fs/dlm/plock.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2005-2008 Red Hat, Inc.  All rights reserved.
   4  */
   5
   6 #include <linux/fs.h>
   7 #include <linux/miscdevice.h>
   8 #include <linux/poll.h>
   9 #include <linux/dlm.h>
  10 #include <linux/dlm_plock.h>
  11 #include <linux/slab.h>
  12
  13 #include "dlm_internal.h"
  14 #include "lockspace.h"
  15
  16 static spinlock_t ops_lock;
  17 static struct list_head send_list;
  18 static struct list_head recv_list;
  19 static wait_queue_head_t send_wq;
  20 static wait_queue_head_t recv_wq;
  21
  22 struct plock_op {
  23         struct list_head list;
  24         int done;
  25         struct dlm_plock_info info;
  26 };
  27
  28 struct plock_xop {
  29         struct plock_op xop;
  30         int (*callback)(struct file_lock *fl, int result);
  31         void *fl;
  32         void *file;
  33         struct file_lock flc;
  34 };
  35
  36
  37 static inline void set_version(struct dlm_plock_info *info)
  38 {
  39         info->version[0] = DLM_PLOCK_VERSION_MAJOR;
  40         info->version[1] = DLM_PLOCK_VERSION_MINOR;
  41         info->version[2] = DLM_PLOCK_VERSION_PATCH;
  42 }
  43
  44 static int check_version(struct dlm_plock_info *info)
  45 {
  46         if ((DLM_PLOCK_VERSION_MAJOR != info->version[0]) ||
  47             (DLM_PLOCK_VERSION_MINOR < info->version[1])) {
  48                 log_print("plock device version mismatch: "
  49                           "kernel (%u.%u.%u), user (%u.%u.%u)",
  50                           DLM_PLOCK_VERSION_MAJOR,
  51                           DLM_PLOCK_VERSION_MINOR,
  52                           DLM_PLOCK_VERSION_PATCH,
  53                           info->version[0],
  54                           info->version[1],
  55                           info->version[2]);
  56                 return -EINVAL;
  57         }
  58         return 0;
  59 }
  60
  61 static void send_op(struct plock_op *op)
  62 {
  63         set_version(&op->info);
  64         INIT_LIST_HEAD(&op->list);
  65         spin_lock(&ops_lock);
  66         list_add_tail(&op->list, &send_list);
  67         spin_unlock(&ops_lock);
  68         wake_up(&send_wq);
  69 }
  70
  71 /* If a process was killed while waiting for the only plock on a file,
  72    locks_remove_posix will not see any lock on the file so it won't
  73    send an unlock-close to us to pass on to userspace to clean up the
  74    abandoned waiter.  So, we have to insert the unlock-close when the
  75    lock call is interrupted. */
  76
  77 static void do_unlock_close(struct dlm_ls *ls, u64 number,
  78                             struct file *file, struct file_lock *fl)
  79 {
  80         struct plock_op *op;
  81
  82         op = kzalloc(sizeof(*op), GFP_NOFS);
  83         if (!op)
  84                 return;
  85
  86         op->info.optype         = DLM_PLOCK_OP_UNLOCK;
  87         op->info.pid            = fl->fl_pid;
  88         op->info.fsid           = ls->ls_global_id;
  89         op->info.number         = number;
  90         op->info.start          = 0;
  91         op->info.end            = OFFSET_MAX;
  92         if (fl->fl_lmops && fl->fl_lmops->lm_grant)
  93                 op->info.owner  = (__u64) fl->fl_pid;
  94         else
  95                 op->info.owner  = (__u64)(long) fl->fl_owner;
  96
  97         op->info.flags |= DLM_PLOCK_FL_CLOSE;
  98         send_op(op);
  99 }
 100
 101 int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
 102                    int cmd, struct file_lock *fl)
 103 {
 104         struct dlm_ls *ls;
 105         struct plock_op *op;
 106         struct plock_xop *xop;
 107         int rv;
 108
 109         ls = dlm_find_lockspace_local(lockspace);
 110         if (!ls)
 111                 return -EINVAL;
 112
 113         xop = kzalloc(sizeof(*xop), GFP_NOFS);
 114         if (!xop) {
 115                 rv = -ENOMEM;
 116                 goto out;
 117         }
 118
 119         op = &xop->xop;
 120         op->info.optype         = DLM_PLOCK_OP_LOCK;
 121         op->info.pid            = fl->fl_pid;
 122         op->info.ex             = (fl->fl_type == F_WRLCK);
