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 <linux/buffer_head.h>
  15 #include "internal.h"
  16
  17 #define list_to_page(head) (list_entry((head)->prev, struct page, lru))
  18
  19 struct cachefiles_lookup_data {
  20         struct cachefiles_xattr *auxdata;       /* auxiliary data */
  21         char                    *key;           /* key path */
  22 };
  23
  24 static int cachefiles_attr_changed(struct fscache_object *_object);
  25
  26 /*
  27  * allocate an object record for a cookie lookup and prepare the lookup data
  28  */
  29 static struct fscache_object *cachefiles_alloc_object(
  30         struct fscache_cache *_cache,
  31         struct fscache_cookie *cookie)
  32 {
  33         struct cachefiles_lookup_data *lookup_data;
  34         struct cachefiles_object *object;
  35         struct cachefiles_cache *cache;
  36         struct cachefiles_xattr *auxdata;
  37         unsigned keylen, auxlen;
  38         void *buffer;
  39         char *key;
  40
  41         cache = container_of(_cache, struct cachefiles_cache, cache);
  42
  43         _enter("{%s},%p,", cache->cache.identifier, cookie);
  44
  45         lookup_data = kmalloc(sizeof(*lookup_data), GFP_KERNEL);
  46         if (!lookup_data)
  47                 goto nomem_lookup_data;
  48
  49         /* create a new object record and a temporary leaf image */
  50         object = kmem_cache_alloc(cachefiles_object_jar, GFP_KERNEL);
  51         if (!object)
  52                 goto nomem_object;
  53
  54         ASSERTCMP(object->backer, ==, NULL);
  55
  56         BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
  57         atomic_set(&object->usage, 1);
  58
  59         fscache_object_init(&object->fscache, cookie, &cache->cache);
  60
  61         object->type = cookie->def->type;
  62
  63         /* get hold of the raw key
  64          * - stick the length on the front and leave space on the back for the
  65          *   encoder
  66          */
  67         buffer = kmalloc((2 + 512) + 3, GFP_KERNEL);
  68         if (!buffer)
  69                 goto nomem_buffer;
  70
  71         keylen = cookie->def->get_key(cookie->netfs_data, buffer + 2, 512);
  72         ASSERTCMP(keylen, <, 512);
  73
  74         *(uint16_t *)buffer = keylen;
  75         ((char *)buffer)[keylen + 2] = 0;
  76         ((char *)buffer)[keylen + 3] = 0;
  77         ((char *)buffer)[keylen + 4] = 0;
  78
  79         /* turn the raw key into something that can work with as a filename */
  80         key = cachefiles_cook_key(buffer, keylen + 2, object->type);
  81         if (!key)
  82                 goto nomem_key;
  83
  84         /* get hold of the auxiliary data and prepend the object type */
  85         auxdata = buffer;
  86         auxlen = 0;
  87         if (cookie->def->get_aux) {
  88                 auxlen = cookie->def->get_aux(cookie->netfs_data,
  89                                               auxdata->data, 511);
  90                 ASSERTCMP(auxlen, <, 511);
  91         }
  92
  93         auxdata->len = auxlen + 1;
  94         auxdata->type = cookie->def->type;
  95
  96         lookup_data->auxdata = auxdata;
  97         lookup_data->key = key;
  98         object->lookup_data = lookup_data;
  99
 100         _leave(" = %p [%p]", &object->fscache, lookup_data);
 101         return &object->fscache;
 102
 103 nomem_key:
 104         kfree(buffer);
 105 nomem_buffer:
 106         BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 107         kmem_cache_free(cachefiles_object_jar, object);
 108         fscache_object_destroyed(&cache->cache);
 109 nomem_object:
 110         kfree(lookup_data);
 111 nomem_lookup_data:
 112         _leave(" = -ENOMEM");
 113         return ERR_PTR(-ENOMEM);
 114 }
 115
 116 /*
 117  * attempt to look up the nominated node in this cache
 118  * - return -ETIMEDOUT to be scheduled again
 119  */
 120 static int cachefiles_lookup_object(struct fscache_object *_object)
 121 {
 122         struct cachefiles_lookup_data *lookup_data;
 123         struct cachefiles_object *parent, *object;
 124         struct cachefiles_cache *cache;
 125         const struct cred *saved_cred;
 126         int ret;
 127
 128         _enter("{OBJ%x}", _object->debug_id);
 129
 130         cache = container_of(_object->cache, struct cachefiles_cache, cache);
