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TOMOYO Linux Cross Reference
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 
 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                         pr_warn("Lookup failed error %d\n", ret);
150                 fscache_object_lookup_error(&object->fscache);
151         }
152 
153         _leave(" [%d]", ret);
154         return 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 auxiliary 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 
213         if (!fscache_use_cookie(_object)) {
214                 _leave(" [relinq]");
215                 return;
216         }
217 
218         cookie = object->fscache.cookie;
219 
220         if (!cookie->def->get_aux) {
221                 fscache_unuse_cookie(_object);
222                 _leave(" [no aux]");
223                 return;
224         }
225 
226         auxdata = kmalloc(2 + 512 + 3, cachefiles_gfp);
227         if (!auxdata) {
228                 fscache_unuse_cookie(_object);
229                 _leave(" [nomem]");
230                 return;
231         }
232 
233         auxlen = cookie->def->get_aux(cookie->netfs_data, auxdata->data, 511);
234         fscache_unuse_cookie(_object);
235         ASSERTCMP(auxlen, <, 511);
236 
237         auxdata->len = auxlen + 1;
238         auxdata->type = cookie->def->type;
239 
240         cachefiles_begin_secure(cache, &saved_cred);
241         cachefiles_update_object_xattr(object, auxdata);
242         cachefiles_end_secure(cache, saved_cred);
243         kfree(auxdata);
244         _leave("");
245 }
246 
247 /*
248  * discard the resources pinned by an object and effect retirement if
249  * requested
250  */
251 static void cachefiles_drop_object(struct fscache_object *_object)
252 {
253         struct cachefiles_object *object;
254         struct cachefiles_cache *cache;
255         const struct cred *saved_cred;
256         struct inode *inode;
257         blkcnt_t i_blocks = 0;
258 
259         ASSERT(_object);
260 
261         object = container_of(_object, struct cachefiles_object, fscache);
262 
263         _enter("{OBJ%x,%d}",
264                object->fscache.debug_id, atomic_read(&object->usage));
265 
266         cache = container_of(object->fscache.cache,
267                              struct cachefiles_cache, cache);
268 
269 #ifdef CACHEFILES_DEBUG_SLAB
270         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
271 #endif
272 
273         /* We need to tidy the object up if we did in fact manage to open it.
274          * It's possible for us to get here before the object is fully
275          * initialised if the parent goes away or the object gets retired
276          * before we set it up.
277          */
278         if (object->dentry) {
279                 /* delete retired objects */
280                 if (test_bit(FSCACHE_OBJECT_RETIRED, &object->fscache.flags) &&
281                     _object != cache->cache.fsdef
282                     ) {
283                         _debug("- retire object OBJ%x", object->fscache.debug_id);
284                         inode = d_backing_inode(object->dentry);
285                         if (inode)
286                                 i_blocks = inode->i_blocks;
287 
288                         cachefiles_begin_secure(cache, &saved_cred);
289                         cachefiles_delete_object(cache, object);
290                         cachefiles_end_secure(cache, saved_cred);
291                 }
292 
293                 /* close the filesystem stuff attached to the object */
294                 if (object->backer != object->dentry)
295                         dput(object->backer);
296                 object->backer = NULL;
297         }
298 
299         /* note that the object is now inactive */
300         if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags))
301                 cachefiles_mark_object_inactive(cache, object, i_blocks);
302 
303         dput(object->dentry);
304         object->dentry = NULL;
305 
306         _leave("");
307 }
308 
309 /*
310  * dispose of a reference to an object
311  */
312 static void cachefiles_put_object(struct fscache_object *_object)
313 {
314         struct cachefiles_object *object;
315         struct fscache_cache *cache;
316 
317         ASSERT(_object);
318 
319         object = container_of(_object, struct cachefiles_object, fscache);
320 
321         _enter("{OBJ%x,%d}",
322                object->fscache.debug_id, atomic_read(&object->usage));
323 
324 #ifdef CACHEFILES_DEBUG_SLAB
