fs/autofs/expire.c

   1 /*
   2  * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
   3  * Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
   4  * Copyright 2001-2006 Ian Kent <raven@themaw.net>
   5  *
   6  * This file is part of the Linux kernel and is made available under
   7  * the terms of the GNU General Public License, version 2, or at your
   8  * option, any later version, incorporated herein by reference.
   9  */
  10
  11 #include "autofs_i.h"
  12
  13 /* Check if a dentry can be expired */
  14 static inline int autofs_can_expire(struct dentry *dentry,
  15                                     unsigned long timeout, unsigned int how)
  16 {
  17         struct autofs_info *ino = autofs_dentry_ino(dentry);
  18
  19         /* dentry in the process of being deleted */
  20         if (ino == NULL)
  21                 return 0;
  22
  23         if (!(how & AUTOFS_EXP_IMMEDIATE)) {
  24                 /* Too young to die */
  25                 if (!timeout || time_after(ino->last_used + timeout, jiffies))
  26                         return 0;
  27         }
  28         return 1;
  29 }
  30
  31 /* Check a mount point for busyness */
  32 static int autofs_mount_busy(struct vfsmount *mnt,
  33                              struct dentry *dentry, unsigned int how)
  34 {
  35         struct dentry *top = dentry;
  36         struct path path = {.mnt = mnt, .dentry = dentry};
  37         int status = 1;
  38
  39         pr_debug("dentry %p %pd\n", dentry, dentry);
  40
  41         path_get(&path);
  42
  43         if (!follow_down_one(&path))
  44                 goto done;
  45
  46         if (is_autofs_dentry(path.dentry)) {
  47                 struct autofs_sb_info *sbi = autofs_sbi(path.dentry->d_sb);
  48
  49                 /* This is an autofs submount, we can't expire it */
  50                 if (autofs_type_indirect(sbi->type))
  51                         goto done;
  52         }
  53
  54         /* Not a submount, has a forced expire been requested */
  55         if (how & AUTOFS_EXP_FORCED) {
  56                 status = 0;
  57                 goto done;
  58         }
  59
  60         /* Update the expiry counter if fs is busy */
  61         if (!may_umount_tree(path.mnt)) {
  62                 struct autofs_info *ino;
  63
  64                 ino = autofs_dentry_ino(top);
  65                 ino->last_used = jiffies;
  66                 goto done;
  67         }
  68
  69         status = 0;
  70 done:
  71         pr_debug("returning = %d\n", status);
  72         path_put(&path);
  73         return status;
  74 }
  75
  76 /*
  77  * Calculate and dget next entry in the subdirs list under root.
  78  */
  79 static struct dentry *get_next_positive_subdir(struct dentry *prev,
  80                                                struct dentry *root)
  81 {
  82         struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
  83         struct list_head *next;
  84         struct dentry *q;
  85
  86         spin_lock(&sbi->lookup_lock);
  87         spin_lock(&root->d_lock);
  88
  89         if (prev)
  90                 next = prev->d_child.next;
  91         else {
  92                 prev = dget_dlock(root);
  93                 next = prev->d_subdirs.next;
  94         }
  95
  96 cont:
  97         if (next == &root->d_subdirs) {
  98                 spin_unlock(&root->d_lock);
  99                 spin_unlock(&sbi->lookup_lock);
 100                 dput(prev);
 101                 return NULL;
 102         }
 103
 104         q = list_entry(next, struct dentry, d_child);
 105
 106         spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
 107         /* Already gone or negative dentry (under construction) - try next */
 108         if (!d_count(q) || !simple_positive(q)) {
 109                 spin_unlock(&q->d_lock);
 110                 next = q->d_child.next;
 111                 goto cont;
 112         }
 113         dget_dlock(q);
 114         spin_unlock(&q->d_lock);
 115         spin_unlock(&root->d_lock);
 116         spin_unlock(&sbi->lookup_lock);
 117
 118         dput(prev);
 119
 120         return q;
 121 }
 122
 123 /*
 124  * Calculate and dget next entry in top down tree traversal.
