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 (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 (!autofs4_follow_mount(&mnt, &dentry))
  60                 goto done;
  61
  62         /* This is an autofs submount, we can't expire it */
  63         if (is_autofs4_dentry(dentry))
  64                 goto done;
  65
  66         /* Update the expiry counter if fs is busy */
  67         if (!may_umount_tree(mnt)) {
  68                 struct autofs_info *ino = autofs4_dentry_ino(top);
  69                 ino->last_used = jiffies;
  70                 goto done;
  71         }
  72
  73         status = 0;
  74 done:
  75         DPRINTK("returning = %d", status);
  76         mntput(mnt);
  77         dput(dentry);
  78         return status;
  79 }
  80
  81 /*
  82  * Calculate next entry in top down tree traversal.
  83  * From next_mnt in namespace.c - elegant.
  84  */
  85 static struct dentry *next_dentry(struct dentry *p, struct dentry *root)
  86 {
  87         struct list_head *next = p->d_subdirs.next;
  88
  89         if (next == &p->d_subdirs) {
  90                 while (1) {
  91                         if (p == root)
  92                                 return NULL;
  93                         next = p->d_u.d_child.next;
  94                         if (next != &p->d_parent->d_subdirs)
  95                                 break;
  96                         p = p->d_parent;
  97                 }
  98         }
  99         return list_entry(next, struct dentry, d_u.d_child);
 100 }
 101
 102 /*
 103  * Check a direct mount point for busyness.
 104  * Direct mounts have similar expiry semantics to tree mounts.
 105  * The tree is not busy iff no mountpoints are busy and there are no
 106  * autofs submounts.
 107  */
 108 static int autofs4_direct_busy(struct vfsmount *mnt,
 109                                 struct dentry *top,
 110                                 unsigned long timeout,
 111                                 int do_now)
 112 {
 113         DPRINTK("top %p %.*s",
 114                 top, (int) top->d_name.len, top->d_name.name);
 115
 116         /* Not a mountpoint - give up */
 117         if (!d_mountpoint(top))
 118                 return 1;
 119
 120         /* If it's busy update the expiry counters */
 121         if (!may_umount_tree(mnt)) {
 122                 struct autofs_info *ino = autofs4_dentry_ino(top);
 123                 if (ino)
 124                         ino->last_used = jiffies;
 125                 return 1;
 126         }
 127
 128         /* Timeout of a direct mount is determined by its top dentry */
 129         if (!autofs4_can_expire(top, timeout, do_now))
 130                 return 1;
 131
 132         return 0;
 133 }
 134
 135 /* Check a directory tree of mount points for busyness
 136  * The tree is not busy iff no mountpoints are busy
 137  */
 138 static int autofs4_tree_busy(struct vfsmount *mnt,
 139                              struct dentry *top,
 140                              unsigned long timeout,
 141                              int do_now)
 142 {
 143         struct autofs_info *top_ino = autofs4_dentry_ino(top);
 144         struct dentry *p;
 145
 146         DPRINTK("top %p %.*s",
 147                 top, (int)top->d_name.len, top->d_name.name);
 148
 149         /* Negative dentry - give up */
 150         if (!simple_positive(top))
 151                 return 1;
 152
 153         spin_lock(&dcache_lock);
 154         for (p = top; p; p = next_dentry(p, top)) {
 155                 /* Negative dentry - give up */
 156                 if (!simple_positive(p))
 157                         continue;
 158
 159                 DPRINTK("dentry %p %.*s",
 160                         p, (int) p->d_name.len, p->d_name.name);
 161
 162                 p = dget(p);
 163                 spin_unlock(&dcache_lock);
 164
 165                 /*
 166                  * Is someone visiting anywhere in the subtree ?
 167                  * If there's no mount we need to check the usage
 168                  * count for the autofs dentry.
 169                  * If the fs is busy update the expiry counter.
