fs/autofs4/expire.c

   1 /* -*- c -*- --------------------------------------------------------------- *
   2  *
   3  * linux/fs/autofs/expire.c
   4  *
   5  *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
   6  *  Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
   7  *  Copyright 2001-2006 Ian Kent <raven@themaw.net>
   8  *
   9  * This file is part of the Linux kernel and is made available under
  10  * the terms of the GNU General Public License, version 2, or at your
  11  * option, any later version, incorporated herein by reference.
  12  *
  13  * ------------------------------------------------------------------------- */
  14
  15 #include "autofs_i.h"
  16
  17 static unsigned long now;
  18
  19 /* Check if a dentry can be expired */
  20 static inline int autofs4_can_expire(struct dentry *dentry,
  21                                         unsigned long timeout, int do_now)
  22 {
  23         struct autofs_info *ino = autofs4_dentry_ino(dentry);
  24
  25         /* dentry in the process of being deleted */
  26         if (ino == NULL)
  27                 return 0;
  28
  29         if (!do_now) {
  30                 /* Too young to die */
  31                 if (!timeout || time_after(ino->last_used + timeout, now))
  32                         return 0;
  33
  34                 /* update last_used here :-
  35                    - obviously makes sense if it is in use now
  36                    - less obviously, prevents rapid-fire expire
  37                      attempts if expire fails the first time */
  38                 ino->last_used = now;
  39         }
  40         return 1;
  41 }
  42
  43 /* Check a mount point for busyness */
  44 static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
  45 {
  46         struct dentry *top = dentry;
  47         struct path path = {.mnt = mnt, .dentry = dentry};
  48         int status = 1;
  49
  50         DPRINTK("dentry %p %.*s",
  51                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
  52
  53         path_get(&path);
  54
  55         if (!follow_down_one(&path))
  56                 goto done;
  57
  58         if (is_autofs4_dentry(path.dentry)) {
  59                 struct autofs_sb_info *sbi = autofs4_sbi(path.dentry->d_sb);
  60
  61                 /* This is an autofs submount, we can't expire it */
  62                 if (autofs_type_indirect(sbi->type))
  63                         goto done;
  64
  65                 /*
  66                  * Otherwise it's an offset mount and we need to check
  67                  * if we can umount its mount, if there is one.
  68                  */
  69                 if (!d_mountpoint(path.dentry)) {
  70                         status = 0;
  71                         goto done;
  72                 }
  73         }
  74
  75         /* Update the expiry counter if fs is busy */
  76         if (!may_umount_tree(path.mnt)) {
  77                 struct autofs_info *ino = autofs4_dentry_ino(top);
  78                 ino->last_used = jiffies;
  79                 goto done;
  80         }
  81
  82         status = 0;
  83 done:
  84         DPRINTK("returning = %d", status);
  85         path_put(&path);
  86         return status;
  87 }
  88
  89 /*
  90  * Calculate and dget next entry in the subdirs list under root.
  91  */
  92 static struct dentry *get_next_positive_subdir(struct dentry *prev,
  93                                                 struct dentry *root)
  94 {
  95         struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
  96         struct list_head *next;
  97         struct dentry *p, *q;
  98
  99         spin_lock(&sbi->lookup_lock);
 100
 101         if (prev == NULL) {
 102                 spin_lock(&root->d_lock);
 103                 prev = dget_dlock(root);
 104                 next = prev->d_subdirs.next;
 105                 p = prev;
 106                 goto start;
 107         }
 108
 109         p = prev;
 110         spin_lock(&p->d_lock);
 111 again:
 112         next = p->d_u.d_child.next;
 113 start:
 114         if (next == &root->d_subdirs) {
 115                 spin_unlock(&p->d_lock);
 116                 spin_unlock(&sbi->lookup_lock);
 117                 dput(prev);
 118                 return NULL;
 119         }
 120
 121         q = list_entry(next, struct dentry, d_u.d_child);
 122
 123         spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
 124         /* Negative dentry - try next */
 125         if (!simple_positive(q)) {
 126                 spin_unlock(&p->d_lock);
 127                 p = q;
 128                 goto again;
 129         }
 130         dget_dlock(q);
 131         spin_unlock(&q->d_lock);
 132         spin_unlock(&p->d_lock);
 133         spin_unlock(&sbi->lookup_lock);
 134
 135         dput(prev);
 136
 137         return q;
 138 }
 139
 140 /*
 141  * Calculate and dget next entry in top down tree traversal.
