fs/autofs4/root.c

   1 /* -*- c -*- --------------------------------------------------------------- *
   2  *
   3  * linux/fs/autofs/root.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 <linux/capability.h>
  16 #include <linux/errno.h>
  17 #include <linux/stat.h>
  18 #include <linux/param.h>
  19 #include <linux/time.h>
  20 #include "autofs_i.h"
  21
  22 static int autofs4_dir_symlink(struct inode *,struct dentry *,const char *);
  23 static int autofs4_dir_unlink(struct inode *,struct dentry *);
  24 static int autofs4_dir_rmdir(struct inode *,struct dentry *);
  25 static int autofs4_dir_mkdir(struct inode *,struct dentry *,int);
  26 static int autofs4_root_ioctl(struct inode *, struct file *,unsigned int,unsigned long);
  27 static int autofs4_dir_open(struct inode *inode, struct file *file);
  28 static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct nameidata *);
  29 static void *autofs4_follow_link(struct dentry *, struct nameidata *);
  30
  31 #define TRIGGER_FLAGS   (LOOKUP_CONTINUE | LOOKUP_DIRECTORY)
  32 #define TRIGGER_INTENTS (LOOKUP_OPEN | LOOKUP_CREATE)
  33
  34 const struct file_operations autofs4_root_operations = {
  35         .open           = dcache_dir_open,
  36         .release        = dcache_dir_close,
  37         .read           = generic_read_dir,
  38         .readdir        = dcache_readdir,
  39         .llseek         = dcache_dir_lseek,
  40         .ioctl          = autofs4_root_ioctl,
  41 };
  42
  43 const struct file_operations autofs4_dir_operations = {
  44         .open           = autofs4_dir_open,
  45         .release        = dcache_dir_close,
  46         .read           = generic_read_dir,
  47         .readdir        = dcache_readdir,
  48         .llseek         = dcache_dir_lseek,
  49 };
  50
  51 const struct inode_operations autofs4_indirect_root_inode_operations = {
  52         .lookup         = autofs4_lookup,
  53         .unlink         = autofs4_dir_unlink,
  54         .symlink        = autofs4_dir_symlink,
  55         .mkdir          = autofs4_dir_mkdir,
  56         .rmdir          = autofs4_dir_rmdir,
  57 };
  58
  59 const struct inode_operations autofs4_direct_root_inode_operations = {
  60         .lookup         = autofs4_lookup,
  61         .unlink         = autofs4_dir_unlink,
  62         .mkdir          = autofs4_dir_mkdir,
  63         .rmdir          = autofs4_dir_rmdir,
  64         .follow_link    = autofs4_follow_link,
  65 };
  66
  67 const struct inode_operations autofs4_dir_inode_operations = {
  68         .lookup         = autofs4_lookup,
  69         .unlink         = autofs4_dir_unlink,
  70         .symlink        = autofs4_dir_symlink,
  71         .mkdir          = autofs4_dir_mkdir,
  72         .rmdir          = autofs4_dir_rmdir,
  73 };
  74
  75 static void autofs4_add_active(struct dentry *dentry)
  76 {
  77         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
  78         struct autofs_info *ino = autofs4_dentry_ino(dentry);
  79         if (ino) {
  80                 spin_lock(&sbi->lookup_lock);
  81                 if (!ino->active_count) {
  82                         if (list_empty(&ino->active))
  83                                 list_add(&ino->active, &sbi->active_list);
  84                 }
  85                 ino->active_count++;
  86                 spin_unlock(&sbi->lookup_lock);
  87         }
  88         return;
  89 }
  90
  91 static void autofs4_del_active(struct dentry *dentry)
  92 {
  93         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
  94         struct autofs_info *ino = autofs4_dentry_ino(dentry);
  95         if (ino) {
  96                 spin_lock(&sbi->lookup_lock);
  97                 ino->active_count--;
  98                 if (!ino->active_count) {
  99                         if (!list_empty(&ino->active))
 100                                 list_del_init(&ino->active);
 101                 }
 102                 spin_unlock(&sbi->lookup_lock);
 103         }
 104         return;
 105 }
 106
 107 static unsigned int autofs4_need_mount(unsigned int flags)
 108 {
 109         unsigned int res = 0;
 110         if (flags & (TRIGGER_FLAGS | TRIGGER_INTENTS))
 111                 res = 1;
 112         return res;
 113 }
 114
 115 static int autofs4_dir_open(struct inode *inode, struct file *file)
 116 {
 117         struct dentry *dentry = file->f_path.dentry;
 118         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 119
 120         DPRINTK("file=%p dentry=%p %.*s",
 121                 file, dentry, dentry->d_name.len, dentry->d_name.name);
 122
 123         if (autofs4_oz_mode(sbi))
 124                 goto out;
 125
 126         /*
 127          * An empty directory in an autofs file system is always a
 128          * mount point. The daemon must have failed to mount this
 129          * during lookup so it doesn't exist. This can happen, for
 130          * example, if user space returns an incorrect status for a
 131          * mount request. Otherwise we're doing a readdir on the
 132          * autofs file system so just let the libfs routines handle
 133          * it.
