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