 131         parent = container_of(_object->parent,
 132                               struct cachefiles_object, fscache);
 133         object = container_of(_object, struct cachefiles_object, fscache);
 134         lookup_data = object->lookup_data;
 135
 136         ASSERTCMP(lookup_data, !=, NULL);
 137
 138         /* look up the key, creating any missing bits */
 139         cachefiles_begin_secure(cache, &saved_cred);
 140         ret = cachefiles_walk_to_object(parent, object,
 141                                         lookup_data->key,
 142                                         lookup_data->auxdata);
 143         cachefiles_end_secure(cache, saved_cred);
 144
 145         /* polish off by setting the attributes of non-index files */
 146         if (ret == 0 &&
 147             object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
 148                 cachefiles_attr_changed(&object->fscache);
 149
 150         if (ret < 0 && ret != -ETIMEDOUT) {
 151                 if (ret != -ENOBUFS)
 152                         printk(KERN_WARNING
 153                                "CacheFiles: Lookup failed error %d\n", ret);
 154                 fscache_object_lookup_error(&object->fscache);
 155         }
 156
 157         _leave(" [%d]", ret);
 158         return ret;
 159 }
 160
 161 /*
 162  * indication of lookup completion
 163  */
 164 static void cachefiles_lookup_complete(struct fscache_object *_object)
 165 {
 166         struct cachefiles_object *object;
 167
 168         object = container_of(_object, struct cachefiles_object, fscache);
 169
 170         _enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);
 171
 172         if (object->lookup_data) {
 173                 kfree(object->lookup_data->key);
 174                 kfree(object->lookup_data->auxdata);
 175                 kfree(object->lookup_data);
 176                 object->lookup_data = NULL;
 177         }
 178 }
 179
 180 /*
 181  * increment the usage count on an inode object (may fail if unmounting)
 182  */
 183 static
 184 struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
 185 {
 186         struct cachefiles_object *object =
 187                 container_of(_object, struct cachefiles_object, fscache);
 188
 189         _enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
 190
 191 #ifdef CACHEFILES_DEBUG_SLAB
 192         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 193 #endif
 194
 195         atomic_inc(&object->usage);
 196         return &object->fscache;
 197 }
 198
 199 /*
 200  * update the auxiliary data for an object object on disk
 201  */
 202 static void cachefiles_update_object(struct fscache_object *_object)
 203 {
 204         struct cachefiles_object *object;
 205         struct cachefiles_xattr *auxdata;
 206         struct cachefiles_cache *cache;
 207         struct fscache_cookie *cookie;
 208         const struct cred *saved_cred;
 209         unsigned auxlen;
 210
 211         _enter("{OBJ%x}", _object->debug_id);
 212
 213         object = container_of(_object, struct cachefiles_object, fscache);
 214         cache = container_of(object->fscache.cache, struct cachefiles_cache,
 215                              cache);
 216         cookie = object->fscache.cookie;
 217
 218         if (!cookie->def->get_aux) {
 219                 _leave(" [no aux]");
 220                 return;
 221         }
 222
 223         auxdata = kmalloc(2 + 512 + 3, GFP_KERNEL);
 224         if (!auxdata) {
 225                 _leave(" [nomem]");
 226                 return;
 227         }
 228
 229         auxlen = cookie->def->get_aux(cookie->netfs_data, auxdata->data, 511);
 230         ASSERTCMP(auxlen, <, 511);
 231
 232         auxdata->len = auxlen + 1;
 233         auxdata->type = cookie->def->type;
 234
 235         cachefiles_begin_secure(cache, &saved_cred);
 236         cachefiles_update_object_xattr(object, auxdata);
 237         cachefiles_end_secure(cache, saved_cred);
 238         kfree(auxdata);
 239         _leave("");
 240 }
 241
 242 /*
 243  * discard the resources pinned by an object and effect retirement if
 244  * requested
 245  */
 246 static void cachefiles_drop_object(struct fscache_object *_object)
 247 {
 248         struct cachefiles_object *object;
 249         struct cachefiles_cache *cache;
 250         const struct cred *saved_cred;