 134          */
 135         spin_lock(&dcache_lock);
 136         if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
 137                 spin_unlock(&dcache_lock);
 138                 return -ENOENT;
 139         }
 140         spin_unlock(&dcache_lock);
 141
 142 out:
 143         return dcache_dir_open(inode, file);
 144 }
 145
 146 static int try_to_fill_dentry(struct dentry *dentry, int flags)
 147 {
 148         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 149         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 150         int status;
 151
 152         DPRINTK("dentry=%p %.*s ino=%p",
 153                  dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
 154
 155         /*
 156          * Wait for a pending mount, triggering one if there
 157          * isn't one already
 158          */
 159         if (dentry->d_inode == NULL) {
 160                 DPRINTK("waiting for mount name=%.*s",
 161                          dentry->d_name.len, dentry->d_name.name);
 162
 163                 status = autofs4_wait(sbi, dentry, NFY_MOUNT);
 164
 165                 DPRINTK("mount done status=%d", status);
 166
 167                 /* Turn this into a real negative dentry? */
 168                 if (status == -ENOENT) {
 169                         spin_lock(&sbi->fs_lock);
 170                         ino->flags &= ~AUTOFS_INF_PENDING;
 171                         spin_unlock(&sbi->fs_lock);
 172                         return status;
 173                 } else if (status) {
 174                         /* Return a negative dentry, but leave it "pending" */
 175                         return status;
 176                 }
 177         /* Trigger mount for path component or follow link */
 178         } else if (ino->flags & AUTOFS_INF_PENDING ||
 179                         autofs4_need_mount(flags) ||
 180                         current->link_count) {
 181                 DPRINTK("waiting for mount name=%.*s",
 182                         dentry->d_name.len, dentry->d_name.name);
 183
 184                 spin_lock(&sbi->fs_lock);
 185                 ino->flags |= AUTOFS_INF_PENDING;
 186                 spin_unlock(&sbi->fs_lock);
 187                 status = autofs4_wait(sbi, dentry, NFY_MOUNT);
 188
 189                 DPRINTK("mount done status=%d", status);
 190
 191                 if (status) {
 192                         spin_lock(&sbi->fs_lock);
 193                         ino->flags &= ~AUTOFS_INF_PENDING;
 194                         spin_unlock(&sbi->fs_lock);
 195                         return status;
 196                 }
 197         }
 198
 199         /* Initialize expiry counter after successful mount */
 200         if (ino)
 201                 ino->last_used = jiffies;
 202
 203         spin_lock(&sbi->fs_lock);
 204         ino->flags &= ~AUTOFS_INF_PENDING;
 205         spin_unlock(&sbi->fs_lock);
 206
 207         return 0;
 208 }
 209
 210 /* For autofs direct mounts the follow link triggers the mount */
 211 static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
 212 {
 213         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 214         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 215         int oz_mode = autofs4_oz_mode(sbi);
 216         unsigned int lookup_type;
 217         int status;
 218
 219         DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
 220                 dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
 221                 nd->flags);
 222         /*
 223          * For an expire of a covered direct or offset mount we need
 224          * to break out of follow_down() at the autofs mount trigger
 225          * (d_mounted--), so we can see the expiring flag, and manage
 226          * the blocking and following here until the expire is completed.