325         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
326 #endif
327 
328         ASSERTIFCMP(object->fscache.parent,
329                     object->fscache.parent->n_children, >, 0);
330 
331         if (atomic_dec_and_test(&object->usage)) {
332                 _debug("- kill object OBJ%x", object->fscache.debug_id);
333 
334                 ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
335                 ASSERTCMP(object->fscache.parent, ==, NULL);
336                 ASSERTCMP(object->backer, ==, NULL);
337                 ASSERTCMP(object->dentry, ==, NULL);
338                 ASSERTCMP(object->fscache.n_ops, ==, 0);
339                 ASSERTCMP(object->fscache.n_children, ==, 0);
340 
341                 if (object->lookup_data) {
342                         kfree(object->lookup_data->key);
343                         kfree(object->lookup_data->auxdata);
344                         kfree(object->lookup_data);
345                         object->lookup_data = NULL;
346                 }
347 
348                 cache = object->fscache.cache;
349                 fscache_object_destroy(&object->fscache);
350                 kmem_cache_free(cachefiles_object_jar, object);
351                 fscache_object_destroyed(cache);
352         }
353 
354         _leave("");
355 }
356 
357 /*
358  * sync a cache
359  */
360 static void cachefiles_sync_cache(struct fscache_cache *_cache)
361 {
362         struct cachefiles_cache *cache;
363         const struct cred *saved_cred;
364         int ret;
365 
366         _enter("%p", _cache);
367 
368         cache = container_of(_cache, struct cachefiles_cache, cache);
369 
370         /* make sure all pages pinned by operations on behalf of the netfs are
371          * written to disc */
372         cachefiles_begin_secure(cache, &saved_cred);
373         down_read(&cache->mnt->mnt_sb->s_umount);
374         ret = sync_filesystem(cache->mnt->mnt_sb);
375         up_read(&cache->mnt->mnt_sb->s_umount);
376         cachefiles_end_secure(cache, saved_cred);
377 
378         if (ret == -EIO)
379                 cachefiles_io_error(cache,
380                                     "Attempt to sync backing fs superblock"
381                                     " returned error %d",
382                                     ret);
383 }
384 
385 /*
386  * check if the backing cache is updated to FS-Cache
387  * - called by FS-Cache when evaluates if need to invalidate the cache
388  */
389 static int cachefiles_check_consistency(struct fscache_operation *op)
390 {
391         struct cachefiles_object *object;
392         struct cachefiles_cache *cache;
393         const struct cred *saved_cred;
394         int ret;
395 
396         _enter("{OBJ%x}", op->object->debug_id);
397 
398         object = container_of(op->object, struct cachefiles_object, fscache);
399         cache = container_of(object->fscache.cache,
400                              struct cachefiles_cache, cache);
401 
402         cachefiles_begin_secure(cache, &saved_cred);
403         ret = cachefiles_check_auxdata(object);
404         cachefiles_end_secure(cache, saved_cred);
405 
406         _leave(" = %d", ret);
407         return ret;
408 }
409 
410 /*
411  * notification the attributes on an object have changed
412  * - called with reads/writes excluded by FS-Cache
413  */
414 static int cachefiles_attr_changed(struct fscache_object *_object)
415 {
416         struct cachefiles_object *object;
417         struct cachefiles_cache *cache;
418         const struct cred *saved_cred;
419         struct iattr newattrs;
420         uint64_t ni_size;
421         loff_t oi_size;
422         int ret;
423 
424         _object->cookie->def->get_attr(_object->cookie->netfs_data, &ni_size);
425 
426         _enter("{OBJ%x},[%llu]",
427                _object->debug_id, (unsigned long long) ni_size);
428 
429         object = container_of(_object, struct cachefiles_object, fscache);
430         cache = container_of(object->fscache.cache,
431                              struct cachefiles_cache, cache);
432 
433         if (ni_size == object->i_size)
434                 return 0;
435 
436         if (!object->backer)
437                 return -ENOBUFS;
438 
439         ASSERT(d_is_reg(object->backer));
440 
441         fscache_set_store_limit(&object->fscache, ni_size);
442 
443         oi_size = i_size_read(d_backing_inode(object->backer));
444         if (oi_size == ni_size)
445                 return 0;
446 
447         cachefiles_begin_secure(cache, &saved_cred);
