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 (dhowells@redhat.com)
   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;
  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->def->get_key(cookie->netfs_data, buffer + 2, 512);
  69         ASSERTCMP(keylen, <, 512);
  70
  71         *(uint16_t *)buffer = keylen;
  72         ((char *)buffer)[keylen + 2] = 0;
  73         ((char *)buffer)[keylen + 3] = 0;
  74         ((char *)buffer)[keylen + 4] = 0;
  75
  76         /* turn the raw key into something that can work with as a filename */
  77         key = cachefiles_cook_key(buffer, keylen + 2, object->type);
  78         if (!key)
  79                 goto nomem_key;
  80
  81         /* get hold of the auxiliary data and prepend the object type */
  82         auxdata = buffer;
  83         auxlen = 0;
  84         if (cookie->def->get_aux) {
  85                 auxlen = cookie->def->get_aux(cookie->netfs_data,
  86                                               auxdata->data, 511);
  87                 ASSERTCMP(auxlen, <, 511);
  88         }
  89
  90         auxdata->len = auxlen + 1;
  91         auxdata->type = cookie->def->type;
  92
  93         lookup_data->auxdata = auxdata;
  94         lookup_data->key = key;
  95         object->lookup_data = lookup_data;
  96
  97         _leave(" = %p [%p]", &object->fscache, lookup_data);
  98         return &object->fscache;
  99
 100 nomem_key:
 101         kfree(buffer);
 102 nomem_buffer:
 103         BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 104         kmem_cache_free(cachefiles_object_jar, object);
 105         fscache_object_destroyed(&cache->cache);
 106 nomem_object:
 107         kfree(lookup_data);
 108 nomem_lookup_data:
 109         _leave(" = -ENOMEM");
 110         return ERR_PTR(-ENOMEM);
 111 }
 112
 113 /*
 114  * attempt to look up the nominated node in this cache
 115  * - return -ETIMEDOUT to be scheduled again
 116  */
 117 static int cachefiles_lookup_object(struct fscache_object *_object)
 118 {
 119         struct cachefiles_lookup_data *lookup_data;
 120         struct cachefiles_object *parent, *object;
 121         struct cachefiles_cache *cache;
 122         const struct cred *saved_cred;
 123         int ret;
 124
 125         _enter("{OBJ%x}", _object->debug_id);
 126
 127         cache = container_of(_object->cache, struct cachefiles_cache, cache);
 128         parent = container_of(_object->parent,
 129                               struct cachefiles_object, fscache);
 130         object = container_of(_object, struct cachefiles_object, fscache);
 131         lookup_data = object->lookup_data;
 132
 133         ASSERTCMP(lookup_data, !=, NULL);
 134
 135         /* look up the key, creating any missing bits */
 136         cachefiles_begin_secure(cache, &saved_cred);
 137         ret = cachefiles_walk_to_object(parent, object,
 138                                         lookup_data->key,
 139                                         lookup_data->auxdata);
 140         cachefiles_end_secure(cache, saved_cred);
 141
 142         /* polish off by setting the attributes of non-index files */
 143         if (ret == 0 &&
 144             object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
 145                 cachefiles_attr_changed(&object->fscache);
 146
 147         if (ret < 0 && ret != -ETIMEDOUT) {
 148                 if (ret != -ENOBUFS)
 149                         printk(KERN_WARNING
 150                                "CacheFiles: Lookup failed error %d\n", ret);
 151                 fscache_object_lookup_error(&object->fscache);
 152         }
 153
 154         _leave(" [%d]", ret);
 155         return ret;
 156 }
 157
 158 /*
 159  * indication of lookup completion
 160  */
 161 static void cachefiles_lookup_complete(struct fscache_object *_object)
 162 {
 163         struct cachefiles_object *object;
 164
 165         object = container_of(_object, struct cachefiles_object, fscache);
 166
 167         _enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);
 168
 169         if (object->lookup_data) {
 170                 kfree(object->lookup_data->key);
 171                 kfree(object->lookup_data->auxdata);
 172                 kfree(object->lookup_data);
 173                 object->lookup_data = NULL;
 174         }
 175 }
 176
 177 /*
 178  * increment the usage count on an inode object (may fail if unmounting)
 179  */
 180 static
 181 struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
 182 {
 183         struct cachefiles_object *object =
 184                 container_of(_object, struct cachefiles_object, fscache);
 185