 227          */
 228         if (oz_mode) {
 229                 spin_lock(&sbi->fs_lock);
 230                 if (ino->flags & AUTOFS_INF_EXPIRING) {
 231                         spin_unlock(&sbi->fs_lock);
 232                         /* Follow down to our covering mount. */
 233                         if (!follow_down(&nd->path))
 234                                 goto done;
 235                         goto follow;
 236                 }
 237                 spin_unlock(&sbi->fs_lock);
 238                 goto done;
 239         }
 240
 241         /* If an expire request is pending everyone must wait. */
 242         autofs4_expire_wait(dentry);
 243
 244         /* We trigger a mount for almost all flags */
 245         lookup_type = autofs4_need_mount(nd->flags);
 246         spin_lock(&sbi->fs_lock);
 247         spin_lock(&dcache_lock);
 248         if (!(lookup_type || ino->flags & AUTOFS_INF_PENDING)) {
 249                 spin_unlock(&dcache_lock);
 250                 spin_unlock(&sbi->fs_lock);
 251                 goto follow;
 252         }
 253
 254         /*
 255          * If the dentry contains directories then it is an autofs
 256          * multi-mount with no root mount offset. So don't try to
 257          * mount it again.
 258          */
 259         if (ino->flags & AUTOFS_INF_PENDING ||
 260             (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))) {
 261                 spin_unlock(&dcache_lock);
 262                 spin_unlock(&sbi->fs_lock);
 263
 264                 status = try_to_fill_dentry(dentry, 0);
 265                 if (status)
 266                         goto out_error;
 267
 268                 goto follow;
 269         }
 270         spin_unlock(&dcache_lock);
 271         spin_unlock(&sbi->fs_lock);
 272 follow:
 273         /*
 274          * If there is no root mount it must be an autofs
 275          * multi-mount with no root offset so we don't need
 276          * to follow it.
 277          */
 278         if (d_mountpoint(dentry)) {
 279                 if (!autofs4_follow_mount(&nd->path)) {
 280                         status = -ENOENT;
 281                         goto out_error;
 282                 }
 283         }
 284
 285 done:
 286         return NULL;
 287
 288 out_error:
 289         path_put(&nd->path);
 290         return ERR_PTR(status);
 291 }
 292
 293 /*
 294  * Revalidate is called on every cache lookup.  Some of those
 295  * cache lookups may actually happen while the dentry is not
 296  * yet completely filled in, and revalidate has to delay such
 297  * lookups..
 298  */
 299 static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 300 {
 301         struct inode *dir = dentry->d_parent->d_inode;
 302         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 303         int oz_mode = autofs4_oz_mode(sbi);
 304         int flags = nd ? nd->flags : 0;
 305         int status = 1;
 306
 307         /* Pending dentry */
 308         spin_lock(&sbi->fs_lock);
 309         if (autofs4_ispending(dentry)) {
 310                 /* The daemon never causes a mount to trigger */
 311                 spin_unlock(&sbi->fs_lock);
 312
 313                 if (oz_mode)
 314                         return 1;
 315
 316                 /*
 317                  * If the directory has gone away due to an expire
 318                  * we have been called as ->d_revalidate() and so
 319                  * we need to return false and proceed to ->lookup().
 320                  */
 321                 if (autofs4_expire_wait(dentry) == -EAGAIN)
 322                         return 0;
 323
 324                 /*
 325                  * A zero status is success otherwise we have a
 326                  * negative error code.
 327                  */
 328                 status = try_to_fill_dentry(dentry, flags);
 329                 if (status == 0)
 330                         return 1;
 331
 332                 return status;
 333         }
 334         spin_unlock(&sbi->fs_lock);
 335
 336         /* Negative dentry.. invalidate if "old" */
 337         if (dentry->d_inode == NULL)
 338                 return 0;
 339
 340         /* Check for a non-mountpoint directory with no contents */
 341         spin_lock(&dcache_lock);
 342         if (S_ISDIR(dentry->d_inode->i_mode) &&
 343             !d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
 344                 DPRINTK("dentry=%p %.*s, emptydir",
 345                          dentry, dentry->d_name.len, dentry->d_name.name);
 346                 spin_unlock(&dcache_lock);
 347
 348                 /* The daemon never causes a mount to trigger */
 349                 if (oz_mode)
 350                         return 1;
 351
 352                 /*
 353                  * A zero status is success otherwise we have a
 354                  * negative error code.
