fs/cachefiles/namei.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* CacheFiles path walking and related routines
   3  *
   4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/fs.h>
   9 #include <linux/namei.h>
  10 #include "internal.h"
  11
  12 /*
  13  * Mark the backing file as being a cache file if it's not already in use.  The
  14  * mark tells the culling request command that it's not allowed to cull the
  15  * file or directory.  The caller must hold the inode lock.
  16  */
  17 static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
  18                                            struct dentry *dentry)
  19 {
  20         struct inode *inode = d_backing_inode(dentry);
  21         bool can_use = false;
  22
  23         if (!(inode->i_flags & S_KERNEL_FILE)) {
  24                 inode->i_flags |= S_KERNEL_FILE;
  25                 trace_cachefiles_mark_active(object, inode);
  26                 can_use = true;
  27         } else {
  28                 trace_cachefiles_mark_failed(object, inode);
  29                 pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
  30                           dentry, inode->i_ino);
  31         }
  32
  33         return can_use;
  34 }
  35
  36 static bool cachefiles_mark_inode_in_use(struct cachefiles_object *object,
  37                                          struct dentry *dentry)
  38 {
  39         struct inode *inode = d_backing_inode(dentry);
  40         bool can_use;
  41
  42         inode_lock(inode);
  43         can_use = __cachefiles_mark_inode_in_use(object, dentry);
  44         inode_unlock(inode);
  45         return can_use;
  46 }
  47
  48 /*
  49  * Unmark a backing inode.  The caller must hold the inode lock.
  50  */
  51 static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
  52                                              struct dentry *dentry)
  53 {
  54         struct inode *inode = d_backing_inode(dentry);
  55
  56         inode->i_flags &= ~S_KERNEL_FILE;
  57         trace_cachefiles_mark_inactive(object, inode);
  58 }
  59
  60 /*
  61  * Unmark a backing inode and tell cachefilesd that there's something that can
  62  * be culled.
  63  */
  64 void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
  65                                     struct file *file)
  66 {
  67         struct cachefiles_cache *cache = object->volume->cache;
  68         struct inode *inode = file_inode(file);
  69
  70         if (inode) {
  71                 inode_lock(inode);
  72                 __cachefiles_unmark_inode_in_use(object, file->f_path.dentry);
  73                 inode_unlock(inode);
  74
  75                 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
  76                         atomic_long_add(inode->i_blocks, &cache->b_released);
  77                         if (atomic_inc_return(&cache->f_released))
  78                                 cachefiles_state_changed(cache);
  79                 }
  80         }
  81 }
  82
  83 /*
  84  * get a subdirectory
  85  */
  86 struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
  87                                         struct dentry *dir,
  88                                         const char *dirname,
  89                                         bool *_is_new)
  90 {
  91         struct dentry *subdir;
  92         struct path path;
  93         int ret;
  94
  95         _enter(",,%s", dirname);
  96
  97         /* search the current directory for the element name */
  98         inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
  99
 100 retry:
 101         ret = cachefiles_inject_read_error();
 102         if (ret == 0)
 103                 subdir = lookup_one_len(dirname, dir, strlen(dirname));
 104         else
 105                 subdir = ERR_PTR(ret);
 106         trace_cachefiles_lookup(NULL, dir, subdir);
 107         if (IS_ERR(subdir)) {
 108                 trace_cachefiles_vfs_error(NULL, d_backing_inode(dir),
 109                                            PTR_ERR(subdir),
 110                                            cachefiles_trace_lookup_error);
 111                 if (PTR_ERR(subdir) == -ENOMEM)
 112                         goto nomem_d_alloc;
