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