 123         op->info.wait           = IS_SETLKW(cmd);
 124         op->info.fsid           = ls->ls_global_id;
 125         op->info.number         = number;
 126         op->info.start          = fl->fl_start;
 127         op->info.end            = fl->fl_end;
 128         if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
 129                 /* fl_owner is lockd which doesn't distinguish
 130                    processes on the nfs client */
 131                 op->info.owner  = (__u64) fl->fl_pid;
 132                 xop->callback   = fl->fl_lmops->lm_grant;
 133                 locks_init_lock(&xop->flc);
 134                 locks_copy_lock(&xop->flc, fl);
 135                 xop->fl         = fl;
 136                 xop->file       = file;
 137         } else {
 138                 op->info.owner  = (__u64)(long) fl->fl_owner;
 139                 xop->callback   = NULL;
 140         }
 141
 142         send_op(op);
 143
 144         if (xop->callback == NULL) {
 145                 rv = wait_event_interruptible(recv_wq, (op->done != 0));
 146                 if (rv == -ERESTARTSYS) {
 147                         log_debug(ls, "dlm_posix_lock: wait killed %llx",
 148                                   (unsigned long long)number);
 149                         spin_lock(&ops_lock);
 150                         list_del(&op->list);
 151                         spin_unlock(&ops_lock);
 152                         kfree(xop);
 153                         do_unlock_close(ls, number, file, fl);
 154                         goto out;
 155                 }
 156         } else {
 157                 rv = FILE_LOCK_DEFERRED;
 158                 goto out;
 159         }
 160
 161         spin_lock(&ops_lock);
 162         if (!list_empty(&op->list)) {
 163                 log_error(ls, "dlm_posix_lock: op on list %llx",
 164                           (unsigned long long)number);
 165                 list_del(&op->list);
 166         }
 167         spin_unlock(&ops_lock);
 168
 169         rv = op->info.rv;
 170
 171         if (!rv) {
 172                 if (locks_lock_file_wait(file, fl) < 0)
 173                         log_error(ls, "dlm_posix_lock: vfs lock error %llx",
 174                                   (unsigned long long)number);
 175         }
 176
 177         kfree(xop);
 178 out:
 179         dlm_put_lockspace(ls);
 180         return rv;
 181 }
 182 EXPORT_SYMBOL_GPL(dlm_posix_lock);
 183
 184 /* Returns failure iff a successful lock operation should be canceled */
 185 static int dlm_plock_callback(struct plock_op *op)
 186 {
 187         struct file *file;
 188         struct file_lock *fl;
 189         struct file_lock *flc;
 190         int (*notify)(struct file_lock *fl, int result) = NULL;
 191         struct plock_xop *xop = (struct plock_xop *)op;
 192         int rv = 0;
 193
 194         spin_lock(&ops_lock);
 195         if (!list_empty(&op->list)) {
 196                 log_print("dlm_plock_callback: op on list %llx",
 197                           (unsigned long long)op->info.number);
 198                 list_del(&op->list);
 199         }
 200         spin_unlock(&ops_lock);
 201
 202         /* check if the following 2 are still valid or make a copy */
 203         file = xop->file;
 204         flc = &xop->flc;
 205         fl = xop->fl;
 206         notify = xop->callback;
 207
 208         if (op->info.rv) {
 209                 notify(fl, op->info.rv);
 210                 goto out;
 211         }
 212
 213         /* got fs lock; bookkeep locally as well: */
 214         flc->fl_flags &= ~FL_SLEEP;
 215         if (posix_lock_file(file, flc, NULL)) {
 216                 /*
 217                  * This can only happen in the case of kmalloc() failure.
 218                  * The filesystem's own lock is the authoritative lock,
 219                  * so a failure to get the lock locally is not a disaster.
 220                  * As long as the fs cannot reliably cancel locks (especially
 221                  * in a low-memory situation), we're better off ignoring
 222                  * this failure than trying to recover.
