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