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 top down tree traversal.
  91  */
  92 static struct dentry *get_next_positive_dentry(struct dentry *prev,
  93                                                 struct dentry *root)
  94 {
  95         struct list_head *next;
  96         struct dentry *p, *ret;
  97
  98         if (prev == NULL)
  99                 return dget(root);
 100
 101         spin_lock(&autofs4_lock);
 102 relock:
 103         p = prev;
 104         spin_lock(&p->d_lock);
 105 again:
 106         next = p->d_subdirs.next;
 107         if (next == &p->d_subdirs) {
 108                 while (1) {
 109                         struct dentry *parent;
 110
 111                         if (p == root) {
 112                                 spin_unlock(&p->d_lock);
 113                                 spin_unlock(&autofs4_lock);
 114                                 dput(prev);
 115                                 return NULL;
 116                         }
 117
 118                         parent = p->d_parent;
 119                         if (!spin_trylock(&parent->d_lock)) {
 120                                 spin_unlock(&p->d_lock);
 121                                 cpu_relax();
 122                                 goto relock;
 123                         }
 124                         spin_unlock(&p->d_lock);
 125                         next = p->d_u.d_child.next;
 126                         p = parent;
 127                         if (next != &parent->d_subdirs)
 128                                 break;
 129                 }
 130         }
 131         ret = list_entry(next, struct dentry, d_u.d_child);
 132
 133         spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
 134         /* Negative dentry - try next */
 135         if (!simple_positive(ret)) {
 136                 spin_unlock(&p->d_lock);
 137                 p = ret;
 138                 goto again;
 139         }
 140         dget_dlock(ret);
 141         spin_unlock(&ret->d_lock);
 142         spin_unlock(&p->d_lock);
 143         spin_unlock(&autofs4_lock);
 144
 145         dput(prev);
 146
 147         return ret;
 148 }
 149
 150 /*
 151  * Check a direct mount point for busyness.
 152  * Direct mounts have similar expiry semantics to tree mounts.
 153  * The tree is not busy iff no mountpoints are busy and there are no
 154  * autofs submounts.
 155  */
 156 static int autofs4_direct_busy(struct vfsmount *mnt,
 157                                 struct dentry *top,
 158                                 unsigned long timeout,
 159                                 int do_now)
 160 {
 161         DPRINTK("top %p %.*s",
 162                 top, (int) top->d_name.len, top->d_name.name);
 163
 164         /* If it's busy update the expiry counters */
 165         if (!may_umount_tree(mnt)) {
 166                 struct autofs_info *ino = autofs4_dentry_ino(top);
 167                 if (ino)
 168                         ino->last_used = jiffies;
 169                 return 1;
 170         }
 171
 172         /* Timeout of a direct mount is determined by its top dentry */
 173         if (!autofs4_can_expire(top, timeout, do_now))
 174                 return 1;
 175
 176         return 0;
 177 }
 178
 179 /* Check a directory tree of mount points for busyness
 180  * The tree is not busy iff no mountpoints are busy
 181  */
 182 static int autofs4_tree_busy(struct vfsmount *mnt,
 183                              struct dentry *top,
 184                              unsigned long timeout,
 185                              int do_now)
 186 {
 187         struct autofs_info *top_ino = autofs4_dentry_ino(top);
 188         struct dentry *p;
 189
 190         DPRINTK("top %p %.*s",
 191                 top, (int)top->d_name.len, top->d_name.name);
 192
 193         /* Negative dentry - give up */
 194         if (!simple_positive(top))
 195                 return 1;
 196
 197         p = NULL;
 198         while ((p = get_next_positive_dentry(p, top))) {
 199                 DPRINTK("dentry %p %.*s",
 200                         p, (int) p->d_name.len, p->d_name.name);
 201
 202                 /*
 203                  * Is someone visiting anywhere in the subtree ?
 204                  * If there's no mount we need to check the usage
 205                  * count for the autofs dentry.
