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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, *p;
 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->key_len;
 69         if (keylen <= sizeof(cookie->inline_key))
 70                 p = cookie->inline_key;
 71         else
 72                 p = cookie->key;
 73         memcpy(buffer + 2, p, keylen);
 74 
 75         *(uint16_t *)buffer = keylen;
 76         ((char *)buffer)[keylen + 2] = 0;
 77         ((char *)buffer)[keylen + 3] = 0;
 78         ((char *)buffer)[keylen + 4] = 0;
 79 
 80         /* turn the raw key into something that can work with as a filename */
 81         key = cachefiles_cook_key(buffer, keylen + 2, object->type);
 82         if (!key)
 83                 goto nomem_key;
 84 
 85         /* get hold of the auxiliary data and prepend the object type */
 86         auxdata = buffer;
 87         auxlen = cookie->aux_len;
 88         if (auxlen) {
 89                 if (auxlen <= sizeof(cookie->inline_aux))
 90                         p = cookie->inline_aux;
 91                 else
 92                         p = cookie->aux;
 93                 memcpy(auxdata->data, p, auxlen);
 94         }
 95 
 96         auxdata->len = auxlen + 1;
 97         auxdata->type = cookie->type;
 98 
 99         lookup_data->auxdata = auxdata;
100         lookup_data->key = key;
101         object->lookup_data = lookup_data;
102 
103         _leave(" = %p [%p]", &object->fscache, lookup_data);
104         return &object->fscache;
105 
106 nomem_key:
107         kfree(buffer);
108 nomem_buffer:
109         BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
110         kmem_cache_free(cachefiles_object_jar, object);
111         fscache_object_destroyed(&cache->cache);
112 nomem_object:
113         kfree(lookup_data);
114 nomem_lookup_data:
115         _leave(" = -ENOMEM");
116         return ERR_PTR(-ENOMEM);
117 }
118 
119 /*
120  * attempt to look up the nominated node in this cache
121  * - return -ETIMEDOUT to be scheduled again
122  */
123 static int cachefiles_lookup_object(struct fscache_object *_object)
124 {
125         struct cachefiles_lookup_data *lookup_data;
126         struct cachefiles_object *parent, *object;
127         struct cachefiles_cache *cache;
128         const struct cred *saved_cred;
129         int ret;
130 
131         _enter("{OBJ%x}", _object->debug_id);
132 
133         cache = container_of(_object->cache, struct cachefiles_cache, cache);
134         parent = container_of(_object->parent,
135                               struct cachefiles_object, fscache);
136         object = container_of(_object, struct cachefiles_object, fscache);
137         lookup_data = object->lookup_data;
138 
139         ASSERTCMP(lookup_data, !=, NULL);
140 
141         /* look up the key, creating any missing bits */
142         cachefiles_begin_secure(cache, &saved_cred);
143         ret = cachefiles_walk_to_object(parent, object,
144                                         lookup_data->key,
145                                         lookup_data->auxdata);
146         cachefiles_end_secure(cache, saved_cred);
147 
148         /* polish off by setting the attributes of non-index files */
149         if (ret == 0 &&
150             object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
151                 cachefiles_attr_changed(&object->fscache);
152 
153         if (ret < 0 && ret != -ETIMEDOUT) {
154                 if (ret != -ENOBUFS)
155                         pr_warn("Lookup failed error %d\n", ret);
156                 fscache_object_lookup_error(&object->fscache);
157         }
158 
159         _leave(" [%d]", ret);
160         return ret;
161 }
162 
163 /*
164  * indication of lookup completion
165  */
166 static void cachefiles_lookup_complete(struct fscache_object *_object)
167 {
168         struct cachefiles_object *object;
169 
170         object = container_of(_object, struct cachefiles_object, fscache);
171 
172         _enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);
173 