 251
 252         ASSERT(_object);
 253
 254         object = container_of(_object, struct cachefiles_object, fscache);
 255
 256         _enter("{OBJ%x,%d}",
 257                object->fscache.debug_id, atomic_read(&object->usage));
 258
 259         cache = container_of(object->fscache.cache,
 260                              struct cachefiles_cache, cache);
 261
 262 #ifdef CACHEFILES_DEBUG_SLAB
 263         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 264 #endif
 265
 266         /* delete retired objects */
 267         if (object->fscache.state == FSCACHE_OBJECT_RECYCLING &&
 268             _object != cache->cache.fsdef
 269             ) {
 270                 _debug("- retire object OBJ%x", object->fscache.debug_id);
 271                 cachefiles_begin_secure(cache, &saved_cred);
 272                 cachefiles_delete_object(cache, object);
 273                 cachefiles_end_secure(cache, saved_cred);
 274         }
 275
 276         /* close the filesystem stuff attached to the object */
 277         if (object->backer != object->dentry)
 278                 dput(object->backer);
 279         object->backer = NULL;
 280
 281         /* note that the object is now inactive */
 282         if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
 283                 write_lock(&cache->active_lock);
 284                 if (!test_and_clear_bit(CACHEFILES_OBJECT_ACTIVE,
 285                                         &object->flags))
 286                         BUG();
 287                 rb_erase(&object->active_node, &cache->active_nodes);
 288                 wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
 289                 write_unlock(&cache->active_lock);
 290         }
 291
 292         dput(object->dentry);
 293         object->dentry = NULL;
 294
 295         _leave("");
 296 }
 297
 298 /*
 299  * dispose of a reference to an object
 300  */
 301 static void cachefiles_put_object(struct fscache_object *_object)
 302 {
 303         struct cachefiles_object *object;
 304         struct fscache_cache *cache;
 305
 306         ASSERT(_object);
 307
 308         object = container_of(_object, struct cachefiles_object, fscache);
 309
 310         _enter("{OBJ%x,%d}",
 311                object->fscache.debug_id, atomic_read(&object->usage));
 312
 313 #ifdef CACHEFILES_DEBUG_SLAB
 314         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 315 #endif
 316
 317         ASSERTIFCMP(object->fscache.parent,
 318                     object->fscache.parent->n_children, >, 0);
 319
 320         if (atomic_dec_and_test(&object->usage)) {
 321                 _debug("- kill object OBJ%x", object->fscache.debug_id);
 322
 323                 ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 324                 ASSERTCMP(object->fscache.parent, ==, NULL);
 325                 ASSERTCMP(object->backer, ==, NULL);
 326                 ASSERTCMP(object->dentry, ==, NULL);
 327                 ASSERTCMP(object->fscache.n_ops, ==, 0);
 328                 ASSERTCMP(object->fscache.n_children, ==, 0);
 329
 330                 if (object->lookup_data) {
 331                         kfree(object->lookup_data->key);
 332                         kfree(object->lookup_data->auxdata);
 333                         kfree(object->lookup_data);
 334                         object->lookup_data = NULL;
 335                 }
 336
 337                 cache = object->fscache.cache;
 338                 fscache_object_destroy(&object->fscache);
 339                 kmem_cache_free(cachefiles_object_jar, object);
 340                 fscache_object_destroyed(cache);
 341         }
 342
 343         _leave("");
 344 }
 345
 346 /*
 347  * sync a cache
 348  */
 349 static void cachefiles_sync_cache(struct fscache_cache *_cache)
 350 {
 351         struct cachefiles_cache *cache;
 352         const struct cred *saved_cred;
 353         int ret;
 354
 355         _enter("%p", _cache);
 356
 357         cache = container_of(_cache, struct cachefiles_cache, cache);
 358
 359         /* make sure all pages pinned by operations on behalf of the netfs are
 360          * written to disc */
 361         cachefiles_begin_secure(cache, &saved_cred);
 362         down_read(&cache->mnt->mnt_sb->s_umount);
 363         ret = sync_filesystem(cache->mnt->mnt_sb);
 364         up_read(&cache->mnt->mnt_sb->s_umount);
