linux/fs/autofs4/root.c
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   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
  22static int autofs4_dir_symlink(struct inode *,struct dentry *,const char *);
  23static int autofs4_dir_unlink(struct inode *,struct dentry *);
  24static int autofs4_dir_rmdir(struct inode *,struct dentry *);
  25static int autofs4_dir_mkdir(struct inode *,struct dentry *,int);
  26static int autofs4_root_ioctl(struct inode *, struct file *,unsigned int,unsigned long);
  27static int autofs4_dir_open(struct inode *inode, struct file *file);
  28static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct nameidata *);
  29static 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
  34const 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
  43const 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
  51const 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
  59const 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
  67const 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
  75static 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
 102out:
 103        return dcache_dir_open(inode, file);
 104}
 105
 106static 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 */
 171static 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);
 226follow:
 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
 240done:
 241        return NULL;
 242
 243out_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 */
 254static 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
 323void 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 */
 352static struct dentry_operations autofs4_root_dentry_operations = {
 353        .d_revalidate   = autofs4_revalidate,
 354        .d_release      = autofs4_dentry_release,
 355};
 356
 357/* For other dentries */
 358static struct dentry_operations autofs4_dentry_operations = {
 359        .d_revalidate   = autofs4_revalidate,
 360        .d_release      = autofs4_dentry_release,
 361};
 362
 363static 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                }
 406next:
 407                spin_unlock(&dentry->d_lock);
 408        }
 409        spin_unlock(&sbi->lookup_lock);
 410        spin_unlock(&dcache_lock);
 411
 412        return NULL;
 413}
 414
 415static 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                }
 458next:
 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 */
 468static 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        expiring = autofs4_lookup_expiring(sbi, dentry->d_parent, &dentry->d_name);
 489        if (expiring) {
 490                /*
 491                 * If we are racing with expire the request might not
 492                 * be quite complete but the directory has been removed
 493                 * so it must have been successful, so just wait for it.
 494                 */
 495                ino = autofs4_dentry_ino(expiring);
 496                autofs4_expire_wait(expiring);
 497                spin_lock(&sbi->lookup_lock);
 498                if (!list_empty(&ino->expiring))
 499                        list_del_init(&ino->expiring);
 500                spin_unlock(&sbi->lookup_lock);
 501                dput(expiring);
 502        }
 503
 504        unhashed = autofs4_lookup_active(sbi, dentry->d_parent, &dentry->d_name);
 505        if (unhashed)
 506                dentry = unhashed;
 507        else {
 508                /*
 509                 * Mark the dentry incomplete but don't hash it. We do this
 510                 * to serialize our inode creation operations (symlink and
 511                 * mkdir) which prevents deadlock during the callback to
 512                 * the daemon. Subsequent user space lookups for the same
 513                 * dentry are placed on the wait queue while the daemon
 514                 * itself is allowed passage unresticted so the create
 515                 * operation itself can then hash the dentry. Finally,
 516                 * we check for the hashed dentry and return the newly
 517                 * hashed dentry.
 518                 */
 519                dentry->d_op = &autofs4_root_dentry_operations;
 520
 521                /*
 522                 * And we need to ensure that the same dentry is used for
 523                 * all following lookup calls until it is hashed so that
 524                 * the dentry flags are persistent throughout the request.
 525                 */
 526                ino = autofs4_init_ino(NULL, sbi, 0555);
 527                if (!ino)
 528                        return ERR_PTR(-ENOMEM);
 529
 530                dentry->d_fsdata = ino;
 531                ino->dentry = dentry;
 532
 533                spin_lock(&sbi->lookup_lock);
 534                list_add(&ino->active, &sbi->active_list);
 535                spin_unlock(&sbi->lookup_lock);
 536
 537                d_instantiate(dentry, NULL);
 538        }
 539
 540        if (!oz_mode) {
 541                spin_lock(&dentry->d_lock);
 542                dentry->d_flags |= DCACHE_AUTOFS_PENDING;
 543                spin_unlock(&dentry->d_lock);
 544                if (dentry->d_op && dentry->d_op->d_revalidate) {
 545                        mutex_unlock(&dir->i_mutex);
 546                        (dentry->d_op->d_revalidate)(dentry, nd);
 547                        mutex_lock(&dir->i_mutex);
 548                }
 549        }
 550
 551        /*
 552         * If we are still pending, check if we had to handle
 553         * a signal. If so we can force a restart..
