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