fs/cachefiles/interface.c

   1 /* FS-Cache interface to CacheFiles
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells ([email protected])
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #include <linux/slab.h>
  13 #include <linux/mount.h>
  14 #include "internal.h"
  15
  16 struct cachefiles_lookup_data {
  17         struct cachefiles_xattr *auxdata;       /* auxiliary data */
  18         char                    *key;           /* key path */
  19 };
  20
  21 static int cachefiles_attr_changed(struct fscache_object *_object);
  22
  23 /*
  24  * allocate an object record for a cookie lookup and prepare the lookup data
  25  */
  26 static struct fscache_object *cachefiles_alloc_object(
  27         struct fscache_cache *_cache,
  28         struct fscache_cookie *cookie)
  29 {
  30         struct cachefiles_lookup_data *lookup_data;
  31         struct cachefiles_object *object;
  32         struct cachefiles_cache *cache;
  33         struct cachefiles_xattr *auxdata;
  34         unsigned keylen, auxlen;
  35         void *buffer, *p;
  36         char *key;
  37
  38         cache = container_of(_cache, struct cachefiles_cache, cache);
  39
  40         _enter("{%s},%p,", cache->cache.identifier, cookie);
  41
  42         lookup_data = kmalloc(sizeof(*lookup_data), cachefiles_gfp);
  43         if (!lookup_data)
  44                 goto nomem_lookup_data;
  45
  46         /* create a new object record and a temporary leaf image */
  47         object = kmem_cache_alloc(cachefiles_object_jar, cachefiles_gfp);
  48         if (!object)
  49                 goto nomem_object;
  50
  51         ASSERTCMP(object->backer, ==, NULL);
  52
  53         BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
  54         atomic_set(&object->usage, 1);
  55
  56         fscache_object_init(&object->fscache, cookie, &cache->cache);
  57
  58         object->type = cookie->def->type;
  59
  60         /* get hold of the raw key
  61          * - stick the length on the front and leave space on the back for the
  62          *   encoder
  63          */
  64         buffer = kmalloc((2 + 512) + 3, cachefiles_gfp);
  65         if (!buffer)
  66                 goto nomem_buffer;
  67
  68         keylen = cookie->key_len;
  69         if (keylen <= sizeof(cookie->inline_key))
  70                 p = cookie->inline_key;
  71         else
  72                 p = cookie->key;
  73         memcpy(buffer + 2, p, keylen);
  74
  75         *(uint16_t *)buffer = keylen;
  76         ((char *)buffer)[keylen + 2] = 0;
  77         ((char *)buffer)[keylen + 3] = 0;
  78         ((char *)buffer)[keylen + 4] = 0;
  79
  80         /* turn the raw key into something that can work with as a filename */
  81         key = cachefiles_cook_key(buffer, keylen + 2, object->type);
  82         if (!key)
  83                 goto nomem_key;
  84
  85         /* get hold of the auxiliary data and prepend the object type */
  86         auxdata = buffer;
  87         auxlen = cookie->aux_len;
  88         if (auxlen) {
  89                 if (auxlen <= sizeof(cookie->inline_aux))
  90                         p = cookie->inline_aux;
  91                 else
  92                         p = cookie->aux;
  93                 memcpy(auxdata->data, p, auxlen);
  94         }
  95
  96         auxdata->len = auxlen + 1;
  97         auxdata->type = cookie->type;
  98
  99         lookup_data->auxdata = auxdata;
 100         lookup_data->key = key;
 101         object->lookup_data = lookup_data;
 102
 103         _leave(" = %p [%p]", &object->fscache, lookup_data);
 104         return &object->fscache;
 105
 106 nomem_key:
 107         kfree(buffer);
 108 nomem_buffer:
 109         BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 110         kmem_cache_free(cachefiles_object_jar, object);
 111         fscache_object_destroyed(&cache->cache);
 112 nomem_object:
 113         kfree(lookup_data);
 114 nomem_lookup_data:
 115         _leave(" = -ENOMEM");
 116         return ERR_PTR(-ENOMEM);
 117 }
 118
 119 /*
 120  * attempt to look up the nominated node in this cache
 121  * - return -ETIMEDOUT to be scheduled again
 122  */
 123 static int cachefiles_lookup_object(struct fscache_object *_object)
 124 {
 125         struct cachefiles_lookup_data *lookup_data;
 126         struct cachefiles_object *parent, *object;