174         if (object->lookup_data) {
175                 kfree(object->lookup_data->key);
176                 kfree(object->lookup_data->auxdata);
177                 kfree(object->lookup_data);
178                 object->lookup_data = NULL;
179         }
180 }
181 
182 /*
183  * increment the usage count on an inode object (may fail if unmounting)
184  */
185 static
186 struct fscache_object *cachefiles_grab_object(struct fscache_object *_object,
187                                               enum fscache_obj_ref_trace why)
188 {
189         struct cachefiles_object *object =
190                 container_of(_object, struct cachefiles_object, fscache);
191         int u;
192 
193         _enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
194 
195 #ifdef CACHEFILES_DEBUG_SLAB
196         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
197 #endif
198 
199         u = atomic_inc_return(&object->usage);
200         trace_cachefiles_ref(object, _object->cookie,
201                              (enum cachefiles_obj_ref_trace)why, u);
202         return &object->fscache;
203 }
204 
205 /*
206  * update the auxiliary data for an object object on disk
207  */
208 static void cachefiles_update_object(struct fscache_object *_object)
209 {
210         struct cachefiles_object *object;
211         struct cachefiles_xattr *auxdata;
212         struct cachefiles_cache *cache;
213         struct fscache_cookie *cookie;
214         const struct cred *saved_cred;
215         const void *aux;
216         unsigned auxlen;
217 
218         _enter("{OBJ%x}", _object->debug_id);
219 
220         object = container_of(_object, struct cachefiles_object, fscache);
221         cache = container_of(object->fscache.cache, struct cachefiles_cache,
222                              cache);
223 
224         if (!fscache_use_cookie(_object)) {
225                 _leave(" [relinq]");
226                 return;
227         }
228 
229         cookie = object->fscache.cookie;
230         auxlen = cookie->aux_len;
231 
232         if (!auxlen) {
233                 fscache_unuse_cookie(_object);
234                 _leave(" [no aux]");
235                 return;
236         }
237 
238         auxdata = kmalloc(2 + auxlen + 3, cachefiles_gfp);
239         if (!auxdata) {
240                 fscache_unuse_cookie(_object);
241                 _leave(" [nomem]");
242                 return;
243         }
244 
245         aux = (auxlen <= sizeof(cookie->inline_aux)) ?
246                 cookie->inline_aux : cookie->aux;
247 
248         memcpy(auxdata->data, aux, auxlen);
249         fscache_unuse_cookie(_object);
250 
251         auxdata->len = auxlen + 1;
252         auxdata->type = cookie->type;
253 
254         cachefiles_begin_secure(cache, &saved_cred);
255         cachefiles_update_object_xattr(object, auxdata);
256         cachefiles_end_secure(cache, saved_cred);
257         kfree(auxdata);
258         _leave("");
259 }
260 
261 /*
262  * discard the resources pinned by an object and effect retirement if
263  * requested
264  */
265 static void cachefiles_drop_object(struct fscache_object *_object)
266 {
267         struct cachefiles_object *object;
268         struct cachefiles_cache *cache;
269         const struct cred *saved_cred;
270         struct inode *inode;
271         blkcnt_t i_blocks = 0;
272 
273         ASSERT(_object);
274 
275         object = container_of(_object, struct cachefiles_object, fscache);
276 
277         _enter("{OBJ%x,%d}",
278                object->fscache.debug_id, atomic_read(&object->usage));
279 
280         cache = container_of(object->fscache.cache,
281                              struct cachefiles_cache, cache);
282 
283 #ifdef CACHEFILES_DEBUG_SLAB
284         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
285 #endif
286 
287         /* We need to tidy the object up if we did in fact manage to open it.
288          * It's possible for us to get here before the object is fully
289          * initialised if the parent goes away or the object gets retired
290          * before we set it up.
