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