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