 142  */
 143 static struct dentry *get_next_positive_dentry(struct dentry *prev,
 144                                                 struct dentry *root)
 145 {
 146         struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
 147         struct list_head *next;
 148         struct dentry *p, *ret;
 149
 150         if (prev == NULL)
 151                 return dget(root);
 152
 153         spin_lock(&sbi->lookup_lock);
 154 relock:
 155         p = prev;
 156         spin_lock(&p->d_lock);
 157 again:
 158         next = p->d_subdirs.next;
 159         if (next == &p->d_subdirs) {
 160                 while (1) {
 161                         struct dentry *parent;
 162
 163                         if (p == root) {
 164                                 spin_unlock(&p->d_lock);
 165                                 spin_unlock(&sbi->lookup_lock);
 166                                 dput(prev);
 167                                 return NULL;
 168                         }
 169
 170                         parent = p->d_parent;
 171                         if (!spin_trylock(&parent->d_lock)) {
 172                                 spin_unlock(&p->d_lock);
 173                                 cpu_relax();
 174                                 goto relock;
 175                         }
 176                         spin_unlock(&p->d_lock);
 177                         next = p->d_u.d_child.next;
 178                         p = parent;
 179                         if (next != &parent->d_subdirs)
 180                                 break;
 181                 }
 182         }
 183         ret = list_entry(next, struct dentry, d_u.d_child);
 184
 185         spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
 186         /* Negative dentry - try next */
 187         if (!simple_positive(ret)) {
 188                 spin_unlock(&p->d_lock);
 189                 p = ret;
 190                 goto again;
 191         }
 192         dget_dlock(ret);
 193         spin_unlock(&ret->d_lock);
 194         spin_unlock(&p->d_lock);
 195         spin_unlock(&sbi->lookup_lock);
 196
 197         dput(prev);
 198
 199         return ret;
 200 }
 201
 202 /*
 203  * Check a direct mount point for busyness.
 204  * Direct mounts have similar expiry semantics to tree mounts.
 205  * The tree is not busy iff no mountpoints are busy and there are no
 206  * autofs submounts.
 207  */
 208 static int autofs4_direct_busy(struct vfsmount *mnt,
 209                                 struct dentry *top,
 210                                 unsigned long timeout,
 211                                 int do_now)
 212 {
 213         DPRINTK("top %p %.*s",
 214                 top, (int) top->d_name.len, top->d_name.name);
 215
 216         /* If it's busy update the expiry counters */
 217         if (!may_umount_tree(mnt)) {
 218                 struct autofs_info *ino = autofs4_dentry_ino(top);
 219                 if (ino)
 220                         ino->last_used = jiffies;
 221                 return 1;
 222         }
 223
 224         /* Timeout of a direct mount is determined by its top dentry */
 225         if (!autofs4_can_expire(top, timeout, do_now))
 226                 return 1;
 227
 228         return 0;
 229 }
 230
 231 /* Check a directory tree of mount points for busyness
 232  * The tree is not busy iff no mountpoints are busy
 233  */
 234 static int autofs4_tree_busy(struct vfsmount *mnt,
 235                              struct dentry *top,
 236                              unsigned long timeout,
 237                              int do_now)
 238 {
 239         struct autofs_info *top_ino = autofs4_dentry_ino(top);
 240         struct dentry *p;
 241
 242         DPRINTK("top %p %.*s",
 243                 top, (int)top->d_name.len, top->d_name.name);
 244
 245         /* Negative dentry - give up */
 246         if (!simple_positive(top))
 247                 return 1;
 248
 249         p = NULL;
 250         while ((p = get_next_positive_dentry(p, top))) {
 251                 DPRINTK("dentry %p %.*s",
 252                         p, (int) p->d_name.len, p->d_name.name);
 253
 254                 /*
 255                  * Is someone visiting anywhere in the subtree ?
