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 int autofs4_dir_close(struct inode *inode, struct file *file);
  29 static int autofs4_dir_readdir(struct file * filp, void * dirent, filldir_t filldir);
  30 static int autofs4_root_readdir(struct file * filp, void * dirent, filldir_t filldir);
  31 static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct nameidata *);
  32 static void *autofs4_follow_link(struct dentry *, struct nameidata *);
  33
  34 #define TRIGGER_FLAGS   (LOOKUP_CONTINUE | LOOKUP_DIRECTORY)
  35 #define TRIGGER_INTENTS (LOOKUP_OPEN | LOOKUP_CREATE)
  36
  37 const struct file_operations autofs4_root_operations = {
  38         .open           = dcache_dir_open,
  39         .release        = dcache_dir_close,
  40         .read           = generic_read_dir,
  41         .readdir        = autofs4_root_readdir,
  42         .ioctl          = autofs4_root_ioctl,
  43 };
  44
  45 const struct file_operations autofs4_dir_operations = {
  46         .open           = autofs4_dir_open,
  47         .release        = autofs4_dir_close,
  48         .read           = generic_read_dir,
  49         .readdir        = autofs4_dir_readdir,
  50 };
  51
  52 const struct inode_operations autofs4_indirect_root_inode_operations = {
  53         .lookup         = autofs4_lookup,
  54         .unlink         = autofs4_dir_unlink,
  55         .symlink        = autofs4_dir_symlink,
  56         .mkdir          = autofs4_dir_mkdir,
  57         .rmdir          = autofs4_dir_rmdir,
  58 };
  59
  60 const struct inode_operations autofs4_direct_root_inode_operations = {
  61         .lookup         = autofs4_lookup,
  62         .unlink         = autofs4_dir_unlink,
  63         .mkdir          = autofs4_dir_mkdir,
  64         .rmdir          = autofs4_dir_rmdir,
  65         .follow_link    = autofs4_follow_link,
  66 };
  67
  68 const struct inode_operations autofs4_dir_inode_operations = {
  69         .lookup         = autofs4_lookup,
  70         .unlink         = autofs4_dir_unlink,
  71         .symlink        = autofs4_dir_symlink,
  72         .mkdir          = autofs4_dir_mkdir,
  73         .rmdir          = autofs4_dir_rmdir,
  74 };
  75
  76 static int autofs4_root_readdir(struct file *file, void *dirent,
  77                                 filldir_t filldir)
  78 {
  79         struct autofs_sb_info *sbi = autofs4_sbi(file->f_path.dentry->d_sb);
  80         int oz_mode = autofs4_oz_mode(sbi);
  81
  82         DPRINTK("called, filp->f_pos = %lld", file->f_pos);
  83
  84         /*
  85          * Don't set reghost flag if:
  86          * 1) f_pos is larger than zero -- we've already been here.
  87          * 2) we haven't even enabled reghosting in the 1st place.
  88          * 3) this is the daemon doing a readdir
  89          */
  90         if (oz_mode && file->f_pos == 0 && sbi->reghost_enabled)
  91                 sbi->needs_reghost = 1;
  92
  93         DPRINTK("needs_reghost = %d", sbi->needs_reghost);
  94
  95         return dcache_readdir(file, dirent, filldir);
  96 }
  97
  98 static int autofs4_dir_open(struct inode *inode, struct file *file)
  99 {
 100         struct dentry *dentry = file->f_path.dentry;
 101         struct vfsmount *mnt = file->f_path.mnt;
 102         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 103         struct dentry *cursor;
 104         int status;
 105
 106         status = dcache_dir_open(inode, file);
 107         if (status)
 108                 goto out;
 109
 110         cursor = file->private_data;
 111         cursor->d_fsdata = NULL;
 112
 113         DPRINTK("file=%p dentry=%p %.*s",
 114                 file, dentry, dentry->d_name.len, dentry->d_name.name);
 115
 116         if (autofs4_oz_mode(sbi))
 117                 goto out;
 118
 119         if (autofs4_ispending(dentry)) {
 120                 DPRINTK("dentry busy");
 121                 dcache_dir_close(inode, file);
 122                 status = -EBUSY;
 123                 goto out;
 124         }
 125
 126         status = -ENOENT;
 127         if (!d_mountpoint(dentry) && dentry->d_op && dentry->d_op->d_revalidate) {
 128                 struct nameidata nd;
 129                 int empty, ret;
 130
 131                 /* In case there are stale directory dentrys from a failed mount */
 132                 spin_lock(&dcache_lock);
 133                 empty = list_empty(&dentry->d_subdirs);
 134                 spin_unlock(&dcache_lock);
 135
 136                 if (!empty)
 137                         d_invalidate(dentry);
 138
 139                 nd.flags = LOOKUP_DIRECTORY;
