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  * - return -ETIMEDOUT to be scheduled again
 118  */
 119 static int cachefiles_lookup_object(struct fscache_object *_object)
 120 {
 121         struct cachefiles_lookup_data *lookup_data;
 122         struct cachefiles_object *parent, *object;
 123         struct cachefiles_cache *cache;
 124         const struct cred *saved_cred;
 125         int ret;
 126
 127         _enter("{OBJ%x}", _object->debug_id);
 128
 129         cache = container_of(_object->cache, struct cachefiles_cache, cache);
 130         parent = container_of(_object->parent,
 131                               struct cachefiles_object, fscache);
 132         object = container_of(_object, struct cachefiles_object, fscache);
 133         lookup_data = object->lookup_data;
 134
 135         ASSERTCMP(lookup_data, !=, NULL);
 136
 137         /* look up the key, creating any missing bits */
 138         cachefiles_begin_secure(cache, &saved_cred);
 139         ret = cachefiles_walk_to_object(parent, object,
 140                                         lookup_data->key,
 141                                         lookup_data->auxdata);
 142         cachefiles_end_secure(cache, saved_cred);
 143
 144         /* polish off by setting the attributes of non-index files */
 145         if (ret == 0 &&
 146             object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
 147                 cachefiles_attr_changed(&object->fscache);
 148
 149         if (ret < 0 && ret != -ETIMEDOUT) {
 150                 if (ret != -ENOBUFS)
 151                         printk(KERN_WARNING
 152                                "CacheFiles: Lookup failed error %d\n", ret);
 153                 fscache_object_lookup_error(&object->fscache);
 154         }
 155
 156         _leave(" [%d]", ret);
 157         return ret;
 158 }
 159
 160 /*
 161  * indication of lookup completion
 162  */
 163 static void cachefiles_lookup_complete(struct fscache_object *_object)
 164 {
 165         struct cachefiles_object *object;
 166
 167         object = container_of(_object, struct cachefiles_object, fscache);
 168
 169         _enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);
 170
 171         if (object->lookup_data) {
 172                 kfree(object->lookup_data->key);
 173                 kfree(object->lookup_data->auxdata);
 174                 kfree(object->lookup_data);
 175                 object->lookup_data = NULL;
 176         }
 177 }
 178
 179 /*
 180  * increment the usage count on an inode object (may fail if unmounting)
 181  */
 182 static
 183 struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
 184 {
 185         struct cachefiles_object *object =
 186                 container_of(_object, struct cachefiles_object, fscache);
 187
 188         _enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
 189
 190 #ifdef CACHEFILES_DEBUG_SLAB
 191         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 192 #endif
 193
 194         atomic_inc(&object->usage);
 195         return &object->fscache;
 196 }
 197
 198 /*
 199  * update the auxilliary data for an object object on disk
 200  */
 201 static void cachefiles_update_object(struct fscache_object *_object)
 202 {
 203         struct cachefiles_object *object;
 204         struct cachefiles_xattr *auxdata;
 205         struct cachefiles_cache *cache;
 206         struct fscache_cookie *cookie;
 207         const struct cred *saved_cred;
 208         unsigned auxlen;
 209
 210         _enter("{OBJ%x}", _object->debug_id);
 211
 212         object = container_of(_object, struct cachefiles_object, fscache);
 213         cache = container_of(object->fscache.cache, struct cachefiles_cache,
 214                              cache);
 215         cookie = object->fscache.cookie;
 216
 217         if (!cookie->def->get_aux) {
 218                 _leave(" [no aux]");
 219                 return;
 220         }
 221
 222         auxdata = kmalloc(2 + 512 + 3, GFP_KERNEL);
 223         if (!auxdata) {
 224                 _leave(" [nomem]");
 225                 return;
 226         }
 227
 228         auxlen = cookie->def->get_aux(cookie->netfs_data, auxdata->data, 511);
 229         ASSERTCMP(auxlen, <, 511);
 230
 231         auxdata->len = auxlen + 1;
 232         auxdata->type = cookie->def->type;
 233
 234         cachefiles_begin_secure(cache, &saved_cred);
 235         cachefiles_update_object_xattr(object, auxdata);
 236         cachefiles_end_secure(cache, saved_cred);
 237         kfree(auxdata);