 554         */
 555        if (dentry->d_flags & DCACHE_AUTOFS_PENDING) {
 556                /* See if we were interrupted */
 557                if (signal_pending(current)) {
 558                        sigset_t *sigset = &current->pending.signal;
 559                        if (sigismember (sigset, SIGKILL) ||
 560                            sigismember (sigset, SIGQUIT) ||
 561                            sigismember (sigset, SIGINT)) {
 562                            if (unhashed)
 563                                dput(unhashed);
 564                            return ERR_PTR(-ERESTARTNOINTR);
 565                        }
 566                }
 567                if (!oz_mode) {
 568                        spin_lock(&dentry->d_lock);
 569                        dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
 570                        spin_unlock(&dentry->d_lock);
 571                }
 572        }
 573
 574        /*
 575         * If this dentry is unhashed, then we shouldn't honour this
 576         * lookup.  Returning ENOENT here doesn't do the right thing
 577         * for all system calls, but it should be OK for the operations
 578         * we permit from an autofs.
 579         */
 580        if (!oz_mode && d_unhashed(dentry)) {
 581                /*
 582                 * A user space application can (and has done in the past)
 583                 * remove and re-create this directory during the callback.
 584                 * This can leave us with an unhashed dentry, but a
 585                 * successful mount!  So we need to perform another
 586                 * cached lookup in case the dentry now exists.
 587                 */
 588                struct dentry *parent = dentry->d_parent;
 589                struct dentry *new = d_lookup(parent, &dentry->d_name);
 590                if (new != NULL)
 591                        dentry = new;
 592                else
 593                        dentry = ERR_PTR(-ENOENT);
 594
 595                if (unhashed)
 596                        dput(unhashed);
 597
 598                return dentry;
 599        }
 600
 601        if (unhashed)
 602                return unhashed;
 603
 604        return NULL;
 605}
 606
 607static int autofs4_dir_symlink(struct inode *dir, 
 608                               struct dentry *dentry,
 609                               const char *symname)
 610{
 611        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 612        struct autofs_info *ino = autofs4_dentry_ino(dentry);
 613        struct autofs_info *p_ino;
 614        struct inode *inode;
 615        char *cp;
 616
 617        DPRINTK("%s <- %.*s", symname,
 618                dentry->d_name.len, dentry->d_name.name);
 619
 620        if (!autofs4_oz_mode(sbi))
 621                return -EACCES;
 622
 623        ino = autofs4_init_ino(ino, sbi, S_IFLNK | 0555);
 624        if (!ino)
 625                return -ENOMEM;
 626
 627        spin_lock(&sbi->lookup_lock);
 628        if (!list_empty(&ino->active))
 629                list_del_init(&ino->active);
 630        spin_unlock(&sbi->lookup_lock);
 631
 632        ino->size = strlen(symname);
 633        cp = kmalloc(ino->size + 1, GFP_KERNEL);
 634        if (!cp) {
 635                if (!dentry->d_fsdata)
 636                        kfree(ino);
 637                return -ENOMEM;
 638        }
 639
 640        strcpy(cp, symname);
 641
 642        inode = autofs4_get_inode(dir->i_sb, ino);
 643        if (!inode) {
 644                kfree(cp);
 645                if (!dentry->d_fsdata)
 646                        kfree(ino);
 647                return -ENOMEM;
 648        }
 649        d_add(dentry, inode);
 650
 651        if (dir == dir->i_sb->s_root->d_inode)
 652                dentry->d_op = &autofs4_root_dentry_operations;
 653        else
 654                dentry->d_op = &autofs4_dentry_operations;
 655
 656        dentry->d_fsdata = ino;
 657        ino->dentry = dget(dentry);
 658        atomic_inc(&ino->count);
 659        p_ino = autofs4_dentry_ino(dentry->d_parent);
 660        if (p_ino && dentry->d_parent != dentry)
 661                atomic_inc(&p_ino->count);
 662        ino->inode = inode;
 663
 664        ino->u.symlink = cp;
 665        dir->i_mtime = CURRENT_TIME;
 666
 667        return 0;
 668}
 669
 670/*
 671 * NOTE!
 672 *
 673 * Normal filesystems would do a "d_delete()" to tell the VFS dcache
 674 * that the file no longer exists. However, doing that means that the
 675 * VFS layer can turn the dentry into a negative dentry.  We don't want
 676 * this, because the unlink is probably the result of an expire.
 677 * We simply d_drop it and add it to a expiring list in the super block,
 678 * which allows the dentry lookup to check for an incomplete expire.
 679 *
 680 * If a process is blocked on the dentry waiting for the expire to finish,
 681 * it will invalidate the dentry and try to mount with a new one.