 113                 goto lookup_error;
 114         }
 115
 116         _debug("subdir -> %pd %s",
 117                subdir, d_backing_inode(subdir) ? "positive" : "negative");
 118
 119         /* we need to create the subdir if it doesn't exist yet */
 120         if (d_is_negative(subdir)) {
 121                 ret = cachefiles_has_space(cache, 1, 0,
 122                                            cachefiles_has_space_for_create);
 123                 if (ret < 0)
 124                         goto mkdir_error;
 125
 126                 _debug("attempt mkdir");
 127
 128                 path.mnt = cache->mnt;
 129                 path.dentry = dir;
 130                 ret = security_path_mkdir(&path, subdir, 0700);
 131                 if (ret < 0)
 132                         goto mkdir_error;
 133                 ret = cachefiles_inject_write_error();
 134                 if (ret == 0)
 135                         ret = vfs_mkdir(&init_user_ns, d_inode(dir), subdir, 0700);
 136                 if (ret < 0) {
 137                         trace_cachefiles_vfs_error(NULL, d_inode(dir), ret,
 138                                                    cachefiles_trace_mkdir_error);
 139                         goto mkdir_error;
 140                 }
 141                 trace_cachefiles_mkdir(dir, subdir);
 142
 143                 if (unlikely(d_unhashed(subdir))) {
 144                         cachefiles_put_directory(subdir);
 145                         goto retry;
 146                 }
 147                 ASSERT(d_backing_inode(subdir));
 148
 149                 _debug("mkdir -> %pd{ino=%lu}",
 150                        subdir, d_backing_inode(subdir)->i_ino);
 151                 if (_is_new)
 152                         *_is_new = true;
 153         }
 154
 155         /* Tell rmdir() it's not allowed to delete the subdir */
 156         inode_lock(d_inode(subdir));
 157         inode_unlock(d_inode(dir));
 158
 159         if (!__cachefiles_mark_inode_in_use(NULL, subdir))
 160                 goto mark_error;
 161
 162         inode_unlock(d_inode(subdir));
 163
 164         /* we need to make sure the subdir is a directory */
 165         ASSERT(d_backing_inode(subdir));
 166
 167         if (!d_can_lookup(subdir)) {
 168                 pr_err("%s is not a directory\n", dirname);
 169                 ret = -EIO;
 170                 goto check_error;
 171         }
 172
 173         ret = -EPERM;
 174         if (!(d_backing_inode(subdir)->i_opflags & IOP_XATTR) ||
 175             !d_backing_inode(subdir)->i_op->lookup ||
 176             !d_backing_inode(subdir)->i_op->mkdir ||
 177             !d_backing_inode(subdir)->i_op->rename ||
 178             !d_backing_inode(subdir)->i_op->rmdir ||
 179             !d_backing_inode(subdir)->i_op->unlink)
 180                 goto check_error;
 181
 182         _leave(" = [%lu]", d_backing_inode(subdir)->i_ino);
 183         return subdir;
 184
 185 check_error:
 186         cachefiles_put_directory(subdir);
 187         _leave(" = %d [check]", ret);
 188         return ERR_PTR(ret);
 189
 190 mark_error:
 191         inode_unlock(d_inode(subdir));
 192         dput(subdir);
 193         return ERR_PTR(-EBUSY);
 194
 195 mkdir_error:
 196         inode_unlock(d_inode(dir));
 197         dput(subdir);
 198         pr_err("mkdir %s failed with error %d\n", dirname, ret);
 199         return ERR_PTR(ret);
 200
 201 lookup_error:
 202         inode_unlock(d_inode(dir));
 203         ret = PTR_ERR(subdir);
 204         pr_err("Lookup %s failed with error %d\n", dirname, ret);
 205         return ERR_PTR(ret);
 206
 207 nomem_d_alloc:
 208         inode_unlock(d_inode(dir));
 209         _leave(" = -ENOMEM");
 210         return ERR_PTR(-ENOMEM);
 211 }
 212
 213 /*
 214  * Put a subdirectory.
 215  */
 216 void cachefiles_put_directory(struct dentry *dir)
 217 {
 218         if (dir) {
 219                 inode_lock(dir->d_inode);
 220                 __cachefiles_unmark_inode_in_use(NULL, dir);
 221                 inode_unlock(dir->d_inode);
 222                 dput(dir);
 223         }
 224 }
 225
 226 /*
 227  * Remove a regular file from the cache.