 127         struct cachefiles_cache *cache;
 128         const struct cred *saved_cred;
 129         int ret;
 130
 131         _enter("{OBJ%x}", _object->debug_id);
 132
 133         cache = container_of(_object->cache, struct cachefiles_cache, cache);
 134         parent = container_of(_object->parent,
 135                               struct cachefiles_object, fscache);
 136         object = container_of(_object, struct cachefiles_object, fscache);
 137         lookup_data = object->lookup_data;
 138
 139         ASSERTCMP(lookup_data, !=, NULL);
 140
 141         /* look up the key, creating any missing bits */
 142         cachefiles_begin_secure(cache, &saved_cred);
 143         ret = cachefiles_walk_to_object(parent, object,
 144                                         lookup_data->key,
 145                                         lookup_data->auxdata);
 146         cachefiles_end_secure(cache, saved_cred);
 147
 148         /* polish off by setting the attributes of non-index files */
 149         if (ret == 0 &&
 150             object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
 151                 cachefiles_attr_changed(&object->fscache);
 152
 153         if (ret < 0 && ret != -ETIMEDOUT) {
 154                 if (ret != -ENOBUFS)
 155                         pr_warn("Lookup failed error %d\n", ret);
 156                 fscache_object_lookup_error(&object->fscache);
 157         }
 158
 159         _leave(" [%d]", ret);
 160         return ret;
 161 }
 162
 163 /*
 164  * indication of lookup completion
 165  */
 166 static void cachefiles_lookup_complete(struct fscache_object *_object)
 167 {
 168         struct cachefiles_object *object;
 169
 170         object = container_of(_object, struct cachefiles_object, fscache);
 171
 172         _enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);
 173
 174         if (object->lookup_data) {
 175                 kfree(object->lookup_data->key);
 176                 kfree(object->lookup_data->auxdata);
 177                 kfree(object->lookup_data);
 178                 object->lookup_data = NULL;
 179         }
 180 }
 181
 182 /*
 183  * increment the usage count on an inode object (may fail if unmounting)
 184  */
 185 static
 186 struct fscache_object *cachefiles_grab_object(struct fscache_object *_object,
 187                                               enum fscache_obj_ref_trace why)
 188 {
 189         struct cachefiles_object *object =
 190                 container_of(_object, struct cachefiles_object, fscache);
 191         int u;
 192
 193         _enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
 194
 195 #ifdef CACHEFILES_DEBUG_SLAB
 196         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 197 #endif
 198
 199         u = atomic_inc_return(&object->usage);
 200         trace_cachefiles_ref(object, _object->cookie,
 201                              (enum cachefiles_obj_ref_trace)why, u);
 202         return &object->fscache;
 203 }
 204
 205 /*
 206  * update the auxiliary data for an object object on disk
 207  */
 208 static void cachefiles_update_object(struct fscache_object *_object)
 209 {
 210         struct cachefiles_object *object;
 211         struct cachefiles_xattr *auxdata;
 212         struct cachefiles_cache *cache;
 213         struct fscache_cookie *cookie;
 214         const struct cred *saved_cred;
 215         const void *aux;
 216         unsigned auxlen;
 217
 218         _enter("{OBJ%x}", _object->debug_id);
 219
 220         object = container_of(_object, struct cachefiles_object, fscache);
 221         cache = container_of(object->fscache.cache, struct cachefiles_cache,
 222                              cache);
 223
 224         if (!fscache_use_cookie(_object)) {
 225                 _leave(" [relinq]");
 226                 return;
 227         }
 228
 229         cookie = object->fscache.cookie;
 230         auxlen = cookie->aux_len;
 231
 232         if (!auxlen) {
 233                 fscache_unuse_cookie(_object);
 234                 _leave(" [no aux]");
 235                 return;
 236         }
 237
 238         auxdata = kmalloc(2 + auxlen + 3, cachefiles_gfp);
 239         if (!auxdata) {
 240                 fscache_unuse_cookie(_object);
 241                 _leave(" [nomem]");
 242                 return;
 243         }
 244
 245         aux = (auxlen <= sizeof(cookie->inline_aux)) ?
