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                         /* 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         /* Timeout of a tree mount is ultimately determined by its top dentry */
 273         if (!autofs4_can_expire(top, timeout, do_now))
 274                 return 1;
 275
 276         return 0;
 277 }
 278
 279 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
 280                                            struct dentry *parent,
 281                                            unsigned long timeout,
 282                                            int do_now)
 283 {
 284         struct dentry *p;
 285
 286         DPRINTK("parent %p %.*s",
 287                 parent, (int)parent->d_name.len, parent->d_name.name);
 288
 289         p = NULL;
 290         while ((p = get_next_positive_dentry(p, parent))) {
 291                 DPRINTK("dentry %p %.*s",
 292                         p, (int) p->d_name.len, p->d_name.name);
 293
 294                 if (d_mountpoint(p)) {
 295                         /* Can we umount this guy */
 296                         if (autofs4_mount_busy(mnt, p))
 297                                 continue;
 298
 299                         /* Can we expire this guy */
 300                         if (autofs4_can_expire(p, timeout, do_now))
 301                                 return p;
 302                 }
 303         }
 304         return NULL;
 305 }
 306
 307 /* Check if we can expire a direct mount (possibly a tree) */
 308 struct dentry *autofs4_expire_direct(struct super_block *sb,
 309                                      struct vfsmount *mnt,
 310                                      struct autofs_sb_info *sbi,
 311                                      int how)
 312 {
 313         unsigned long timeout;
 314         struct dentry *root = dget(sb->s_root);
 315         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 316         struct autofs_info *ino;
 317
 318         if (!root)
 319                 return NULL;
 320
 321         now = jiffies;
 322         timeout = sbi->exp_timeout;
 323
 324         spin_lock(&sbi->fs_lock);
 325         ino = autofs4_dentry_ino(root);
 326         /* No point expiring a pending mount */
 327         if (ino->flags & AUTOFS_INF_PENDING)
 328                 goto out;
 329         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
 330                 ino->flags |= AUTOFS_INF_EXPIRING;
 331                 init_completion(&ino->expire_complete);
 332                 spin_unlock(&sbi->fs_lock);
 333                 return root;
 334         }
 335 out:
 336         spin_unlock(&sbi->fs_lock);
 337         dput(root);
 338
 339         return NULL;
 340 }
 341
 342 /* Check if 'dentry' should expire, or return a nearby
 343  * dentry that is suitable.
 344  * If returned dentry is different from arg dentry,
 345  * then a dget() reference was taken, else not.
 346  */
 347 static struct dentry *should_expire(struct dentry *dentry,
 348                                     struct vfsmount *mnt,
 349                                     unsigned long timeout,
 350                                     int how)
 351 {
 352         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 353         int exp_leaves = how & AUTOFS_EXP_LEAVES;
 354         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 355         unsigned int ino_count;
 356
 357         /* No point expiring a pending mount */
 358         if (ino->flags & AUTOFS_INF_PENDING)
 359                 return NULL;
 360
 361         /*
 362          * Case 1: (i) indirect mount or top level pseudo direct mount
 363          *         (autofs-4.1).
 364          *         (ii) indirect mount with offset mount, check the "/"
 365          *         offset (autofs-5.0+).
 366          */
 367         if (d_mountpoint(dentry)) {
 368                 DPRINTK("checking mountpoint %p %.*s",
 369                         dentry, (int)dentry->d_name.len, dentry->d_name.name);
 370
 371                 /* Can we umount this guy */
 372                 if (autofs4_mount_busy(mnt, dentry))
 373                         return NULL;
 374
 375                 /* Can we expire this guy */
 376                 if (autofs4_can_expire(dentry, timeout, do_now))
 377                         return dentry;
 378                 return NULL;
 379         }
 380
 381         if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
 382                 DPRINTK("checking symlink %p %.*s",
 383                         dentry, (int)dentry->d_name.len, dentry->d_name.name);
 384                 /*
 385                  * A symlink can't be "busy" in the usual sense so
 386                  * just check last used for expire timeout.
 387                  */
 388                 if (autofs4_can_expire(dentry, timeout, do_now))
 389                         return dentry;
 390                 return NULL;
 391         }
 392
 393         if (simple_empty(dentry))
 394                 return NULL;
 395
 396         /* Case 2: tree mount, expire iff entire tree is not busy */
 397         if (!exp_leaves) {
 398                 /* Path walk currently on this dentry? */
 399                 ino_count = atomic_read(&ino->count) + 1;
 400                 if (d_count(dentry) > ino_count)
 401                         return NULL;
 402
 403                 if (!autofs4_tree_busy(mnt, dentry, timeout, do_now))
 404                         return dentry;
 405         /*
 406          * Case 3: pseudo direct mount, expire individual leaves
 407          *         (autofs-4.1).