 223                  */
 224                 log_print("dlm_plock_callback: vfs lock error %llx file %p fl %p",
 225                           (unsigned long long)op->info.number, file, fl);
 226         }
 227
 228         rv = notify(fl, 0);
 229         if (rv) {
 230                 /* XXX: We need to cancel the fs lock here: */
 231                 log_print("dlm_plock_callback: lock granted after lock request "
 232                           "failed; dangling lock!\n");
 233                 goto out;
 234         }
 235
 236 out:
 237         kfree(xop);
 238         return rv;
 239 }
 240
 241 int dlm_posix_unlock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
 242                      struct file_lock *fl)
 243 {
 244         struct dlm_ls *ls;
 245         struct plock_op *op;
 246         int rv;
 247         unsigned char fl_flags = fl->fl_flags;
 248
 249         ls = dlm_find_lockspace_local(lockspace);
 250         if (!ls)
 251                 return -EINVAL;
 252
 253         op = kzalloc(sizeof(*op), GFP_NOFS);
 254         if (!op) {
 255                 rv = -ENOMEM;
 256                 goto out;
 257         }
 258
 259         /* cause the vfs unlock to return ENOENT if lock is not found */
 260         fl->fl_flags |= FL_EXISTS;
 261
 262         rv = locks_lock_file_wait(file, fl);
 263         if (rv == -ENOENT) {
 264                 rv = 0;
 265                 goto out_free;
 266         }
 267         if (rv < 0) {
 268                 log_error(ls, "dlm_posix_unlock: vfs unlock error %d %llx",
 269                           rv, (unsigned long long)number);
 270         }
 271
 272         op->info.optype         = DLM_PLOCK_OP_UNLOCK;
 273         op->info.pid            = fl->fl_pid;
 274         op->info.fsid           = ls->ls_global_id;
 275         op->info.number         = number;
 276         op->info.start          = fl->fl_start;
 277         op->info.end            = fl->fl_end;
 278         if (fl->fl_lmops && fl->fl_lmops->lm_grant)
 279                 op->info.owner  = (__u64) fl->fl_pid;
 280         else
 281                 op->info.owner  = (__u64)(long) fl->fl_owner;
 282
 283         if (fl->fl_flags & FL_CLOSE) {
 284                 op->info.flags |= DLM_PLOCK_FL_CLOSE;
 285                 send_op(op);
 286                 rv = 0;
 287                 goto out;
 288         }
 289
 290         send_op(op);
 291         wait_event(recv_wq, (op->done != 0));
 292
 293         spin_lock(&ops_lock);
 294         if (!list_empty(&op->list)) {
 295                 log_error(ls, "dlm_posix_unlock: op on list %llx",
 296                           (unsigned long long)number);
 297                 list_del(&op->list);
 298         }
 299         spin_unlock(&ops_lock);
 300
 301         rv = op->info.rv;
 302
 303         if (rv == -ENOENT)
 304                 rv = 0;
 305
 306 out_free:
 307         kfree(op);
 308 out:
 309         dlm_put_lockspace(ls);
 310         fl->fl_flags = fl_flags;
 311         return rv;
 312 }
 313 EXPORT_SYMBOL_GPL(dlm_posix_unlock);
 314
 315 int dlm_posix_get(dlm_lockspace_t *lockspace, u64 number, struct file *file,
 316                   struct file_lock *fl)
 317 {
 318         struct dlm_ls *ls;
 319         struct plock_op *op;
 320         int rv;
 321
 322         ls = dlm_find_lockspace_local(lockspace);
 323         if (!ls)
 324                 return -EINVAL;
 325
 326         op = kzalloc(sizeof(*op), GFP_NOFS);
 327         if (!op) {
 328                 rv = -ENOMEM;
 329                 goto out;
 330         }
 331
 332         op->info.optype         = DLM_PLOCK_OP_GET;
 333         op->info.pid            = fl->fl_pid;
 334         op->info.ex             = (fl->fl_type == F_WRLCK);
 335         op->info.fsid           = ls->ls_global_id;
 336         op->info.number         = number;
 337         op->info.start          = fl->fl_start;
 338         op->info.end            = fl->fl_end;
 339         if (fl->fl_lmops && fl->fl_lmops->lm_grant)
 340                 op->info.owner  = (__u64) fl->fl_pid;
 341         else
 342                 op->info.owner  = (__u64)(long) fl->fl_owner;
 343
 344         send_op(op);
 345         wait_event(recv_wq, (op->done != 0));
 346
 347         spin_lock(&ops_lock);
 348         if (!list_empty(&op->list)) {
 349                 log_error(ls, "dlm_posix_get: op on list %llx",
 350                           (unsigned long long)number);
 351                 list_del(&op->list);
 352         }
 353         spin_unlock(&ops_lock);
 354
 355         /* info.rv from userspace is 1 for conflict, 0 for no-conflict,
 356            -ENOENT if there are no locks on the file */
 357
 358         rv = op->info.rv;
 359
 360         fl->fl_type = F_UNLCK;
 361         if (rv == -ENOENT)
 362                 rv = 0;
 363         else if (rv > 0) {
 364                 locks_init_lock(fl);
