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 *q;
  98
  99         spin_lock(&sbi->lookup_lock);
 100         spin_lock(&root->d_lock);
 101
 102         if (prev)
 103                 next = prev->d_u.d_child.next;
 104         else {
 105                 prev = dget_dlock(root);
 106                 next = prev->d_subdirs.next;
 107         }
 108
 109 cont:
 110         if (next == &root->d_subdirs) {
 111                 spin_unlock(&root->d_lock);
 112                 spin_unlock(&sbi->lookup_lock);
 113                 dput(prev);
 114                 return NULL;
 115         }
 116
 117         q = list_entry(next, struct dentry, d_u.d_child);
 118
 119         spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
 120         /* Already gone or negative dentry (under construction) - try next */
 121         if (q->d_count == 0 || !simple_positive(q)) {
 122                 spin_unlock(&q->d_lock);
 123                 next = q->d_u.d_child.next;
 124                 goto cont;
 125         }
 126         dget_dlock(q);
 127         spin_unlock(&q->d_lock);
 128         spin_unlock(&root->d_lock);
 129         spin_unlock(&sbi->lookup_lock);
 130
 131         dput(prev);
 132
 133         return q;
 134 }
 135
 136 /*
 137  * Calculate and dget next entry in top down tree traversal.
 138  */
 139 static struct dentry *get_next_positive_dentry(struct dentry *prev,
 140                                                 struct dentry *root)
 141 {
 142         struct autofs_sb_info *sbi = autofs4_sbi(root->d_sb);
 143         struct list_head *next;
 144         struct dentry *p, *ret;
 145
 146         if (prev == NULL)
 147                 return dget(root);
 148
 149         spin_lock(&sbi->lookup_lock);
 150 relock:
 151         p = prev;
 152         spin_lock(&p->d_lock);
 153 again:
 154         next = p->d_subdirs.next;
 155         if (next == &p->d_subdirs) {
 156                 while (1) {
 157                         struct dentry *parent;
 158
 159                         if (p == root) {
 160                                 spin_unlock(&p->d_lock);
 161                                 spin_unlock(&sbi->lookup_lock);
 162                                 dput(prev);
 163                                 return NULL;
 164                         }
 165
 166                         parent = p->d_parent;
 167                         if (!spin_trylock(&parent->d_lock)) {
 168                                 spin_unlock(&p->d_lock);
 169                                 cpu_relax();
 170                                 goto relock;
 171                         }
 172                         spin_unlock(&p->d_lock);
 173                         next = p->d_u.d_child.next;
 174                         p = parent;
 175                         if (next != &parent->d_subdirs)
 176                                 break;
 177                 }
 178         }
 179         ret = list_entry(next, struct dentry, d_u.d_child);
 180
 181         spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
 182         /* Negative dentry - try next */
 183         if (!simple_positive(ret)) {
 184                 spin_unlock(&p->d_lock);
 185                 lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
 186                 p = ret;
 187                 goto again;
 188         }
 189         dget_dlock(ret);
 190         spin_unlock(&ret->d_lock);
 191         spin_unlock(&p->d_lock);
 192         spin_unlock(&sbi->lookup_lock);
 193
 194         dput(prev);
 195
 196         return ret;
 197 }
 198
 199 /*
 200  * Check a direct mount point for busyness.
 201  * Direct mounts have similar expiry semantics to tree mounts.
 202  * The tree is not busy iff no mountpoints are busy and there are no
 203  * autofs submounts.