 170                  */
 171                 if (d_mountpoint(p)) {
 172                         if (autofs4_mount_busy(mnt, p)) {
 173                                 top_ino->last_used = jiffies;
 174                                 dput(p);
 175                                 return 1;
 176                         }
 177                 } else {
 178                         struct autofs_info *ino = autofs4_dentry_ino(p);
 179                         unsigned int ino_count = atomic_read(&ino->count);
 180
 181                         /* allow for dget above and top is already dgot */
 182                         if (p == top)
 183                                 ino_count += 2;
 184                         else
 185                                 ino_count++;
 186
 187                         if (atomic_read(&p->d_count) > ino_count) {
 188                                 top_ino->last_used = jiffies;
 189                                 dput(p);
 190                                 return 1;
 191                         }
 192                 }
 193                 dput(p);
 194                 spin_lock(&dcache_lock);
 195         }
 196         spin_unlock(&dcache_lock);
 197
 198         /* Timeout of a tree mount is ultimately determined by its top dentry */
 199         if (!autofs4_can_expire(top, timeout, do_now))
 200                 return 1;
 201
 202         return 0;
 203 }
 204
 205 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
 206                                            struct dentry *parent,
 207                                            unsigned long timeout,
 208                                            int do_now)
 209 {
 210         struct dentry *p;
 211
 212         DPRINTK("parent %p %.*s",
 213                 parent, (int)parent->d_name.len, parent->d_name.name);
 214
 215         spin_lock(&dcache_lock);
 216         for (p = parent; p; p = next_dentry(p, parent)) {
 217                 /* Negative dentry - give up */
 218                 if (!simple_positive(p))
 219                         continue;
 220
 221                 DPRINTK("dentry %p %.*s",
 222                         p, (int) p->d_name.len, p->d_name.name);
 223
 224                 p = dget(p);
 225                 spin_unlock(&dcache_lock);
 226
 227                 if (d_mountpoint(p)) {
 228                         /* Can we umount this guy */
 229                         if (autofs4_mount_busy(mnt, p))
 230                                 goto cont;
 231
 232                         /* Can we expire this guy */
 233                         if (autofs4_can_expire(p, timeout, do_now))
 234                                 return p;
 235                 }
 236 cont:
 237                 dput(p);
 238                 spin_lock(&dcache_lock);
 239         }
 240         spin_unlock(&dcache_lock);
 241         return NULL;
 242 }
 243
 244 /* Check if we can expire a direct mount (possibly a tree) */
 245 static struct dentry *autofs4_expire_direct(struct super_block *sb,
 246                                             struct vfsmount *mnt,
 247                                             struct autofs_sb_info *sbi,
 248                                             int how)
 249 {
 250         unsigned long timeout;
 251         struct dentry *root = dget(sb->s_root);
 252         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 253
 254         if (!sbi->exp_timeout || !root)
 255                 return NULL;
 256
 257         now = jiffies;
 258         timeout = sbi->exp_timeout;
 259
 260         /* Lock the tree as we must expire as a whole */
 261         spin_lock(&sbi->fs_lock);
 262         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
 263                 struct autofs_info *ino = autofs4_dentry_ino(root);
 264
 265                 /* Set this flag early to catch sys_chdir and the like */
 266                 ino->flags |= AUTOFS_INF_EXPIRING;
 267                 spin_unlock(&sbi->fs_lock);
 268                 return root;
 269         }
 270         spin_unlock(&sbi->fs_lock);
 271         dput(root);
 272
 273         return NULL;
 274 }
 275
 276 /*
 277  * Find an eligible tree to time-out
 278  * A tree is eligible if :-
 279  *  - it is unused by any user process
 280  *  - it has been unused for exp_timeout time
 281  */
 282 static struct dentry *autofs4_expire_indirect(struct super_block *sb,
 283                                               struct vfsmount *mnt,
 284                                               struct autofs_sb_info *sbi,
 285                                               int how)
 286 {
 287         unsigned long timeout;
 288         struct dentry *root = sb->s_root;
 289         struct dentry *expired = NULL;
 290         struct list_head *next;
 291         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 292         int exp_leaves = how & AUTOFS_EXP_LEAVES;
 293
 294         if ( !sbi->exp_timeout || !root )
 295                 return NULL;
 296
 297         now = jiffies;
 298         timeout = sbi->exp_timeout;
 299
 300         spin_lock(&dcache_lock);
 301         next = root->d_subdirs.next;
 302
 303         /* On exit from the loop expire is set to a dgot dentry
 304          * to expire or it's NULL */
 305         while ( next != &root->d_subdirs ) {
 306                 struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
 307
 308                 /* Negative dentry - give up */
 309                 if (!simple_positive(dentry)) {
 310                         next = next->next;
 311                         continue;
 312                 }
 313
 314                 dentry = dget(dentry);
 315                 spin_unlock(&dcache_lock);
 316
 317                 /*
 318                  * Case 1: (i) indirect mount or top level pseudo direct mount
 319                  *         (autofs-4.1).
