 482 int dlm_plock_init(void)
 483 {
 484         int rv;
 485
 486         spin_lock_init(&ops_lock);
 487         INIT_LIST_HEAD(&send_list);
 488         INIT_LIST_HEAD(&recv_list);
 489         init_waitqueue_head(&send_wq);
 490         init_waitqueue_head(&recv_wq);
 491
 492         rv = misc_register(&plock_dev_misc);
 493         if (rv)
 494                 log_print("dlm_plock_init: misc_register failed %d", rv);
 495         return rv;
 496 }
 497
 498 void dlm_plock_exit(void)
 499 {
 500         if (misc_deregister(&plock_dev_misc) < 0)
 501                 log_print("dlm_plock_exit: misc_deregister failed");
 502 }
 503