 355                  */
 356                 status = try_to_fill_dentry(dentry, flags);
 357                 if (status == 0)
 358                         return 1;
 359
 360                 return status;
 361         }
 362         spin_unlock(&dcache_lock);
 363
 364         return 1;
 365 }
 366
 367 void autofs4_dentry_release(struct dentry *de)
 368 {
 369         struct autofs_info *inf;
 370
 371         DPRINTK("releasing %p", de);
 372
 373         inf = autofs4_dentry_ino(de);
 374         de->d_fsdata = NULL;
 375
 376         if (inf) {
 377                 struct autofs_sb_info *sbi = autofs4_sbi(de->d_sb);
 378
 379                 if (sbi) {
 380                         spin_lock(&sbi->lookup_lock);
 381                         if (!list_empty(&inf->active))
 382                                 list_del(&inf->active);
 383                         if (!list_empty(&inf->expiring))
 384                                 list_del(&inf->expiring);
 385                         spin_unlock(&sbi->lookup_lock);
 386                 }
 387
 388                 inf->dentry = NULL;
 389                 inf->inode = NULL;
 390
 391                 autofs4_free_ino(inf);
 392         }
 393 }
 394
 395 /* For dentries of directories in the root dir */
 396 static const struct dentry_operations autofs4_root_dentry_operations = {
 397         .d_revalidate   = autofs4_revalidate,
 398         .d_release      = autofs4_dentry_release,
 399 };
 400
 401 /* For other dentries */
 402 static const struct dentry_operations autofs4_dentry_operations = {
 403         .d_revalidate   = autofs4_revalidate,
 404         .d_release      = autofs4_dentry_release,
 405 };
 406
 407 static struct dentry *autofs4_lookup_active(struct dentry *dentry)
 408 {
 409         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 410         struct dentry *parent = dentry->d_parent;
 411         struct qstr *name = &dentry->d_name;
 412         unsigned int len = name->len;
 413         unsigned int hash = name->hash;
 414         const unsigned char *str = name->name;
 415         struct list_head *p, *head;
 416
 417         spin_lock(&dcache_lock);
 418         spin_lock(&sbi->lookup_lock);
 419         head = &sbi->active_list;
 420         list_for_each(p, head) {
 421                 struct autofs_info *ino;
 422                 struct dentry *active;
 423                 struct qstr *qstr;
 424
 425                 ino = list_entry(p, struct autofs_info, active);
 426                 active = ino->dentry;
 427
 428                 spin_lock(&active->d_lock);
 429
 430                 /* Already gone? */
 431                 if (atomic_read(&active->d_count) == 0)
 432                         goto next;
 433
 434                 qstr = &active->d_name;
 435
 436                 if (active->d_name.hash != hash)
 437                         goto next;
 438                 if (active->d_parent != parent)
 439                         goto next;
 440
 441                 if (qstr->len != len)
 442                         goto next;
 443                 if (memcmp(qstr->name, str, len))
 444                         goto next;
 445
 446                 if (d_unhashed(active)) {
 447                         dget(active);
 448                         spin_unlock(&active->d_lock);
 449                         spin_unlock(&sbi->lookup_lock);
 450                         spin_unlock(&dcache_lock);
 451                         return active;
 452                 }
 453 next:
 454                 spin_unlock(&active->d_lock);
 455         }
 456         spin_unlock(&sbi->lookup_lock);
 457         spin_unlock(&dcache_lock);
 458
 459         return NULL;
 460 }
 461
 462 static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
 463 {
 464         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 465         struct dentry *parent = dentry->d_parent;
 466         struct qstr *name = &dentry->d_name;
 467         unsigned int len = name->len;
 468         unsigned int hash = name->hash;
 469         const unsigned char *str = name->name;
 470         struct list_head *p, *head;
 471
 472         spin_lock(&dcache_lock);
 473         spin_lock(&sbi->lookup_lock);
 474         head = &sbi->expiring_list;
 475         list_for_each(p, head) {
 476                 struct autofs_info *ino;
 477                 struct dentry *expiring;
 478                 struct qstr *qstr;
 479
 480                 ino = list_entry(p, struct autofs_info, expiring);
 481                 expiring = ino->dentry;
 482
 483                 spin_lock(&expiring->d_lock);
 484
 485                 /* Bad luck, we've already been dentry_iput */