 206                  * If the fs is busy update the expiry counter.
 207                  */
 208                 if (d_mountpoint(p)) {
 209                         if (autofs4_mount_busy(mnt, p)) {
 210                                 top_ino->last_used = jiffies;
 211                                 dput(p);
 212                                 return 1;
 213                         }
 214                 } else {
 215                         struct autofs_info *ino = autofs4_dentry_ino(p);
 216                         unsigned int ino_count = atomic_read(&ino->count);
 217
 218                         /*
 219                          * Clean stale dentries below that have not been
 220                          * invalidated after a mount fail during lookup
 221                          */
 222                         d_invalidate(p);
 223
 224                         /* allow for dget above and top is already dgot */
 225                         if (p == top)
 226                                 ino_count += 2;
 227                         else
 228                                 ino_count++;
 229
 230                         if (p->d_count > ino_count) {
 231                                 top_ino->last_used = jiffies;
 232                                 dput(p);
 233                                 return 1;
 234                         }
 235                 }
 236         }
 237
 238         /* Timeout of a tree mount is ultimately determined by its top dentry */
 239         if (!autofs4_can_expire(top, timeout, do_now))
 240                 return 1;
 241
 242         return 0;
 243 }
 244
 245 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
 246                                            struct dentry *parent,
 247                                            unsigned long timeout,
 248                                            int do_now)
 249 {
 250         struct dentry *p;
 251
 252         DPRINTK("parent %p %.*s",
 253                 parent, (int)parent->d_name.len, parent->d_name.name);
 254
 255         p = NULL;
 256         while ((p = get_next_positive_dentry(p, parent))) {
 257                 DPRINTK("dentry %p %.*s",
 258                         p, (int) p->d_name.len, p->d_name.name);
 259
 260                 if (d_mountpoint(p)) {
 261                         /* Can we umount this guy */
 262                         if (autofs4_mount_busy(mnt, p))
 263                                 continue;
 264
 265                         /* Can we expire this guy */
 266                         if (autofs4_can_expire(p, timeout, do_now))
 267                                 return p;
 268                 }
 269         }
 270         return NULL;
 271 }
 272
 273 /* Check if we can expire a direct mount (possibly a tree) */
 274 struct dentry *autofs4_expire_direct(struct super_block *sb,
 275                                      struct vfsmount *mnt,
 276                                      struct autofs_sb_info *sbi,
 277                                      int how)
 278 {
 279         unsigned long timeout;
 280         struct dentry *root = dget(sb->s_root);
 281         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 282         struct autofs_info *ino;
 283
 284         if (!root)
 285                 return NULL;
 286
 287         now = jiffies;
 288         timeout = sbi->exp_timeout;
 289
 290         spin_lock(&sbi->fs_lock);
 291         ino = autofs4_dentry_ino(root);
 292         /* No point expiring a pending mount */
 293         if (ino->flags & AUTOFS_INF_PENDING) {
 294                 spin_unlock(&sbi->fs_lock);
 295                 return NULL;
 296         }
 297         managed_dentry_set_transit(root);
 298         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
 299                 struct autofs_info *ino = autofs4_dentry_ino(root);
 300                 ino->flags |= AUTOFS_INF_EXPIRING;
 301                 init_completion(&ino->expire_complete);
 302                 spin_unlock(&sbi->fs_lock);
 303                 return root;
 304         }
 305         managed_dentry_clear_transit(root);
 306         spin_unlock(&sbi->fs_lock);
 307         dput(root);
 308
 309         return NULL;
 310 }
 311
 312 /*
 313  * Find an eligible tree to time-out
 314  * A tree is eligible if :-
 315  *  - it is unused by any user process
 316  *  - it has been unused for exp_timeout time
 317  */
 318 struct dentry *autofs4_expire_indirect(struct super_block *sb,
 319                                        struct vfsmount *mnt,
 320                                        struct autofs_sb_info *sbi,
 321                                        int how)
 322 {
 323         unsigned long timeout;
 324         struct dentry *root = sb->s_root;
 325         struct dentry *dentry;
 326         struct dentry *expired = NULL;
 327         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 328         int exp_leaves = how & AUTOFS_EXP_LEAVES;
 329         struct autofs_info *ino;
 330         unsigned int ino_count;
 331
 332         if (!root)
 333                 return NULL;
 334
 335         now = jiffies;
 336         timeout = sbi->exp_timeout;
 337
 338         dentry = NULL;
 339         while ((dentry = get_next_positive_dentry(dentry, root))) {
 340                 spin_lock(&sbi->fs_lock);
 341                 ino = autofs4_dentry_ino(dentry);
 342                 /* No point expiring a pending mount */
 343                 if (ino->flags & AUTOFS_INF_PENDING)
 344                         goto cont;
 345                 managed_dentry_set_transit(dentry);
 346
 347                 /*
 348                  * Case 1: (i) indirect mount or top level pseudo direct mount
 349                  *         (autofs-4.1).