 140                 ret = (dentry->d_op->d_revalidate)(dentry, &nd);
 141
 142                 if (ret <= 0) {
 143                         if (ret < 0)
 144                                 status = ret;
 145                         dcache_dir_close(inode, file);
 146                         goto out;
 147                 }
 148         }
 149
 150         if (d_mountpoint(dentry)) {
 151                 struct file *fp = NULL;
 152                 struct path fp_path = { .dentry = dentry, .mnt = mnt };
 153
 154                 path_get(&fp_path);
 155
 156                 if (!autofs4_follow_mount(&fp_path.mnt, &fp_path.dentry)) {
 157                         path_put(&fp_path);
 158                         dcache_dir_close(inode, file);
 159                         goto out;
 160                 }
 161
 162                 fp = dentry_open(fp_path.dentry, fp_path.mnt, file->f_flags);
 163                 status = PTR_ERR(fp);
 164                 if (IS_ERR(fp)) {
 165                         dcache_dir_close(inode, file);
 166                         goto out;
 167                 }
 168                 cursor->d_fsdata = fp;
 169         }
 170         return 0;
 171 out:
 172         return status;
 173 }
 174
 175 static int autofs4_dir_close(struct inode *inode, struct file *file)
 176 {
 177         struct dentry *dentry = file->f_path.dentry;
 178         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 179         struct dentry *cursor = file->private_data;
 180         int status = 0;
 181
 182         DPRINTK("file=%p dentry=%p %.*s",
 183                 file, dentry, dentry->d_name.len, dentry->d_name.name);
 184
 185         if (autofs4_oz_mode(sbi))
 186                 goto out;
 187
 188         if (autofs4_ispending(dentry)) {
 189                 DPRINTK("dentry busy");
 190                 status = -EBUSY;
 191                 goto out;
 192         }
 193
 194         if (d_mountpoint(dentry)) {
 195                 struct file *fp = cursor->d_fsdata;
 196                 if (!fp) {
 197                         status = -ENOENT;
 198                         goto out;
 199                 }
 200                 filp_close(fp, current->files);
 201         }
 202 out:
 203         dcache_dir_close(inode, file);
 204         return status;
 205 }
 206
 207 static int autofs4_dir_readdir(struct file *file, void *dirent, filldir_t filldir)
 208 {
 209         struct dentry *dentry = file->f_path.dentry;
 210         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 211         struct dentry *cursor = file->private_data;
 212         int status;
 213
 214         DPRINTK("file=%p dentry=%p %.*s",
 215                 file, dentry, dentry->d_name.len, dentry->d_name.name);
 216
 217         if (autofs4_oz_mode(sbi))
 218                 goto out;
 219
 220         if (autofs4_ispending(dentry)) {
 221                 DPRINTK("dentry busy");
 222                 return -EBUSY;
 223         }
 224
 225         if (d_mountpoint(dentry)) {
 226                 struct file *fp = cursor->d_fsdata;
 227
 228                 if (!fp)
 229                         return -ENOENT;
 230
 231                 if (!fp->f_op || !fp->f_op->readdir)
 232                         goto out;
 233
 234                 status = vfs_readdir(fp, filldir, dirent);
 235                 file->f_pos = fp->f_pos;
 236                 if (status)
 237                         autofs4_copy_atime(file, fp);
 238                 return status;
 239         }
 240 out:
 241         return dcache_readdir(file, dirent, filldir);
 242 }
 243
 244 static int try_to_fill_dentry(struct dentry *dentry, int flags)
 245 {
 246         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 247         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 248         int status;
 249
 250         /* Block on any pending expiry here; invalidate the dentry
 251            when expiration is done to trigger mount request with a new
 252            dentry */
 253         if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
 254                 DPRINTK("waiting for expire %p name=%.*s",
 255                          dentry, dentry->d_name.len, dentry->d_name.name);
 256
 257                 status = autofs4_wait(sbi, dentry, NFY_NONE);
 258
 259                 DPRINTK("expire done status=%d", status);
 260
 261                 /*
 262                  * If the directory still exists the mount request must
 263                  * continue otherwise it can't be followed at the right
 264                  * time during the walk.