 125  */
 126 static struct dentry *get_next_positive_dentry(struct dentry *prev,
 127                                                struct dentry *root)
 128 {
 129         struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
 130         struct list_head *next;
 131         struct dentry *p, *ret;
 132
 133         if (prev == NULL)
 134                 return dget(root);
 135
 136         spin_lock(&sbi->lookup_lock);
 137 relock:
 138         p = prev;
 139         spin_lock(&p->d_lock);
 140 again:
 141         next = p->d_subdirs.next;
 142         if (next == &p->d_subdirs) {
 143                 while (1) {
 144                         struct dentry *parent;
 145
 146                         if (p == root) {
 147                                 spin_unlock(&p->d_lock);
 148                                 spin_unlock(&sbi->lookup_lock);
 149                                 dput(prev);
 150                                 return NULL;
 151                         }
 152
 153                         parent = p->d_parent;
 154                         if (!spin_trylock(&parent->d_lock)) {
 155                                 spin_unlock(&p->d_lock);
 156                                 cpu_relax();
 157                                 goto relock;
 158                         }
 159                         spin_unlock(&p->d_lock);
 160                         next = p->d_child.next;
 161                         p = parent;
 162                         if (next != &parent->d_subdirs)
 163                                 break;
 164                 }
 165         }
 166         ret = list_entry(next, struct dentry, d_child);
 167
 168         spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
 169         /* Negative dentry - try next */
 170         if (!simple_positive(ret)) {
 171                 spin_unlock(&p->d_lock);
 172                 lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
 173                 p = ret;
 174                 goto again;
 175         }
 176         dget_dlock(ret);
 177         spin_unlock(&ret->d_lock);
 178         spin_unlock(&p->d_lock);
 179         spin_unlock(&sbi->lookup_lock);
 180
 181         dput(prev);
 182
 183         return ret;
 184 }
 185
 186 /*
 187  * Check a direct mount point for busyness.
 188  * Direct mounts have similar expiry semantics to tree mounts.
 189  * The tree is not busy iff no mountpoints are busy and there are no
 190  * autofs submounts.
 191  */
 192 static int autofs_direct_busy(struct vfsmount *mnt,
 193                               struct dentry *top,
 194                               unsigned long timeout,
 195                               unsigned int how)
 196 {
 197         pr_debug("top %p %pd\n", top, top);
 198
 199         /* Forced expire, user space handles busy mounts */
 200         if (how & AUTOFS_EXP_FORCED)
 201                 return 0;
 202
 203         /* If it's busy update the expiry counters */
 204         if (!may_umount_tree(mnt)) {
 205                 struct autofs_info *ino;
 206
 207                 ino = autofs_dentry_ino(top);
 208                 if (ino)
 209                         ino->last_used = jiffies;
 210                 return 1;
 211         }
 212
 213         /* Timeout of a direct mount is determined by its top dentry */
 214         if (!autofs_can_expire(top, timeout, how))
 215                 return 1;
 216
 217         return 0;
 218 }
 219
 220 /*
 221  * Check a directory tree of mount points for busyness
 222  * The tree is not busy iff no mountpoints are busy
 223  */
 224 static int autofs_tree_busy(struct vfsmount *mnt,
 225                             struct dentry *top,
 226                             unsigned long timeout,
 227                             unsigned int how)
 228 {
 229         struct autofs_info *top_ino = autofs_dentry_ino(top);
 230         struct dentry *p;
 231
 232         pr_debug("top %p %pd\n", top, top);
 233
 234         /* Negative dentry - give up */
 235         if (!simple_positive(top))
 236                 return 1;
 237
 238         p = NULL;
 239         while ((p = get_next_positive_dentry(p, top))) {
 240                 pr_debug("dentry %p %pd\n", p, p);
 241
 242                 /*
 243                  * Is someone visiting anywhere in the subtree ?
 244                  * If there's no mount we need to check the usage
 245                  * count for the autofs dentry.
 246                  * If the fs is busy update the expiry counter.