 350                  *         (ii) indirect mount with offset mount, check the "/"
 351                  *         offset (autofs-5.0+).
 352                  */
 353                 if (d_mountpoint(dentry)) {
 354                         DPRINTK("checking mountpoint %p %.*s",
 355                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
 356
 357                         /* Path walk currently on this dentry? */
 358                         ino_count = atomic_read(&ino->count) + 2;
 359                         if (dentry->d_count > ino_count)
 360                                 goto next;
 361
 362                         /* Can we umount this guy */
 363                         if (autofs4_mount_busy(mnt, dentry))
 364                                 goto next;
 365
 366                         /* Can we expire this guy */
 367                         if (autofs4_can_expire(dentry, timeout, do_now)) {
 368                                 expired = dentry;
 369                                 goto found;
 370                         }
 371                         goto next;
 372                 }
 373
 374                 if (simple_empty(dentry))
 375                         goto next;
 376
 377                 /* Case 2: tree mount, expire iff entire tree is not busy */
 378                 if (!exp_leaves) {
 379                         /* Path walk currently on this dentry? */
 380                         ino_count = atomic_read(&ino->count) + 1;
 381                         if (dentry->d_count > ino_count)
 382                                 goto next;
 383
 384                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
 385                                 expired = dentry;
 386                                 goto found;
 387                         }
 388                 /*
 389                  * Case 3: pseudo direct mount, expire individual leaves
 390                  *         (autofs-4.1).
 391                  */
 392                 } else {
 393                         /* Path walk currently on this dentry? */
 394                         ino_count = atomic_read(&ino->count) + 1;
 395                         if (dentry->d_count > ino_count)
 396                                 goto next;
 397
 398                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
 399                         if (expired) {
 400                                 dput(dentry);
 401                                 goto found;
 402                         }
 403                 }
 404 next:
 405                 managed_dentry_clear_transit(dentry);
 406 cont:
 407                 spin_unlock(&sbi->fs_lock);
 408         }
 409         return NULL;
 410
 411 found:
 412         DPRINTK("returning %p %.*s",
 413                 expired, (int)expired->d_name.len, expired->d_name.name);
 414         ino = autofs4_dentry_ino(expired);
 415         ino->flags |= AUTOFS_INF_EXPIRING;
 416         init_completion(&ino->expire_complete);
 417         spin_unlock(&sbi->fs_lock);
 418         spin_lock(&autofs4_lock);
 419         spin_lock(&expired->d_parent->d_lock);
 420         spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
 421         list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
 422         spin_unlock(&expired->d_lock);
 423         spin_unlock(&expired->d_parent->d_lock);
 424         spin_unlock(&autofs4_lock);
 425         return expired;
 426 }
 427
 428 int autofs4_expire_wait(struct dentry *dentry)
 429 {
 430         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 431         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 432         int status;
 433
 434         /* Block on any pending expire */
 435         spin_lock(&sbi->fs_lock);
 436         if (ino->flags & AUTOFS_INF_EXPIRING) {
 437                 spin_unlock(&sbi->fs_lock);
 438
 439                 DPRINTK("waiting for expire %p name=%.*s",
