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         /* No point expiring a pending mount */
  30         if (ino->flags & AUTOFS_INF_PENDING)
  31                 return 0;
  32
  33         if (!do_now) {
  34                 /* Too young to die */
  35                 if (!timeout || time_after(ino->last_used + timeout, now))
  36                         return 0;
  37
  38                 /* update last_used here :-
  39                    - obviously makes sense if it is in use now
  40                    - less obviously, prevents rapid-fire expire
  41                      attempts if expire fails the first time */
  42                 ino->last_used = now;
  43         }
  44         return 1;
  45 }
  46
  47 /* Check a mount point for busyness */
  48 static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
  49 {
  50         struct dentry *top = dentry;
  51         struct path path = {.mnt = mnt, .dentry = dentry};
  52         int status = 1;
  53
  54         DPRINTK("dentry %p %.*s",
  55                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
  56
  57         path_get(&path);
  58
  59         if (!follow_down(&path))
  60                 goto done;
  61
  62         if (is_autofs4_dentry(path.dentry)) {
  63                 struct autofs_sb_info *sbi = autofs4_sbi(path.dentry->d_sb);
  64
  65                 /* This is an autofs submount, we can't expire it */
  66                 if (autofs_type_indirect(sbi->type))
  67                         goto done;
  68
  69                 /*
  70                  * Otherwise it's an offset mount and we need to check
  71                  * if we can umount its mount, if there is one.
  72                  */
  73                 if (!d_mountpoint(path.dentry)) {
  74                         status = 0;
  75                         goto done;
  76                 }
  77         }
  78
  79         /* Update the expiry counter if fs is busy */
  80         if (!may_umount_tree(path.mnt)) {
  81                 struct autofs_info *ino = autofs4_dentry_ino(top);
  82                 ino->last_used = jiffies;
  83                 goto done;
  84         }
  85
  86         status = 0;
  87 done:
  88         DPRINTK("returning = %d", status);
  89         path_put(&path);
  90         return status;
  91 }
  92
  93 /*
  94  * Calculate and dget next entry in top down tree traversal.
  95  */
  96 static struct dentry *get_next_positive_dentry(struct dentry *prev,
  97                                                 struct dentry *root)
  98 {
  99         struct list_head *next;
 100         struct dentry *p, *ret;
 101
 102         if (prev == NULL)
 103                 return dget(prev);
 104
 105         spin_lock(&autofs4_lock);
 106 relock:
 107         p = prev;
 108         spin_lock(&p->d_lock);
 109 again:
 110         next = p->d_subdirs.next;
 111         if (next == &p->d_subdirs) {
 112                 while (1) {
 113                         struct dentry *parent;
 114
 115                         if (p == root) {
 116                                 spin_unlock(&p->d_lock);
 117                                 spin_unlock(&autofs4_lock);
 118                                 dput(prev);
 119                                 return NULL;
 120                         }
 121
 122                         parent = p->d_parent;
 123                         if (!spin_trylock(&parent->d_lock)) {
 124                                 spin_unlock(&p->d_lock);
 125                                 cpu_relax();
 126                                 goto relock;
 127                         }
 128                         spin_unlock(&p->d_lock);
 129                         next = p->d_u.d_child.next;
 130                         p = parent;
 131                         if (next != &parent->d_subdirs)
 132                                 break;
 133                 }
 134         }
 135         ret = list_entry(next, struct dentry, d_u.d_child);
 136
 137         spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
 138         /* Negative dentry - try next */
 139         if (!simple_positive(ret)) {
 140                 spin_unlock(&ret->d_lock);
 141                 p = ret;
 142                 goto again;
 143         }
 144         dget_dlock(ret);
 145         spin_unlock(&ret->d_lock);
 146         spin_unlock(&p->d_lock);
 147         spin_unlock(&autofs4_lock);
 148
 149         dput(prev);
 150
 151         return ret;
 152 }
 153
 154 /*
 155  * Check a direct mount point for busyness.
 156  * Direct mounts have similar expiry semantics to tree mounts.
 157  * The tree is not busy iff no mountpoints are busy and there are no
 158  * autofs submounts.