 247                  */
 248                 if (d_mountpoint(p)) {
 249                         if (autofs_mount_busy(mnt, p, how)) {
 250                                 top_ino->last_used = jiffies;
 251                                 dput(p);
 252                                 return 1;
 253                         }
 254                 } else {
 255                         struct autofs_info *ino = autofs_dentry_ino(p);
 256                         unsigned int ino_count = atomic_read(&ino->count);
 257
 258                         /* allow for dget above and top is already dgot */
 259                         if (p == top)
 260                                 ino_count += 2;
 261                         else
 262                                 ino_count++;
 263
 264                         if (d_count(p) > ino_count) {
 265                                 top_ino->last_used = jiffies;
 266                                 dput(p);
 267                                 return 1;
 268                         }
 269                 }
 270         }
 271
 272         /* Forced expire, user space handles busy mounts */
 273         if (how & AUTOFS_EXP_FORCED)
 274                 return 0;
 275
 276         /* Timeout of a tree mount is ultimately determined by its top dentry */
 277         if (!autofs_can_expire(top, timeout, how))
 278                 return 1;
 279
 280         return 0;
 281 }
 282
 283 static struct dentry *autofs_check_leaves(struct vfsmount *mnt,
 284                                           struct dentry *parent,
 285                                           unsigned long timeout,
 286                                           unsigned int how)
 287 {
 288         struct dentry *p;
 289
 290         pr_debug("parent %p %pd\n", parent, parent);
 291
 292         p = NULL;
 293         while ((p = get_next_positive_dentry(p, parent))) {
 294                 pr_debug("dentry %p %pd\n", p, p);
 295
 296                 if (d_mountpoint(p)) {
 297                         /* Can we umount this guy */
 298                         if (autofs_mount_busy(mnt, p, how))
 299                                 continue;
 300
 301                         /* This isn't a submount so if a forced expire
 302                          * has been requested, user space handles busy
 303                          * mounts */
 304                         if (how & AUTOFS_EXP_FORCED)
 305                                 return p;
 306
 307                         /* Can we expire this guy */
 308                         if (autofs_can_expire(p, timeout, how))
 309                                 return p;
 310                 }
 311         }
 312         return NULL;
 313 }
 314
 315 /* Check if we can expire a direct mount (possibly a tree) */
 316 static struct dentry *autofs_expire_direct(struct super_block *sb,
 317                                            struct vfsmount *mnt,
 318                                            struct autofs_sb_info *sbi,
 319                                            unsigned int how)
 320 {
 321         struct dentry *root = dget(sb->s_root);
 322         struct autofs_info *ino;
 323         unsigned long timeout;
 324
 325         if (!root)
 326                 return NULL;
 327
 328         timeout = sbi->exp_timeout;
 329
 330         if (!autofs_direct_busy(mnt, root, timeout, how)) {
 331                 spin_lock(&sbi->fs_lock);
 332                 ino = autofs_dentry_ino(root);
 333                 /* No point expiring a pending mount */
 334                 if (ino->flags & AUTOFS_INF_PENDING) {
 335                         spin_unlock(&sbi->fs_lock);
 336                         goto out;
 337                 }
 338                 ino->flags |= AUTOFS_INF_WANT_EXPIRE;
 339                 spin_unlock(&sbi->fs_lock);
 340                 synchronize_rcu();
 341                 if (!autofs_direct_busy(mnt, root, timeout, how)) {
 342                         spin_lock(&sbi->fs_lock);
 343                         ino->flags |= AUTOFS_INF_EXPIRING;
 344                         init_completion(&ino->expire_complete);
 345                         spin_unlock(&sbi->fs_lock);
 346                         return root;
 347                 }
 348                 spin_lock(&sbi->fs_lock);
 349                 ino->flags &= ~AUTOFS_INF_WANT_EXPIRE;
 350                 spin_unlock(&sbi->fs_lock);
 351         }
 352 out:
 353         dput(root);
 354
 355         return NULL;
 356 }
 357
 358 /* Check if 'dentry' should expire, or return a nearby
 359  * dentry that is suitable.
 360  * If returned dentry is different from arg dentry,
 361  * then a dget() reference was taken, else not.
 362  */
 363 static struct dentry *should_expire(struct dentry *dentry,
 364                                     struct vfsmount *mnt,
 365                                     unsigned long timeout,
 366                                     unsigned int how)
 367 {
 368         struct autofs_info *ino = autofs_dentry_ino(dentry);
 369         unsigned int ino_count;
 370
 371         /* No point expiring a pending mount */
 372         if (ino->flags & AUTOFS_INF_PENDING)
 373                 return NULL;
 374
 375         /*
 376          * Case 1: (i) indirect mount or top level pseudo direct mount
 377          *         (autofs-4.1).
 378          *         (ii) indirect mount with offset mount, check the "/"
 379          *         offset (autofs-5.0+).
 380          */
 381         if (d_mountpoint(dentry)) {
 382                 pr_debug("checking mountpoint %p %pd\n", dentry, dentry);
 383
 384                 /* Can we umount this guy */
 385                 if (autofs_mount_busy(mnt, dentry, how))
 386                         return NULL;
 387
 388                 /* This isn't a submount so if a forced expire
 389                  * has been requested, user space handles busy
 390                  * mounts */
 391                 if (how & AUTOFS_EXP_FORCED)
 392                         return dentry;
 393
 394                 /* Can we expire this guy */
 395                 if (autofs_can_expire(dentry, timeout, how))
 396                         return dentry;
 397                 return NULL;
 398         }
 399
 400         if (d_really_is_positive(dentry) && d_is_symlink(dentry)) {
 401                 pr_debug("checking symlink %p %pd\n", dentry, dentry);
 402
 403                 /* Forced expire, user space handles busy mounts */
 404                 if (how & AUTOFS_EXP_FORCED)
 405                         return dentry;
 406
 407                 /*
 408                  * A symlink can't be "busy" in the usual sense so
 409                  * just check last used for expire timeout.