 440                          dentry, dentry->d_name.len, dentry->d_name.name);
 441
 442                 status = autofs4_wait(sbi, dentry, NFY_NONE);
 443                 wait_for_completion(&ino->expire_complete);
 444
 445                 DPRINTK("expire done status=%d", status);
 446
 447                 if (d_unhashed(dentry))
 448                         return -EAGAIN;
 449
 450                 return status;
 451         }
 452         spin_unlock(&sbi->fs_lock);
 453
 454         return 0;
 455 }
 456
 457 /* Perform an expiry operation */
 458 int autofs4_expire_run(struct super_block *sb,
 459                       struct vfsmount *mnt,
 460                       struct autofs_sb_info *sbi,
 461                       struct autofs_packet_expire __user *pkt_p)
 462 {
 463         struct autofs_packet_expire pkt;
 464         struct autofs_info *ino;
 465         struct dentry *dentry;
 466         int ret = 0;
 467
 468         memset(&pkt,0,sizeof pkt);
 469
 470         pkt.hdr.proto_version = sbi->version;
 471         pkt.hdr.type = autofs_ptype_expire;
 472
 473         if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
 474                 return -EAGAIN;
 475
 476         pkt.len = dentry->d_name.len;
 477         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 478         pkt.name[pkt.len] = '\0';
 479         dput(dentry);
 480
 481         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
 482                 ret = -EFAULT;
 483
 484         spin_lock(&sbi->fs_lock);
 485         ino = autofs4_dentry_ino(dentry);
 486         ino->flags &= ~AUTOFS_INF_EXPIRING;
 487         if (!d_unhashed(dentry))
 488                 managed_dentry_clear_transit(dentry);
 489         complete_all(&ino->expire_complete);
 490         spin_unlock(&sbi->fs_lock);
 491
 492         return ret;
 493 }
 494
 495 int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 496                             struct autofs_sb_info *sbi, int when)
 497 {
 498         struct dentry *dentry;
 499         int ret = -EAGAIN;
 500
 501         if (autofs_type_trigger(sbi->type))
 502                 dentry = autofs4_expire_direct(sb, mnt, sbi, when);
 503         else
 504                 dentry = autofs4_expire_indirect(sb, mnt, sbi, when);
 505
 506         if (dentry) {
 507                 struct autofs_info *ino = autofs4_dentry_ino(dentry);
 508
 509                 /* This is synchronous because it makes the daemon a
 510                    little easier */
 511                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 512
 513                 spin_lock(&sbi->fs_lock);
 514                 ino->flags &= ~AUTOFS_INF_EXPIRING;
 515                 spin_lock(&dentry->d_lock);
 516                 if (ret)
 517                         __managed_dentry_clear_transit(dentry);
 518                 else {
 519                         if ((IS_ROOT(dentry) ||
 520                             (autofs_type_indirect(sbi->type) &&
 521                              IS_ROOT(dentry->d_parent))) &&
 522                             !(dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
 523                                 __managed_dentry_set_automount(dentry);
 524                 }
 525                 spin_unlock(&dentry->d_lock);
 526                 complete_all(&ino->expire_complete);
 527                 spin_unlock(&sbi->fs_lock);
 528                 dput(dentry);
 529         }
 530
 531         return ret;
 532 }
 533
 534 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
 535    more to be done */
 536 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 537                         struct autofs_sb_info *sbi, int __user *arg)
 538 {
 539         int do_now = 0;
 540
 541         if (arg && get_user(do_now, arg))
 542                 return -EFAULT;
 543
 544         return autofs4_do_expire_multi(sb, mnt, sbi, do_now);
 545 }
 546