 265                  */
 266                 status = d_invalidate(dentry);
 267                 if (status != -EBUSY)
 268                         return -EAGAIN;
 269         }
 270
 271         DPRINTK("dentry=%p %.*s ino=%p",
 272                  dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
 273
 274         /*
 275          * Wait for a pending mount, triggering one if there
 276          * isn't one already
 277          */
 278         if (dentry->d_inode == NULL) {
 279                 DPRINTK("waiting for mount name=%.*s",
 280                          dentry->d_name.len, dentry->d_name.name);
 281
 282                 status = autofs4_wait(sbi, dentry, NFY_MOUNT);
 283
 284                 DPRINTK("mount done status=%d", status);
 285
 286                 /* Turn this into a real negative dentry? */
 287                 if (status == -ENOENT) {
 288                         spin_lock(&dentry->d_lock);
 289                         dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
 290                         spin_unlock(&dentry->d_lock);
 291                         return status;
 292                 } else if (status) {
 293                         /* Return a negative dentry, but leave it "pending" */
 294                         return status;
 295                 }
 296         /* Trigger mount for path component or follow link */
 297         } else if (flags & (TRIGGER_FLAGS | TRIGGER_INTENTS) ||
 298                         current->link_count) {
 299                 DPRINTK("waiting for mount name=%.*s",
 300                         dentry->d_name.len, dentry->d_name.name);
 301
 302                 spin_lock(&dentry->d_lock);
 303                 dentry->d_flags |= DCACHE_AUTOFS_PENDING;
 304                 spin_unlock(&dentry->d_lock);
 305                 status = autofs4_wait(sbi, dentry, NFY_MOUNT);
 306
 307                 DPRINTK("mount done status=%d", status);
 308
 309                 if (status) {
 310                         spin_lock(&dentry->d_lock);
 311                         dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
 312                         spin_unlock(&dentry->d_lock);
 313                         return status;
 314                 }
 315         }
 316
 317         /* Initialize expiry counter after successful mount */
 318         if (ino)
 319                 ino->last_used = jiffies;
 320
 321         spin_lock(&dentry->d_lock);
 322         dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
 323         spin_unlock(&dentry->d_lock);
 324
 325         return 0;
 326 }
 327
 328 /* For autofs direct mounts the follow link triggers the mount */
 329 static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
 330 {
 331         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 332         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 333         int oz_mode = autofs4_oz_mode(sbi);
 334         unsigned int lookup_type;
 335         int status;
 336
 337         DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
 338                 dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
 339                 nd->flags);
 340
 341         /* If it's our master or we shouldn't trigger a mount we're done */
 342         lookup_type = nd->flags & (TRIGGER_FLAGS | TRIGGER_INTENTS);
 343         if (oz_mode || !lookup_type)
 344                 goto done;
 345
 346         /* If an expire request is pending wait for it. */
 347         if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
 348                 DPRINTK("waiting for active request %p name=%.*s",
 349                         dentry, dentry->d_name.len, dentry->d_name.name);
 350
 351                 status = autofs4_wait(sbi, dentry, NFY_NONE);
 352
 353                 DPRINTK("request done status=%d", status);
 354         }
 355
 356         /*
 357          * If the dentry contains directories then it is an
 358          * autofs multi-mount with no root mount offset. So
 359          * don't try to mount it again.
 360          */
 361         spin_lock(&dcache_lock);
 362         if (!d_mountpoint(dentry) && __simple_empty(dentry)) {
 363                 spin_unlock(&dcache_lock);
 364
 365                 status = try_to_fill_dentry(dentry, 0);
 366                 if (status)
 367                         goto out_error;
 368
 369                 /*
 370                  * The mount succeeded but if there is no root mount
 371                  * it must be an autofs multi-mount with no root offset
 372                  * so we don't need to follow the mount.
 373                  */
 374                 if (d_mountpoint(dentry)) {
 375                         if (!autofs4_follow_mount(&nd->path.mnt,
 376                                                   &nd->path.dentry)) {
 377                                 status = -ENOENT;
 378                                 goto out_error;
 379                         }
 380                 }
 381
 382                 goto done;
 383         }
 384         spin_unlock(&dcache_lock);
 385
 386 done:
 387         return NULL;
 388
 389 out_error:
 390         path_put(&nd->path);
 391         return ERR_PTR(status);
 392 }
 393
 394 /*
 395  * Revalidate is called on every cache lookup.  Some of those
 396  * cache lookups may actually happen while the dentry is not
 397  * yet completely filled in, and revalidate has to delay such
 398  * lookups..
 399  */
 400 static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 401 {
 402         struct inode *dir = dentry->d_parent->d_inode;
 403         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 404         int oz_mode = autofs4_oz_mode(sbi);
 405         int flags = nd ? nd->flags : 0;
 406         int status = 1;
 407
 408         /* Pending dentry */
 409         if (autofs4_ispending(dentry)) {
 410                 /* The daemon never causes a mount to trigger */
 411                 if (oz_mode)
 412                         return 1;
 413
 414                 /*
 415                  * A zero status is success otherwise we have a
 416                  * negative error code.
 417                  */
 418                 status = try_to_fill_dentry(dentry, flags);
 419                 if (status == 0)
 420                         return 1;
 421
 422                 /*
 423                  * A status of EAGAIN here means that the dentry has gone
 424                  * away while waiting for an expire to complete. If we are
 425                  * racing with expire lookup will wait for it so this must
 426                  * be a revalidate and we need to send it to lookup.