 186         _enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
 187
 188 #ifdef CACHEFILES_DEBUG_SLAB
 189         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 190 #endif
 191
 192         atomic_inc(&object->usage);
 193         return &object->fscache;
 194 }
 195
 196 /*
 197  * update the auxiliary data for an object object on disk
 198  */
 199 static void cachefiles_update_object(struct fscache_object *_object)
 200 {
 201         struct cachefiles_object *object;
 202         struct cachefiles_xattr *auxdata;
 203         struct cachefiles_cache *cache;
 204         struct fscache_cookie *cookie;
 205         const struct cred *saved_cred;
 206         unsigned auxlen;
 207
 208         _enter("{OBJ%x}", _object->debug_id);
 209
 210         object = container_of(_object, struct cachefiles_object, fscache);
 211         cache = container_of(object->fscache.cache, struct cachefiles_cache,
 212                              cache);
 213
 214         if (!fscache_use_cookie(_object)) {
 215                 _leave(" [relinq]");
 216                 return;
 217         }
 218
 219         cookie = object->fscache.cookie;
 220
 221         if (!cookie->def->get_aux) {
 222                 fscache_unuse_cookie(_object);
 223                 _leave(" [no aux]");
 224                 return;
 225         }
 226
 227         auxdata = kmalloc(2 + 512 + 3, cachefiles_gfp);
 228         if (!auxdata) {
 229                 fscache_unuse_cookie(_object);
 230                 _leave(" [nomem]");
 231                 return;
 232         }
 233
 234         auxlen = cookie->def->get_aux(cookie->netfs_data, auxdata->data, 511);
 235         fscache_unuse_cookie(_object);
 236         ASSERTCMP(auxlen, <, 511);
 237
 238         auxdata->len = auxlen + 1;
 239         auxdata->type = cookie->def->type;
 240
 241         cachefiles_begin_secure(cache, &saved_cred);
 242         cachefiles_update_object_xattr(object, auxdata);
 243         cachefiles_end_secure(cache, saved_cred);
 244         kfree(auxdata);
 245         _leave("");
 246 }
 247
 248 /*
 249  * discard the resources pinned by an object and effect retirement if
 250  * requested
 251  */
 252 static void cachefiles_drop_object(struct fscache_object *_object)
 253 {
 254         struct cachefiles_object *object;
 255         struct cachefiles_cache *cache;
 256         const struct cred *saved_cred;
 257
 258         ASSERT(_object);
 259
 260         object = container_of(_object, struct cachefiles_object, fscache);
 261
 262         _enter("{OBJ%x,%d}",
 263                object->fscache.debug_id, atomic_read(&object->usage));
 264
 265         cache = container_of(object->fscache.cache,
 266                              struct cachefiles_cache, cache);
 267
 268 #ifdef CACHEFILES_DEBUG_SLAB
 269         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 270 #endif
 271
 272         /* delete retired objects */
 273         if (test_bit(FSCACHE_COOKIE_RETIRED, &object->fscache.cookie->flags) &&
 274             _object != cache->cache.fsdef
 275             ) {
 276                 _debug("- retire object OBJ%x", object->fscache.debug_id);
 277                 cachefiles_begin_secure(cache, &saved_cred);
 278                 cachefiles_delete_object(cache, object);
 279                 cachefiles_end_secure(cache, saved_cred);
 280         }
 281
 282         /* close the filesystem stuff attached to the object */
 283         if (object->backer != object->dentry)
 284                 dput(object->backer);
 285         object->backer = NULL;
 286
 287         /* note that the object is now inactive */
 288         if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
 289                 write_lock(&cache->active_lock);
 290                 if (!test_and_clear_bit(CACHEFILES_OBJECT_ACTIVE,
 291                                         &object->flags))
 292                         BUG();
 293                 rb_erase(&object->active_node, &cache->active_nodes);
 294                 wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
 295                 write_unlock(&cache->active_lock);
 296         }
 297
 298         dput(object->dentry);
 299         object->dentry = NULL;
 300
 301         _leave("");
 302 }
 303
 304 /*
 305  * dispose of a reference to an object
 306  */
 307 static void cachefiles_put_object(struct fscache_object *_object)
 308 {
 309         struct cachefiles_object *object;
 310         struct fscache_cache *cache;
 311
 312         ASSERT(_object);
 313
 314         object = container_of(_object, struct cachefiles_object, fscache);
 315
 316         _enter("{OBJ%x,%d}",
