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/slab.h>
  19 #include <linux/param.h>
  20 #include <linux/time.h>
  21 #include <linux/smp_lock.h>
  22 #include "autofs_i.h"
  23
  24 static int autofs4_dir_symlink(struct inode *,struct dentry *,const char *);
  25 static int autofs4_dir_unlink(struct inode *,struct dentry *);
  26 static int autofs4_dir_rmdir(struct inode *,struct dentry *);
  27 static int autofs4_dir_mkdir(struct inode *,struct dentry *,int);
  28 static long autofs4_root_ioctl(struct file *,unsigned int,unsigned long);
  29 static int autofs4_dir_open(struct inode *inode, struct file *file);
  30 static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct nameidata *);
  31 static void *autofs4_follow_link(struct dentry *, struct nameidata *);
  32
  33 #define TRIGGER_FLAGS   (LOOKUP_CONTINUE | LOOKUP_DIRECTORY)
  34 #define TRIGGER_INTENTS (LOOKUP_OPEN | LOOKUP_CREATE)
  35
  36 const struct file_operations autofs4_root_operations = {
  37         .open           = dcache_dir_open,
  38         .release        = dcache_dir_close,
  39         .read           = generic_read_dir,
  40         .readdir        = dcache_readdir,
  41         .llseek         = dcache_dir_lseek,
  42         .unlocked_ioctl = autofs4_root_ioctl,
  43 };
  44
  45 const struct file_operations autofs4_dir_operations = {
  46         .open           = autofs4_dir_open,
  47         .release        = dcache_dir_close,
  48         .read           = generic_read_dir,
  49         .readdir        = dcache_readdir,
  50         .llseek         = dcache_dir_lseek,
  51 };
  52
  53 const struct inode_operations autofs4_indirect_root_inode_operations = {
  54         .lookup         = autofs4_lookup,
  55         .unlink         = autofs4_dir_unlink,
  56         .symlink        = autofs4_dir_symlink,
  57         .mkdir          = autofs4_dir_mkdir,
  58         .rmdir          = autofs4_dir_rmdir,
  59 };
  60
  61 const struct inode_operations autofs4_direct_root_inode_operations = {
  62         .lookup         = autofs4_lookup,
  63         .unlink         = autofs4_dir_unlink,
  64         .mkdir          = autofs4_dir_mkdir,
  65         .rmdir          = autofs4_dir_rmdir,
  66         .follow_link    = autofs4_follow_link,
  67 };
  68
  69 const struct inode_operations autofs4_dir_inode_operations = {
  70         .lookup         = autofs4_lookup,
  71         .unlink         = autofs4_dir_unlink,
  72         .symlink        = autofs4_dir_symlink,
  73         .mkdir          = autofs4_dir_mkdir,
  74         .rmdir          = autofs4_dir_rmdir,
  75 };
  76
  77 static void autofs4_add_active(struct dentry *dentry)
  78 {
  79         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
  80         struct autofs_info *ino = autofs4_dentry_ino(dentry);
  81         if (ino) {
  82                 spin_lock(&sbi->lookup_lock);
  83                 if (!ino->active_count) {
  84                         if (list_empty(&ino->active))
  85                                 list_add(&ino->active, &sbi->active_list);
  86                 }
  87                 ino->active_count++;
  88                 spin_unlock(&sbi->lookup_lock);
  89         }
  90         return;
  91 }
  92
  93 static void autofs4_del_active(struct dentry *dentry)
  94 {
  95         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
  96         struct autofs_info *ino = autofs4_dentry_ino(dentry);
  97         if (ino) {
  98                 spin_lock(&sbi->lookup_lock);
  99                 ino->active_count--;
 100                 if (!ino->active_count) {
 101                         if (!list_empty(&ino->active))
 102                                 list_del_init(&ino->active);
 103                 }
 104                 spin_unlock(&sbi->lookup_lock);
 105         }
 106         return;
 107 }
 108
 109 static unsigned int autofs4_need_mount(unsigned int flags)
 110 {
 111         unsigned int res = 0;
 112         if (flags & (TRIGGER_FLAGS | TRIGGER_INTENTS))
 113                 res = 1;
 114         return res;
 115 }
 116
 117 static int autofs4_dir_open(struct inode *inode, struct file *file)
 118 {
 119         struct dentry *dentry = file->f_path.dentry;
 120         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 121
 122         DPRINTK("file=%p dentry=%p %.*s",
 123                 file, dentry, dentry->d_name.len, dentry->d_name.name);
 124
 125         if (autofs4_oz_mode(sbi))
 126                 goto out;
 127
 128         /*
 129          * An empty directory in an autofs file system is always a
 130          * mount point. The daemon must have failed to mount this
 131          * during lookup so it doesn't exist. This can happen, for
 132          * example, if user space returns an incorrect status for a
 133          * mount request. Otherwise we're doing a readdir on the
 134          * autofs file system so just let the libfs routines handle
 135          * it.