 256                  * If there's no mount we need to check the usage
 257                  * count for the autofs dentry.
 258                  * If the fs is busy update the expiry counter.
 259                  */
 260                 if (d_mountpoint(p)) {
 261                         if (autofs4_mount_busy(mnt, p)) {
 262                                 top_ino->last_used = jiffies;
 263                                 dput(p);
 264                                 return 1;
 265                         }
 266                 } else {
 267                         struct autofs_info *ino = autofs4_dentry_ino(p);
 268                         unsigned int ino_count = atomic_read(&ino->count);
 269
 270                         /*
 271                          * Clean stale dentries below that have not been
 272                          * invalidated after a mount fail during lookup
 273                          */
 274                         d_invalidate(p);
 275
 276                         /* allow for dget above and top is already dgot */
 277                         if (p == top)
 278                                 ino_count += 2;
 279                         else
 280                                 ino_count++;
 281
 282                         if (p->d_count > ino_count) {
 283                                 top_ino->last_used = jiffies;
 284                                 dput(p);
 285                                 return 1;
 286                         }
 287                 }
 288         }
 289
 290         /* Timeout of a tree mount is ultimately determined by its top dentry */
 291         if (!autofs4_can_expire(top, timeout, do_now))
 292                 return 1;
 293
 294         return 0;
 295 }
 296
 297 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
 298                                            struct dentry *parent,
 299                                            unsigned long timeout,
 300                                            int do_now)
 301 {
 302         struct dentry *p;
 303
 304         DPRINTK("parent %p %.*s",
 305                 parent, (int)parent->d_name.len, parent->d_name.name);
 306
 307         p = NULL;
 308         while ((p = get_next_positive_dentry(p, parent))) {
 309                 DPRINTK("dentry %p %.*s",
 310                         p, (int) p->d_name.len, p->d_name.name);
 311
 312                 if (d_mountpoint(p)) {
 313                         /* Can we umount this guy */
 314                         if (autofs4_mount_busy(mnt, p))
 315                                 continue;
 316
 317                         /* Can we expire this guy */
 318                         if (autofs4_can_expire(p, timeout, do_now))
 319                                 return p;
 320                 }
 321         }
 322         return NULL;
 323 }
 324
 325 /* Check if we can expire a direct mount (possibly a tree) */
 326 struct dentry *autofs4_expire_direct(struct super_block *sb,
 327                                      struct vfsmount *mnt,
 328                                      struct autofs_sb_info *sbi,
 329                                      int how)
 330 {
 331         unsigned long timeout;
 332         struct dentry *root = dget(sb->s_root);
 333         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 334         struct autofs_info *ino;
 335
 336         if (!root)
 337                 return NULL;
 338
 339         now = jiffies;
 340         timeout = sbi->exp_timeout;
 341
 342         spin_lock(&sbi->fs_lock);
 343         ino = autofs4_dentry_ino(root);
 344         /* No point expiring a pending mount */
 345         if (ino->flags & AUTOFS_INF_PENDING)
 346                 goto out;
 347         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