 159  */
 160 static int autofs4_direct_busy(struct vfsmount *mnt,
 161                                 struct dentry *top,
 162                                 unsigned long timeout,
 163                                 int do_now)
 164 {
 165         DPRINTK("top %p %.*s",
 166                 top, (int) top->d_name.len, top->d_name.name);
 167
 168         /* If it's busy update the expiry counters */
 169         if (!may_umount_tree(mnt)) {
 170                 struct autofs_info *ino = autofs4_dentry_ino(top);
 171                 if (ino)
 172                         ino->last_used = jiffies;
 173                 return 1;
 174         }
 175
 176         /* Timeout of a direct mount is determined by its top dentry */
 177         if (!autofs4_can_expire(top, timeout, do_now))
 178                 return 1;
 179
 180         return 0;
 181 }
 182
 183 /* Check a directory tree of mount points for busyness
 184  * The tree is not busy iff no mountpoints are busy
 185  */
 186 static int autofs4_tree_busy(struct vfsmount *mnt,
 187                              struct dentry *top,
 188                              unsigned long timeout,
 189                              int do_now)
 190 {
 191         struct autofs_info *top_ino = autofs4_dentry_ino(top);
 192         struct dentry *p;
 193
 194         DPRINTK("top %p %.*s",
 195                 top, (int)top->d_name.len, top->d_name.name);
 196
 197         /* Negative dentry - give up */
 198         if (!simple_positive(top))
 199                 return 1;
 200
 201         p = NULL;
 202         while ((p = get_next_positive_dentry(p, top))) {
 203                 DPRINTK("dentry %p %.*s",
 204                         p, (int) p->d_name.len, p->d_name.name);
 205
 206                 /*
 207                  * Is someone visiting anywhere in the subtree ?
 208                  * If there's no mount we need to check the usage
 209                  * count for the autofs dentry.
 210                  * If the fs is busy update the expiry counter.
 211                  */
 212                 if (d_mountpoint(p)) {
 213                         if (autofs4_mount_busy(mnt, p)) {
 214                                 top_ino->last_used = jiffies;
 215                                 dput(p);
 216                                 return 1;
 217                         }
 218                 } else {
 219                         struct autofs_info *ino = autofs4_dentry_ino(p);
 220                         unsigned int ino_count = atomic_read(&ino->count);
 221
 222                         /*
 223                          * Clean stale dentries below that have not been
 224                          * invalidated after a mount fail during lookup
 225                          */
 226                         d_invalidate(p);
 227
 228                         /* allow for dget above and top is already dgot */
 229                         if (p == top)
 230                                 ino_count += 2;
 231                         else
 232                                 ino_count++;
 233
 234                         if (p->d_count > ino_count) {
 235                                 top_ino->last_used = jiffies;
 236                                 dput(p);
 237                                 return 1;
 238                         }
 239                 }
 240         }
 241
 242         /* Timeout of a tree mount is ultimately determined by its top dentry */
 243         if (!autofs4_can_expire(top, timeout, do_now))
 244                 return 1;
 245
 246         return 0;
 247 }
 248
 249 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
 250                                            struct dentry *parent,
 251                                            unsigned long timeout,
 252                                            int do_now)
 253 {
 254         struct dentry *p;
 255
 256         DPRINTK("parent %p %.*s",
 257                 parent, (int)parent->d_name.len, parent->d_name.name);
 258
 259         p = NULL;
 260         while ((p = get_next_positive_dentry(p, parent))) {
 261                 DPRINTK("dentry %p %.*s",
 262                         p, (int) p->d_name.len, p->d_name.name);
 263
 264                 if (d_mountpoint(p)) {
 265                         /* Can we umount this guy */
 266                         if (autofs4_mount_busy(mnt, p))
 267                                 continue;
 268
 269                         /* Can we expire this guy */
 270                         if (autofs4_can_expire(p, timeout, do_now))
 271                                 return p;
 272                 }
 273         }
 274         return NULL;
 275 }
 276