 136          */
 137         spin_lock(&dcache_lock);
 138         if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
 139                 spin_unlock(&dcache_lock);
 140                 return -ENOENT;
 141         }
 142         spin_unlock(&dcache_lock);
 143
 144 out:
 145         return dcache_dir_open(inode, file);
 146 }
 147
 148 static int try_to_fill_dentry(struct dentry *dentry, int flags)
 149 {
 150         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 151         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 152         int status;
 153
 154         DPRINTK("dentry=%p %.*s ino=%p",
 155                  dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
 156
 157         /*
 158          * Wait for a pending mount, triggering one if there
 159          * isn't one already
 160          */
 161         if (dentry->d_inode == NULL) {
 162                 DPRINTK("waiting for mount name=%.*s",
 163                          dentry->d_name.len, dentry->d_name.name);
 164
 165                 status = autofs4_wait(sbi, dentry, NFY_MOUNT);
 166
 167                 DPRINTK("mount done status=%d", status);
 168
 169                 /* Turn this into a real negative dentry? */
 170                 if (status == -ENOENT) {
 171                         spin_lock(&sbi->fs_lock);
 172                         ino->flags &= ~AUTOFS_INF_PENDING;
 173                         spin_unlock(&sbi->fs_lock);
 174                         return status;
 175                 } else if (status) {
 176                         /* Return a negative dentry, but leave it "pending" */
 177                         return status;
 178                 }
 179         /* Trigger mount for path component or follow link */
 180         } else if (ino->flags & AUTOFS_INF_PENDING ||
 181                         autofs4_need_mount(flags)) {
 182                 DPRINTK("waiting for mount name=%.*s",
 183                         dentry->d_name.len, dentry->d_name.name);
 184
 185                 spin_lock(&sbi->fs_lock);
 186                 ino->flags |= AUTOFS_INF_PENDING;
 187                 spin_unlock(&sbi->fs_lock);
 188                 status = autofs4_wait(sbi, dentry, NFY_MOUNT);
 189
 190                 DPRINTK("mount done status=%d", status);
 191
 192                 if (status) {
 193                         spin_lock(&sbi->fs_lock);
 194                         ino->flags &= ~AUTOFS_INF_PENDING;
 195                         spin_unlock(&sbi->fs_lock);
 196                         return status;
 197                 }
 198         }
 199
 200         /* Initialize expiry counter after successful mount */
 201         if (ino)
 202                 ino->last_used = jiffies;
 203
 204         spin_lock(&sbi->fs_lock);
 205         ino->flags &= ~AUTOFS_INF_PENDING;
 206         spin_unlock(&sbi->fs_lock);
 207
 208         return 0;
 209 }
 210
 211 /* For autofs direct mounts the follow link triggers the mount */
 212 static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
 213 {
 214         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 215         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 216         int oz_mode = autofs4_oz_mode(sbi);
 217         unsigned int lookup_type;
 218         int status;
 219
 220         DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
 221                 dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
 222                 nd->flags);
 223         /*
 224          * For an expire of a covered direct or offset mount we need
 225          * to break out of follow_down() at the autofs mount trigger
 226          * (d_mounted--), so we can see the expiring flag, and manage
 227          * the blocking and following here until the expire is completed.