291          */
292         if (object->dentry) {
293                 /* delete retired objects */
294                 if (test_bit(FSCACHE_OBJECT_RETIRED, &object->fscache.flags) &&
295                     _object != cache->cache.fsdef
296                     ) {
297                         _debug("- retire object OBJ%x", object->fscache.debug_id);
298                         inode = d_backing_inode(object->dentry);
299                         if (inode)
300                                 i_blocks = inode->i_blocks;
301 
302                         cachefiles_begin_secure(cache, &saved_cred);
303                         cachefiles_delete_object(cache, object);
304                         cachefiles_end_secure(cache, saved_cred);
305                 }
306 
307                 /* close the filesystem stuff attached to the object */
308                 if (object->backer != object->dentry)
309                         dput(object->backer);
310                 object->backer = NULL;
311         }
312 
313         /* note that the object is now inactive */
314         if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags))
315                 cachefiles_mark_object_inactive(cache, object, i_blocks);
316 
317         dput(object->dentry);
318         object->dentry = NULL;
319 
320         _leave("");
321 }
322 
323 /*
324  * dispose of a reference to an object
325  */
326 static void cachefiles_put_object(struct fscache_object *_object,
327                                   enum fscache_obj_ref_trace why)
328 {
329         struct cachefiles_object *object;
330         struct fscache_cache *cache;
331         int u;
332 
333         ASSERT(_object);
334 
335         object = container_of(_object, struct cachefiles_object, fscache);
336 
337         _enter("{OBJ%x,%d}",
338                object->fscache.debug_id, atomic_read(&object->usage));
339 
340 #ifdef CACHEFILES_DEBUG_SLAB
341         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
342 #endif
343 
344         ASSERTIFCMP(object->fscache.parent,
345                     object->fscache.parent->n_children, >, 0);
346 
347         u = atomic_dec_return(&object->usage);
348         trace_cachefiles_ref(object, _object->cookie,
349                              (enum cachefiles_obj_ref_trace)why, u);
350         ASSERTCMP(u, !=, -1);
351         if (u == 0) {
352                 _debug("- kill object OBJ%x", object->fscache.debug_id);
353 
354                 ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
355                 ASSERTCMP(object->fscache.parent, ==, NULL);
356                 ASSERTCMP(object->backer, ==, NULL);
357                 ASSERTCMP(object->dentry, ==, NULL);
358                 ASSERTCMP(object->fscache.n_ops, ==, 0);
359                 ASSERTCMP(object->fscache.n_children, ==, 0);
360 
361                 if (object->lookup_data) {
362                         kfree(object->lookup_data->key);
363                         kfree(object->lookup_data->auxdata);
364                         kfree(object->lookup_data);
365                         object->lookup_data = NULL;
366                 }
367 
368                 cache = object->fscache.cache;
369                 fscache_object_destroy(&object->fscache);
370                 kmem_cache_free(cachefiles_object_jar, object);
371                 fscache_object_destroyed(cache);
372         }
373 
374         _leave("");
375 }
376 
377 /*
378  * sync a cache
379  */
380 static void cachefiles_sync_cache(struct fscache_cache *_cache)
381 {
382         struct cachefiles_cache *cache;
383         const struct cred *saved_cred;
384         int ret;
385 
386         _enter("%p", _cache);
387 
388         cache = container_of(_cache, struct cachefiles_cache, cache);
389 
390         /* make sure all pages pinned by operations on behalf of the netfs are
391          * written to disc */
392         cachefiles_begin_secure(cache, &saved_cred);
393         down_read(&cache->mnt->mnt_sb->s_umount);
394         ret = sync_filesystem(cache->mnt->mnt_sb);
395         up_read(&cache->mnt->mnt_sb->s_umount);
396         cachefiles_end_secure(cache, saved_cred);
397 
398         if (ret == -EIO)
399                 cachefiles_io_error(cache,
400                                     "Attempt to sync backing fs superblock"
401                                     " returned error %d",
402                                     ret);
403 }
404 
405 /*
406  * check if the backing cache is updated to FS-Cache
407  * - called by FS-Cache when evaluates if need to invalidate the cache
408  */
409 static int cachefiles_check_consistency(struct fscache_operation *op)
410 {
411         struct cachefiles_object *object;
412         struct cachefiles_cache *cache;
413         const struct cred *saved_cred;
414         int ret;
415 
416         _enter("{OBJ%x}", op->object->debug_id);
417 
418         object = container_of(op->object, struct cachefiles_object, fscache);
419         cache = container_of(object->fscache.cache,
420                              struct cachefiles_cache, cache);
421 
422         cachefiles_begin_secure(cache, &saved_cred);
423         ret = cachefiles_check_auxdata(object);
424         cachefiles_end_secure(cache, saved_cred);
425 
426         _leave(" = %d", ret);
427         return ret;
428 }
429 
430 /*
431  * notification the attributes on an object have changed
432  * - called with reads/writes excluded by FS-Cache
433  */
434 static int cachefiles_attr_changed(struct fscache_object *_object)
435 {