 246                 cookie->inline_aux : cookie->aux;
 247
 248         memcpy(auxdata->data, aux, auxlen);
 249         fscache_unuse_cookie(_object);
 250
 251         auxdata->len = auxlen + 1;
 252         auxdata->type = cookie->type;
 253
 254         cachefiles_begin_secure(cache, &saved_cred);
 255         cachefiles_update_object_xattr(object, auxdata);
 256         cachefiles_end_secure(cache, saved_cred);
 257         kfree(auxdata);
 258         _leave("");
 259 }
 260
 261 /*
 262  * discard the resources pinned by an object and effect retirement if
 263  * requested
 264  */
 265 static void cachefiles_drop_object(struct fscache_object *_object)
 266 {
 267         struct cachefiles_object *object;
 268         struct cachefiles_cache *cache;
 269         const struct cred *saved_cred;
 270         struct inode *inode;
 271         blkcnt_t i_blocks = 0;
 272
 273         ASSERT(_object);
 274
 275         object = container_of(_object, struct cachefiles_object, fscache);
 276
 277         _enter("{OBJ%x,%d}",
 278                object->fscache.debug_id, atomic_read(&object->usage));
 279
 280         cache = container_of(object->fscache.cache,
 281                              struct cachefiles_cache, cache);
 282
 283 #ifdef CACHEFILES_DEBUG_SLAB
 284         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 285 #endif
 286
 287         /* We need to tidy the object up if we did in fact manage to open it.
 288          * It's possible for us to get here before the object is fully
 289          * initialised if the parent goes away or the object gets retired
 290          * before we set it up.
 291          */
 292         if (object->dentry) {
 293                 /* delete retired objects */
 294                 if (test_bit(FSCACHE_OBJECT_RETIRED, &object->fscache.flags) &&
 295                     _object != cache->cache.fsdef
 296                     ) {
 297                         _debug("- retire object OBJ%x", object->fscache.debug_id);
 298                         inode = d_backing_inode(object->dentry);
 299                         if (inode)
 300                                 i_blocks = inode->i_blocks;
 301
 302                         cachefiles_begin_secure(cache, &saved_cred);
 303                         cachefiles_delete_object(cache, object);
 304                         cachefiles_end_secure(cache, saved_cred);
 305                 }
 306
 307                 /* close the filesystem stuff attached to the object */
 308                 if (object->backer != object->dentry)
 309                         dput(object->backer);
 310                 object->backer = NULL;
 311         }
 312
 313         /* note that the object is now inactive */
 314         if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags))
 315                 cachefiles_mark_object_inactive(cache, object, i_blocks);
 316
 317         dput(object->dentry);
 318         object->dentry = NULL;
 319
 320         _leave("");
 321 }
 322
 323 /*
 324  * dispose of a reference to an object
 325  */
 326 static void cachefiles_put_object(struct fscache_object *_object,
 327                                   enum fscache_obj_ref_trace why)
 328 {
 329         struct cachefiles_object *object;
 330         struct fscache_cache *cache;
 331         int u;
 332
 333         ASSERT(_object);
 334
 335         object = container_of(_object, struct cachefiles_object, fscache);
 336
 337         _enter("{OBJ%x,%d}",
 338                object->fscache.debug_id, atomic_read(&object->usage));
 339
 340 #ifdef CACHEFILES_DEBUG_SLAB
 341         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 342 #endif
 343
 344         ASSERTIFCMP(object->fscache.parent,
 345                     object->fscache.parent->n_children, >, 0);
 346
 347         u = atomic_dec_return(&object->usage);
 348         trace_cachefiles_ref(object, _object->cookie,
 349                              (enum cachefiles_obj_ref_trace)why, u);
 350         ASSERTCMP(u, !=, -1);
 351         if (u == 0) {
 352                 _debug("- kill object OBJ%x", object->fscache.debug_id);
 353
 354                 ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 355                 ASSERTCMP(object->fscache.parent, ==, NULL);