 238         _leave("");
 239 }
 240
 241 /*
 242  * discard the resources pinned by an object and effect retirement if
 243  * requested
 244  */
 245 static void cachefiles_drop_object(struct fscache_object *_object)
 246 {
 247         struct cachefiles_object *object;
 248         struct cachefiles_cache *cache;
 249         const struct cred *saved_cred;
 250
 251         ASSERT(_object);
 252
 253         object = container_of(_object, struct cachefiles_object, fscache);
 254
 255         _enter("{OBJ%x,%d}",
 256                object->fscache.debug_id, atomic_read(&object->usage));
 257
 258         cache = container_of(object->fscache.cache,
 259                              struct cachefiles_cache, cache);
 260
 261 #ifdef CACHEFILES_DEBUG_SLAB
 262         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 263 #endif
 264
 265         /* delete retired objects */
 266         if (object->fscache.state == FSCACHE_OBJECT_RECYCLING &&
 267             _object != cache->cache.fsdef
 268             ) {
 269                 _debug("- retire object OBJ%x", object->fscache.debug_id);
 270                 cachefiles_begin_secure(cache, &saved_cred);
 271                 cachefiles_delete_object(cache, object);
 272                 cachefiles_end_secure(cache, saved_cred);
 273         }
 274
 275         /* close the filesystem stuff attached to the object */
 276         if (object->backer != object->dentry)
 277                 dput(object->backer);
 278         object->backer = NULL;
 279
 280         /* note that the object is now inactive */
 281         if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
 282                 write_lock(&cache->active_lock);
 283                 if (!test_and_clear_bit(CACHEFILES_OBJECT_ACTIVE,
 284                                         &object->flags))
 285                         BUG();
 286                 rb_erase(&object->active_node, &cache->active_nodes);
 287                 wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
 288                 write_unlock(&cache->active_lock);
 289         }
 290
 291         dput(object->dentry);
 292         object->dentry = NULL;
 293
 294         _leave("");
 295 }
 296
 297 /*
 298  * dispose of a reference to an object
 299  */
 300 static void cachefiles_put_object(struct fscache_object *_object)
 301 {
 302         struct cachefiles_object *object;
 303         struct fscache_cache *cache;
 304
 305         ASSERT(_object);
 306
 307         object = container_of(_object, struct cachefiles_object, fscache);
 308
 309         _enter("{OBJ%x,%d}",
 310                object->fscache.debug_id, atomic_read(&object->usage));
 311
 312 #ifdef CACHEFILES_DEBUG_SLAB
 313         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 314 #endif
 315
 316         ASSERTIFCMP(object->fscache.parent,
 317                     object->fscache.parent->n_children, >, 0);
 318
 319         if (atomic_dec_and_test(&object->usage)) {
 320                 _debug("- kill object OBJ%x", object->fscache.debug_id);
 321
 322                 ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
 323                 ASSERTCMP(object->fscache.parent, ==, NULL);
 324                 ASSERTCMP(object->backer, ==, NULL);
 325                 ASSERTCMP(object->dentry, ==, NULL);
 326                 ASSERTCMP(object->fscache.n_ops, ==, 0);
 327                 ASSERTCMP(object->fscache.n_children, ==, 0);
 328
 329                 if (object->lookup_data) {
 330                         kfree(object->lookup_data->key);
 331                         kfree(object->lookup_data->auxdata);
 332                         kfree(object->lookup_data);
 333                         object->lookup_data = NULL;
 334                 }
 335
 336                 cache = object->fscache.cache;
 337                 fscache_object_destroy(&object->fscache);
 338                 kmem_cache_free(cachefiles_object_jar, object);
 339                 fscache_object_destroyed(cache);
 340         }
 341
 342         _leave("");
 343 }
 344
 345 /*
 346  * sync a cache
 347  */
 348 static void cachefiles_sync_cache(struct fscache_cache *_cache)
 349 {
 350         struct cachefiles_cache *cache;
 351         const struct cred *saved_cred;
 352         int ret;
 353
 354         _enter("%p", _cache);
 355
 356         cache = container_of(_cache, struct cachefiles_cache, cache);
 357
 358         /* make sure all pages pinned by operations on behalf of the netfs are
 359          * written to disc */