 228          */
 229         if (oz_mode) {
 230                 spin_lock(&sbi->fs_lock);
 231                 if (ino->flags & AUTOFS_INF_EXPIRING) {
 232                         spin_unlock(&sbi->fs_lock);
 233                         /* Follow down to our covering mount. */
 234                         if (!follow_down(&nd->path))
 235                                 goto done;
 236                         goto follow;
 237                 }
 238                 spin_unlock(&sbi->fs_lock);
 239                 goto done;
 240         }
 241
 242         /* If an expire request is pending everyone must wait. */
 243         autofs4_expire_wait(dentry);
 244
 245         /* We trigger a mount for almost all flags */
 246         lookup_type = autofs4_need_mount(nd->flags);
 247         spin_lock(&sbi->fs_lock);
 248         spin_lock(&dcache_lock);
 249         if (!(lookup_type || ino->flags & AUTOFS_INF_PENDING)) {
 250                 spin_unlock(&dcache_lock);
 251                 spin_unlock(&sbi->fs_lock);
 252                 goto follow;
 253         }
 254
 255         /*
 256          * If the dentry contains directories then it is an autofs
 257          * multi-mount with no root mount offset. So don't try to
 258          * mount it again.
 259          */
 260         if (ino->flags & AUTOFS_INF_PENDING ||
 261             (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))) {
 262                 spin_unlock(&dcache_lock);
 263                 spin_unlock(&sbi->fs_lock);
 264
 265                 status = try_to_fill_dentry(dentry, nd->flags);
 266                 if (status)
 267                         goto out_error;
 268
 269                 goto follow;
 270         }
 271         spin_unlock(&dcache_lock);
 272         spin_unlock(&sbi->fs_lock);
 273 follow:
 274         /*
 275          * If there is no root mount it must be an autofs
 276          * multi-mount with no root offset so we don't need
 277          * to follow it.
 278          */
 279         if (d_mountpoint(dentry)) {
 280                 if (!autofs4_follow_mount(&nd->path)) {
 281                         status = -ENOENT;
 282                         goto out_error;
 283                 }
 284         }
 285
 286 done:
 287         return NULL;
 288
 289 out_error:
 290         path_put(&nd->path);
 291         return ERR_PTR(status);
 292 }
 293
 294 /*
 295  * Revalidate is called on every cache lookup.  Some of those
 296  * cache lookups may actually happen while the dentry is not
 297  * yet completely filled in, and revalidate has to delay such
 298  * lookups..
 299  */
 300 static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 301 {
 302         struct inode *dir = dentry->d_parent->d_inode;
 303         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 304         int oz_mode = autofs4_oz_mode(sbi);
 305         int flags = nd ? nd->flags : 0;
 306         int status = 1;
 307
 308         /* Pending dentry */
 309         spin_lock(&sbi->fs_lock);
 310         if (autofs4_ispending(dentry)) {
 311                 /* The daemon never causes a mount to trigger */
 312                 spin_unlock(&sbi->fs_lock);
 313
 314                 if (oz_mode)
 315                         return 1;
 316
 317                 /*
 318                  * If the directory has gone away due to an expire
 319                  * we have been called as ->d_revalidate() and so
 320                  * we need to return false and proceed to ->lookup().
 321                  */
 322                 if (autofs4_expire_wait(dentry) == -EAGAIN)
 323                         return 0;
 324
 325                 /*
 326                  * A zero status is success otherwise we have a
 327                  * negative error code.
 328                  */
 329                 status = try_to_fill_dentry(dentry, flags);
 330                 if (status == 0)
 331                         return 1;
 332
 333                 return status;
 334         }
 335         spin_unlock(&sbi->fs_lock);
 336
 337         /* Negative dentry.. invalidate if "old" */
 338         if (dentry->d_inode == NULL)
 339                 return 0;
 340
 341         /* Check for a non-mountpoint directory with no contents */
 342         spin_lock(&dcache_lock);
 343         if (S_ISDIR(dentry->d_inode->i_mode) &&
 344             !d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
 345                 DPRINTK("dentry=%p %.*s, emptydir",
 346                          dentry, dentry->d_name.len, dentry->d_name.name);
 347                 spin_unlock(&dcache_lock);
 348
 349                 /* The daemon never causes a mount to trigger */
 350                 if (oz_mode)
 351                         return 1;
 352
 353                 /*
 354                  * A zero status is success otherwise we have a
 355                  * negative error code.
