linux/fs/cachefiles/interface.c
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   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
  16struct cachefiles_lookup_data {
  17        struct cachefiles_xattr *auxdata;       /* auxiliary data */
  18        char                    *key;           /* key path */
  19};
  20
  21static 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 */
  26static 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
 100nomem_key:
 101        kfree(buffer);
 102nomem_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);
 106nomem_object:
 107        kfree(lookup_data);
 108nomem_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 */
 117static 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 */
 161static 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 */
 180static
 181struct 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 */
 199static 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 */
 252static 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 */
 307static 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 */
 355static 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 * notification the attributes on an object have changed
 382 * - called with reads/writes excluded by FS-Cache
 383 */
 384static int cachefiles_attr_changed(struct fscache_object *_object)
 385{
 386        struct cachefiles_object *object;
 387        struct cachefiles_cache *cache;
 388        const struct cred *saved_cred;
 389        struct iattr newattrs;
 390        uint64_t ni_size;
 391        loff_t oi_size;
 392        int ret;
 393
 394        _object->cookie->def->get_attr(_object->cookie->netfs_data, &ni_size);
 395
 396        _enter("{OBJ%x},[%llu]",
 397               _object->debug_id, (unsigned long long) ni_size);
 398
 399        object = container_of(_object, struct cachefiles_object, fscache);
 400        cache = container_of(object->fscache.cache,
 401                             struct cachefiles_cache, cache);
 402
 403        if (ni_size == object->i_size)
 404                return 0;
 405
 406        if (!object->backer)
 407                return -ENOBUFS;
 408
 409        ASSERT(S_ISREG(object->backer->d_inode->i_mode));
 410
 411        fscache_set_store_limit(&object->fscache, ni_size);
 412
 413        oi_size = i_size_read(object->backer->d_inode);
 414        if (oi_size == ni_size)
 415                return 0;
 416
 417        cachefiles_begin_secure(cache, &saved_cred);
 418        mutex_lock(&object->backer->d_inode->i_mutex);
 419
 420        /* if there's an extension to a partial page at the end of the backing
 421         * file, we need to discard the partial page so that we pick up new
 422         * data after it */
 423        if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
 424                _debug("discard tail %llx", oi_size);
 425                newattrs.ia_valid = ATTR_SIZE;
 426                newattrs.ia_size = oi_size & PAGE_MASK;
 427                ret = notify_change(object->backer, &newattrs);
 428                if (ret < 0)
 429                        goto truncate_failed;
 430        }
 431
 432        newattrs.ia_valid = ATTR_SIZE;
 433        newattrs.ia_size = ni_size;
 434        ret = notify_change(object->backer, &newattrs);
 435
 436truncate_failed:
 437        mutex_unlock(&object->backer->d_inode->i_mutex);
 438        cachefiles_end_secure(cache, saved_cred);
 439
 440        if (ret == -EIO) {
 441                fscache_set_store_limit(&object->fscache, 0);
 442                cachefiles_io_error_obj(object, "Size set failed");
 443                ret = -ENOBUFS;
 444        }
 445
 446        _leave(" = %d", ret);
 447        return ret;
 448}
 449
 450/*
 451 * Invalidate an object
 452 */
 453static void cachefiles_invalidate_object(struct fscache_operation *op)
 454{
 455        struct cachefiles_object *object;
 456        struct cachefiles_cache *cache;
 457        const struct cred *saved_cred;
 458        struct path path;
 459        uint64_t ni_size;
 460        int ret;
 461
 462        object = container_of(op->object, struct cachefiles_object, fscache);
 463        cache = container_of(object->fscache.cache,
 464                             struct cachefiles_cache, cache);
 465
 466        op->object->cookie->def->get_attr(op->object->cookie->netfs_data,
 467                                          &ni_size);
 468
 469        _enter("{OBJ%x},[%llu]",
 470               op->object->debug_id, (unsigned long long)ni_size);
 471
 472        if (object->backer) {
 473                ASSERT(S_ISREG(object->backer->d_inode->i_mode));
 474
 475                fscache_set_store_limit(&object->fscache, ni_size);
 476
 477                path.dentry = object->backer;
 478                path.mnt = cache->mnt;
 479
 480                cachefiles_begin_secure(cache, &saved_cred);
 481                ret = vfs_truncate(&path, 0);
 482                if (ret == 0)
 483                        ret = vfs_truncate(&path, ni_size);
 484                cachefiles_end_secure(cache, saved_cred);
 485
 486                if (ret != 0) {
 487                        fscache_set_store_limit(&object->fscache, 0);
 488                        if (ret == -EIO)
 489                                cachefiles_io_error_obj(object,
 490                                                        "Invalidate failed");
 491                }
 492        }
 493
 494        fscache_op_complete(op, true);
 495        _leave("");
 496}
 497
 498/*
 499 * dissociate a cache from all the pages it was backing
 500 */
 501static void cachefiles_dissociate_pages(struct fscache_cache *cache)
 502{
 503        _enter("");
 504}
 505
 506const struct fscache_cache_ops cachefiles_cache_ops = {
 507        .name                   = "cachefiles",
 508        .alloc_object           = cachefiles_alloc_object,
 509        .lookup_object          = cachefiles_lookup_object,
 510        .lookup_complete        = cachefiles_lookup_complete,
 511        .grab_object            = cachefiles_grab_object,
 512        .update_object          = cachefiles_update_object,
 513        .invalidate_object      = cachefiles_invalidate_object,
 514        .drop_object            = cachefiles_drop_object,
 515        .put_object             = cachefiles_put_object,
 516        .sync_cache             = cachefiles_sync_cache,
 517        .attr_changed           = cachefiles_attr_changed,
 518        .read_or_alloc_page     = cachefiles_read_or_alloc_page,
 519        .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
 520        .allocate_page          = cachefiles_allocate_page,
 521        .allocate_pages         = cachefiles_allocate_pages,
 522        .write_page             = cachefiles_write_page,
 523        .uncache_page           = cachefiles_uncache_page,
 524        .dissociate_pages       = cachefiles_dissociate_pages,
 525};
 526
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