 427                  */
 428                 if (status == -EAGAIN)
 429                         return 0;
 430
 431                 return status;
 432         }
 433
 434         /* Negative dentry.. invalidate if "old" */
 435         if (dentry->d_inode == NULL)
 436                 return 0;
 437
 438         /* Check for a non-mountpoint directory with no contents */
 439         spin_lock(&dcache_lock);
 440         if (S_ISDIR(dentry->d_inode->i_mode) &&
 441             !d_mountpoint(dentry) &&
 442             __simple_empty(dentry)) {
 443                 DPRINTK("dentry=%p %.*s, emptydir",
 444                          dentry, dentry->d_name.len, dentry->d_name.name);
 445                 spin_unlock(&dcache_lock);
 446                 /* The daemon never causes a mount to trigger */
 447                 if (oz_mode)
 448                         return 1;
 449
 450                 /*
 451                  * A zero status is success otherwise we have a
 452                  * negative error code.
 453                  */
 454                 status = try_to_fill_dentry(dentry, flags);
 455                 if (status == 0)
 456                         return 1;
 457
 458                 return status;
 459         }
 460         spin_unlock(&dcache_lock);
 461
 462         return 1;
 463 }
 464
 465 void autofs4_dentry_release(struct dentry *de)
 466 {
 467         struct autofs_info *inf;
 468
 469         DPRINTK("releasing %p", de);
 470
 471         inf = autofs4_dentry_ino(de);
 472         de->d_fsdata = NULL;
 473
 474         if (inf) {
 475                 struct autofs_sb_info *sbi = autofs4_sbi(de->d_sb);
 476
 477                 if (sbi) {
 478                         spin_lock(&sbi->lookup_lock);
 479                         if (!list_empty(&inf->active))
 480                                 list_del(&inf->active);
 481                         if (!list_empty(&inf->expiring))
 482                                 list_del(&inf->expiring);
 483                         spin_unlock(&sbi->lookup_lock);
 484                 }
 485
 486                 inf->dentry = NULL;
 487                 inf->inode = NULL;
 488
 489                 autofs4_free_ino(inf);
 490         }
 491 }
 492
 493 /* For dentries of directories in the root dir */
 494 static struct dentry_operations autofs4_root_dentry_operations = {
 495         .d_revalidate   = autofs4_revalidate,
 496         .d_release      = autofs4_dentry_release,
 497 };
 498
 499 /* For other dentries */
 500 static struct dentry_operations autofs4_dentry_operations = {
 501         .d_revalidate   = autofs4_revalidate,
 502         .d_release      = autofs4_dentry_release,
 503 };
 504
 505 static struct dentry *autofs4_lookup_active(struct autofs_sb_info *sbi, struct dentry *parent, struct qstr *name)
 506 {
 507         unsigned int len = name->len;
 508         unsigned int hash = name->hash;
 509         const unsigned char *str = name->name;
 510         struct list_head *p, *head;
 511
 512         spin_lock(&dcache_lock);
 513         spin_lock(&sbi->lookup_lock);
 514         head = &sbi->active_list;
 515         list_for_each(p, head) {
 516                 struct autofs_info *ino;
 517                 struct dentry *dentry;
 518                 struct qstr *qstr;
 519
 520                 ino = list_entry(p, struct autofs_info, active);
 521                 dentry = ino->dentry;
 522
 523                 spin_lock(&dentry->d_lock);
 524
 525                 /* Already gone? */
 526                 if (atomic_read(&dentry->d_count) == 0)
 527                         goto next;
 528
 529                 qstr = &dentry->d_name;
 530
 531                 if (dentry->d_name.hash != hash)
 532                         goto next;
 533                 if (dentry->d_parent != parent)
 534                         goto next;
 535
 536                 if (qstr->len != len)
 537                         goto next;
 538                 if (memcmp(qstr->name, str, len))
 539                         goto next;
 540
 541                 if (d_unhashed(dentry)) {
 542                         dget(dentry);
 543                         spin_unlock(&dentry->d_lock);
 544                         spin_unlock(&sbi->lookup_lock);
 545                         spin_unlock(&dcache_lock);
 546                         return dentry;
 547                 }
 548 next:
 549                 spin_unlock(&dentry->d_lock);
 550         }
 551         spin_unlock(&sbi->lookup_lock);
 552         spin_unlock(&dcache_lock);
 553
 554         return NULL;
 555 }
 556
 557 static struct dentry *autofs4_lookup_expiring(struct autofs_sb_info *sbi, struct dentry *parent, struct qstr *name)
 558 {
 559         unsigned int len = name->len;
 560         unsigned int hash = name->hash;
 561         const unsigned char *str = name->name;
 562         struct list_head *p, *head;
 563
 564         spin_lock(&dcache_lock);
 565         spin_lock(&sbi->lookup_lock);
 566         head = &sbi->expiring_list;
 567         list_for_each(p, head) {
 568                 struct autofs_info *ino;
 569                 struct dentry *dentry;
 570                 struct qstr *qstr;
 571
 572                 ino = list_entry(p, struct autofs_info, expiring);
 573                 dentry = ino->dentry;
 574
 575                 spin_lock(&dentry->d_lock);
 576