 348                 struct autofs_info *ino = autofs4_dentry_ino(root);
 349                 ino->flags |= AUTOFS_INF_EXPIRING;
 350                 init_completion(&ino->expire_complete);
 351                 spin_unlock(&sbi->fs_lock);
 352                 return root;
 353         }
 354 out:
 355         spin_unlock(&sbi->fs_lock);
 356         dput(root);
 357
 358         return NULL;
 359 }
 360
 361 /*
 362  * Find an eligible tree to time-out
 363  * A tree is eligible if :-
 364  *  - it is unused by any user process
 365  *  - it has been unused for exp_timeout time
 366  */
 367 struct dentry *autofs4_expire_indirect(struct super_block *sb,
 368                                        struct vfsmount *mnt,
 369                                        struct autofs_sb_info *sbi,
 370                                        int how)
 371 {
 372         unsigned long timeout;
 373         struct dentry *root = sb->s_root;
 374         struct dentry *dentry;
 375         struct dentry *expired = NULL;
 376         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 377         int exp_leaves = how & AUTOFS_EXP_LEAVES;
 378         struct autofs_info *ino;
 379         unsigned int ino_count;
 380
 381         if (!root)
 382                 return NULL;
 383
 384         now = jiffies;
 385         timeout = sbi->exp_timeout;
 386
 387         dentry = NULL;
 388         while ((dentry = get_next_positive_subdir(dentry, root))) {
 389                 spin_lock(&sbi->fs_lock);
 390                 ino = autofs4_dentry_ino(dentry);
 391                 /* No point expiring a pending mount */
 392                 if (ino->flags & AUTOFS_INF_PENDING)
 393                         goto next;
 394
 395                 /*
 396                  * Case 1: (i) indirect mount or top level pseudo direct mount
 397                  *         (autofs-4.1).
 398                  *         (ii) indirect mount with offset mount, check the "/"
 399                  *         offset (autofs-5.0+).
 400                  */
 401                 if (d_mountpoint(dentry)) {
 402                         DPRINTK("checking mountpoint %p %.*s",
 403                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
 404
 405                         /* Path walk currently on this dentry? */
 406                         ino_count = atomic_read(&ino->count) + 2;
 407                         if (dentry->d_count > ino_count)
 408                                 goto next;
 409
 410                         /* Can we umount this guy */
 411                         if (autofs4_mount_busy(mnt, dentry))
 412                                 goto next;
 413
 414                         /* Can we expire this guy */
 415                         if (autofs4_can_expire(dentry, timeout, do_now)) {
 416                                 expired = dentry;
 417                                 goto found;
 418                         }
 419                         goto next;
 420                 }
 421
 422                 if (simple_empty(dentry))
 423                         goto next;
 424
 425                 /* Case 2: tree mount, expire iff entire tree is not busy */
 426                 if (!exp_leaves) {
 427                         /* Path walk currently on this dentry? */
 428                         ino_count = atomic_read(&ino->count) + 1;
 429                         if (dentry->d_count > ino_count)
 430                                 goto next;
 431
 432                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
 433                                 expired = dentry;
 434                                 goto found;
 435                         }
 436                 /*
 437                  * Case 3: pseudo direct mount, expire individual leaves
 438                  *         (autofs-4.1).