 228  */
 229 static int cachefiles_unlink(struct cachefiles_cache *cache,
 230                              struct cachefiles_object *object,
 231                              struct dentry *dir, struct dentry *dentry,
 232                              enum fscache_why_object_killed why)
 233 {
 234         struct path path = {
 235                 .mnt    = cache->mnt,
 236                 .dentry = dir,
 237         };
 238         int ret;
 239
 240         trace_cachefiles_unlink(object, d_inode(dentry)->i_ino, why);
 241         ret = security_path_unlink(&path, dentry);
 242         if (ret < 0) {
 243                 cachefiles_io_error(cache, "Unlink security error");
 244                 return ret;
 245         }
 246
 247         ret = cachefiles_inject_remove_error();
 248         if (ret == 0) {
 249                 ret = vfs_unlink(&init_user_ns, d_backing_inode(dir), dentry, NULL);
 250                 if (ret == -EIO)
 251                         cachefiles_io_error(cache, "Unlink failed");
 252         }
 253         if (ret != 0)
 254                 trace_cachefiles_vfs_error(object, d_backing_inode(dir), ret,
 255                                            cachefiles_trace_unlink_error);
 256         return ret;
 257 }
 258
 259 /*
 260  * Delete an object representation from the cache
 261  * - File backed objects are unlinked
 262  * - Directory backed objects are stuffed into the graveyard for userspace to
 263  *   delete
 264  */
 265 int cachefiles_bury_object(struct cachefiles_cache *cache,
 266                            struct cachefiles_object *object,
 267                            struct dentry *dir,
 268                            struct dentry *rep,
 269                            enum fscache_why_object_killed why)
 270 {
 271         struct dentry *grave, *trap;
 272         struct path path, path_to_graveyard;
 273         char nbuffer[8 + 8 + 1];
 274         int ret;
 275
 276         _enter(",'%pd','%pd'", dir, rep);
 277
 278         if (rep->d_parent != dir) {
 279                 inode_unlock(d_inode(dir));
 280                 _leave(" = -ESTALE");
 281                 return -ESTALE;
 282         }
 283
 284         /* non-directories can just be unlinked */
 285         if (!d_is_dir(rep)) {
 286                 dget(rep); /* Stop the dentry being negated if it's only pinned
 287                             * by a file struct.
 288                             */
 289                 ret = cachefiles_unlink(cache, object, dir, rep, why);
 290                 dput(rep);
 291
 292                 inode_unlock(d_inode(dir));
 293                 _leave(" = %d", ret);
 294                 return ret;
 295         }
 296
 297         /* directories have to be moved to the graveyard */
 298         _debug("move stale object to graveyard");
 299         inode_unlock(d_inode(dir));
 300
 301 try_again:
 302         /* first step is to make up a grave dentry in the graveyard */
 303         sprintf(nbuffer, "%08x%08x",
 304                 (uint32_t) ktime_get_real_seconds(),
 305                 (uint32_t) atomic_inc_return(&cache->gravecounter));
 306
 307         /* do the multiway lock magic */
 308         trap = lock_rename(cache->graveyard, dir);
 309
 310         /* do some checks before getting the grave dentry */
 311         if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
 312                 /* the entry was probably culled when we dropped the parent dir
 313                  * lock */
 314                 unlock_rename(cache->graveyard, dir);
 315                 _leave(" = 0 [culled?]");
 316                 return 0;
 317         }
 318
 319         if (!d_can_lookup(cache->graveyard)) {
 320                 unlock_rename(cache->graveyard, dir);
 321                 cachefiles_io_error(cache, "Graveyard no longer a directory");
 322                 return -EIO;
 323         }
 324
 325         if (trap == rep) {
 326                 unlock_rename(cache->graveyard, dir);
 327                 cachefiles_io_error(cache, "May not make directory loop");
 328                 return -EIO;
 329         }
 330
 331         if (d_mountpoint(rep)) {
 332                 unlock_rename(cache->graveyard, dir);
 333                 cachefiles_io_error(cache, "Mountpoint in cache");
 334                 return -EIO;
 335         }
 336
 337         grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
 338         if (IS_ERR(grave)) {
 339                 unlock_rename(cache->graveyard, dir);
 340                 trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
 341                                            PTR_ERR(grave),
 342                                            cachefiles_trace_lookup_error);
 343
 344                 if (PTR_ERR(grave) == -ENOMEM) {
 345                         _leave(" = -ENOMEM");
 346                         return -ENOMEM;
 347                 }
 348