 204  */
 205 static int autofs4_direct_busy(struct vfsmount *mnt,
 206                                 struct dentry *top,
 207                                 unsigned long timeout,
 208                                 int do_now)
 209 {
 210         DPRINTK("top %p %.*s",
 211                 top, (int) top->d_name.len, top->d_name.name);
 212
 213         /* If it's busy update the expiry counters */
 214         if (!may_umount_tree(mnt)) {
 215                 struct autofs_info *ino = autofs4_dentry_ino(top);
 216                 if (ino)
 217                         ino->last_used = jiffies;
 218                 return 1;
 219         }
 220
 221         /* Timeout of a direct mount is determined by its top dentry */
 222         if (!autofs4_can_expire(top, timeout, do_now))
 223                 return 1;
 224
 225         return 0;
 226 }
 227
 228 /* Check a directory tree of mount points for busyness
 229  * The tree is not busy iff no mountpoints are busy
 230  */
 231 static int autofs4_tree_busy(struct vfsmount *mnt,
 232                              struct dentry *top,
 233                              unsigned long timeout,
 234                              int do_now)
 235 {
 236         struct autofs_info *top_ino = autofs4_dentry_ino(top);
 237         struct dentry *p;
 238
 239         DPRINTK("top %p %.*s",
 240                 top, (int)top->d_name.len, top->d_name.name);
 241
 242         /* Negative dentry - give up */
 243         if (!simple_positive(top))
 244                 return 1;
 245
 246         p = NULL;
 247         while ((p = get_next_positive_dentry(p, top))) {
 248                 DPRINTK("dentry %p %.*s",
 249                         p, (int) p->d_name.len, p->d_name.name);
 250
 251                 /*
 252                  * Is someone visiting anywhere in the subtree ?
 253                  * If there's no mount we need to check the usage
 254                  * count for the autofs dentry.
 255                  * If the fs is busy update the expiry counter.
 256                  */
 257                 if (d_mountpoint(p)) {
 258                         if (autofs4_mount_busy(mnt, p)) {
 259                                 top_ino->last_used = jiffies;
 260                                 dput(p);
 261                                 return 1;
 262                         }
 263                 } else {
 264                         struct autofs_info *ino = autofs4_dentry_ino(p);
 265                         unsigned int ino_count = atomic_read(&ino->count);
 266
 267                         /*
 268                          * Clean stale dentries below that have not been
 269                          * invalidated after a mount fail during lookup
 270                          */
 271                         d_invalidate(p);
 272
 273                         /* allow for dget above and top is already dgot */
 274                         if (p == top)
 275                                 ino_count += 2;
 276                         else
 277                                 ino_count++;
 278
 279                         if (p->d_count > ino_count) {
 280                                 top_ino->last_used = jiffies;
 281                                 dput(p);
 282                                 return 1;
 283                         }
 284                 }
 285         }
 286
 287         /* Timeout of a tree mount is ultimately determined by its top dentry */
 288         if (!autofs4_can_expire(top, timeout, do_now))
 289                 return 1;
 290
 291         return 0;
 292 }
 293
 294 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
 295                                            struct dentry *parent,
 296                                            unsigned long timeout,
 297                                            int do_now)
 298 {
 299         struct dentry *p;
 300
 301         DPRINTK("parent %p %.*s",
 302                 parent, (int)parent->d_name.len, parent->d_name.name);
 303
 304         p = NULL;
 305         while ((p = get_next_positive_dentry(p, parent))) {
 306                 DPRINTK("dentry %p %.*s",
 307                         p, (int) p->d_name.len, p->d_name.name);
 308
 309                 if (d_mountpoint(p)) {
 310                         /* Can we umount this guy */
 311                         if (autofs4_mount_busy(mnt, p))
 312                                 continue;
 313
 314                         /* Can we expire this guy */
 315                         if (autofs4_can_expire(p, timeout, do_now))
 316                                 return p;