 365                 fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
 366                 fl->fl_flags = FL_POSIX;
 367                 fl->fl_pid = -op->info.pid;
 368                 fl->fl_start = op->info.start;
 369                 fl->fl_end = op->info.end;
 370                 rv = 0;
 371         }
 372
 373         kfree(op);
 374 out:
 375         dlm_put_lockspace(ls);
 376         return rv;
 377 }
 378 EXPORT_SYMBOL_GPL(dlm_posix_get);
 379
 380 /* a read copies out one plock request from the send list */
 381 static ssize_t dev_read(struct file *file, char __user *u, size_t count,
 382                         loff_t *ppos)
 383 {
 384         struct dlm_plock_info info;
 385         struct plock_op *op = NULL;
 386
 387         if (count < sizeof(info))
 388                 return -EINVAL;
 389
 390         spin_lock(&ops_lock);
 391         if (!list_empty(&send_list)) {
 392                 op = list_entry(send_list.next, struct plock_op, list);
 393                 if (op->info.flags & DLM_PLOCK_FL_CLOSE)
 394                         list_del(&op->list);
 395                 else
 396                         list_move(&op->list, &recv_list);
 397                 memcpy(&info, &op->info, sizeof(info));
 398         }
 399         spin_unlock(&ops_lock);
 400
 401         if (!op)
 402                 return -EAGAIN;
 403
 404         /* there is no need to get a reply from userspace for unlocks
 405            that were generated by the vfs cleaning up for a close
 406            (the process did not make an unlock call). */
 407
 408         if (op->info.flags & DLM_PLOCK_FL_CLOSE)
 409                 kfree(op);
 410
 411         if (copy_to_user(u, &info, sizeof(info)))
 412                 return -EFAULT;
 413         return sizeof(info);
 414 }
 415
 416 /* a write copies in one plock result that should match a plock_op
 417    on the recv list */
 418 static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
 419                          loff_t *ppos)
 420 {
 421         struct dlm_plock_info info;
 422         struct plock_op *op;
 423         int found = 0, do_callback = 0;
 424
 425         if (count != sizeof(info))
 426                 return -EINVAL;
 427
 428         if (copy_from_user(&info, u, sizeof(info)))
 429                 return -EFAULT;
 430
 431         if (check_version(&info))
 432                 return -EINVAL;
 433
 434         spin_lock(&ops_lock);
 435         list_for_each_entry(op, &recv_list, list) {
 436                 if (op->info.fsid == info.fsid &&
 437                     op->info.number == info.number &&
 438                     op->info.owner == info.owner) {
 439                         struct plock_xop *xop = (struct plock_xop *)op;
 440                         list_del_init(&op->list);
 441                         memcpy(&op->info, &info, sizeof(info));
 442                         if (xop->callback)
 443                                 do_callback = 1;
 444                         else
 445                                 op->done = 1;
 446                         found = 1;
 447                         break;
 448                 }
 449         }
 450         spin_unlock(&ops_lock);
 451
 452         if (found) {
 453                 if (do_callback)
 454                         dlm_plock_callback(op);
 455                 else
 456                         wake_up(&recv_wq);
 457         } else
 458                 log_print("dev_write no op %x %llx", info.fsid,
 459                           (unsigned long long)info.number);
 460         return count;
 461 }
 462
 463 static __poll_t dev_poll(struct file *file, poll_table *wait)
 464 {
 465         __poll_t mask = 0;
 466
 467         poll_wait(file, &send_wq, wait);
 468
 469         spin_lock(&ops_lock);
 470         if (!list_empty(&send_list))
 471                 mask = EPOLLIN | EPOLLRDNORM;
 472         spin_unlock(&ops_lock);
 473
 474         return mask;
 475 }
 476
 477 static const struct file_operations dev_fops = {
 478         .read    = dev_read,
 479         .write   = dev_write,
 480         .poll    = dev_poll,
 481         .owner   = THIS_MODULE,
 482         .llseek  = noop_llseek,
 483 };
 484
 485 static struct miscdevice plock_dev_misc = {
 486         .minor = MISC_DYNAMIC_MINOR,
 487         .name = DLM_PLOCK_MISC_NAME,
 488         .fops = &dev_fops
 489 };
 490
 491 int dlm_plock_init(void)
 492 {
 493         int rv;
 494
 495         spin_lock_init(&ops_lock);
 496         INIT_LIST_HEAD(&send_list);
 497         INIT_LIST_HEAD(&recv_list);
 498         init_waitqueue_head(&send_wq);
 499         init_waitqueue_head(&recv_wq);
 500
 501         rv = misc_register(&plock_dev_misc);
 502         if (rv)
 503                 log_print("dlm_plock_init: misc_register failed %d", rv);
 504         return rv;
 505 }
 506
 507 void dlm_plock_exit(void)
 508 {
 509         misc_deregister(&plock_dev_misc);
 510 }
 511