 356                  */
 357                 status = try_to_fill_dentry(dentry, flags);
 358                 if (status == 0)
 359                         return 1;
 360
 361                 return status;
 362         }
 363         spin_unlock(&dcache_lock);
 364
 365         return 1;
 366 }
 367
 368 void autofs4_dentry_release(struct dentry *de)
 369 {
 370         struct autofs_info *inf;
 371
 372         DPRINTK("releasing %p", de);
 373
 374         inf = autofs4_dentry_ino(de);
 375         de->d_fsdata = NULL;
 376
 377         if (inf) {
 378                 struct autofs_sb_info *sbi = autofs4_sbi(de->d_sb);
 379
 380                 if (sbi) {
 381                         spin_lock(&sbi->lookup_lock);
 382                         if (!list_empty(&inf->active))
 383                                 list_del(&inf->active);
 384                         if (!list_empty(&inf->expiring))
 385                                 list_del(&inf->expiring);
 386                         spin_unlock(&sbi->lookup_lock);
 387                 }
 388
 389                 inf->dentry = NULL;
 390                 inf->inode = NULL;
 391
 392                 autofs4_free_ino(inf);
 393         }
 394 }
 395
 396 /* For dentries of directories in the root dir */
 397 static const struct dentry_operations autofs4_root_dentry_operations = {
 398         .d_revalidate   = autofs4_revalidate,
 399         .d_release      = autofs4_dentry_release,
 400 };
 401
 402 /* For other dentries */
 403 static const struct dentry_operations autofs4_dentry_operations = {
 404         .d_revalidate   = autofs4_revalidate,
 405         .d_release      = autofs4_dentry_release,
 406 };
 407
 408 static struct dentry *autofs4_lookup_active(struct dentry *dentry)
 409 {
 410         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 411         struct dentry *parent = dentry->d_parent;
 412         struct qstr *name = &dentry->d_name;
 413         unsigned int len = name->len;
 414         unsigned int hash = name->hash;
 415         const unsigned char *str = name->name;
 416         struct list_head *p, *head;
 417
 418         spin_lock(&dcache_lock);
 419         spin_lock(&sbi->lookup_lock);
 420         head = &sbi->active_list;
 421         list_for_each(p, head) {
 422                 struct autofs_info *ino;
 423                 struct dentry *active;
 424                 struct qstr *qstr;
 425
 426                 ino = list_entry(p, struct autofs_info, active);
 427                 active = ino->dentry;
 428
 429                 spin_lock(&active->d_lock);
 430
 431                 /* Already gone? */
 432                 if (atomic_read(&active->d_count) == 0)
 433                         goto next;
 434
 435                 qstr = &active->d_name;
 436
 437                 if (active->d_name.hash != hash)
 438                         goto next;
 439                 if (active->d_parent != parent)
 440                         goto next;
 441
 442                 if (qstr->len != len)
 443                         goto next;
 444                 if (memcmp(qstr->name, str, len))
 445                         goto next;
 446
 447                 if (d_unhashed(active)) {
 448                         dget(active);
 449                         spin_unlock(&active->d_lock);
 450                         spin_unlock(&sbi->lookup_lock);
 451                         spin_unlock(&dcache_lock);
 452                         return active;
 453                 }
 454 next:
 455                 spin_unlock(&active->d_lock);
 456         }
 457         spin_unlock(&sbi->lookup_lock);
 458         spin_unlock(&dcache_lock);
 459
 460         return NULL;
 461 }
 462
 463 static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
 464 {
 465         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 466         struct dentry *parent = dentry->d_parent;
 467         struct qstr *name = &dentry->d_name;
 468         unsigned int len = name->len;
 469         unsigned int hash = name->hash;
 470         const unsigned char *str = name->name;
 471         struct list_head *p, *head;
 472
 473         spin_lock(&dcache_lock);
 474         spin_lock(&sbi->lookup_lock);
 475         head = &sbi->expiring_list;
 476         list_for_each(p, head) {
 477                 struct autofs_info *ino;
 478                 struct dentry *expiring;
 479                 struct qstr *qstr;
 480
 481                 ino = list_entry(p, struct autofs_info, expiring);
 482                 expiring = ino->dentry;
 483
 484                 spin_lock(&expiring->d_lock);
 485
 486                 /* Bad luck, we've already been dentry_iput */