 360         cachefiles_begin_secure(cache, &saved_cred);
 361         down_read(&cache->mnt->mnt_sb->s_umount);
 362         ret = sync_filesystem(cache->mnt->mnt_sb);
 363         up_read(&cache->mnt->mnt_sb->s_umount);
 364         cachefiles_end_secure(cache, saved_cred);
 365
 366         if (ret == -EIO)
 367                 cachefiles_io_error(cache,
 368                                     "Attempt to sync backing fs superblock"
 369                                     " returned error %d",
 370                                     ret);
 371 }
 372
 373 /*
 374  * notification the attributes on an object have changed
 375  * - called with reads/writes excluded by FS-Cache
 376  */
 377 static int cachefiles_attr_changed(struct fscache_object *_object)
 378 {
 379         struct cachefiles_object *object;
 380         struct cachefiles_cache *cache;
 381         const struct cred *saved_cred;
 382         struct iattr newattrs;
 383         uint64_t ni_size;
 384         loff_t oi_size;
 385         int ret;
 386
 387         _object->cookie->def->get_attr(_object->cookie->netfs_data, &ni_size);
 388
 389         _enter("{OBJ%x},[%llu]",
 390                _object->debug_id, (unsigned long long) ni_size);
 391
 392         object = container_of(_object, struct cachefiles_object, fscache);
 393         cache = container_of(object->fscache.cache,
 394                              struct cachefiles_cache, cache);
 395
 396         if (ni_size == object->i_size)
 397                 return 0;
 398
 399         if (!object->backer)
 400                 return -ENOBUFS;
 401
 402         ASSERT(S_ISREG(object->backer->d_inode->i_mode));
 403
 404         fscache_set_store_limit(&object->fscache, ni_size);
 405
 406         oi_size = i_size_read(object->backer->d_inode);
 407         if (oi_size == ni_size)
 408                 return 0;
 409
 410         cachefiles_begin_secure(cache, &saved_cred);
 411         mutex_lock(&object->backer->d_inode->i_mutex);
 412
 413         /* if there's an extension to a partial page at the end of the backing
 414          * file, we need to discard the partial page so that we pick up new
 415          * data after it */
 416         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
 417                 _debug("discard tail %llx", oi_size);
 418                 newattrs.ia_valid = ATTR_SIZE;
 419                 newattrs.ia_size = oi_size & PAGE_MASK;
 420                 ret = notify_change(object->backer, &newattrs);
 421                 if (ret < 0)
 422                         goto truncate_failed;
 423         }
 424
 425         newattrs.ia_valid = ATTR_SIZE;
 426         newattrs.ia_size = ni_size;
 427         ret = notify_change(object->backer, &newattrs);
 428
 429 truncate_failed:
 430         mutex_unlock(&object->backer->d_inode->i_mutex);
 431         cachefiles_end_secure(cache, saved_cred);
 432
 433         if (ret == -EIO) {
 434                 fscache_set_store_limit(&object->fscache, 0);
 435                 cachefiles_io_error_obj(object, "Size set failed");
 436                 ret = -ENOBUFS;
 437         }
 438
 439         _leave(" = %d", ret);
 440         return ret;
 441 }
 442
 443 /*
 444  * dissociate a cache from all the pages it was backing
 445  */
 446 static void cachefiles_dissociate_pages(struct fscache_cache *cache)
 447 {
 448         _enter("");
 449 }
 450
 451 const struct fscache_cache_ops cachefiles_cache_ops = {
 452         .name                   = "cachefiles",
 453         .alloc_object           = cachefiles_alloc_object,
 454         .lookup_object          = cachefiles_lookup_object,
 455         .lookup_complete        = cachefiles_lookup_complete,
 456         .grab_object            = cachefiles_grab_object,
 457         .update_object          = cachefiles_update_object,
 458         .drop_object            = cachefiles_drop_object,
 459         .put_object             = cachefiles_put_object,
 460         .sync_cache             = cachefiles_sync_cache,
 461         .attr_changed           = cachefiles_attr_changed,
 462         .read_or_alloc_page     = cachefiles_read_or_alloc_page,
 463         .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
 464         .allocate_page          = cachefiles_allocate_page,
 465         .allocate_pages         = cachefiles_allocate_pages,
 466         .write_page             = cachefiles_write_page,
 467         .uncache_page           = cachefiles_uncache_page,
 468         .dissociate_pages       = cachefiles_dissociate_pages,
 469 };