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