 487                 if (!expiring->d_inode)
 488                         goto next;
 489
 490                 qstr = &expiring->d_name;
 491
 492                 if (expiring->d_name.hash != hash)
 493                         goto next;
 494                 if (expiring->d_parent != parent)
 495                         goto next;
 496
 497                 if (qstr->len != len)
 498                         goto next;
 499                 if (memcmp(qstr->name, str, len))
 500                         goto next;
 501
 502                 if (d_unhashed(expiring)) {
 503                         dget(expiring);
 504                         spin_unlock(&expiring->d_lock);
 505                         spin_unlock(&sbi->lookup_lock);
 506                         spin_unlock(&dcache_lock);
 507                         return expiring;
 508                 }
 509 next:
 510                 spin_unlock(&expiring->d_lock);
 511         }
 512         spin_unlock(&sbi->lookup_lock);
 513         spin_unlock(&dcache_lock);
 514
 515         return NULL;
 516 }
 517
 518 /* Lookups in the root directory */
 519 static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 520 {
 521         struct autofs_sb_info *sbi;
 522         struct autofs_info *ino;
 523         struct dentry *expiring, *active;
 524         int oz_mode;
 525
 526         DPRINTK("name = %.*s",
 527                 dentry->d_name.len, dentry->d_name.name);
 528
 529         /* File name too long to exist */
 530         if (dentry->d_name.len > NAME_MAX)
 531                 return ERR_PTR(-ENAMETOOLONG);
 532
 533         sbi = autofs4_sbi(dir->i_sb);
 534         oz_mode = autofs4_oz_mode(sbi);
 535
 536         DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
 537                  current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode);
 538
 539         active = autofs4_lookup_active(dentry);
 540         if (active) {
 541                 dentry = active;
 542                 ino = autofs4_dentry_ino(dentry);
 543         } else {
 544                 /*
 545                  * Mark the dentry incomplete but don't hash it. We do this
 546                  * to serialize our inode creation operations (symlink and
 547                  * mkdir) which prevents deadlock during the callback to
 548                  * the daemon. Subsequent user space lookups for the same
 549                  * dentry are placed on the wait queue while the daemon
 550                  * itself is allowed passage unresticted so the create
 551                  * operation itself can then hash the dentry. Finally,
 552                  * we check for the hashed dentry and return the newly
 553                  * hashed dentry.
 554                  */
 555                 dentry->d_op = &autofs4_root_dentry_operations;
 556
 557                 /*
 558                  * And we need to ensure that the same dentry is used for
 559                  * all following lookup calls until it is hashed so that
 560                  * the dentry flags are persistent throughout the request.
 561                  */
 562                 ino = autofs4_init_ino(NULL, sbi, 0555);
 563                 if (!ino)
 564                         return ERR_PTR(-ENOMEM);
 565
 566                 dentry->d_fsdata = ino;
 567                 ino->dentry = dentry;
 568
 569                 autofs4_add_active(dentry);
 570
 571                 d_instantiate(dentry, NULL);
 572         }
 573
 574         if (!oz_mode) {
 575                 mutex_unlock(&dir->i_mutex);
 576                 expiring = autofs4_lookup_expiring(dentry);
 577                 if (expiring) {
 578                         /*
 579                          * If we are racing with expire the request might not
 580                          * be quite complete but the directory has been removed
 581                          * so it must have been successful, so just wait for it.
 582                          */
 583                         autofs4_expire_wait(expiring);
 584                         autofs4_del_expiring(expiring);
 585                         dput(expiring);
 586                 }
 587
 588                 spin_lock(&sbi->fs_lock);
 589                 ino->flags |= AUTOFS_INF_PENDING;
 590                 spin_unlock(&sbi->fs_lock);
 591                 if (dentry->d_op && dentry->d_op->d_revalidate)
 592                         (dentry->d_op->d_revalidate)(dentry, nd);
 593                 mutex_lock(&dir->i_mutex);
 594         }
 595
 596         /*
 597          * If we are still pending, check if we had to handle
 598          * a signal. If so we can force a restart..