 349                 cachefiles_io_error(cache, "Lookup error %ld", PTR_ERR(grave));
 350                 return -EIO;
 351         }
 352
 353         if (d_is_positive(grave)) {
 354                 unlock_rename(cache->graveyard, dir);
 355                 dput(grave);
 356                 grave = NULL;
 357                 cond_resched();
 358                 goto try_again;
 359         }
 360
 361         if (d_mountpoint(grave)) {
 362                 unlock_rename(cache->graveyard, dir);
 363                 dput(grave);
 364                 cachefiles_io_error(cache, "Mountpoint in graveyard");
 365                 return -EIO;
 366         }
 367
 368         /* target should not be an ancestor of source */
 369         if (trap == grave) {
 370                 unlock_rename(cache->graveyard, dir);
 371                 dput(grave);
 372                 cachefiles_io_error(cache, "May not make directory loop");
 373                 return -EIO;
 374         }
 375
 376         /* attempt the rename */
 377         path.mnt = cache->mnt;
 378         path.dentry = dir;
 379         path_to_graveyard.mnt = cache->mnt;
 380         path_to_graveyard.dentry = cache->graveyard;
 381         ret = security_path_rename(&path, rep, &path_to_graveyard, grave, 0);
 382         if (ret < 0) {
 383                 cachefiles_io_error(cache, "Rename security error %d", ret);
 384         } else {
 385                 struct renamedata rd = {
 386                         .old_mnt_userns = &init_user_ns,
 387                         .old_dir        = d_inode(dir),
 388                         .old_dentry     = rep,
 389                         .new_mnt_userns = &init_user_ns,
 390                         .new_dir        = d_inode(cache->graveyard),
 391                         .new_dentry     = grave,
 392                 };
 393                 trace_cachefiles_rename(object, d_inode(rep)->i_ino, why);
 394                 ret = cachefiles_inject_read_error();
 395                 if (ret == 0)
 396                         ret = vfs_rename(&rd);
 397                 if (ret != 0)
 398                         trace_cachefiles_vfs_error(object, d_inode(dir), ret,
 399                                                    cachefiles_trace_rename_error);
 400                 if (ret != 0 && ret != -ENOMEM)
 401                         cachefiles_io_error(cache,
 402                                             "Rename failed with error %d", ret);
 403         }
 404
 405         __cachefiles_unmark_inode_in_use(object, rep);
 406         unlock_rename(cache->graveyard, dir);
 407         dput(grave);
 408         _leave(" = 0");
 409         return 0;
 410 }
 411
 412 /*
 413  * Delete a cache file.
 414  */
 415 int cachefiles_delete_object(struct cachefiles_object *object,
 416                              enum fscache_why_object_killed why)
 417 {
 418         struct cachefiles_volume *volume = object->volume;
 419         struct dentry *dentry = object->file->f_path.dentry;
 420         struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash];
 421         int ret;
 422
 423         _enter(",OBJ%x{%pD}", object->debug_id, object->file);
 424
 425         /* Stop the dentry being negated if it's only pinned by a file struct. */
 426         dget(dentry);
 427
 428         inode_lock_nested(d_backing_inode(fan), I_MUTEX_PARENT);
 429         ret = cachefiles_unlink(volume->cache, object, fan, dentry, why);
 430         inode_unlock(d_backing_inode(fan));
 431         dput(dentry);
 432         return ret;
 433 }
 434
 435 /*
 436  * Create a temporary file and leave it unattached and un-xattr'd until the
 437  * time comes to discard the object from memory.
 438  */
 439 struct file *cachefiles_create_tmpfile(struct cachefiles_object *object)
 440 {
 441         struct cachefiles_volume *volume = object->volume;
 442         struct cachefiles_cache *cache = volume->cache;
 443         const struct cred *saved_cred;
 444         struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash];
 445         struct file *file;
 446         struct path path;
 447         uint64_t ni_size = object->cookie->object_size;
 448         long ret;
 449
 450         ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);
 451
 452         cachefiles_begin_secure(cache, &saved_cred);
 453
 454         path.mnt = cache->mnt;
 455         ret = cachefiles_inject_write_error();
 456         if (ret == 0)
 457                 path.dentry = vfs_tmpfile(&init_user_ns, fan, S_IFREG, O_RDWR);
 458         else
 459                 path.dentry = ERR_PTR(ret);
 460         if (IS_ERR(path.dentry)) {
 461                 trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(path.dentry),
 462                                            cachefiles_trace_tmpfile_error);
 463                 if (PTR_ERR(path.dentry) == -EIO)