 577                 /* Bad luck, we've already been dentry_iput */
 578                 if (!dentry->d_inode)
 579                         goto next;
 580
 581                 qstr = &dentry->d_name;
 582
 583                 if (dentry->d_name.hash != hash)
 584                         goto next;
 585                 if (dentry->d_parent != parent)
 586                         goto next;
 587
 588                 if (qstr->len != len)
 589                         goto next;
 590                 if (memcmp(qstr->name, str, len))
 591                         goto next;
 592
 593                 if (d_unhashed(dentry)) {
 594                         dget(dentry);
 595                         spin_unlock(&dentry->d_lock);
 596                         spin_unlock(&sbi->lookup_lock);
 597                         spin_unlock(&dcache_lock);
 598                         return dentry;
 599                 }
 600 next:
 601                 spin_unlock(&dentry->d_lock);
 602         }
 603         spin_unlock(&sbi->lookup_lock);
 604         spin_unlock(&dcache_lock);
 605
 606         return NULL;
 607 }
 608
 609 /* Lookups in the root directory */
 610 static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 611 {
 612         struct autofs_sb_info *sbi;
 613         struct autofs_info *ino;
 614         struct dentry *expiring, *unhashed;
 615         int oz_mode;
 616
 617         DPRINTK("name = %.*s",
 618                 dentry->d_name.len, dentry->d_name.name);
 619
 620         /* File name too long to exist */
 621         if (dentry->d_name.len > NAME_MAX)
 622                 return ERR_PTR(-ENAMETOOLONG);
 623
 624         sbi = autofs4_sbi(dir->i_sb);
 625         oz_mode = autofs4_oz_mode(sbi);
 626
 627         DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
 628                  current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode);
 629
 630         expiring = autofs4_lookup_expiring(sbi, dentry->d_parent, &dentry->d_name);
 631         if (expiring) {
 632                 /*
 633                  * If we are racing with expire the request might not
 634                  * be quite complete but the directory has been removed
 635                  * so it must have been successful, so just wait for it.
 636                  */
 637                 ino = autofs4_dentry_ino(expiring);
 638                 while (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
 639                         DPRINTK("wait for incomplete expire %p name=%.*s",
 640                                 expiring, expiring->d_name.len,
 641                                 expiring->d_name.name);
 642                         autofs4_wait(sbi, expiring, NFY_NONE);
 643                         DPRINTK("request completed");
 644                 }
 645                 spin_lock(&sbi->lookup_lock);
 646                 if (!list_empty(&ino->expiring))
 647                         list_del_init(&ino->expiring);
 648                 spin_unlock(&sbi->lookup_lock);
 649                 dput(expiring);
 650         }
 651
 652         unhashed = autofs4_lookup_active(sbi, dentry->d_parent, &dentry->d_name);
 653         if (unhashed)
 654                 dentry = unhashed;
 655         else {
 656                 /*
 657                  * Mark the dentry incomplete but don't hash it. We do this
 658                  * to serialize our inode creation operations (symlink and
 659                  * mkdir) which prevents deadlock during the callback to
 660                  * the daemon. Subsequent user space lookups for the same
 661                  * dentry are placed on the wait queue while the daemon
 662                  * itself is allowed passage unresticted so the create
 663                  * operation itself can then hash the dentry. Finally,
 664                  * we check for the hashed dentry and return the newly
 665                  * hashed dentry.
 666                  */
 667                 dentry->d_op = &autofs4_root_dentry_operations;
 668
 669                 /*
 670                  * And we need to ensure that the same dentry is used for
 671                  * all following lookup calls until it is hashed so that
 672                  * the dentry flags are persistent throughout the request.
 673                  */
 674                 ino = autofs4_init_ino(NULL, sbi, 0555);
 675                 if (!ino)
 676                         return ERR_PTR(-ENOMEM);
 677
 678                 dentry->d_fsdata = ino;
 679                 ino->dentry = dentry;
 680
 681                 spin_lock(&sbi->lookup_lock);
 682                 list_add(&ino->active, &sbi->active_list);
 683                 spin_unlock(&sbi->lookup_lock);
 684
 685                 d_instantiate(dentry, NULL);
 686         }
 687
 688         if (!oz_mode) {
 689                 spin_lock(&dentry->d_lock);
 690                 dentry->d_flags |= DCACHE_AUTOFS_PENDING;
 691                 spin_unlock(&dentry->d_lock);
 692                 if (dentry->d_op && dentry->d_op->d_revalidate) {
 693                         mutex_unlock(&dir->i_mutex);
 694                         (dentry->d_op->d_revalidate)(dentry, nd);
 695                         mutex_lock(&dir->i_mutex);
 696                 }
 697         }
 698
 699         /*
 700          * If we are still pending, check if we had to handle
 701          * a signal. If so we can force a restart..
