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