 464                         cachefiles_io_error_obj(object, "Failed to create tmpfile");
 465                 file = ERR_CAST(path.dentry);
 466                 goto out;
 467         }
 468
 469         trace_cachefiles_tmpfile(object, d_backing_inode(path.dentry));
 470
 471         if (!cachefiles_mark_inode_in_use(object, path.dentry)) {
 472                 file = ERR_PTR(-EBUSY);
 473                 goto out_dput;
 474         }
 475
 476         if (ni_size > 0) {
 477                 trace_cachefiles_trunc(object, d_backing_inode(path.dentry), 0, ni_size,
 478                                        cachefiles_trunc_expand_tmpfile);
 479                 ret = cachefiles_inject_write_error();
 480                 if (ret == 0)
 481                         ret = vfs_truncate(&path, ni_size);
 482                 if (ret < 0) {
 483                         trace_cachefiles_vfs_error(
 484                                 object, d_backing_inode(path.dentry), ret,
 485                                 cachefiles_trace_trunc_error);
 486                         file = ERR_PTR(ret);
 487                         goto out_dput;
 488                 }
 489         }
 490
 491         file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
 492                                    d_backing_inode(path.dentry), cache->cache_cred);
 493         if (IS_ERR(file)) {
 494                 trace_cachefiles_vfs_error(object, d_backing_inode(path.dentry),
 495                                            PTR_ERR(file),
 496                                            cachefiles_trace_open_error);
 497                 goto out_dput;
 498         }
 499         if (unlikely(!file->f_op->read_iter) ||
 500             unlikely(!file->f_op->write_iter)) {
 501                 fput(file);
 502                 pr_notice("Cache does not support read_iter and write_iter\n");
 503                 file = ERR_PTR(-EINVAL);
 504         }
 505
 506 out_dput:
 507         dput(path.dentry);
 508 out:
 509         cachefiles_end_secure(cache, saved_cred);
 510         return file;
 511 }
 512
 513 /*
 514  * Create a new file.
 515  */
 516 static bool cachefiles_create_file(struct cachefiles_object *object)
 517 {
 518         struct file *file;
 519         int ret;
 520
 521         ret = cachefiles_has_space(object->volume->cache, 1, 0,
 522                                    cachefiles_has_space_for_create);
 523         if (ret < 0)
 524                 return false;
 525
 526         file = cachefiles_create_tmpfile(object);
 527         if (IS_ERR(file))
 528                 return false;
 529
 530         set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
 531         set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 532         _debug("create -> %pD{ino=%lu}", file, file_inode(file)->i_ino);
 533         object->file = file;
 534         return true;
 535 }
 536
 537 /*
 538  * Open an existing file, checking its attributes and replacing it if it is
 539  * stale.
 540  */
 541 static bool cachefiles_open_file(struct cachefiles_object *object,
 542                                  struct dentry *dentry)
 543 {
 544         struct cachefiles_cache *cache = object->volume->cache;
 545         struct file *file;
 546         struct path path;
 547         int ret;
 548
 549         _enter("%pd", dentry);
 550
 551         if (!cachefiles_mark_inode_in_use(object, dentry))
 552                 return false;
 553
 554         /* We need to open a file interface onto a data file now as we can't do
 555          * it on demand because writeback called from do_exit() sees
 556          * current->fs == NULL - which breaks d_path() called from ext4 open.
 557          */
 558         path.mnt = cache->mnt;
 559         path.dentry = dentry;
 560         file = open_with_fake_path(&path, O_RDWR | O_LARGEFILE | O_DIRECT,
 561                                    d_backing_inode(dentry), cache->cache_cred);
 562         if (IS_ERR(file)) {
 563                 trace_cachefiles_vfs_error(object, d_backing_inode(dentry),
 564                                            PTR_ERR(file),
 565                                            cachefiles_trace_open_error);
 566                 goto error;
 567         }
 568
 569         if (unlikely(!file->f_op->read_iter) ||
 570             unlikely(!file->f_op->write_iter)) {
 571                 pr_notice("Cache does not support read_iter and write_iter\n");
 572                 goto error_fput;
 573         }
 574         _debug("file -> %pd positive", dentry);
 575
 576         ret = cachefiles_check_auxdata(object, file);
 577         if (ret < 0)
 578                 goto check_failed;
 579
 580         object->file = file;
 581
 582         /* Always update the atime on an object we've just looked up (this is
 583          * used to keep track of culling, and atimes are only updated by read,
 584          * write and readdir but not lookup or open).