 356                 ASSERTCMP(object->backer, ==, NULL);
 357                 ASSERTCMP(object->dentry, ==, NULL);
 358                 ASSERTCMP(object->fscache.n_ops, ==, 0);
 359                 ASSERTCMP(object->fscache.n_children, ==, 0);
 360
 361                 if (object->lookup_data) {
 362                         kfree(object->lookup_data->key);
 363                         kfree(object->lookup_data->auxdata);
 364                         kfree(object->lookup_data);
 365                         object->lookup_data = NULL;
 366                 }
 367
 368                 cache = object->fscache.cache;
 369                 fscache_object_destroy(&object->fscache);
 370                 kmem_cache_free(cachefiles_object_jar, object);
 371                 fscache_object_destroyed(cache);
 372         }
 373
 374         _leave("");
 375 }
 376
 377 /*
 378  * sync a cache
 379  */
 380 static void cachefiles_sync_cache(struct fscache_cache *_cache)
 381 {
 382         struct cachefiles_cache *cache;
 383         const struct cred *saved_cred;
 384         int ret;
 385
 386         _enter("%p", _cache);
 387
 388         cache = container_of(_cache, struct cachefiles_cache, cache);
 389
 390         /* make sure all pages pinned by operations on behalf of the netfs are
 391          * written to disc */
 392         cachefiles_begin_secure(cache, &saved_cred);
 393         down_read(&cache->mnt->mnt_sb->s_umount);
 394         ret = sync_filesystem(cache->mnt->mnt_sb);
 395         up_read(&cache->mnt->mnt_sb->s_umount);
 396         cachefiles_end_secure(cache, saved_cred);
 397
 398         if (ret == -EIO)
 399                 cachefiles_io_error(cache,
 400                                     "Attempt to sync backing fs superblock"
 401                                     " returned error %d",
 402                                     ret);
 403 }
 404
 405 /*
 406  * check if the backing cache is updated to FS-Cache
 407  * - called by FS-Cache when evaluates if need to invalidate the cache
 408  */
 409 static int cachefiles_check_consistency(struct fscache_operation *op)
 410 {
 411         struct cachefiles_object *object;
 412         struct cachefiles_cache *cache;
 413         const struct cred *saved_cred;
 414         int ret;
 415
 416         _enter("{OBJ%x}", op->object->debug_id);
 417
 418         object = container_of(op->object, struct cachefiles_object, fscache);
 419         cache = container_of(object->fscache.cache,
 420                              struct cachefiles_cache, cache);
 421
 422         cachefiles_begin_secure(cache, &saved_cred);
 423         ret = cachefiles_check_auxdata(object);
 424         cachefiles_end_secure(cache, saved_cred);
 425
 426         _leave(" = %d", ret);
 427         return ret;
 428 }
 429
 430 /*
 431  * notification the attributes on an object have changed
 432  * - called with reads/writes excluded by FS-Cache
 433  */
 434 static int cachefiles_attr_changed(struct fscache_object *_object)
 435 {
 436         struct cachefiles_object *object;
 437         struct cachefiles_cache *cache;
 438         const struct cred *saved_cred;
 439         struct iattr newattrs;
 440         uint64_t ni_size;
 441         loff_t oi_size;
 442         int ret;
 443
 444         ni_size = _object->store_limit_l;
 445
 446         _enter("{OBJ%x},[%llu]",
 447                _object->debug_id, (unsigned long long) ni_size);
 448
 449         object = container_of(_object, struct cachefiles_object, fscache);
 450         cache = container_of(object->fscache.cache,
 451                              struct cachefiles_cache, cache);
 452
 453         if (ni_size == object->i_size)
 454                 return 0;
 455
 456         if (!object->backer)
 457                 return -ENOBUFS;
 458
 459         ASSERT(d_is_reg(object->backer));
 460
 461         fscache_set_store_limit(&object->fscache, ni_size);
 462
 463         oi_size = i_size_read(d_backing_inode(object->backer));
 464         if (oi_size == ni_size)
 465                 return 0;
 466
 467         cachefiles_begin_secure(cache, &saved_cred);
 468         inode_lock(d_inode(object->backer));
 469
 470         /* if there's an extension to a partial page at the end of the backing
 471          * file, we need to discard the partial page so that we pick up new