 702          */
 703         if (dentry->d_flags & DCACHE_AUTOFS_PENDING) {
 704                 /* See if we were interrupted */
 705                 if (signal_pending(current)) {
 706                         sigset_t *sigset = &current->pending.signal;
 707                         if (sigismember (sigset, SIGKILL) ||
 708                             sigismember (sigset, SIGQUIT) ||
 709                             sigismember (sigset, SIGINT)) {
 710                             if (unhashed)
 711                                 dput(unhashed);
 712                             return ERR_PTR(-ERESTARTNOINTR);
 713                         }
 714                 }
 715                 if (!oz_mode) {
 716                         spin_lock(&dentry->d_lock);
 717                         dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
 718                         spin_unlock(&dentry->d_lock);
 719                 }
 720         }
 721
 722         /*
 723          * If this dentry is unhashed, then we shouldn't honour this
 724          * lookup.  Returning ENOENT here doesn't do the right thing
 725          * for all system calls, but it should be OK for the operations
 726          * we permit from an autofs.
 727          */
 728         if (!oz_mode && d_unhashed(dentry)) {
 729                 /*
 730                  * A user space application can (and has done in the past)
 731                  * remove and re-create this directory during the callback.
 732                  * This can leave us with an unhashed dentry, but a
 733                  * successful mount!  So we need to perform another
 734                  * cached lookup in case the dentry now exists.
 735                  */
 736                 struct dentry *parent = dentry->d_parent;
 737                 struct dentry *new = d_lookup(parent, &dentry->d_name);
 738                 if (new != NULL)
 739                         dentry = new;
 740                 else
 741                         dentry = ERR_PTR(-ENOENT);
 742
 743                 if (unhashed)
 744                         dput(unhashed);
 745
 746                 return dentry;
 747         }
 748
 749         if (unhashed)
 750                 return unhashed;
 751
 752         return NULL;
 753 }
 754
 755 static int autofs4_dir_symlink(struct inode *dir,
 756                                struct dentry *dentry,
 757                                const char *symname)
 758 {
 759         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 760         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 761         struct autofs_info *p_ino;
 762         struct inode *inode;
 763         char *cp;
 764
 765         DPRINTK("%s <- %.*s", symname,
 766                 dentry->d_name.len, dentry->d_name.name);
 767
 768         if (!autofs4_oz_mode(sbi))
 769                 return -EACCES;
 770
 771         ino = autofs4_init_ino(ino, sbi, S_IFLNK | 0555);
 772         if (!ino)
 773                 return -ENOMEM;
 774
 775         spin_lock(&sbi->lookup_lock);
 776         if (!list_empty(&ino->active))
 777                 list_del_init(&ino->active);
 778         spin_unlock(&sbi->lookup_lock);
 779
 780         ino->size = strlen(symname);
 781         cp = kmalloc(ino->size + 1, GFP_KERNEL);
 782         if (!cp) {
 783                 if (!dentry->d_fsdata)
 784                         kfree(ino);
 785                 return -ENOMEM;
 786         }
 787
 788         strcpy(cp, symname);
 789
 790         inode = autofs4_get_inode(dir->i_sb, ino);
 791         if (!inode) {
 792                 kfree(cp);
 793                 if (!dentry->d_fsdata)
 794                         kfree(ino);
 795                 return -ENOMEM;
 796         }
 797         d_add(dentry, inode);
 798
 799         if (dir == dir->i_sb->s_root->d_inode)
 800                 dentry->d_op = &autofs4_root_dentry_operations;
 801         else
 802                 dentry->d_op = &autofs4_dentry_operations;
 803
 804         dentry->d_fsdata = ino;
 805         ino->dentry = dget(dentry);
 806         atomic_inc(&ino->count);
 807         p_ino = autofs4_dentry_ino(dentry->d_parent);
 808         if (p_ino && dentry->d_parent != dentry)
 809                 atomic_inc(&p_ino->count);
 810         ino->inode = inode;
 811
 812         ino->u.symlink = cp;
 813         dir->i_mtime = CURRENT_TIME;
 814
 815         return 0;
 816 }
 817
 818 /*
 819  * NOTE!
 820  *
 821  * Normal filesystems would do a "d_delete()" to tell the VFS dcache
 822  * that the file no longer exists. However, doing that means that the
 823  * VFS layer can turn the dentry into a negative dentry.  We don't want
 824  * this, because the unlink is probably the result of an expire.
 825  * We simply d_drop it and add it to a expiring list in the super block,
 826  * which allows the dentry lookup to check for an incomplete expire.
 827  *
 828  * If a process is blocked on the dentry waiting for the expire to finish,
 829  * it will invalidate the dentry and try to mount with a new one.
 830  *
 831  * Also see autofs4_dir_rmdir()..