 585          */
 586         touch_atime(&file->f_path);
 587         dput(dentry);
 588         return true;
 589
 590 check_failed:
 591         fscache_cookie_lookup_negative(object->cookie);
 592         cachefiles_unmark_inode_in_use(object, file);
 593         if (ret == -ESTALE) {
 594                 fput(file);
 595                 dput(dentry);
 596                 return cachefiles_create_file(object);
 597         }
 598 error_fput:
 599         fput(file);
 600 error:
 601         dput(dentry);
 602         return false;
 603 }
 604
 605 /*
 606  * walk from the parent object to the child object through the backing
 607  * filesystem, creating directories as we go
 608  */
 609 bool cachefiles_look_up_object(struct cachefiles_object *object)
 610 {
 611         struct cachefiles_volume *volume = object->volume;
 612         struct dentry *dentry, *fan = volume->fanout[(u8)object->cookie->key_hash];
 613         int ret;
 614
 615         _enter("OBJ%x,%s,", object->debug_id, object->d_name);
 616
 617         /* Look up path "cache/vol/fanout/file". */
 618         ret = cachefiles_inject_read_error();
 619         if (ret == 0)
 620                 dentry = lookup_positive_unlocked(object->d_name, fan,
 621                                                   object->d_name_len);
 622         else
 623                 dentry = ERR_PTR(ret);
 624         trace_cachefiles_lookup(object, fan, dentry);
 625         if (IS_ERR(dentry)) {
 626                 if (dentry == ERR_PTR(-ENOENT))
 627                         goto new_file;
 628                 if (dentry == ERR_PTR(-EIO))
 629                         cachefiles_io_error_obj(object, "Lookup failed");
 630                 return false;
 631         }
 632
 633         if (!d_is_reg(dentry)) {
 634                 pr_err("%pd is not a file\n", dentry);
 635                 inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
 636                 ret = cachefiles_bury_object(volume->cache, object, fan, dentry,
 637                                              FSCACHE_OBJECT_IS_WEIRD);
 638                 dput(dentry);
 639                 if (ret < 0)
 640                         return false;
 641                 goto new_file;
 642         }
 643
 644         if (!cachefiles_open_file(object, dentry))
 645                 return false;
 646
 647         _leave(" = t [%lu]", file_inode(object->file)->i_ino);
 648         return true;
 649
 650 new_file:
 651         fscache_cookie_lookup_negative(object->cookie);
 652         return cachefiles_create_file(object);
 653 }
 654
 655 /*
 656  * Attempt to link a temporary file into its rightful place in the cache.
 657  */
 658 bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
 659                                struct cachefiles_object *object)
 660 {
 661         struct cachefiles_volume *volume = object->volume;
 662         struct dentry *dentry, *fan = volume->fanout[(u8)object->cookie->key_hash];
 663         bool success = false;
 664         int ret;
 665
 666         _enter(",%pD", object->file);
 667
 668         inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
 669         ret = cachefiles_inject_read_error();
 670         if (ret == 0)
 671                 dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
 672         else
 673                 dentry = ERR_PTR(ret);
 674         if (IS_ERR(dentry)) {
 675                 trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
 676                                            cachefiles_trace_lookup_error);
 677                 _debug("lookup fail %ld", PTR_ERR(dentry));
 678                 goto out_unlock;
 679         }
 680
 681         if (!d_is_negative(dentry)) {
 682                 if (d_backing_inode(dentry) == file_inode(object->file)) {
 683                         success = true;
 684                         goto out_dput;
 685                 }
 686
 687                 ret = cachefiles_unlink(volume->cache, object, fan, dentry,
 688                                         FSCACHE_OBJECT_IS_STALE);
 689                 if (ret < 0)
 690                         goto out_dput;
 691
 692                 dput(dentry);
 693                 ret = cachefiles_inject_read_error();
 694                 if (ret == 0)
 695                         dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
 696                 else
 697                         dentry = ERR_PTR(ret);
 698                 if (IS_ERR(dentry)) {
 699                         trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
 700                                                    cachefiles_trace_lookup_error);
 701                         _debug("lookup fail %ld", PTR_ERR(dentry));
 702                         goto out_unlock;
 703                 }
 704         }
 705
 706         ret = cachefiles_inject_read_error();
 707         if (ret == 0)
 708                 ret = vfs_link(object->file->f_path.dentry, &init_user_ns,
 709                                d_inode(fan), dentry, NULL);
 710         if (ret < 0) {
 711                 trace_cachefiles_vfs_error(object, d_inode(fan), ret,
 712                                            cachefiles_trace_link_error);
 713                 _debug("link fail %d", ret);
 714         } else {
 715                 trace_cachefiles_link(object, file_inode(object->file));
 716                 spin_lock(&object->lock);
 717                 /* TODO: Do we want to switch the file pointer to the new dentry? */
 718                 clear_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 719                 spin_unlock(&object->lock);
 720                 success = true;
 721         }
 722
 723 out_dput:
 724         dput(dentry);
 725 out_unlock:
 726         inode_unlock(d_inode(fan));
 727         _leave(" = %u", success);
 728         return success;
 729 }
 730
 731 /*
 732  * Look up an inode to be checked or culled.  Return -EBUSY if the inode is
 733  * marked in use.