 682 *
 683 * Also see autofs4_dir_rmdir()..
 684 */
 685static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
 686{
 687        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 688        struct autofs_info *ino = autofs4_dentry_ino(dentry);
 689        struct autofs_info *p_ino;
 690        
 691        /* This allows root to remove symlinks */
 692        if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
 693                return -EACCES;
 694
 695        if (atomic_dec_and_test(&ino->count)) {
 696                p_ino = autofs4_dentry_ino(dentry->d_parent);
 697                if (p_ino && dentry->d_parent != dentry)
 698                        atomic_dec(&p_ino->count);
 699        }
 700        dput(ino->dentry);
 701
 702        dentry->d_inode->i_size = 0;
 703        clear_nlink(dentry->d_inode);
 704
 705        dir->i_mtime = CURRENT_TIME;
 706
 707        spin_lock(&dcache_lock);
 708        spin_lock(&sbi->lookup_lock);
 709        if (list_empty(&ino->expiring))
 710                list_add(&ino->expiring, &sbi->expiring_list);
 711        spin_unlock(&sbi->lookup_lock);
 712        spin_lock(&dentry->d_lock);
 713        __d_drop(dentry);
 714        spin_unlock(&dentry->d_lock);
 715        spin_unlock(&dcache_lock);
 716
 717        return 0;
 718}
 719
 720static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
 721{
 722        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 723        struct autofs_info *ino = autofs4_dentry_ino(dentry);
 724        struct autofs_info *p_ino;
 725        
 726        DPRINTK("dentry %p, removing %.*s",
 727                dentry, dentry->d_name.len, dentry->d_name.name);
 728
 729        if (!autofs4_oz_mode(sbi))
 730                return -EACCES;
 731
 732        spin_lock(&dcache_lock);
 733        if (!list_empty(&dentry->d_subdirs)) {
 734                spin_unlock(&dcache_lock);
 735                return -ENOTEMPTY;
 736        }
 737        spin_lock(&sbi->lookup_lock);
 738        if (list_empty(&ino->expiring))
 739                list_add(&ino->expiring, &sbi->expiring_list);
 740        spin_unlock(&sbi->lookup_lock);
 741        spin_lock(&dentry->d_lock);
 742        __d_drop(dentry);
 743        spin_unlock(&dentry->d_lock);
 744        spin_unlock(&dcache_lock);
 745
 746        if (atomic_dec_and_test(&ino->count)) {
 747                p_ino = autofs4_dentry_ino(dentry->d_parent);
 748                if (p_ino && dentry->d_parent != dentry)
 749                        atomic_dec(&p_ino->count);
 750        }
 751        dput(ino->dentry);
 752        dentry->d_inode->i_size = 0;
 753        clear_nlink(dentry->d_inode);
 754
 755        if (dir->i_nlink)
 756                drop_nlink(dir);
 757
 758        return 0;
 759}
 760
 761static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 762{
 763        struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 764        struct autofs_info *ino = autofs4_dentry_ino(dentry);
 765        struct autofs_info *p_ino;
 766        struct inode *inode;
 767
 768        if (!autofs4_oz_mode(sbi))
 769                return -EACCES;
 770
 771        DPRINTK("dentry %p, creating %.*s",
 772                dentry, dentry->d_name.len, dentry->d_name.name);
 773
 774        ino = autofs4_init_ino(ino, sbi, S_IFDIR | 0555);
 775        if (!ino)
 776                return -ENOMEM;
 777
 778        spin_lock(&sbi->lookup_lock);
 779        if (!list_empty(&ino->active))
 780                list_del_init(&ino->active);
 781        spin_unlock(&sbi->lookup_lock);
 782
 783        inode = autofs4_get_inode(dir->i_sb, ino);
 784        if (!inode) {
 785                if (!dentry->d_fsdata)
 786                        kfree(ino);
 787                return -ENOMEM;
 788        }
 789        d_add(dentry, inode);
 790
 791        if (dir == dir->i_sb->s_root->d_inode)
 792                dentry->d_op = &autofs4_root_dentry_operations;
 793        else
 794                dentry->d_op = &autofs4_dentry_operations;
 795
 796        dentry->d_fsdata = ino;
 797        ino->dentry = dget(dentry);
 798        atomic_inc(&ino->count);
 799        p_ino = autofs4_dentry_ino(dentry->d_parent);
 800        if (p_ino && dentry->d_parent != dentry)
 801                atomic_inc(&p_ino->count);
 802        ino->inode = inode;
 803        inc_nlink(dir);
 804        dir->i_mtime = CURRENT_TIME;
 805
 806        return 0;
 807}
 808
 809/* Get/set timeout ioctl() operation */
 810static inline int autofs4_get_set_timeout(struct autofs_sb_info *sbi,
 811                                         unsigned long __user *p)
 812{
 813        int rv;
 814        unsigned long ntimeout;
 815
 816        if ((rv = get_user(ntimeout, p)) ||
 817             (rv = put_user(sbi->exp_timeout/HZ, p)))
 818                return rv;
 819
 820        if (ntimeout > ULONG_MAX/HZ)
 821                sbi->exp_timeout = 0;
 822        else
 823                sbi->exp_timeout = ntimeout * HZ;
 824
 825        return 0;
 826}
 827
 828/* Return protocol version */
 829static inline int autofs4_get_protover(struct autofs_sb_info *sbi, int __user *p)
 830{
 831        return put_user(sbi->version, p);
 832}
 833
 834/* Return protocol sub version */
 835static inline int autofs4_get_protosubver(struct autofs_sb_info *sbi, int __user *p)
 836{
 837        return put_user(sbi->sub_version, p);
 838}
 839
 840/*
 841* Tells the daemon whether it can umount the autofs mount.