 277 /* Check if we can expire a direct mount (possibly a tree) */
 278 struct dentry *autofs4_expire_direct(struct super_block *sb,
 279                                      struct vfsmount *mnt,
 280                                      struct autofs_sb_info *sbi,
 281                                      int how)
 282 {
 283         unsigned long timeout;
 284         struct dentry *root = dget(sb->s_root);
 285         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 286
 287         if (!root)
 288                 return NULL;
 289
 290         now = jiffies;
 291         timeout = sbi->exp_timeout;
 292
 293         spin_lock(&sbi->fs_lock);
 294         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
 295                 struct autofs_info *ino = autofs4_dentry_ino(root);
 296                 if (d_mountpoint(root)) {
 297                         ino->flags |= AUTOFS_INF_MOUNTPOINT;
 298                         spin_lock(&root->d_lock);
 299                         root->d_flags &= ~DCACHE_MOUNTED;
 300                         spin_unlock(&root->d_lock);
 301                 }
 302                 ino->flags |= AUTOFS_INF_EXPIRING;
 303                 init_completion(&ino->expire_complete);
 304                 spin_unlock(&sbi->fs_lock);
 305                 return root;
 306         }
 307         spin_unlock(&sbi->fs_lock);
 308         dput(root);
 309
 310         return NULL;
 311 }
 312
 313 /*
 314  * Find an eligible tree to time-out
 315  * A tree is eligible if :-
 316  *  - it is unused by any user process
 317  *  - it has been unused for exp_timeout time
 318  */
 319 struct dentry *autofs4_expire_indirect(struct super_block *sb,
 320                                        struct vfsmount *mnt,
 321                                        struct autofs_sb_info *sbi,
 322                                        int how)
 323 {
 324         unsigned long timeout;
 325         struct dentry *root = sb->s_root;
 326         struct dentry *dentry;
 327         struct dentry *expired = NULL;
 328         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 329         int exp_leaves = how & AUTOFS_EXP_LEAVES;
 330         struct autofs_info *ino;
 331         unsigned int ino_count;
 332
 333         if (!root)
 334                 return NULL;
 335
 336         now = jiffies;
 337         timeout = sbi->exp_timeout;
 338
 339         dentry = NULL;
 340         while ((dentry = get_next_positive_dentry(dentry, root))) {
 341                 spin_lock(&sbi->fs_lock);
 342                 ino = autofs4_dentry_ino(dentry);
 343
 344                 /*
 345                  * Case 1: (i) indirect mount or top level pseudo direct mount
 346                  *         (autofs-4.1).
 347                  *         (ii) indirect mount with offset mount, check the "/"
 348                  *         offset (autofs-5.0+).
 349                  */
 350                 if (d_mountpoint(dentry)) {
 351                         DPRINTK("checking mountpoint %p %.*s",
 352                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
 353
 354                         /* Path walk currently on this dentry? */
 355                         ino_count = atomic_read(&ino->count) + 2;
 356                         if (dentry->d_count > ino_count)
 357                                 goto next;
 358
 359                         /* Can we umount this guy */
 360                         if (autofs4_mount_busy(mnt, dentry))
 361                                 goto next;
 362
 363                         /* Can we expire this guy */
 364                         if (autofs4_can_expire(dentry, timeout, do_now)) {
 365                                 expired = dentry;
 366                                 goto found;
 367                         }
 368                         goto next;
 369                 }
 370
 371                 if (simple_empty(dentry))
 372                         goto next;
 373
 374                 /* Case 2: tree mount, expire iff entire tree is not busy */
 375                 if (!exp_leaves) {
 376                         /* Path walk currently on this dentry? */
 377                         ino_count = atomic_read(&ino->count) + 1;
 378                         if (dentry->d_count > ino_count)
 379                                 goto next;
 380
 381                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
 382                                 expired = dentry;
 383                                 goto found;
 384                         }
 385                 /*
 386                  * Case 3: pseudo direct mount, expire individual leaves
 387                  *         (autofs-4.1).