 599          */
 600         if (ino->flags & AUTOFS_INF_PENDING) {
 601                 /* See if we were interrupted */
 602                 if (signal_pending(current)) {
 603                         sigset_t *sigset = &current->pending.signal;
 604                         if (sigismember (sigset, SIGKILL) ||
 605                             sigismember (sigset, SIGQUIT) ||
 606                             sigismember (sigset, SIGINT)) {
 607                             if (active)
 608                                 dput(active);
 609                             return ERR_PTR(-ERESTARTNOINTR);
 610                         }
 611                 }
 612                 if (!oz_mode) {
 613                         spin_lock(&sbi->fs_lock);
 614                         ino->flags &= ~AUTOFS_INF_PENDING;
 615                         spin_unlock(&sbi->fs_lock);
 616                 }
 617         }
 618
 619         /*
 620          * If this dentry is unhashed, then we shouldn't honour this
 621          * lookup.  Returning ENOENT here doesn't do the right thing
 622          * for all system calls, but it should be OK for the operations
 623          * we permit from an autofs.
 624          */
 625         if (!oz_mode && d_unhashed(dentry)) {
 626                 /*
 627                  * A user space application can (and has done in the past)
 628                  * remove and re-create this directory during the callback.
 629                  * This can leave us with an unhashed dentry, but a
 630                  * successful mount!  So we need to perform another
 631                  * cached lookup in case the dentry now exists.
 632                  */
 633                 struct dentry *parent = dentry->d_parent;
 634                 struct dentry *new = d_lookup(parent, &dentry->d_name);
 635                 if (new != NULL)
 636                         dentry = new;
 637                 else
 638                         dentry = ERR_PTR(-ENOENT);
 639
 640                 if (active)
 641                         dput(active);
 642
 643                 return dentry;
 644         }
 645
 646         if (active)
 647                 return active;
 648
 649         return NULL;
 650 }
 651
 652 static int autofs4_dir_symlink(struct inode *dir,
 653                                struct dentry *dentry,
 654                                const char *symname)
 655 {
 656         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 657         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 658         struct autofs_info *p_ino;
 659         struct inode *inode;
 660         char *cp;
 661
 662         DPRINTK("%s <- %.*s", symname,
 663                 dentry->d_name.len, dentry->d_name.name);
 664
 665         if (!autofs4_oz_mode(sbi))
 666                 return -EACCES;
 667
 668         ino = autofs4_init_ino(ino, sbi, S_IFLNK | 0555);
 669         if (!ino)
 670                 return -ENOMEM;
 671
 672         autofs4_del_active(dentry);
 673
 674         ino->size = strlen(symname);
 675         cp = kmalloc(ino->size + 1, GFP_KERNEL);
 676         if (!cp) {
 677                 if (!dentry->d_fsdata)
 678                         kfree(ino);
 679                 return -ENOMEM;
 680         }
 681
 682         strcpy(cp, symname);
 683
 684         inode = autofs4_get_inode(dir->i_sb, ino);
 685         if (!inode) {
 686                 kfree(cp);
 687                 if (!dentry->d_fsdata)
 688                         kfree(ino);
 689                 return -ENOMEM;
 690         }
 691         d_add(dentry, inode);
 692
 693         if (dir == dir->i_sb->s_root->d_inode)
 694                 dentry->d_op = &autofs4_root_dentry_operations;
 695         else
 696                 dentry->d_op = &autofs4_dentry_operations;
 697
 698         dentry->d_fsdata = ino;
 699         ino->dentry = dget(dentry);
 700         atomic_inc(&ino->count);
 701         p_ino = autofs4_dentry_ino(dentry->d_parent);
 702         if (p_ino && dentry->d_parent != dentry)
 703                 atomic_inc(&p_ino->count);
 704         ino->inode = inode;
 705
 706         ino->u.symlink = cp;
 707         dir->i_mtime = CURRENT_TIME;
 708
 709         return 0;
 710 }
 711
 712 /*
 713  * NOTE!
 714  *
 715  * Normal filesystems would do a "d_delete()" to tell the VFS dcache
 716  * that the file no longer exists. However, doing that means that the
 717  * VFS layer can turn the dentry into a negative dentry.  We don't want
 718  * this, because the unlink is probably the result of an expire.
 719  * We simply d_drop it and add it to a expiring list in the super block,
 720  * which allows the dentry lookup to check for an incomplete expire.
 721  *
 722  * If a process is blocked on the dentry waiting for the expire to finish,
 723  * it will invalidate the dentry and try to mount with a new one.
 724  *
 725  * Also see autofs4_dir_rmdir()..