 734  */
 735 static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache,
 736                                                  struct dentry *dir,
 737                                                  char *filename)
 738 {
 739         struct dentry *victim;
 740         int ret = -ENOENT;
 741
 742         inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
 743
 744         victim = lookup_one_len(filename, dir, strlen(filename));
 745         if (IS_ERR(victim))
 746                 goto lookup_error;
 747         if (d_is_negative(victim))
 748                 goto lookup_put;
 749         if (d_inode(victim)->i_flags & S_KERNEL_FILE)
 750                 goto lookup_busy;
 751         return victim;
 752
 753 lookup_busy:
 754         ret = -EBUSY;
 755 lookup_put:
 756         inode_unlock(d_inode(dir));
 757         dput(victim);
 758         return ERR_PTR(ret);
 759
 760 lookup_error:
 761         inode_unlock(d_inode(dir));
 762         ret = PTR_ERR(victim);
 763         if (ret == -ENOENT)
 764                 return ERR_PTR(-ESTALE); /* Probably got retired by the netfs */
 765
 766         if (ret == -EIO) {
 767                 cachefiles_io_error(cache, "Lookup failed");
 768         } else if (ret != -ENOMEM) {
 769                 pr_err("Internal error: %d\n", ret);
 770                 ret = -EIO;
 771         }
 772
 773         return ERR_PTR(ret);
 774 }
 775
 776 /*
 777  * Cull an object if it's not in use
 778  * - called only by cache manager daemon
 779  */
 780 int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
 781                     char *filename)
 782 {
 783         struct dentry *victim;
 784         struct inode *inode;
 785         int ret;
 786
 787         _enter(",%pd/,%s", dir, filename);
 788
 789         victim = cachefiles_lookup_for_cull(cache, dir, filename);
 790         if (IS_ERR(victim))
 791                 return PTR_ERR(victim);
 792
 793         /* check to see if someone is using this object */
 794         inode = d_inode(victim);
 795         inode_lock(inode);
 796         if (inode->i_flags & S_KERNEL_FILE) {
 797                 ret = -EBUSY;
 798         } else {
 799                 /* Stop the cache from picking it back up */
 800                 inode->i_flags |= S_KERNEL_FILE;
 801                 ret = 0;
 802         }
 803         inode_unlock(inode);
 804         if (ret < 0)
 805                 goto error_unlock;
 806
 807         ret = cachefiles_bury_object(cache, NULL, dir, victim,
 808                                      FSCACHE_OBJECT_WAS_CULLED);
 809         if (ret < 0)
 810                 goto error;
 811
 812         fscache_count_culled();
 813         dput(victim);
 814         _leave(" = 0");
 815         return 0;
 816
 817 error_unlock:
 818         inode_unlock(d_inode(dir));
 819 error:
 820         dput(victim);
 821         if (ret == -ENOENT)
 822                 return -ESTALE; /* Probably got retired by the netfs */
 823
 824         if (ret != -ENOMEM) {
 825                 pr_err("Internal error: %d\n", ret);
 826                 ret = -EIO;
 827         }
 828
 829         _leave(" = %d", ret);
 830         return ret;
 831 }
 832
 833 /*
 834  * Find out if an object is in use or not
 835  * - called only by cache manager daemon
 836  * - returns -EBUSY or 0 to indicate whether an object is in use or not
 837  */
 838 int cachefiles_check_in_use(struct cachefiles_cache *cache, struct dentry *dir,
 839                             char *filename)
 840 {
 841         struct dentry *victim;
 842         int ret = 0;
 843
 844         victim = cachefiles_lookup_for_cull(cache, dir, filename);
 845         if (IS_ERR(victim))
 846                 return PTR_ERR(victim);
 847
 848         inode_unlock(d_inode(dir));
 849         dput(victim);
 850         return ret;
 851 }