 439                  */
 440                 } else {
 441                         /* Path walk currently on this dentry? */
 442                         ino_count = atomic_read(&ino->count) + 1;
 443                         if (dentry->d_count > ino_count)
 444                                 goto next;
 445
 446                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
 447                         if (expired) {
 448                                 dput(dentry);
 449                                 goto found;
 450                         }
 451                 }
 452 next:
 453                 spin_unlock(&sbi->fs_lock);
 454         }
 455         return NULL;
 456
 457 found:
 458         DPRINTK("returning %p %.*s",
 459                 expired, (int)expired->d_name.len, expired->d_name.name);
 460         ino = autofs4_dentry_ino(expired);
 461         ino->flags |= AUTOFS_INF_EXPIRING;
 462         init_completion(&ino->expire_complete);
 463         spin_unlock(&sbi->fs_lock);
 464         spin_lock(&sbi->lookup_lock);
 465         spin_lock(&expired->d_parent->d_lock);
 466         spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
 467         list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
 468         spin_unlock(&expired->d_lock);
 469         spin_unlock(&expired->d_parent->d_lock);
 470         spin_unlock(&sbi->lookup_lock);
 471         return expired;
 472 }
 473
 474 int autofs4_expire_wait(struct dentry *dentry)
 475 {
 476         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 477         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 478         int status;
 479
 480         /* Block on any pending expire */
 481         spin_lock(&sbi->fs_lock);
 482         if (ino->flags & AUTOFS_INF_EXPIRING) {
 483                 spin_unlock(&sbi->fs_lock);
 484
 485                 DPRINTK("waiting for expire %p name=%.*s",
 486                          dentry, dentry->d_name.len, dentry->d_name.name);
 487
 488                 status = autofs4_wait(sbi, dentry, NFY_NONE);
 489                 wait_for_completion(&ino->expire_complete);
 490
 491                 DPRINTK("expire done status=%d", status);
 492
 493                 if (d_unhashed(dentry))
 494                         return -EAGAIN;
 495
 496                 return status;
 497         }
 498         spin_unlock(&sbi->fs_lock);
 499
 500         return 0;
 501 }
 502
 503 /* Perform an expiry operation */
 504 int autofs4_expire_run(struct super_block *sb,
 505                       struct vfsmount *mnt,
 506                       struct autofs_sb_info *sbi,
 507                       struct autofs_packet_expire __user *pkt_p)
 508 {
 509         struct autofs_packet_expire pkt;
 510         struct autofs_info *ino;
 511         struct dentry *dentry;
 512         int ret = 0;
 513
 514         memset(&pkt,0,sizeof pkt);
 515
 516         pkt.hdr.proto_version = sbi->version;
 517         pkt.hdr.type = autofs_ptype_expire;
 518
 519         if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
 520                 return -EAGAIN;
 521
 522         pkt.len = dentry->d_name.len;
 523         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 524         pkt.name[pkt.len] = '\0';
 525         dput(dentry);
 526
 527         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
 528                 ret = -EFAULT;
 529
 530         spin_lock(&sbi->fs_lock);
 531         ino = autofs4_dentry_ino(dentry);
 532         ino->flags &= ~AUTOFS_INF_EXPIRING;
 533         complete_all(&ino->expire_complete);
 534         spin_unlock(&sbi->fs_lock);
 535
 536         return ret;
 537 }
 538
 539 int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 540                             struct autofs_sb_info *sbi, int when)
 541 {
 542         struct dentry *dentry;
 543         int ret = -EAGAIN;
 544
 545         if (autofs_type_trigger(sbi->type))
 546                 dentry = autofs4_expire_direct(sb, mnt, sbi, when);
 547         else
 548                 dentry = autofs4_expire_indirect(sb, mnt, sbi, when);
 549
 550         if (dentry) {
 551                 struct autofs_info *ino = autofs4_dentry_ino(dentry);
 552
 553                 /* This is synchronous because it makes the daemon a
 554                    little easier */
 555                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 556
 557                 spin_lock(&sbi->fs_lock);
 558                 ino->flags &= ~AUTOFS_INF_EXPIRING;
 559                 spin_lock(&dentry->d_lock);
 560                 if (!ret) {
 561                         if ((IS_ROOT(dentry) ||
 562                             (autofs_type_indirect(sbi->type) &&
 563                              IS_ROOT(dentry->d_parent))) &&
 564                             !(dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
 565                                 __managed_dentry_set_automount(dentry);
 566                 }
 567                 spin_unlock(&dentry->d_lock);
 568                 complete_all(&ino->expire_complete);
 569                 spin_unlock(&sbi->fs_lock);
 570                 dput(dentry);
 571         }
 572
 573         return ret;
 574 }
 575
 576 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
 577    more to be done */
 578 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 579                         struct autofs_sb_info *sbi, int __user *arg)
 580 {
 581         int do_now = 0;
 582
 583         if (arg && get_user(do_now, arg))
 584                 return -EFAULT;
 585
 586         return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
 587 }
 588