431accd475a73aba67ad8d24a80b31da2c94db24
[linux-2.6.git] / 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 };