 365         cachefiles_end_secure(cache, saved_cred);
 366
 367         if (ret == -EIO)
 368                 cachefiles_io_error(cache,
 369                                     "Attempt to sync backing fs superblock"
 370                                     " returned error %d",
 371                                     ret);
 372 }
 373
 374 /*
 375  * notification the attributes on an object have changed
 376  * - called with reads/writes excluded by FS-Cache
 377  */
 378 static int cachefiles_attr_changed(struct fscache_object *_object)
 379 {
 380         struct cachefiles_object *object;
 381         struct cachefiles_cache *cache;
 382         const struct cred *saved_cred;
 383         struct iattr newattrs;
 384         uint64_t ni_size;
 385         loff_t oi_size;
 386         int ret;
 387
 388         _object->cookie->def->get_attr(_object->cookie->netfs_data, &ni_size);
 389
 390         _enter("{OBJ%x},[%llu]",
 391                _object->debug_id, (unsigned long long) ni_size);
 392
 393         object = container_of(_object, struct cachefiles_object, fscache);
 394         cache = container_of(object->fscache.cache,
 395                              struct cachefiles_cache, cache);
 396
 397         if (ni_size == object->i_size)
 398                 return 0;
 399
 400         if (!object->backer)
 401                 return -ENOBUFS;
 402
 403         ASSERT(S_ISREG(object->backer->d_inode->i_mode));
 404
 405         fscache_set_store_limit(&object->fscache, ni_size);
 406
 407         oi_size = i_size_read(object->backer->d_inode);
 408         if (oi_size == ni_size)
 409                 return 0;
 410
 411         cachefiles_begin_secure(cache, &saved_cred);
 412         mutex_lock(&object->backer->d_inode->i_mutex);
 413
 414         /* if there's an extension to a partial page at the end of the backing
 415          * file, we need to discard the partial page so that we pick up new
 416          * data after it */
 417         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
 418                 _debug("discard tail %llx", oi_size);
 419                 newattrs.ia_valid = ATTR_SIZE;
 420                 newattrs.ia_size = oi_size & PAGE_MASK;
 421                 ret = notify_change(object->backer, &newattrs);
 422                 if (ret < 0)
 423                         goto truncate_failed;
 424         }
 425
 426         newattrs.ia_valid = ATTR_SIZE;
 427         newattrs.ia_size = ni_size;
 428         ret = notify_change(object->backer, &newattrs);
 429
 430 truncate_failed:
 431         mutex_unlock(&object->backer->d_inode->i_mutex);
 432         cachefiles_end_secure(cache, saved_cred);
 433
 434         if (ret == -EIO) {
 435                 fscache_set_store_limit(&object->fscache, 0);
 436                 cachefiles_io_error_obj(object, "Size set failed");
 437                 ret = -ENOBUFS;
 438         }
 439
 440         _leave(" = %d", ret);
 441         return ret;
 442 }
 443
 444 /*
 445  * dissociate a cache from all the pages it was backing
 446  */
 447 static void cachefiles_dissociate_pages(struct fscache_cache *cache)
 448 {
 449         _enter("");
 450 }
 451
 452 const struct fscache_cache_ops cachefiles_cache_ops = {
 453         .name                   = "cachefiles",
 454         .alloc_object           = cachefiles_alloc_object,
 455         .lookup_object          = cachefiles_lookup_object,
 456         .lookup_complete        = cachefiles_lookup_complete,
 457         .grab_object            = cachefiles_grab_object,
 458         .update_object          = cachefiles_update_object,
 459         .drop_object            = cachefiles_drop_object,
 460         .put_object             = cachefiles_put_object,
 461         .sync_cache             = cachefiles_sync_cache,
 462         .attr_changed           = cachefiles_attr_changed,
 463         .read_or_alloc_page     = cachefiles_read_or_alloc_page,
 464         .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
 465         .allocate_page          = cachefiles_allocate_page,
 466         .allocate_pages         = cachefiles_allocate_pages,
 467         .write_page             = cachefiles_write_page,
 468         .uncache_page           = cachefiles_uncache_page,
 469         .dissociate_pages       = cachefiles_dissociate_pages,
 470 };