 410                  */
 411                 if (autofs_can_expire(dentry, timeout, how))
 412                         return dentry;
 413                 return NULL;
 414         }
 415
 416         if (simple_empty(dentry))
 417                 return NULL;
 418
 419         /* Case 2: tree mount, expire iff entire tree is not busy */
 420         if (!(how & AUTOFS_EXP_LEAVES)) {
 421                 /* Not a forced expire? */
 422                 if (!(how & AUTOFS_EXP_FORCED)) {
 423                         /* ref-walk currently on this dentry? */
 424                         ino_count = atomic_read(&ino->count) + 1;
 425                         if (d_count(dentry) > ino_count)
 426                                 return NULL;
 427                 }
 428
 429                 if (!autofs_tree_busy(mnt, dentry, timeout, how))
 430                         return dentry;
 431         /*
 432          * Case 3: pseudo direct mount, expire individual leaves
 433          *         (autofs-4.1).
 434          */
 435         } else {
 436                 struct dentry *expired;
 437
 438                 /* Not a forced expire? */
 439                 if (!(how & AUTOFS_EXP_FORCED)) {
 440                         /* ref-walk currently on this dentry? */
 441                         ino_count = atomic_read(&ino->count) + 1;
 442                         if (d_count(dentry) > ino_count)
 443                                 return NULL;
 444                 }
 445
 446                 expired = autofs_check_leaves(mnt, dentry, timeout, how);
 447                 if (expired) {
 448                         if (expired == dentry)
 449                                 dput(dentry);
 450                         return expired;
 451                 }
 452         }
 453         return NULL;
 454 }
 455
 456 /*
 457  * Find an eligible tree to time-out
 458  * A tree is eligible if :-
 459  *  - it is unused by any user process
 460  *  - it has been unused for exp_timeout time
 461  */
 462 static struct dentry *autofs_expire_indirect(struct super_block *sb,
 463                                              struct vfsmount *mnt,
 464                                              struct autofs_sb_info *sbi,
 465                                              unsigned int how)
 466 {
 467         unsigned long timeout;
 468         struct dentry *root = sb->s_root;
 469         struct dentry *dentry;
 470         struct dentry *expired;
 471         struct dentry *found;
 472         struct autofs_info *ino;
 473
 474         if (!root)
 475                 return NULL;
 476
 477         timeout = sbi->exp_timeout;
 478
 479         dentry = NULL;
 480         while ((dentry = get_next_positive_subdir(dentry, root))) {
 481                 spin_lock(&sbi->fs_lock);
 482                 ino = autofs_dentry_ino(dentry);
 483                 if (ino->flags & AUTOFS_INF_WANT_EXPIRE) {
 484                         spin_unlock(&sbi->fs_lock);
 485                         continue;
 486                 }
 487                 spin_unlock(&sbi->fs_lock);
 488
 489                 expired = should_expire(dentry, mnt, timeout, how);
 490                 if (!expired)
 491                         continue;
 492
 493                 spin_lock(&sbi->fs_lock);
 494                 ino = autofs_dentry_ino(expired);
 495                 ino->flags |= AUTOFS_INF_WANT_EXPIRE;
 496                 spin_unlock(&sbi->fs_lock);
 497                 synchronize_rcu();
 498
 499                 /* Make sure a reference is not taken on found if
 500                  * things have changed.
 501                  */
 502                 how &= ~AUTOFS_EXP_LEAVES;
 503                 found = should_expire(expired, mnt, timeout, how);
 504                 if (!found || found != expired)
 505                         /* Something has changed, continue */
 506                         goto next;
 507
 508                 if (expired != dentry)
 509                         dput(dentry);
 510
 511                 spin_lock(&sbi->fs_lock);
 512                 goto found;
 513 next:
 514                 spin_lock(&sbi->fs_lock);
 515                 ino->flags &= ~AUTOFS_INF_WANT_EXPIRE;
 516                 spin_unlock(&sbi->fs_lock);
 517                 if (expired != dentry)
 518                         dput(expired);
 519         }
 520         return NULL;
 521
 522 found:
 523         pr_debug("returning %p %pd\n", expired, expired);
 524         ino->flags |= AUTOFS_INF_EXPIRING;
 525         init_completion(&ino->expire_complete);
 526         spin_unlock(&sbi->fs_lock);
 527         return expired;
 528 }
 529
 530 int autofs_expire_wait(const struct path *path, int rcu_walk)
 531 {
 532         struct dentry *dentry = path->dentry;
 533         struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
 534         struct autofs_info *ino = autofs_dentry_ino(dentry);
 535         int status;
 536         int state;
 537
 538         /* Block on any pending expire */
 539         if (!(ino->flags & AUTOFS_INF_WANT_EXPIRE))
 540                 return 0;
 541         if (rcu_walk)
 542                 return -ECHILD;
 543
 544 retry:
 545         spin_lock(&sbi->fs_lock);
 546         state = ino->flags & (AUTOFS_INF_WANT_EXPIRE | AUTOFS_INF_EXPIRING);
 547         if (state == AUTOFS_INF_WANT_EXPIRE) {
 548                 spin_unlock(&sbi->fs_lock);
 549                 /*
 550                  * Possibly being selected for expire, wait until
 551                  * it's selected or not.