 317                object->fscache.debug_id, atomic_read(&object->usage));
 318
 319 #ifdef CACHEFILES_DEBUG_SLAB
 320         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 321 #endif
 322
 323         ASSERTIFCMP(object->fscache.parent,
 324                     object->fscache.parent->n_children, >, 0);
 325
 326         if (atomic_dec_and_test(&object->usage)) {
 327                 _debug("- kill object OBJ%x", object->fscache.debug_id);
 328
 329                 ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 330                 ASSERTCMP(object->fscache.parent, ==, NULL);
 331                 ASSERTCMP(object->backer, ==, NULL);
 332                 ASSERTCMP(object->dentry, ==, NULL);
 333                 ASSERTCMP(object->fscache.n_ops, ==, 0);
 334                 ASSERTCMP(object->fscache.n_children, ==, 0);
 335
 336                 if (object->lookup_data) {
 337                         kfree(object->lookup_data->key);
 338                         kfree(object->lookup_data->auxdata);
 339                         kfree(object->lookup_data);
 340                         object->lookup_data = NULL;
 341                 }
 342
 343                 cache = object->fscache.cache;
 344                 fscache_object_destroy(&object->fscache);
 345                 kmem_cache_free(cachefiles_object_jar, object);
 346                 fscache_object_destroyed(cache);
 347         }
 348
 349         _leave("");
 350 }
 351
 352 /*
 353  * sync a cache
 354  */
 355 static void cachefiles_sync_cache(struct fscache_cache *_cache)
 356 {
 357         struct cachefiles_cache *cache;
 358         const struct cred *saved_cred;
 359         int ret;
 360
 361         _enter("%p", _cache);
 362
 363         cache = container_of(_cache, struct cachefiles_cache, cache);
 364
 365         /* make sure all pages pinned by operations on behalf of the netfs are
 366          * written to disc */
 367         cachefiles_begin_secure(cache, &saved_cred);
 368         down_read(&cache->mnt->mnt_sb->s_umount);
 369         ret = sync_filesystem(cache->mnt->mnt_sb);
 370         up_read(&cache->mnt->mnt_sb->s_umount);
 371         cachefiles_end_secure(cache, saved_cred);
 372
 373         if (ret == -EIO)
 374                 cachefiles_io_error(cache,
 375                                     "Attempt to sync backing fs superblock"
 376                                     " returned error %d",
 377                                     ret);
 378 }
 379
 380 /*
 381  * check if the backing cache is updated to FS-Cache
 382  * - called by FS-Cache when evaluates if need to invalidate the cache
 383  */
 384 static bool cachefiles_check_consistency(struct fscache_operation *op)
 385 {
 386         struct cachefiles_object *object;
 387         struct cachefiles_cache *cache;
 388         const struct cred *saved_cred;
 389         int ret;
 390
 391         _enter("{OBJ%x}", op->object->debug_id);
 392
 393         object = container_of(op->object, struct cachefiles_object, fscache);
 394         cache = container_of(object->fscache.cache,
 395                              struct cachefiles_cache, cache);
 396
 397         cachefiles_begin_secure(cache, &saved_cred);
 398         ret = cachefiles_check_auxdata(object);
 399         cachefiles_end_secure(cache, saved_cred);
 400
 401         _leave(" = %d", ret);
 402         return ret;
 403 }
 404
 405 /*
 406  * notification the attributes on an object have changed
 407  * - called with reads/writes excluded by FS-Cache
 408  */
 409 static int cachefiles_attr_changed(struct fscache_object *_object)
 410 {
 411         struct cachefiles_object *object;
 412         struct cachefiles_cache *cache;
 413         const struct cred *saved_cred;
 414         struct iattr newattrs;
 415         uint64_t ni_size;
 416         loff_t oi_size;
 417         int ret;
 418
 419         _object->cookie->def->get_attr(_object->cookie->netfs_data, &ni_size);
 420
 421         _enter("{OBJ%x},[%llu]",
 422                _object->debug_id, (unsigned long long) ni_size);
 423
 424         object = container_of(_object, struct cachefiles_object, fscache);
 425         cache = container_of(object->fscache.cache,
 426                              struct cachefiles_cache, cache);
 427
 428         if (ni_size == object->i_size)
 429                 return 0;
 430
 431         if (!object->backer)
 432                 return -ENOBUFS;
 433
 434         ASSERT(S_ISREG(object->backer->d_inode->i_mode));
 435
 436         fscache_set_store_limit(&object->fscache, ni_size);
 437
 438         oi_size = i_size_read(object->backer->d_inode);
 439         if (oi_size == ni_size)
 440                 return 0;