 832  */
 833 static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
 834 {
 835         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 836         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 837         struct autofs_info *p_ino;
 838
 839         /* This allows root to remove symlinks */
 840         if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
 841                 return -EACCES;
 842
 843         if (atomic_dec_and_test(&ino->count)) {
 844                 p_ino = autofs4_dentry_ino(dentry->d_parent);
 845                 if (p_ino && dentry->d_parent != dentry)
 846                         atomic_dec(&p_ino->count);
 847         }
 848         dput(ino->dentry);
 849
 850         dentry->d_inode->i_size = 0;
 851         clear_nlink(dentry->d_inode);
 852
 853         dir->i_mtime = CURRENT_TIME;
 854
 855         spin_lock(&dcache_lock);
 856         spin_lock(&sbi->lookup_lock);
 857         if (list_empty(&ino->expiring))
 858                 list_add(&ino->expiring, &sbi->expiring_list);
 859         spin_unlock(&sbi->lookup_lock);
 860         spin_lock(&dentry->d_lock);
 861         __d_drop(dentry);
 862         spin_unlock(&dentry->d_lock);
 863         spin_unlock(&dcache_lock);
 864
 865         return 0;
 866 }
 867
 868 static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
 869 {
 870         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 871         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 872         struct autofs_info *p_ino;
 873
 874         DPRINTK("dentry %p, removing %.*s",
 875                 dentry, dentry->d_name.len, dentry->d_name.name);
 876
 877         if (!autofs4_oz_mode(sbi))
 878                 return -EACCES;
 879
 880         spin_lock(&dcache_lock);
 881         if (!list_empty(&dentry->d_subdirs)) {
 882                 spin_unlock(&dcache_lock);
 883                 return -ENOTEMPTY;
 884         }
 885         spin_lock(&sbi->lookup_lock);
 886         if (list_empty(&ino->expiring))
 887                 list_add(&ino->expiring, &sbi->expiring_list);
 888         spin_unlock(&sbi->lookup_lock);
 889         spin_lock(&dentry->d_lock);
 890         __d_drop(dentry);
 891         spin_unlock(&dentry->d_lock);
 892         spin_unlock(&dcache_lock);
 893
 894         if (atomic_dec_and_test(&ino->count)) {
 895                 p_ino = autofs4_dentry_ino(dentry->d_parent);
 896                 if (p_ino && dentry->d_parent != dentry)
 897                         atomic_dec(&p_ino->count);
 898         }
 899         dput(ino->dentry);
 900         dentry->d_inode->i_size = 0;
 901         clear_nlink(dentry->d_inode);
 902
 903         if (dir->i_nlink)
 904                 drop_nlink(dir);
 905
 906         return 0;
 907 }
 908
 909 static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 910 {
 911         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
 912         struct autofs_info *ino = autofs4_dentry_ino(dentry);
 913         struct autofs_info *p_ino;
 914         struct inode *inode;
 915
 916         if (!autofs4_oz_mode(sbi))
 917                 return -EACCES;
 918
 919         DPRINTK("dentry %p, creating %.*s",
 920                 dentry, dentry->d_name.len, dentry->d_name.name);
 921
 922         ino = autofs4_init_ino(ino, sbi, S_IFDIR | 0555);
 923         if (!ino)
 924                 return -ENOMEM;
 925
 926         spin_lock(&sbi->lookup_lock);
 927         if (!list_empty(&ino->active))
 928                 list_del_init(&ino->active);
 929         spin_unlock(&sbi->lookup_lock);
 930
 931         inode = autofs4_get_inode(dir->i_sb, ino);
 932         if (!inode) {
 933                 if (!dentry->d_fsdata)
 934                         kfree(ino);
 935                 return -ENOMEM;
 936         }
 937         d_add(dentry, inode);
 938
 939         if (dir == dir->i_sb->s_root->d_inode)
 940                 dentry->d_op = &autofs4_root_dentry_operations;
 941         else
 942                 dentry->d_op = &autofs4_dentry_operations;
 943
 944         dentry->d_fsdata = ino;
 945         ino->dentry = dget(dentry);
 946         atomic_inc(&ino->count);
 947         p_ino = autofs4_dentry_ino(dentry->d_parent);
 948         if (p_ino && dentry->d_parent != dentry)
 949                 atomic_inc(&p_ino->count);
 950         ino->inode = inode;
 951         inc_nlink(dir);
 952         dir->i_mtime = CURRENT_TIME;
 953
 954         return 0;
 955 }
 956
 957 /* Get/set timeout ioctl() operation */
 958 static inline int autofs4_get_set_timeout(struct autofs_sb_info *sbi,
 959                                          unsigned long __user *p)
 960 {
 961         int rv;
 962         unsigned long ntimeout;
 963
 964         if ((rv = get_user(ntimeout, p)) ||
 965              (rv = put_user(sbi->exp_timeout/HZ, p)))
 966                 return rv;
 967
 968         if (ntimeout > ULONG_MAX/HZ)
 969                 sbi->exp_timeout = 0;
 970         else
 971                 sbi->exp_timeout = ntimeout * HZ;
 972
 973         return 0;
 974 }
 975
 976 /* Return protocol version */
 977 static inline int autofs4_get_protover(struct autofs_sb_info *sbi, int __user *p)
 978 {
 979         return put_user(sbi->version, p);
 980 }
 981
 982 /* Return protocol sub version */
 983 static inline int autofs4_get_protosubver(struct autofs_sb_info *sbi, int __user *p)
 984 {
 985         return put_user(sbi->sub_version, p);
 986 }
 987
 988 /*
 989  * Tells the daemon whether we need to reghost or not. Also, clears
 990  * the reghost_needed flag.