448         inode_lock(d_inode(object->backer));
449 
450         /* if there's an extension to a partial page at the end of the backing
451          * file, we need to discard the partial page so that we pick up new
452          * data after it */
453         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
454                 _debug("discard tail %llx", oi_size);
455                 newattrs.ia_valid = ATTR_SIZE;
456                 newattrs.ia_size = oi_size & PAGE_MASK;
457                 ret = notify_change(object->backer, &newattrs, NULL);
458                 if (ret < 0)
459                         goto truncate_failed;
460         }
461 
462         newattrs.ia_valid = ATTR_SIZE;
463         newattrs.ia_size = ni_size;
464         ret = notify_change(object->backer, &newattrs, NULL);
465 
466 truncate_failed:
467         inode_unlock(d_inode(object->backer));
468         cachefiles_end_secure(cache, saved_cred);
469 
470         if (ret == -EIO) {
471                 fscache_set_store_limit(&object->fscache, 0);
472                 cachefiles_io_error_obj(object, "Size set failed");
473                 ret = -ENOBUFS;
474         }
475 
476         _leave(" = %d", ret);
477         return ret;
478 }
479 
480 /*
481  * Invalidate an object
482  */
483 static void cachefiles_invalidate_object(struct fscache_operation *op)
484 {
485         struct cachefiles_object *object;
486         struct cachefiles_cache *cache;
487         const struct cred *saved_cred;
488         struct path path;
489         uint64_t ni_size;
490         int ret;
491 
492         object = container_of(op->object, struct cachefiles_object, fscache);
493         cache = container_of(object->fscache.cache,
494                              struct cachefiles_cache, cache);
495 
496         op->object->cookie->def->get_attr(op->object->cookie->netfs_data,
497                                           &ni_size);
498 
499         _enter("{OBJ%x},[%llu]",
500                op->object->debug_id, (unsigned long long)ni_size);
501 
502         if (object->backer) {
503                 ASSERT(d_is_reg(object->backer));
504 
505                 fscache_set_store_limit(&object->fscache, ni_size);
506 
507                 path.dentry = object->backer;
508                 path.mnt = cache->mnt;
509 
510                 cachefiles_begin_secure(cache, &saved_cred);
511                 ret = vfs_truncate(&path, 0);
512                 if (ret == 0)
513                         ret = vfs_truncate(&path, ni_size);
514                 cachefiles_end_secure(cache, saved_cred);
515 
516                 if (ret != 0) {
517                         fscache_set_store_limit(&object->fscache, 0);
518                         if (ret == -EIO)
519                                 cachefiles_io_error_obj(object,
520                                                         "Invalidate failed");
521                 }
522         }
523 
524         fscache_op_complete(op, true);
525         _leave("");
526 }
527 
528 /*
529  * dissociate a cache from all the pages it was backing
530  */
531 static void cachefiles_dissociate_pages(struct fscache_cache *cache)
532 {
533         _enter("");
534 }
535 
536 const struct fscache_cache_ops cachefiles_cache_ops = {
537         .name                   = "cachefiles",
538         .alloc_object           = cachefiles_alloc_object,
539         .lookup_object          = cachefiles_lookup_object,
540         .lookup_complete        = cachefiles_lookup_complete,
541         .grab_object            = cachefiles_grab_object,
542         .update_object          = cachefiles_update_object,
543         .invalidate_object      = cachefiles_invalidate_object,
544         .drop_object            = cachefiles_drop_object,
545         .put_object             = cachefiles_put_object,
546         .sync_cache             = cachefiles_sync_cache,
547         .attr_changed           = cachefiles_attr_changed,
548         .read_or_alloc_page     = cachefiles_read_or_alloc_page,
549         .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
550         .allocate_page          = cachefiles_allocate_page,
551         .allocate_pages         = cachefiles_allocate_pages,
552         .write_page             = cachefiles_write_page,
553         .uncache_page           = cachefiles_uncache_page,
554         .dissociate_pages       = cachefiles_dissociate_pages,
555         .check_consistency      = cachefiles_check_consistency,
556 };
557 

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