 320                  *         (ii) indirect mount with offset mount, check the "/"
 321                  *         offset (autofs-5.0+).
 322                  */
 323                 if (d_mountpoint(dentry)) {
 324                         DPRINTK("checking mountpoint %p %.*s",
 325                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
 326
 327                         /* Can we umount this guy */
 328                         if (autofs4_mount_busy(mnt, dentry))
 329                                 goto next;
 330
 331                         /* Can we expire this guy */
 332                         if (autofs4_can_expire(dentry, timeout, do_now)) {
 333                                 expired = dentry;
 334                                 break;
 335                         }
 336                         goto next;
 337                 }
 338
 339                 if (simple_empty(dentry))
 340                         goto next;
 341
 342                 /* Case 2: tree mount, expire iff entire tree is not busy */
 343                 if (!exp_leaves) {
 344                         /* Lock the tree as we must expire as a whole */
 345                         spin_lock(&sbi->fs_lock);
 346                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
 347                                 struct autofs_info *inf = autofs4_dentry_ino(dentry);
 348
 349                                 /* Set this flag early to catch sys_chdir and the like */
 350                                 inf->flags |= AUTOFS_INF_EXPIRING;
 351                                 spin_unlock(&sbi->fs_lock);
 352                                 expired = dentry;
 353                                 break;
 354                         }
 355                         spin_unlock(&sbi->fs_lock);
 356                 /*
 357                  * Case 3: pseudo direct mount, expire individual leaves
 358                  *         (autofs-4.1).
 359                  */
 360                 } else {
 361                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
 362                         if (expired) {
 363                                 dput(dentry);
 364                                 break;
 365                         }
 366                 }
 367 next:
 368                 dput(dentry);
 369                 spin_lock(&dcache_lock);
 370                 next = next->next;
 371         }
 372
 373         if (expired) {
 374                 DPRINTK("returning %p %.*s",
 375                         expired, (int)expired->d_name.len, expired->d_name.name);
 376                 spin_lock(&dcache_lock);
 377                 list_del(&expired->d_parent->d_subdirs);
 378                 list_add(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
 379                 spin_unlock(&dcache_lock);
 380                 return expired;
 381         }
 382         spin_unlock(&dcache_lock);
 383
 384         return NULL;
 385 }
 386
 387 /* Perform an expiry operation */
 388 int autofs4_expire_run(struct super_block *sb,
 389                       struct vfsmount *mnt,
 390                       struct autofs_sb_info *sbi,
 391                       struct autofs_packet_expire __user *pkt_p)
 392 {
 393         struct autofs_packet_expire pkt;
 394         struct dentry *dentry;
 395
 396         memset(&pkt,0,sizeof pkt);
 397
 398         pkt.hdr.proto_version = sbi->version;
 399         pkt.hdr.type = autofs_ptype_expire;
 400
 401         if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL)
 402                 return -EAGAIN;
 403
 404         pkt.len = dentry->d_name.len;
 405         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 406         pkt.name[pkt.len] = '\0';
 407         dput(dentry);
 408
 409         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
 410                 return -EFAULT;
 411
 412         return 0;
 413 }
 414
 415 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
 416    more to be done */
 417 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 418                         struct autofs_sb_info *sbi, int __user *arg)
 419 {
 420         struct dentry *dentry;
 421         int ret = -EAGAIN;
 422         int do_now = 0;
 423
 424         if (arg && get_user(do_now, arg))
 425                 return -EFAULT;
 426
 427         if (sbi->type & AUTOFS_TYPE_DIRECT)
 428                 dentry = autofs4_expire_direct(sb, mnt, sbi, do_now);
 429         else
 430                 dentry = autofs4_expire_indirect(sb, mnt, sbi, do_now);
 431
 432         if (dentry) {
 433                 struct autofs_info *ino = autofs4_dentry_ino(dentry);
 434
 435                 /* This is synchronous because it makes the daemon a
 436                    little easier */
 437                 ino->flags |= AUTOFS_INF_EXPIRING;
 438                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 439                 ino->flags &= ~AUTOFS_INF_EXPIRING;
 440                 dput(dentry);
 441         }
 442
 443         return ret;
 444 }
 445