 552                  */
 553                 schedule_timeout_uninterruptible(HZ/10);
 554                 goto retry;
 555         }
 556         if (state & AUTOFS_INF_EXPIRING) {
 557                 spin_unlock(&sbi->fs_lock);
 558
 559                 pr_debug("waiting for expire %p name=%pd\n", dentry, dentry);
 560
 561                 status = autofs_wait(sbi, path, NFY_NONE);
 562                 wait_for_completion(&ino->expire_complete);
 563
 564                 pr_debug("expire done status=%d\n", status);
 565
 566                 if (d_unhashed(dentry))
 567                         return -EAGAIN;
 568
 569                 return status;
 570         }
 571         spin_unlock(&sbi->fs_lock);
 572
 573         return 0;
 574 }
 575
 576 /* Perform an expiry operation */
 577 int autofs_expire_run(struct super_block *sb,
 578                       struct vfsmount *mnt,
 579                       struct autofs_sb_info *sbi,
 580                       struct autofs_packet_expire __user *pkt_p)
 581 {
 582         struct autofs_packet_expire pkt;
 583         struct autofs_info *ino;
 584         struct dentry *dentry;
 585         int ret = 0;
 586
 587         memset(&pkt, 0, sizeof(pkt));
 588
 589         pkt.hdr.proto_version = sbi->version;
 590         pkt.hdr.type = autofs_ptype_expire;
 591
 592         dentry = autofs_expire_indirect(sb, mnt, sbi, 0);
 593         if (!dentry)
 594                 return -EAGAIN;
 595
 596         pkt.len = dentry->d_name.len;
 597         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 598         pkt.name[pkt.len] = '\0';
 599
 600         if (copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)))
 601                 ret = -EFAULT;
 602
 603         spin_lock(&sbi->fs_lock);
 604         ino = autofs_dentry_ino(dentry);
 605         /* avoid rapid-fire expire attempts if expiry fails */
 606         ino->last_used = jiffies;
 607         ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE);
 608         complete_all(&ino->expire_complete);
 609         spin_unlock(&sbi->fs_lock);
 610
 611         dput(dentry);
 612
 613         return ret;
 614 }
 615
 616 int autofs_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 617                            struct autofs_sb_info *sbi, unsigned int how)
 618 {
 619         struct dentry *dentry;
 620         int ret = -EAGAIN;
 621
 622         if (autofs_type_trigger(sbi->type))
 623                 dentry = autofs_expire_direct(sb, mnt, sbi, how);
 624         else
 625                 dentry = autofs_expire_indirect(sb, mnt, sbi, how);
 626
 627         if (dentry) {
 628                 struct autofs_info *ino = autofs_dentry_ino(dentry);
 629                 const struct path path = { .mnt = mnt, .dentry = dentry };
 630
 631                 /* This is synchronous because it makes the daemon a
 632                  * little easier
 633                  */
 634                 ret = autofs_wait(sbi, &path, NFY_EXPIRE);
 635
 636                 spin_lock(&sbi->fs_lock);
 637                 /* avoid rapid-fire expire attempts if expiry fails */
 638                 ino->last_used = jiffies;
 639                 ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE);
 640                 complete_all(&ino->expire_complete);
 641                 spin_unlock(&sbi->fs_lock);
 642                 dput(dentry);
 643         }
 644
 645         return ret;
 646 }
 647
 648 /*
 649  * Call repeatedly until it returns -EAGAIN, meaning there's nothing
 650  * more to be done.
 651  */
 652 int autofs_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 653                         struct autofs_sb_info *sbi, int __user *arg)
 654 {
 655         unsigned int how = 0;
 656
 657         if (arg && get_user(how, arg))
 658                 return -EFAULT;
 659
 660         return autofs_do_expire_multi(sb, mnt, sbi, how);
 661 }