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