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