 317                 }
 318         }
 319         return NULL;
 320 }
 321
 322 /* Check if we can expire a direct mount (possibly a tree) */
 323 struct dentry *autofs4_expire_direct(struct super_block *sb,
 324                                      struct vfsmount *mnt,
 325                                      struct autofs_sb_info *sbi,
 326                                      int how)
 327 {
 328         unsigned long timeout;
 329         struct dentry *root = dget(sb->s_root);
 330         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 331         struct autofs_info *ino;
 332
 333         if (!root)
 334                 return NULL;
 335
 336         now = jiffies;
 337         timeout = sbi->exp_timeout;
 338
 339         spin_lock(&sbi->fs_lock);
 340         ino = autofs4_dentry_ino(root);
 341         /* No point expiring a pending mount */
 342         if (ino->flags & AUTOFS_INF_PENDING)
 343                 goto out;
 344         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
 345                 struct autofs_info *ino = autofs4_dentry_ino(root);
 346                 ino->flags |= AUTOFS_INF_EXPIRING;
 347                 init_completion(&ino->expire_complete);
 348                 spin_unlock(&sbi->fs_lock);
 349                 return root;
 350         }
 351 out:
 352         spin_unlock(&sbi->fs_lock);
 353         dput(root);
 354
 355         return NULL;
 356 }
 357
 358 /*
 359  * Find an eligible tree to time-out
 360  * A tree is eligible if :-
 361  *  - it is unused by any user process
 362  *  - it has been unused for exp_timeout time
 363  */
 364 struct dentry *autofs4_expire_indirect(struct super_block *sb,
 365                                        struct vfsmount *mnt,
 366                                        struct autofs_sb_info *sbi,
 367                                        int how)
 368 {
 369         unsigned long timeout;
 370         struct dentry *root = sb->s_root;
 371         struct dentry *dentry;
 372         struct dentry *expired = NULL;
 373         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 374         int exp_leaves = how & AUTOFS_EXP_LEAVES;
 375         struct autofs_info *ino;
 376         unsigned int ino_count;
 377
 378         if (!root)
 379                 return NULL;
 380
 381         now = jiffies;
 382         timeout = sbi->exp_timeout;
 383
 384         dentry = NULL;
 385         while ((dentry = get_next_positive_subdir(dentry, root))) {
 386                 spin_lock(&sbi->fs_lock);
 387                 ino = autofs4_dentry_ino(dentry);
 388                 /* No point expiring a pending mount */
 389                 if (ino->flags & AUTOFS_INF_PENDING)
 390                         goto next;
 391
 392                 /*
 393                  * Case 1: (i) indirect mount or top level pseudo direct mount
 394                  *         (autofs-4.1).
 395                  *         (ii) indirect mount with offset mount, check the "/"
 396                  *         offset (autofs-5.0+).
 397                  */
 398                 if (d_mountpoint(dentry)) {
 399                         DPRINTK("checking mountpoint %p %.*s",
 400                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
 401
 402                         /* Can we umount this guy */
 403                         if (autofs4_mount_busy(mnt, dentry))
 404                                 goto next;
 405
 406                         /* Can we expire this guy */
 407                         if (autofs4_can_expire(dentry, timeout, do_now)) {
 408                                 expired = dentry;
 409                                 goto found;
 410                         }
 411                         goto next;
 412                 }
 413
 414                 if (simple_empty(dentry))
 415                         goto next;
 416
 417                 /* Case 2: tree mount, expire iff entire tree is not busy */
 418                 if (!exp_leaves) {
 419                         /* Path walk currently on this dentry? */
 420                         ino_count = atomic_read(&ino->count) + 1;
 421                         if (dentry->d_count > ino_count)
 422                                 goto next;
 423
 424                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
 425                                 expired = dentry;
 426                                 goto found;
 427                         }
 428                 /*
 429                  * Case 3: pseudo direct mount, expire individual leaves
 430                  *         (autofs-4.1).