 408          */
 409         } else {
 410                 /* Path walk currently on this dentry? */
 411                 struct dentry *expired;
 412                 ino_count = atomic_read(&ino->count) + 1;
 413                 if (d_count(dentry) > ino_count)
 414                         return NULL;
 415
 416                 expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
 417                 if (expired) {
 418                         if (expired == dentry)
 419                                 dput(dentry);
 420                         return expired;
 421                 }
 422         }
 423         return NULL;
 424 }
 425 /*
 426  * Find an eligible tree to time-out
 427  * A tree is eligible if :-
 428  *  - it is unused by any user process
 429  *  - it has been unused for exp_timeout time
 430  */
 431 struct dentry *autofs4_expire_indirect(struct super_block *sb,
 432                                        struct vfsmount *mnt,
 433                                        struct autofs_sb_info *sbi,
 434                                        int how)
 435 {
 436         unsigned long timeout;
 437         struct dentry *root = sb->s_root;
 438         struct dentry *dentry;
 439         struct dentry *expired;
 440         struct autofs_info *ino;
 441
 442         if (!root)
 443                 return NULL;
 444
 445         now = jiffies;
 446         timeout = sbi->exp_timeout;
 447
 448         dentry = NULL;
 449         while ((dentry = get_next_positive_subdir(dentry, root))) {
 450                 spin_lock(&sbi->fs_lock);
 451                 expired = should_expire(dentry, mnt, timeout, how);
 452                 if (expired) {
 453                         if (expired != dentry)
 454                                 dput(dentry);
 455                         goto found;
 456                 }
 457                 spin_unlock(&sbi->fs_lock);
 458         }
 459         return NULL;
 460
 461 found:
 462         DPRINTK("returning %p %.*s",
 463                 expired, (int)expired->d_name.len, expired->d_name.name);
 464         ino = autofs4_dentry_ino(expired);
 465         ino->flags |= AUTOFS_INF_EXPIRING;
 466         init_completion(&ino->expire_complete);
 467         spin_unlock(&sbi->fs_lock);
 468         spin_lock(&sbi->lookup_lock);
 469         spin_lock(&expired->d_parent->d_lock);
 470         spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
 471         list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
 472         spin_unlock(&expired->d_lock);
 473         spin_unlock(&expired->d_parent->d_lock);
 474         spin_unlock(&sbi->lookup_lock);
 475         return expired;
 476 }
 477
 478 int autofs4_expire_wait(struct dentry *dentry, int rcu_walk)
 479 {
 480         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 481         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 482         int status;
 483
 484         /* Block on any pending expire */
 485         spin_lock(&sbi->fs_lock);
 486         if (ino->flags & AUTOFS_INF_EXPIRING) {
 487                 spin_unlock(&sbi->fs_lock);
 488                 if (rcu_walk)
 489                         return -ECHILD;
 490
 491                 DPRINTK("waiting for expire %p name=%.*s",
 492                          dentry, dentry->d_name.len, dentry->d_name.name);
 493
 494                 status = autofs4_wait(sbi, dentry, NFY_NONE);
 495                 wait_for_completion(&ino->expire_complete);
 496
 497                 DPRINTK("expire done status=%d", status);
 498
 499                 if (d_unhashed(dentry))
 500                         return -EAGAIN;
 501
 502                 return status;
 503         }
 504         spin_unlock(&sbi->fs_lock);
 505
 506         return 0;
 507 }
 508
 509 /* Perform an expiry operation */
 510 int autofs4_expire_run(struct super_block *sb,
 511                       struct vfsmount *mnt,
 512                       struct autofs_sb_info *sbi,
 513                       struct autofs_packet_expire __user *pkt_p)
 514 {
 515         struct autofs_packet_expire pkt;
 516         struct autofs_info *ino;
 517         struct dentry *dentry;
 518         int ret = 0;
 519
 520         memset(&pkt,0,sizeof pkt);
 521
 522         pkt.hdr.proto_version = sbi->version;
 523         pkt.hdr.type = autofs_ptype_expire;
 524
 525         if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
 526                 return -EAGAIN;
 527
 528         pkt.len = dentry->d_name.len;
 529         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 530         pkt.name[pkt.len] = '\0';
 531         dput(dentry);
 532
 533         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
 534                 ret = -EFAULT;
 535
 536         spin_lock(&sbi->fs_lock);
 537         ino = autofs4_dentry_ino(dentry);
 538         ino->flags &= ~AUTOFS_INF_EXPIRING;
 539         complete_all(&ino->expire_complete);
 540         spin_unlock(&sbi->fs_lock);
 541
 542         return ret;
 543 }
 544
 545 int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 546                             struct autofs_sb_info *sbi, int when)
 547 {
 548         struct dentry *dentry;
 549         int ret = -EAGAIN;
 550
 551         if (autofs_type_trigger(sbi->type))
 552                 dentry = autofs4_expire_direct(sb, mnt, sbi, when);
 553         else
 554                 dentry = autofs4_expire_indirect(sb, mnt, sbi, when);
 555
 556         if (dentry) {
 557                 struct autofs_info *ino = autofs4_dentry_ino(dentry);
 558
 559                 /* This is synchronous because it makes the daemon a
 560                    little easier */
 561                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 562
 563                 spin_lock(&sbi->fs_lock);
 564                 ino->flags &= ~AUTOFS_INF_EXPIRING;
 565                 complete_all(&ino->expire_complete);
 566                 spin_unlock(&sbi->fs_lock);
 567                 dput(dentry);
 568         }
 569
 570         return ret;
 571 }
 572
 573 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
 574    more to be done */
 575 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 576                         struct autofs_sb_info *sbi, int __user *arg)
 577 {
 578         int do_now = 0;
 579
 580         if (arg && get_user(do_now, arg))
 581                 return -EFAULT;
 582
 583         return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
 584 }
 585