 486                 if (!expiring->d_inode)
 487                         goto next;
 488
 489                 qstr = &expiring->d_name;
 490
 491                 if (expiring->d_name.hash != hash)
 492                         goto next;
 493                 if (expiring->d_parent != parent)
 494                         goto next;
 495
 496                 if (qstr->len != len)
 497                         goto next;
 498                 if (memcmp(qstr->name, str, len))
 499                         goto next;
 500
 501                 if (d_unhashed(expiring)) {
 502                         dget(expiring);
 503                         spin_unlock(&expiring->d_lock);
 504                         spin_unlock(&sbi->lookup_lock);
 505                         spin_unlock(&dcache_lock);
 506                         return expiring;
 507                 }
 508 next:
 509                 spin_unlock(&expiring->d_lock);
 510         }
 511         spin_unlock(&sbi->lookup_lock);
 512         spin_unlock(&dcache_lock);
 513
 514         return NULL;
 515 }
 516
 517 /* Lookups in the root directory */
 518 static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 519 {
 520         struct autofs_sb_info *sbi;
 521         struct autofs_info *ino;
 522         struct dentry *expiring, *active;
 523         int oz_mode;
 524
 525         DPRINTK("name = %.*s",
 526                 dentry->d_name.len, dentry->d_name.name);
 527
 528         /* File name too long to exist */
 529         if (dentry->d_name.len > NAME_MAX)
 530                 return ERR_PTR(-ENAMETOOLONG);
 531
 532         sbi = autofs4_sbi(dir->i_sb);
 533         oz_mode = autofs4_oz_mode(sbi);
 534
 535         DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
 536                  current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode);
 537
 538         active = autofs4_lookup_active(dentry);
 539         if (active) {
 540                 dentry = active;
 541                 ino = autofs4_dentry_ino(dentry);
 542         } else {
 543                 /*
 544                  * Mark the dentry incomplete but don't hash it. We do this
 545                  * to serialize our inode creation operations (symlink and
 546                  * mkdir) which prevents deadlock during the callback to
 547                  * the daemon. Subsequent user space lookups for the same
 548                  * dentry are placed on the wait queue while the daemon
 549                  * itself is allowed passage unresticted so the create
 550                  * operation itself can then hash the dentry. Finally,
 551                  * we check for the hashed dentry and return the newly
 552                  * hashed dentry.
 553                  */
 554                 dentry->d_op = &autofs4_root_dentry_operations;
 555
 556                 /*
 557                  * And we need to ensure that the same dentry is used for
 558                  * all following lookup calls until it is hashed so that
 559                  * the dentry flags are persistent throughout the request.
 560                  */
 561                 ino = autofs4_init_ino(NULL, sbi, 0555);
 562                 if (!ino)
 563                         return ERR_PTR(-ENOMEM);
 564
 565                 dentry->d_fsdata = ino;
 566                 ino->dentry = dentry;
 567
 568                 autofs4_add_active(dentry);
 569
 570                 d_instantiate(dentry, NULL);
 571         }
 572
 573         if (!oz_mode) {
 574                 mutex_unlock(&dir->i_mutex);
 575                 expiring = autofs4_lookup_expiring(dentry);
 576                 if (expiring) {
 577                         /*
 578                          * If we are racing with expire the request might not
 579                          * be quite complete but the directory has been removed
 580                          * so it must have been successful, so just wait for it.
 581                          */
 582                         autofs4_expire_wait(expiring);
 583                         autofs4_del_expiring(expiring);
 584                         dput(expiring);
 585                 }
 586
 587                 spin_lock(&sbi->fs_lock);
 588                 ino->flags |= AUTOFS_INF_PENDING;
 589                 spin_unlock(&sbi->fs_lock);
 590                 if (dentry->d_op && dentry->d_op->d_revalidate)
 591                         (dentry->d_op->d_revalidate)(dentry, nd);
 592                 mutex_lock(&dir->i_mutex);
 593         }
 594
 595         /*
 596          * If we are still pending, check if we had to handle
 597          * a signal. If so we can force a restart..