 431                  */
 432                 } else {
 433                         /* Path walk currently on this dentry? */
 434                         ino_count = atomic_read(&ino->count) + 1;
 435                         if (dentry->d_count > ino_count)
 436                                 goto next;
 437
 438                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
 439                         if (expired) {
 440                                 dput(dentry);
 441                                 goto found;
 442                         }
 443                 }
 444 next:
 445                 spin_unlock(&sbi->fs_lock);
 446         }
 447         return NULL;
 448
 449 found:
 450         DPRINTK("returning %p %.*s",
 451                 expired, (int)expired->d_name.len, expired->d_name.name);
 452         ino = autofs4_dentry_ino(expired);
 453         ino->flags |= AUTOFS_INF_EXPIRING;
 454         init_completion(&ino->expire_complete);
 455         spin_unlock(&sbi->fs_lock);
 456         spin_lock(&sbi->lookup_lock);
 457         spin_lock(&expired->d_parent->d_lock);
 458         spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
 459         list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
 460         spin_unlock(&expired->d_lock);
 461         spin_unlock(&expired->d_parent->d_lock);
 462         spin_unlock(&sbi->lookup_lock);
 463         return expired;
 464 }
 465
 466 int autofs4_expire_wait(struct dentry *dentry)
 467 {
 468         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 469         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 470         int status;
 471
 472         /* Block on any pending expire */
 473         spin_lock(&sbi->fs_lock);
 474         if (ino->flags & AUTOFS_INF_EXPIRING) {
 475                 spin_unlock(&sbi->fs_lock);
 476
 477                 DPRINTK("waiting for expire %p name=%.*s",
 478                          dentry, dentry->d_name.len, dentry->d_name.name);
 479
 480                 status = autofs4_wait(sbi, dentry, NFY_NONE);
 481                 wait_for_completion(&ino->expire_complete);
 482
 483                 DPRINTK("expire done status=%d", status);
 484
 485                 if (d_unhashed(dentry))
 486                         return -EAGAIN;
 487
 488                 return status;
 489         }
 490         spin_unlock(&sbi->fs_lock);
 491
 492         return 0;
 493 }
 494
 495 /* Perform an expiry operation */
 496 int autofs4_expire_run(struct super_block *sb,
 497                       struct vfsmount *mnt,
 498                       struct autofs_sb_info *sbi,
 499                       struct autofs_packet_expire __user *pkt_p)
 500 {
 501         struct autofs_packet_expire pkt;
 502         struct autofs_info *ino;
 503         struct dentry *dentry;
 504         int ret = 0;
 505
 506         memset(&pkt,0,sizeof pkt);
 507
 508         pkt.hdr.proto_version = sbi->version;
 509         pkt.hdr.type = autofs_ptype_expire;
 510
 511         if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
 512                 return -EAGAIN;
 513
 514         pkt.len = dentry->d_name.len;
 515         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 516         pkt.name[pkt.len] = '\0';
 517         dput(dentry);
 518
 519         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
 520                 ret = -EFAULT;
 521
 522         spin_lock(&sbi->fs_lock);
 523         ino = autofs4_dentry_ino(dentry);
 524         ino->flags &= ~AUTOFS_INF_EXPIRING;
 525         complete_all(&ino->expire_complete);
 526         spin_unlock(&sbi->fs_lock);
 527
 528         return ret;
 529 }
 530
 531 int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 532                             struct autofs_sb_info *sbi, int when)
 533 {
 534         struct dentry *dentry;
 535         int ret = -EAGAIN;
 536
 537         if (autofs_type_trigger(sbi->type))
 538                 dentry = autofs4_expire_direct(sb, mnt, sbi, when);
 539         else
 540                 dentry = autofs4_expire_indirect(sb, mnt, sbi, when);
 541
 542         if (dentry) {
 543                 struct autofs_info *ino = autofs4_dentry_ino(dentry);
 544
 545                 /* This is synchronous because it makes the daemon a
 546                    little easier */
 547                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 548
 549                 spin_lock(&sbi->fs_lock);
 550                 ino->flags &= ~AUTOFS_INF_EXPIRING;
 551                 complete_all(&ino->expire_complete);
 552                 spin_unlock(&sbi->fs_lock);
 553                 dput(dentry);
 554         }
 555
 556         return ret;
 557 }
 558
 559 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
 560    more to be done */
 561 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 562                         struct autofs_sb_info *sbi, int __user *arg)
 563 {
 564         int do_now = 0;
 565
 566         if (arg && get_user(do_now, arg))
 567                 return -EFAULT;
 568
 569         return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
 570 }
 571