 842*/
 843static inline int autofs4_ask_umount(struct vfsmount *mnt, int __user *p)
 844{
 845        int status = 0;
 846
 847        if (may_umount(mnt))
 848                status = 1;
 849
 850        DPRINTK("returning %d", status);
 851
 852        status = put_user(status, p);
 853
 854        return status;
 855}
 856
 857/* Identify autofs4_dentries - this is so we can tell if there's
 858   an extra dentry refcount or not.  We only hold a refcount on the
 859   dentry if its non-negative (ie, d_inode != NULL)
 860*/
 861int is_autofs4_dentry(struct dentry *dentry)
 862{
 863        return dentry && dentry->d_inode &&
 864                (dentry->d_op == &autofs4_root_dentry_operations ||
 865                 dentry->d_op == &autofs4_dentry_operations) &&
 866                dentry->d_fsdata != NULL;
 867}
 868
 869/*
 870 * ioctl()'s on the root directory is the chief method for the daemon to
 871 * generate kernel reactions
 872 */
 873static int autofs4_root_ioctl(struct inode *inode, struct file *filp,
 874                             unsigned int cmd, unsigned long arg)
 875{
 876        struct autofs_sb_info *sbi = autofs4_sbi(inode->i_sb);
 877        void __user *p = (void __user *)arg;
 878
 879        DPRINTK("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u",
 880                cmd,arg,sbi,task_pgrp_nr(current));
 881
 882        if (_IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
 883             _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT)
 884                return -ENOTTY;
 885        
 886        if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
 887                return -EPERM;
 888        
 889        switch(cmd) {
 890        case AUTOFS_IOC_READY:  /* Wait queue: go ahead and retry */
 891                return autofs4_wait_release(sbi,(autofs_wqt_t)arg,0);
 892        case AUTOFS_IOC_FAIL:   /* Wait queue: fail with ENOENT */
 893                return autofs4_wait_release(sbi,(autofs_wqt_t)arg,-ENOENT);
 894        case AUTOFS_IOC_CATATONIC: /* Enter catatonic mode (daemon shutdown) */
 895                autofs4_catatonic_mode(sbi);
 896                return 0;
 897        case AUTOFS_IOC_PROTOVER: /* Get protocol version */
 898                return autofs4_get_protover(sbi, p);
 899        case AUTOFS_IOC_PROTOSUBVER: /* Get protocol sub version */
 900                return autofs4_get_protosubver(sbi, p);
 901        case AUTOFS_IOC_SETTIMEOUT:
 902                return autofs4_get_set_timeout(sbi, p);
 903
 904        case AUTOFS_IOC_ASKUMOUNT:
 905                return autofs4_ask_umount(filp->f_path.mnt, p);
 906
 907        /* return a single thing to expire */
 908        case AUTOFS_IOC_EXPIRE:
 909                return autofs4_expire_run(inode->i_sb,filp->f_path.mnt,sbi, p);
 910        /* same as above, but can send multiple expires through pipe */
 911        case AUTOFS_IOC_EXPIRE_MULTI:
 912                return autofs4_expire_multi(inode->i_sb,filp->f_path.mnt,sbi, p);
 913
 914        default:
 915                return -ENOSYS;
 916        }
 917}
 918
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