 598          */
 599         if (ino->flags & AUTOFS_INF_PENDING) {
 600                 /* See if we were interrupted */
 601                 if (signal_pending(current)) {
 602                         sigset_t *sigset = &current->pending.signal;
 603                         if (sigismember (sigset, SIGKILL) ||
 604                             sigismember (sigset, SIGQUIT) ||
 605                             sigismember (sigset, SIGINT)) {
 606                             if (active)
 607                                 dput(active);
 608                             return ERR_PTR(-ERESTARTNOINTR);
 609                         }
 610                 }
 611                 if (!oz_mode) {
 612                         spin_lock(&sbi->fs_lock);
 613                         ino->flags &= ~AUTOFS_INF_PENDING;
 614                         spin_unlock(&sbi->fs_lock);
 615                 }
 616         }
 617
 618         /*
 619          * If this dentry is unhashed, then we shouldn't honour this
 620          * lookup.  Returning ENOENT here doesn't do the right thing
 621          * for all system calls, but it should be OK for the operations
 622          * we permit from an autofs.
 623          */
 624         if (!oz_mode && d_unhashed(dentry)) {
 625                 /*
 626                  * A user space application can (and has done in the past)
 627                  * remove and re-create this directory during the callback.
 628                  * This can leave us with an unhashed dentry, but a
 629                  * successful mount!  So we need to perform another
 630                  * cached lookup in case the dentry now exists.
 631                  */
 632                 struct dentry *parent = dentry->d_parent;
 633                 struct dentry *new = d_lookup(parent, &dentry->d_name);
 634                 if (new != NULL)
 635                         dentry = new;
 636                 else
 637                         dentry = ERR_PTR(-ENOENT);
 638
 639                 if (active)
 640                         dput(active);
 641
 642                 return dentry;
 643         }
 644
 645         if (active)
 646                 return active;
 647
 648         return NULL;
 649 }
 650
 651 static int autofs4_dir_symlink(struct inode *dir,
 652                                struct dentry *dentry,
 653                                const char *symname)
 654 {
 655         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 656         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 657         struct autofs_info *p_ino;
 658         struct inode *inode;
 659         char *cp;
 660
 661         DPRINTK("%s <- %.*s", symname,
 662                 dentry->d_name.len, dentry->d_name.name);
 663
 664         if (!autofs4_oz_mode(sbi))
 665                 return -EACCES;
 666
 667         ino = autofs4_init_ino(ino, sbi, S_IFLNK | 0555);
 668         if (!ino)
 669                 return -ENOMEM;
 670
 671         autofs4_del_active(dentry);
 672
 673         ino->size = strlen(symname);
 674         cp = kmalloc(ino->size + 1, GFP_KERNEL);
 675         if (!cp) {
 676                 if (!dentry->d_fsdata)
 677                         kfree(ino);
 678                 return -ENOMEM;
 679         }
 680
 681         strcpy(cp, symname);
 682
 683         inode = autofs4_get_inode(dir->i_sb, ino);
 684         if (!inode) {
 685                 kfree(cp);
 686                 if (!dentry->d_fsdata)
 687                         kfree(ino);
 688                 return -ENOMEM;
 689         }
 690         d_add(dentry, inode);
 691
 692         if (dir == dir->i_sb->s_root->d_inode)
 693                 dentry->d_op = &autofs4_root_dentry_operations;
 694         else
 695                 dentry->d_op = &autofs4_dentry_operations;
 696
 697         dentry->d_fsdata = ino;
 698         ino->dentry = dget(dentry);
 699         atomic_inc(&ino->count);
 700         p_ino = autofs4_dentry_ino(dentry->d_parent);
 701         if (p_ino && dentry->d_parent != dentry)
 702                 atomic_inc(&p_ino->count);
 703         ino->inode = inode;
 704
 705         ino->u.symlink = cp;
 706         dir->i_mtime = CURRENT_TIME;
 707
 708         return 0;
 709 }
 710
 711 /*
 712  * NOTE!
 713  *
 714  * Normal filesystems would do a "d_delete()" to tell the VFS dcache
 715  * that the file no longer exists. However, doing that means that the
 716  * VFS layer can turn the dentry into a negative dentry.  We don't want
 717  * this, because the unlink is probably the result of an expire.
 718  * We simply d_drop it and add it to a expiring list in the super block,
 719  * which allows the dentry lookup to check for an incomplete expire.