 388                  */
 389                 } else {
 390                         /* Path walk currently on this dentry? */
 391                         ino_count = atomic_read(&ino->count) + 1;
 392                         if (dentry->d_count > ino_count)
 393                                 goto next;
 394
 395                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
 396                         if (expired) {
 397                                 dput(dentry);
 398                                 goto found;
 399                         }
 400                 }
 401 next:
 402                 spin_unlock(&sbi->fs_lock);
 403         }
 404         return NULL;
 405
 406 found:
 407         DPRINTK("returning %p %.*s",
 408                 expired, (int)expired->d_name.len, expired->d_name.name);
 409         ino = autofs4_dentry_ino(expired);
 410         ino->flags |= AUTOFS_INF_EXPIRING;
 411         init_completion(&ino->expire_complete);
 412         spin_unlock(&sbi->fs_lock);
 413         spin_lock(&autofs4_lock);
 414         spin_lock(&expired->d_parent->d_lock);
 415         spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
 416         list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
 417         spin_unlock(&expired->d_lock);
 418         spin_unlock(&expired->d_parent->d_lock);
 419         spin_unlock(&autofs4_lock);
 420         return expired;
 421 }
 422
 423 int autofs4_expire_wait(struct dentry *dentry)
 424 {
 425         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 426         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 427         int status;
 428
 429         /* Block on any pending expire */
 430         spin_lock(&sbi->fs_lock);
 431         if (ino->flags & AUTOFS_INF_EXPIRING) {
 432                 spin_unlock(&sbi->fs_lock);
 433
 434                 DPRINTK("waiting for expire %p name=%.*s",
 435                          dentry, dentry->d_name.len, dentry->d_name.name);
 436
 437                 status = autofs4_wait(sbi, dentry, NFY_NONE);
 438                 wait_for_completion(&ino->expire_complete);
 439
 440                 DPRINTK("expire done status=%d", status);
 441
 442                 if (d_unhashed(dentry))
 443                         return -EAGAIN;
 444
 445                 return status;
 446         }
 447         spin_unlock(&sbi->fs_lock);
 448
 449         return 0;
 450 }
 451
 452 /* Perform an expiry operation */
 453 int autofs4_expire_run(struct super_block *sb,
 454                       struct vfsmount *mnt,
 455                       struct autofs_sb_info *sbi,
 456                       struct autofs_packet_expire __user *pkt_p)
 457 {
 458         struct autofs_packet_expire pkt;
 459         struct autofs_info *ino;
 460         struct dentry *dentry;
 461         int ret = 0;
 462
 463         memset(&pkt,0,sizeof pkt);
 464
 465         pkt.hdr.proto_version = sbi->version;
 466         pkt.hdr.type = autofs_ptype_expire;
 467
 468         if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
 469                 return -EAGAIN;
 470
 471         pkt.len = dentry->d_name.len;
 472         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 473         pkt.name[pkt.len] = '\0';
 474         dput(dentry);
 475
 476         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
 477                 ret = -EFAULT;
 478
 479         spin_lock(&sbi->fs_lock);
 480         ino = autofs4_dentry_ino(dentry);
 481         ino->flags &= ~AUTOFS_INF_EXPIRING;
 482         complete_all(&ino->expire_complete);
 483         spin_unlock(&sbi->fs_lock);
 484
 485         return ret;
 486 }
 487
 488 int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 489                             struct autofs_sb_info *sbi, int when)
 490 {
 491         struct dentry *dentry;
 492         int ret = -EAGAIN;
 493
 494         if (autofs_type_trigger(sbi->type))
 495                 dentry = autofs4_expire_direct(sb, mnt, sbi, when);
 496         else
 497                 dentry = autofs4_expire_indirect(sb, mnt, sbi, when);
 498
 499         if (dentry) {
 500                 struct autofs_info *ino = autofs4_dentry_ino(dentry);
 501
 502                 /* This is synchronous because it makes the daemon a
 503                    little easier */
 504                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 505
 506                 spin_lock(&sbi->fs_lock);
 507                 if (ino->flags & AUTOFS_INF_MOUNTPOINT) {
 508                         spin_lock(&sb->s_root->d_lock);
 509                         /*
 510                          * If we haven't been expired away, then reset
 511                          * mounted status.
 512                          */
 513                         if (mnt->mnt_parent != mnt)
 514                                 sb->s_root->d_flags |= DCACHE_MOUNTED;
 515                         spin_unlock(&sb->s_root->d_lock);
 516                         ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
 517                 }
 518                 ino->flags &= ~AUTOFS_INF_EXPIRING;
 519                 complete_all(&ino->expire_complete);
 520                 spin_unlock(&sbi->fs_lock);
 521                 dput(dentry);
 522         }
 523
 524         return ret;
 525 }
 526
 527 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
 528    more to be done */
 529 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 530                         struct autofs_sb_info *sbi, int __user *arg)
 531 {
 532         int do_now = 0;
 533
 534         if (arg && get_user(do_now, arg))
 535                 return -EFAULT;
 536
 537         return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
 538 }
 539