 726  */
 727 static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
 728 {
 729         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 730         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 731         struct autofs_info *p_ino;
 732
 733         /* This allows root to remove symlinks */
 734         if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
 735                 return -EACCES;
 736
 737         if (atomic_dec_and_test(&ino->count)) {
 738                 p_ino = autofs4_dentry_ino(dentry->d_parent);
 739                 if (p_ino && dentry->d_parent != dentry)
 740                         atomic_dec(&p_ino->count);
 741         }
 742         dput(ino->dentry);
 743
 744         dentry->d_inode->i_size = 0;
 745         clear_nlink(dentry->d_inode);
 746
 747         dir->i_mtime = CURRENT_TIME;
 748
 749         spin_lock(&dcache_lock);
 750         autofs4_add_expiring(dentry);
 751         spin_lock(&dentry->d_lock);
 752         __d_drop(dentry);
 753         spin_unlock(&dentry->d_lock);
 754         spin_unlock(&dcache_lock);
 755
 756         return 0;
 757 }
 758
 759 static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
 760 {
 761         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 762         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 763         struct autofs_info *p_ino;
 764
 765         DPRINTK("dentry %p, removing %.*s",
 766                 dentry, dentry->d_name.len, dentry->d_name.name);
 767
 768         if (!autofs4_oz_mode(sbi))
 769                 return -EACCES;
 770
 771         spin_lock(&dcache_lock);
 772         if (!list_empty(&dentry->d_subdirs)) {
 773                 spin_unlock(&dcache_lock);
 774                 return -ENOTEMPTY;
 775         }
 776         autofs4_add_expiring(dentry);
 777         spin_lock(&dentry->d_lock);
 778         __d_drop(dentry);
 779         spin_unlock(&dentry->d_lock);
 780         spin_unlock(&dcache_lock);
 781
 782         if (atomic_dec_and_test(&ino->count)) {
 783                 p_ino = autofs4_dentry_ino(dentry->d_parent);
 784                 if (p_ino && dentry->d_parent != dentry)
 785                         atomic_dec(&p_ino->count);
 786         }
 787         dput(ino->dentry);
 788         dentry->d_inode->i_size = 0;
 789         clear_nlink(dentry->d_inode);
 790
 791         if (dir->i_nlink)
 792                 drop_nlink(dir);
 793
 794         return 0;
 795 }
 796
 797 static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 798 {
 799         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 800         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 801         struct autofs_info *p_ino;
 802         struct inode *inode;
 803
 804         if (!autofs4_oz_mode(sbi))
 805                 return -EACCES;
 806
 807         DPRINTK("dentry %p, creating %.*s",
 808                 dentry, dentry->d_name.len, dentry->d_name.name);
 809
 810         ino = autofs4_init_ino(ino, sbi, S_IFDIR | 0555);
 811         if (!ino)
 812                 return -ENOMEM;
 813
 814         autofs4_del_active(dentry);
 815
 816         inode = autofs4_get_inode(dir->i_sb, ino);
 817         if (!inode) {
 818                 if (!dentry->d_fsdata)
 819                         kfree(ino);
 820                 return -ENOMEM;
 821         }
 822         d_add(dentry, inode);
 823
 824         if (dir == dir->i_sb->s_root->d_inode)
 825                 dentry->d_op = &autofs4_root_dentry_operations;
 826         else
 827                 dentry->d_op = &autofs4_dentry_operations;
 828
 829         dentry->d_fsdata = ino;
 830         ino->dentry = dget(dentry);
 831         atomic_inc(&ino->count);
 832         p_ino = autofs4_dentry_ino(dentry->d_parent);
 833         if (p_ino && dentry->d_parent != dentry)
 834                 atomic_inc(&p_ino->count);
 835         ino->inode = inode;
 836         inc_nlink(dir);
 837         dir->i_mtime = CURRENT_TIME;
 838
 839         return 0;
 840 }
 841
 842 /* Get/set timeout ioctl() operation */
 843 static inline int autofs4_get_set_timeout(struct autofs_sb_info *sbi,
 844                                          unsigned long __user *p)
 845 {
 846         int rv;
 847         unsigned long ntimeout;
 848
 849         if ((rv = get_user(ntimeout, p)) ||
 850              (rv = put_user(sbi->exp_timeout/HZ, p)))
 851                 return rv;
 852
 853         if (ntimeout > ULONG_MAX/HZ)
 854                 sbi->exp_timeout = 0;
 855         else
 856                 sbi->exp_timeout = ntimeout * HZ;
 857
 858         return 0;
 859 }
 860
 861 /* Return protocol version */
 862 static inline int autofs4_get_protover(struct autofs_sb_info *sbi, int __user *p)
 863 {
 864         return put_user(sbi->version, p);
 865 }
 866
 867 /* Return protocol sub version */
 868 static inline int autofs4_get_protosubver(struct autofs_sb_info *sbi, int __user *p)
 869 {
 870         return put_user(sbi->sub_version, p);
 871 }
 872
 873 /*
 874 * Tells the daemon whether it can umount the autofs mount.