 720  *
 721  * If a process is blocked on the dentry waiting for the expire to finish,
 722  * it will invalidate the dentry and try to mount with a new one.
 723  *
 724  * Also see autofs4_dir_rmdir()..
 725  */
 726 static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
 727 {
 728         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 729         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 730         struct autofs_info *p_ino;
 731
 732         /* This allows root to remove symlinks */
 733         if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
 734                 return -EACCES;
 735
 736         if (atomic_dec_and_test(&ino->count)) {
 737                 p_ino = autofs4_dentry_ino(dentry->d_parent);
 738                 if (p_ino && dentry->d_parent != dentry)
 739                         atomic_dec(&p_ino->count);
 740         }
 741         dput(ino->dentry);
 742
 743         dentry->d_inode->i_size = 0;
 744         clear_nlink(dentry->d_inode);
 745
 746         dir->i_mtime = CURRENT_TIME;
 747
 748         spin_lock(&dcache_lock);
 749         autofs4_add_expiring(dentry);
 750         spin_lock(&dentry->d_lock);
 751         __d_drop(dentry);
 752         spin_unlock(&dentry->d_lock);
 753         spin_unlock(&dcache_lock);
 754
 755         return 0;
 756 }
 757
 758 static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
 759 {
 760         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 761         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 762         struct autofs_info *p_ino;
 763
 764         DPRINTK("dentry %p, removing %.*s",
 765                 dentry, dentry->d_name.len, dentry->d_name.name);
 766
 767         if (!autofs4_oz_mode(sbi))
 768                 return -EACCES;
 769
 770         spin_lock(&dcache_lock);
 771         if (!list_empty(&dentry->d_subdirs)) {
 772                 spin_unlock(&dcache_lock);
 773                 return -ENOTEMPTY;
 774         }
 775         autofs4_add_expiring(dentry);
 776         spin_lock(&dentry->d_lock);
 777         __d_drop(dentry);
 778         spin_unlock(&dentry->d_lock);
 779         spin_unlock(&dcache_lock);
 780
 781         if (atomic_dec_and_test(&ino->count)) {
 782                 p_ino = autofs4_dentry_ino(dentry->d_parent);
 783                 if (p_ino && dentry->d_parent != dentry)
 784                         atomic_dec(&p_ino->count);
 785         }
 786         dput(ino->dentry);
 787         dentry->d_inode->i_size = 0;
 788         clear_nlink(dentry->d_inode);
 789
 790         if (dir->i_nlink)
 791                 drop_nlink(dir);
 792
 793         return 0;
 794 }
 795
 796 static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 797 {
 798         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 799         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 800         struct autofs_info *p_ino;
 801         struct inode *inode;
 802
 803         if (!autofs4_oz_mode(sbi))
 804                 return -EACCES;
 805
 806         DPRINTK("dentry %p, creating %.*s",
 807                 dentry, dentry->d_name.len, dentry->d_name.name);
 808
 809         ino = autofs4_init_ino(ino, sbi, S_IFDIR | 0555);
 810         if (!ino)
 811                 return -ENOMEM;
 812
 813         autofs4_del_active(dentry);
 814
 815         inode = autofs4_get_inode(dir->i_sb, ino);
 816         if (!inode) {
 817                 if (!dentry->d_fsdata)
 818                         kfree(ino);
 819                 return -ENOMEM;
 820         }
 821         d_add(dentry, inode);
 822
 823         if (dir == dir->i_sb->s_root->d_inode)
 824                 dentry->d_op = &autofs4_root_dentry_operations;
 825         else
 826                 dentry->d_op = &autofs4_dentry_operations;
 827
 828         dentry->d_fsdata = ino;
 829         ino->dentry = dget(dentry);
 830         atomic_inc(&ino->count);
 831         p_ino = autofs4_dentry_ino(dentry->d_parent);
 832         if (p_ino && dentry->d_parent != dentry)
 833                 atomic_inc(&p_ino->count);
 834         ino->inode = inode;
 835         inc_nlink(dir);
 836         dir->i_mtime = CURRENT_TIME;
 837
 838         return 0;
 839 }
 840
 841 /* Get/set timeout ioctl() operation */
 842 static inline int autofs4_get_set_timeout(struct autofs_sb_info *sbi,
 843                                          unsigned long __user *p)
 844 {
 845         int rv;
 846         unsigned long ntimeout;
 847
 848         if ((rv = get_user(ntimeout, p)) ||
 849              (rv = put_user(sbi->exp_timeout/HZ, p)))
 850                 return rv;
 851
 852         if (ntimeout > ULONG_MAX/HZ)
 853                 sbi->exp_timeout = 0;
 854         else
 855                 sbi->exp_timeout = ntimeout * HZ;
 856
 857         return 0;
 858 }
 859
 860 /* Return protocol version */
 861 static inline int autofs4_get_protover(struct autofs_sb_info *sbi, int __user *p)
 862 {
 863         return put_user(sbi->version, p);
 864 }
 865
 866 /* Return protocol sub version */
 867 static inline int autofs4_get_protosubver(struct autofs_sb_info *sbi, int __user *p)
 868 {
 869         return put_user(sbi->sub_version, p);
 870 }
 871
 872 /*
 873 * Tells the daemon whether it can umount the autofs mount.