436         struct cachefiles_object *object;
437         struct cachefiles_cache *cache;
438         const struct cred *saved_cred;
439         struct iattr newattrs;
440         uint64_t ni_size;
441         loff_t oi_size;
442         int ret;
443 
444         ni_size = _object->store_limit_l;
445 
446         _enter("{OBJ%x},[%llu]",
447                _object->debug_id, (unsigned long long) ni_size);
448 
449         object = container_of(_object, struct cachefiles_object, fscache);
450         cache = container_of(object->fscache.cache,
451                              struct cachefiles_cache, cache);
452 
453         if (ni_size == object->i_size)
454                 return 0;
455 
456         if (!object->backer)
457                 return -ENOBUFS;
458 
459         ASSERT(d_is_reg(object->backer));
460 
461         fscache_set_store_limit(&object->fscache, ni_size);
462 
463         oi_size = i_size_read(d_backing_inode(object->backer));
464         if (oi_size == ni_size)
465                 return 0;
466 
467         cachefiles_begin_secure(cache, &saved_cred);
468         inode_lock(d_inode(object->backer));
469 
470         /* if there's an extension to a partial page at the end of the backing
471          * file, we need to discard the partial page so that we pick up new
472          * data after it */
473         if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
474                 _debug("discard tail %llx", oi_size);
475                 newattrs.ia_valid = ATTR_SIZE;
476                 newattrs.ia_size = oi_size & PAGE_MASK;
477                 ret = notify_change(object->backer, &newattrs, NULL);
478                 if (ret < 0)
479                         goto truncate_failed;
480         }
481 
482         newattrs.ia_valid = ATTR_SIZE;
483         newattrs.ia_size = ni_size;
484         ret = notify_change(object->backer, &newattrs, NULL);
485 
486 truncate_failed:
487         inode_unlock(d_inode(object->backer));
488         cachefiles_end_secure(cache, saved_cred);
489 
490         if (ret == -EIO) {
491                 fscache_set_store_limit(&object->fscache, 0);
492                 cachefiles_io_error_obj(object, "Size set failed");
493                 ret = -ENOBUFS;
494         }
495 
496         _leave(" = %d", ret);
497         return ret;
498 }
499 
500 /*
501  * Invalidate an object
502  */
503 static void cachefiles_invalidate_object(struct fscache_operation *op)
504 {
505         struct cachefiles_object *object;
506         struct cachefiles_cache *cache;
507         const struct cred *saved_cred;
508         struct path path;
509         uint64_t ni_size;
510         int ret;
511 
512         object = container_of(op->object, struct cachefiles_object, fscache);
513         cache = container_of(object->fscache.cache,
514                              struct cachefiles_cache, cache);
515 
516         ni_size = op->object->store_limit_l;
517 
518         _enter("{OBJ%x},[%llu]",
519                op->object->debug_id, (unsigned long long)ni_size);
520 
521         if (object->backer) {
522                 ASSERT(d_is_reg(object->backer));
523 
524                 fscache_set_store_limit(&object->fscache, ni_size);
525 
526                 path.dentry = object->backer;
527                 path.mnt = cache->mnt;
528 
529                 cachefiles_begin_secure(cache, &saved_cred);
530                 ret = vfs_truncate(&path, 0);
531                 if (ret == 0)
532                         ret = vfs_truncate(&path, ni_size);
533                 cachefiles_end_secure(cache, saved_cred);
534 
535                 if (ret != 0) {
536                         fscache_set_store_limit(&object->fscache, 0);
537                         if (ret == -EIO)
538                                 cachefiles_io_error_obj(object,
539                                                         "Invalidate failed");
540                 }
541         }
542 
543         fscache_op_complete(op, true);
544         _leave("");
545 }
546 
547 /*
548  * dissociate a cache from all the pages it was backing
549  */
550 static void cachefiles_dissociate_pages(struct fscache_cache *cache)
551 {
552         _enter("");
553 }
554 
555 const struct fscache_cache_ops cachefiles_cache_ops = {
556         .name                   = "cachefiles",
557         .alloc_object           = cachefiles_alloc_object,
558         .lookup_object          = cachefiles_lookup_object,
559         .lookup_complete        = cachefiles_lookup_complete,
560         .grab_object            = cachefiles_grab_object,
561         .update_object          = cachefiles_update_object,
562         .invalidate_object      = cachefiles_invalidate_object,
563         .drop_object            = cachefiles_drop_object,
564         .put_object             = cachefiles_put_object,
565         .sync_cache             = cachefiles_sync_cache,
566         .attr_changed           = cachefiles_attr_changed,
567         .read_or_alloc_page     = cachefiles_read_or_alloc_page,
568         .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
569         .allocate_page          = cachefiles_allocate_page,
570         .allocate_pages         = cachefiles_allocate_pages,
571         .write_page             = cachefiles_write_page,
572         .uncache_page           = cachefiles_uncache_page,
573         .dissociate_pages       = cachefiles_dissociate_pages,
574         .check_consistency      = cachefiles_check_consistency,
575 };
576 

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