 875 */
 876 static inline int autofs4_ask_umount(struct vfsmount *mnt, int __user *p)
 877 {
 878         int status = 0;
 879
 880         if (may_umount(mnt))
 881                 status = 1;
 882
 883         DPRINTK("returning %d", status);
 884
 885         status = put_user(status, p);
 886
 887         return status;
 888 }
 889
 890 /* Identify autofs4_dentries - this is so we can tell if there's
 891    an extra dentry refcount or not.  We only hold a refcount on the
 892    dentry if its non-negative (ie, d_inode != NULL)
 893 */
 894 int is_autofs4_dentry(struct dentry *dentry)
 895 {
 896         return dentry && dentry->d_inode &&
 897                 (dentry->d_op == &autofs4_root_dentry_operations ||
 898                  dentry->d_op == &autofs4_dentry_operations) &&
 899                 dentry->d_fsdata != NULL;
 900 }
 901
 902 /*
 903  * ioctl()'s on the root directory is the chief method for the daemon to
 904  * generate kernel reactions
 905  */
 906 static int autofs4_root_ioctl_unlocked(struct inode *inode, struct file *filp,
 907                                        unsigned int cmd, unsigned long arg)
 908 {
 909         struct autofs_sb_info *sbi = autofs4_sbi(inode->i_sb);
 910         void __user *p = (void __user *)arg;
 911
 912         DPRINTK("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u",
 913                 cmd,arg,sbi,task_pgrp_nr(current));
 914
 915         if (_IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
 916              _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT)
 917                 return -ENOTTY;
 918
 919         if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
 920                 return -EPERM;
 921
 922         switch(cmd) {
 923         case AUTOFS_IOC_READY:  /* Wait queue: go ahead and retry */
 924                 return autofs4_wait_release(sbi,(autofs_wqt_t)arg,0);
 925         case AUTOFS_IOC_FAIL:   /* Wait queue: fail with ENOENT */
 926                 return autofs4_wait_release(sbi,(autofs_wqt_t)arg,-ENOENT);
 927         case AUTOFS_IOC_CATATONIC: /* Enter catatonic mode (daemon shutdown) */
 928                 autofs4_catatonic_mode(sbi);
 929                 return 0;
 930         case AUTOFS_IOC_PROTOVER: /* Get protocol version */
 931                 return autofs4_get_protover(sbi, p);
 932         case AUTOFS_IOC_PROTOSUBVER: /* Get protocol sub version */
 933                 return autofs4_get_protosubver(sbi, p);
 934         case AUTOFS_IOC_SETTIMEOUT:
 935                 return autofs4_get_set_timeout(sbi, p);
 936
 937         case AUTOFS_IOC_ASKUMOUNT:
 938                 return autofs4_ask_umount(filp->f_path.mnt, p);
 939
 940         /* return a single thing to expire */
 941         case AUTOFS_IOC_EXPIRE:
 942                 return autofs4_expire_run(inode->i_sb,filp->f_path.mnt,sbi, p);
 943         /* same as above, but can send multiple expires through pipe */
 944         case AUTOFS_IOC_EXPIRE_MULTI:
 945                 return autofs4_expire_multi(inode->i_sb,filp->f_path.mnt,sbi, p);
 946
 947         default:
 948                 return -ENOSYS;
 949         }
 950 }
 951
 952 static long autofs4_root_ioctl(struct file *filp,
 953                                unsigned int cmd, unsigned long arg)
 954 {
 955         long ret;
 956         struct inode *inode = filp->f_dentry->d_inode;
 957
 958         lock_kernel();
 959         ret = autofs4_root_ioctl_unlocked(inode, filp, cmd, arg);
 960         unlock_kernel();
 961
 962         return ret;
 963 }