 874 */
 875 static inline int autofs4_ask_umount(struct vfsmount *mnt, int __user *p)
 876 {
 877         int status = 0;
 878
 879         if (may_umount(mnt))
 880                 status = 1;
 881
 882         DPRINTK("returning %d", status);
 883
 884         status = put_user(status, p);
 885
 886         return status;
 887 }
 888
 889 /* Identify autofs4_dentries - this is so we can tell if there's
 890    an extra dentry refcount or not.  We only hold a refcount on the
 891    dentry if its non-negative (ie, d_inode != NULL)
 892 */
 893 int is_autofs4_dentry(struct dentry *dentry)
 894 {
 895         return dentry && dentry->d_inode &&
 896                 (dentry->d_op == &autofs4_root_dentry_operations ||
 897                  dentry->d_op == &autofs4_dentry_operations) &&
 898                 dentry->d_fsdata != NULL;
 899 }
 900
 901 /*
 902  * ioctl()'s on the root directory is the chief method for the daemon to
 903  * generate kernel reactions
 904  */
 905 static int autofs4_root_ioctl(struct inode *inode, struct file *filp,
 906                              unsigned int cmd, unsigned long arg)
 907 {
 908         struct autofs_sb_info *sbi = autofs4_sbi(inode->i_sb);
 909         void __user *p = (void __user *)arg;
 910
 911         DPRINTK("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u",
 912                 cmd,arg,sbi,task_pgrp_nr(current));
 913
 914         if (_IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
 915              _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT)
 916                 return -ENOTTY;
 917
 918         if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
 919                 return -EPERM;
 920
 921         switch(cmd) {
 922         case AUTOFS_IOC_READY:  /* Wait queue: go ahead and retry */
 923                 return autofs4_wait_release(sbi,(autofs_wqt_t)arg,0);
 924         case AUTOFS_IOC_FAIL:   /* Wait queue: fail with ENOENT */
 925                 return autofs4_wait_release(sbi,(autofs_wqt_t)arg,-ENOENT);
 926         case AUTOFS_IOC_CATATONIC: /* Enter catatonic mode (daemon shutdown) */
 927                 autofs4_catatonic_mode(sbi);
 928                 return 0;
 929         case AUTOFS_IOC_PROTOVER: /* Get protocol version */
 930                 return autofs4_get_protover(sbi, p);
 931         case AUTOFS_IOC_PROTOSUBVER: /* Get protocol sub version */
 932                 return autofs4_get_protosubver(sbi, p);
 933         case AUTOFS_IOC_SETTIMEOUT:
 934                 return autofs4_get_set_timeout(sbi, p);
 935
 936         case AUTOFS_IOC_ASKUMOUNT:
 937                 return autofs4_ask_umount(filp->f_path.mnt, p);
 938
 939         /* return a single thing to expire */
 940         case AUTOFS_IOC_EXPIRE:
 941                 return autofs4_expire_run(inode->i_sb,filp->f_path.mnt,sbi, p);
 942         /* same as above, but can send multiple expires through pipe */
 943         case AUTOFS_IOC_EXPIRE_MULTI:
 944                 return autofs4_expire_multi(inode->i_sb,filp->f_path.mnt,sbi, p);
 945
 946         default:
 947                 return -ENOSYS;
 948         }
 949 }