 472          * data after it */
 473         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
 474                 _debug("discard tail %llx", oi_size);
 475                 newattrs.ia_valid = ATTR_SIZE;
 476                 newattrs.ia_size = oi_size & PAGE_MASK;
 477                 ret = notify_change(object->backer, &newattrs, NULL);
 478                 if (ret < 0)
 479                         goto truncate_failed;
 480         }
 481
 482         newattrs.ia_valid = ATTR_SIZE;
 483         newattrs.ia_size = ni_size;
 484         ret = notify_change(object->backer, &newattrs, NULL);
 485
 486 truncate_failed:
 487         inode_unlock(d_inode(object->backer));
 488         cachefiles_end_secure(cache, saved_cred);
 489
 490         if (ret == -EIO) {
 491                 fscache_set_store_limit(&object->fscache, 0);
 492                 cachefiles_io_error_obj(object, "Size set failed");
 493                 ret = -ENOBUFS;
 494         }
 495
 496         _leave(" = %d", ret);
 497         return ret;
 498 }
 499
 500 /*
 501  * Invalidate an object
 502  */
 503 static void cachefiles_invalidate_object(struct fscache_operation *op)
 504 {
 505         struct cachefiles_object *object;
 506         struct cachefiles_cache *cache;
 507         const struct cred *saved_cred;
 508         struct path path;
 509         uint64_t ni_size;
 510         int ret;
 511
 512         object = container_of(op->object, struct cachefiles_object, fscache);
 513         cache = container_of(object->fscache.cache,
 514                              struct cachefiles_cache, cache);
 515
 516         ni_size = op->object->store_limit_l;
 517
 518         _enter("{OBJ%x},[%llu]",
 519                op->object->debug_id, (unsigned long long)ni_size);
 520
 521         if (object->backer) {
 522                 ASSERT(d_is_reg(object->backer));
 523
 524                 fscache_set_store_limit(&object->fscache, ni_size);
 525
 526                 path.dentry = object->backer;
 527                 path.mnt = cache->mnt;
 528
 529                 cachefiles_begin_secure(cache, &saved_cred);
 530                 ret = vfs_truncate(&path, 0);
 531                 if (ret == 0)
 532                         ret = vfs_truncate(&path, ni_size);
 533                 cachefiles_end_secure(cache, saved_cred);
 534
 535                 if (ret != 0) {
 536                         fscache_set_store_limit(&object->fscache, 0);
 537                         if (ret == -EIO)
 538                                 cachefiles_io_error_obj(object,
 539                                                         "Invalidate failed");
 540                 }
 541         }
 542
 543         fscache_op_complete(op, true);
 544         _leave("");
 545 }
 546
 547 /*
 548  * dissociate a cache from all the pages it was backing
 549  */
 550 static void cachefiles_dissociate_pages(struct fscache_cache *cache)
 551 {
 552         _enter("");
 553 }
 554
 555 const struct fscache_cache_ops cachefiles_cache_ops = {
 556         .name                   = "cachefiles",
 557         .alloc_object           = cachefiles_alloc_object,
 558         .lookup_object          = cachefiles_lookup_object,
 559         .lookup_complete        = cachefiles_lookup_complete,
 560         .grab_object            = cachefiles_grab_object,
 561         .update_object          = cachefiles_update_object,
 562         .invalidate_object      = cachefiles_invalidate_object,
 563         .drop_object            = cachefiles_drop_object,
 564         .put_object             = cachefiles_put_object,
 565         .sync_cache             = cachefiles_sync_cache,
 566         .attr_changed           = cachefiles_attr_changed,
 567         .read_or_alloc_page     = cachefiles_read_or_alloc_page,
 568         .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
 569         .allocate_page          = cachefiles_allocate_page,
 570         .allocate_pages         = cachefiles_allocate_pages,
 571         .write_page             = cachefiles_write_page,
 572         .uncache_page           = cachefiles_uncache_page,
 573         .dissociate_pages       = cachefiles_dissociate_pages,
 574         .check_consistency      = cachefiles_check_consistency,
 575 };