Merge branch 'for-2.6.34' of git://linux-nfs.org/~bfields/linux
[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  * - 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 };