 991  */
 992 static inline int autofs4_ask_reghost(struct autofs_sb_info *sbi, int __user *p)
 993 {
 994         int status;
 995
 996         DPRINTK("returning %d", sbi->needs_reghost);
 997
 998         status = put_user(sbi->needs_reghost, p);
 999         if (status)
1000                 return status;
1001
1002         sbi->needs_reghost = 0;
1003         return 0;
1004 }
1005
1006 /*
1007  * Enable / Disable reghosting ioctl() operation
1008  */
1009 static inline int autofs4_toggle_reghost(struct autofs_sb_info *sbi, int __user *p)
1010 {
1011         int status;
1012         int val;
1013
1014         status = get_user(val, p);
1015
1016         DPRINTK("reghost = %d", val);
1017
1018         if (status)
1019                 return status;
1020
1021         /* turn on/off reghosting, with the val */
1022         sbi->reghost_enabled = val;
1023         return 0;
1024 }
1025
1026 /*
1027 * Tells the daemon whether it can umount the autofs mount.
1028 */
1029 static inline int autofs4_ask_umount(struct vfsmount *mnt, int __user *p)
1030 {
1031         int status = 0;
1032
1033         if (may_umount(mnt))
1034                 status = 1;
1035
1036         DPRINTK("returning %d", status);
1037
1038         status = put_user(status, p);
1039
1040         return status;
1041 }
1042
1043 /* Identify autofs4_dentries - this is so we can tell if there's
1044    an extra dentry refcount or not.  We only hold a refcount on the
1045    dentry if its non-negative (ie, d_inode != NULL)
1046 */
1047 int is_autofs4_dentry(struct dentry *dentry)
1048 {
1049         return dentry && dentry->d_inode &&
1050                 (dentry->d_op == &autofs4_root_dentry_operations ||
1051                  dentry->d_op == &autofs4_dentry_operations) &&
1052                 dentry->d_fsdata != NULL;
1053 }
1054
1055 /*
1056  * ioctl()'s on the root directory is the chief method for the daemon to
1057  * generate kernel reactions
1058  */
1059 static int autofs4_root_ioctl(struct inode *inode, struct file *filp,
1060                              unsigned int cmd, unsigned long arg)
1061 {
1062         struct autofs_sb_info *sbi = autofs4_sbi(inode->i_sb);
1063         void __user *p = (void __user *)arg;
1064
1065         DPRINTK("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u",
1066                 cmd,arg,sbi,task_pgrp_nr(current));
1067
1068         if (_IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
1069              _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT)
1070                 return -ENOTTY;
1071
1072         if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
1073                 return -EPERM;
1074
1075         switch(cmd) {
1076         case AUTOFS_IOC_READY:  /* Wait queue: go ahead and retry */
1077                 return autofs4_wait_release(sbi,(autofs_wqt_t)arg,0);
1078         case AUTOFS_IOC_FAIL:   /* Wait queue: fail with ENOENT */
1079                 return autofs4_wait_release(sbi,(autofs_wqt_t)arg,-ENOENT);
1080         case AUTOFS_IOC_CATATONIC: /* Enter catatonic mode (daemon shutdown) */
1081                 autofs4_catatonic_mode(sbi);
1082                 return 0;
1083         case AUTOFS_IOC_PROTOVER: /* Get protocol version */
1084                 return autofs4_get_protover(sbi, p);
1085         case AUTOFS_IOC_PROTOSUBVER: /* Get protocol sub version */
1086                 return autofs4_get_protosubver(sbi, p);
1087         case AUTOFS_IOC_SETTIMEOUT:
1088                 return autofs4_get_set_timeout(sbi, p);
1089
1090         case AUTOFS_IOC_TOGGLEREGHOST:
1091                 return autofs4_toggle_reghost(sbi, p);
1092         case AUTOFS_IOC_ASKREGHOST:
1093                 return autofs4_ask_reghost(sbi, p);
1094
1095         case AUTOFS_IOC_ASKUMOUNT:
1096                 return autofs4_ask_umount(filp->f_path.mnt, p);
1097
1098         /* return a single thing to expire */
1099         case AUTOFS_IOC_EXPIRE:
1100                 return autofs4_expire_run(inode->i_sb,filp->f_path.mnt,sbi, p);
1101         /* same as above, but can send multiple expires through pipe */
1102         case AUTOFS_IOC_EXPIRE_MULTI:
1103                 return autofs4_expire_multi(inode->i_sb,filp->f_path.mnt,sbi, p);
1104
1105         default:
1106                 return -ENOSYS;
1107         }
1108 }