 441
 442         cachefiles_begin_secure(cache, &saved_cred);
 443         mutex_lock(&object->backer->d_inode->i_mutex);
 444
 445         /* if there's an extension to a partial page at the end of the backing
 446          * file, we need to discard the partial page so that we pick up new
 447          * data after it */
 448         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
 449                 _debug("discard tail %llx", oi_size);
 450                 newattrs.ia_valid = ATTR_SIZE;
 451                 newattrs.ia_size = oi_size & PAGE_MASK;
 452                 ret = notify_change(object->backer, &newattrs);
 453                 if (ret < 0)
 454                         goto truncate_failed;
 455         }
 456
 457         newattrs.ia_valid = ATTR_SIZE;
 458         newattrs.ia_size = ni_size;
 459         ret = notify_change(object->backer, &newattrs);
 460
 461 truncate_failed:
 462         mutex_unlock(&object->backer->d_inode->i_mutex);
 463         cachefiles_end_secure(cache, saved_cred);
 464
 465         if (ret == -EIO) {
 466                 fscache_set_store_limit(&object->fscache, 0);
 467                 cachefiles_io_error_obj(object, "Size set failed");
 468                 ret = -ENOBUFS;
 469         }
 470
 471         _leave(" = %d", ret);
 472         return ret;
 473 }
 474
 475 /*
 476  * Invalidate an object
 477  */
 478 static void cachefiles_invalidate_object(struct fscache_operation *op)
 479 {
 480         struct cachefiles_object *object;
 481         struct cachefiles_cache *cache;
 482         const struct cred *saved_cred;
 483         struct path path;
 484         uint64_t ni_size;
 485         int ret;
 486
 487         object = container_of(op->object, struct cachefiles_object, fscache);
 488         cache = container_of(object->fscache.cache,
 489                              struct cachefiles_cache, cache);
 490
 491         op->object->cookie->def->get_attr(op->object->cookie->netfs_data,
 492                                           &ni_size);
 493
 494         _enter("{OBJ%x},[%llu]",
 495                op->object->debug_id, (unsigned long long)ni_size);
 496
 497         if (object->backer) {
 498                 ASSERT(S_ISREG(object->backer->d_inode->i_mode));
 499
 500                 fscache_set_store_limit(&object->fscache, ni_size);
 501
 502                 path.dentry = object->backer;
 503                 path.mnt = cache->mnt;
 504
 505                 cachefiles_begin_secure(cache, &saved_cred);
 506                 ret = vfs_truncate(&path, 0);
 507                 if (ret == 0)
 508                         ret = vfs_truncate(&path, ni_size);
 509                 cachefiles_end_secure(cache, saved_cred);
 510
 511                 if (ret != 0) {
 512                         fscache_set_store_limit(&object->fscache, 0);
 513                         if (ret == -EIO)
 514                                 cachefiles_io_error_obj(object,
 515                                                         "Invalidate failed");
 516                 }
 517         }
 518
 519         fscache_op_complete(op, true);
 520         _leave("");
 521 }
 522
 523 /*
 524  * dissociate a cache from all the pages it was backing
 525  */
 526 static void cachefiles_dissociate_pages(struct fscache_cache *cache)
 527 {
 528         _enter("");
 529 }
 530
 531 const struct fscache_cache_ops cachefiles_cache_ops = {
 532         .name                   = "cachefiles",
 533         .alloc_object           = cachefiles_alloc_object,
 534         .lookup_object          = cachefiles_lookup_object,
 535         .lookup_complete        = cachefiles_lookup_complete,
 536         .grab_object            = cachefiles_grab_object,
 537         .update_object          = cachefiles_update_object,
 538         .invalidate_object      = cachefiles_invalidate_object,
 539         .drop_object            = cachefiles_drop_object,
 540         .put_object             = cachefiles_put_object,
 541         .sync_cache             = cachefiles_sync_cache,
 542         .attr_changed           = cachefiles_attr_changed,
 543         .read_or_alloc_page     = cachefiles_read_or_alloc_page,
 544         .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
 545         .allocate_page          = cachefiles_allocate_page,
 546         .allocate_pages         = cachefiles_allocate_pages,
 547         .write_page             = cachefiles_write_page,
 548         .uncache_page           = cachefiles_uncache_page,
 549         .dissociate_pages       = cachefiles_dissociate_pages,
 550         .check_consistency      = cachefiles_check_consistency,
 551 };