interface.c revision 8beabdde
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* FS-Cache interface to CacheFiles
3 *
4 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#include <linux/slab.h>
9#include <linux/mount.h>
10#include "internal.h"
11
12struct cachefiles_lookup_data {
13	struct cachefiles_xattr	*auxdata;	/* auxiliary data */
14	char			*key;		/* key path */
15};
16
17static int cachefiles_attr_changed(struct fscache_object *_object);
18
19/*
20 * allocate an object record for a cookie lookup and prepare the lookup data
21 */
22static struct fscache_object *cachefiles_alloc_object(
23	struct fscache_cache *_cache,
24	struct fscache_cookie *cookie)
25{
26	struct cachefiles_lookup_data *lookup_data;
27	struct cachefiles_object *object;
28	struct cachefiles_cache *cache;
29	struct cachefiles_xattr *auxdata;
30	unsigned keylen, auxlen;
31	void *buffer, *p;
32	char *key;
33
34	cache = container_of(_cache, struct cachefiles_cache, cache);
35
36	_enter("{%s},%x,", cache->cache.identifier, cookie->debug_id);
37
38	lookup_data = kmalloc(sizeof(*lookup_data), cachefiles_gfp);
39	if (!lookup_data)
40		goto nomem_lookup_data;
41
42	/* create a new object record and a temporary leaf image */
43	object = kmem_cache_alloc(cachefiles_object_jar, cachefiles_gfp);
44	if (!object)
45		goto nomem_object;
46
47	ASSERTCMP(object->backer, ==, NULL);
48
49	BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
50	atomic_set(&object->usage, 1);
51
52	fscache_object_init(&object->fscache, cookie, &cache->cache);
53
54	object->type = cookie->def->type;
55
56	/* get hold of the raw key
57	 * - stick the length on the front and leave space on the back for the
58	 *   encoder
59	 */
60	buffer = kmalloc((2 + 512) + 3, cachefiles_gfp);
61	if (!buffer)
62		goto nomem_buffer;
63
64	keylen = cookie->key_len;
65	if (keylen <= sizeof(cookie->inline_key))
66		p = cookie->inline_key;
67	else
68		p = cookie->key;
69	memcpy(buffer + 2, p, keylen);
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 = cookie->aux_len;
84	if (auxlen) {
85		if (auxlen <= sizeof(cookie->inline_aux))
86			p = cookie->inline_aux;
87		else
88			p = cookie->aux;
89		memcpy(auxdata->data, p, auxlen);
90	}
91
92	auxdata->len = auxlen + 1;
93	auxdata->type = cookie->type;
94
95	lookup_data->auxdata = auxdata;
96	lookup_data->key = key;
97	object->lookup_data = lookup_data;
98
99	_leave(" = %x [%p]", object->fscache.debug_id, lookup_data);
100	return &object->fscache;
101
102nomem_key:
103	kfree(buffer);
104nomem_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);
108nomem_object:
109	kfree(lookup_data);
110nomem_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 */
119static 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			pr_warn("Lookup failed error %d\n", ret);
152		fscache_object_lookup_error(&object->fscache);
153	}
154
155	_leave(" [%d]", ret);
156	return ret;
157}
158
159/*
160 * indication of lookup completion
161 */
162static void cachefiles_lookup_complete(struct fscache_object *_object)
163{
164	struct cachefiles_object *object;
165
166	object = container_of(_object, struct cachefiles_object, fscache);
167
168	_enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);
169
170	if (object->lookup_data) {
171		kfree(object->lookup_data->key);
172		kfree(object->lookup_data->auxdata);
173		kfree(object->lookup_data);
174		object->lookup_data = NULL;
175	}
176}
177
178/*
179 * increment the usage count on an inode object (may fail if unmounting)
180 */
181static
182struct fscache_object *cachefiles_grab_object(struct fscache_object *_object,
183					      enum fscache_obj_ref_trace why)
184{
185	struct cachefiles_object *object =
186		container_of(_object, struct cachefiles_object, fscache);
187	int u;
188
189	_enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
190
191#ifdef CACHEFILES_DEBUG_SLAB
192	ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
193#endif
194
195	u = atomic_inc_return(&object->usage);
196	trace_cachefiles_ref(object, _object->cookie,
197			     (enum cachefiles_obj_ref_trace)why, u);
198	return &object->fscache;
199}
200
201/*
202 * update the auxiliary data for an object object on disk
203 */
204static void cachefiles_update_object(struct fscache_object *_object)
205{
206	struct cachefiles_object *object;
207	struct cachefiles_xattr *auxdata;
208	struct cachefiles_cache *cache;
209	struct fscache_cookie *cookie;
210	const struct cred *saved_cred;
211	const void *aux;
212	unsigned auxlen;
213
214	_enter("{OBJ%x}", _object->debug_id);
215
216	object = container_of(_object, struct cachefiles_object, fscache);
217	cache = container_of(object->fscache.cache, struct cachefiles_cache,
218			     cache);
219
220	if (!fscache_use_cookie(_object)) {
221		_leave(" [relinq]");
222		return;
223	}
224
225	cookie = object->fscache.cookie;
226	auxlen = cookie->aux_len;
227
228	if (!auxlen) {
229		fscache_unuse_cookie(_object);
230		_leave(" [no aux]");
231		return;
232	}
233
234	auxdata = kmalloc(2 + auxlen + 3, cachefiles_gfp);
235	if (!auxdata) {
236		fscache_unuse_cookie(_object);
237		_leave(" [nomem]");
238		return;
239	}
240
241	aux = (auxlen <= sizeof(cookie->inline_aux)) ?
242		cookie->inline_aux : cookie->aux;
243
244	memcpy(auxdata->data, aux, auxlen);
245	fscache_unuse_cookie(_object);
246
247	auxdata->len = auxlen + 1;
248	auxdata->type = cookie->type;
249
250	cachefiles_begin_secure(cache, &saved_cred);
251	cachefiles_update_object_xattr(object, auxdata);
252	cachefiles_end_secure(cache, saved_cred);
253	kfree(auxdata);
254	_leave("");
255}
256
257/*
258 * discard the resources pinned by an object and effect retirement if
259 * requested
260 */
261static void cachefiles_drop_object(struct fscache_object *_object)
262{
263	struct cachefiles_object *object;
264	struct cachefiles_cache *cache;
265	const struct cred *saved_cred;
266	struct inode *inode;
267	blkcnt_t i_blocks = 0;
268
269	ASSERT(_object);
270
271	object = container_of(_object, struct cachefiles_object, fscache);
272
273	_enter("{OBJ%x,%d}",
274	       object->fscache.debug_id, atomic_read(&object->usage));
275
276	cache = container_of(object->fscache.cache,
277			     struct cachefiles_cache, cache);
278
279#ifdef CACHEFILES_DEBUG_SLAB
280	ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
281#endif
282
283	/* We need to tidy the object up if we did in fact manage to open it.
284	 * It's possible for us to get here before the object is fully
285	 * initialised if the parent goes away or the object gets retired
286	 * before we set it up.
287	 */
288	if (object->dentry) {
289		/* delete retired objects */
290		if (test_bit(FSCACHE_OBJECT_RETIRED, &object->fscache.flags) &&
291		    _object != cache->cache.fsdef
292		    ) {
293			_debug("- retire object OBJ%x", object->fscache.debug_id);
294			inode = d_backing_inode(object->dentry);
295			if (inode)
296				i_blocks = inode->i_blocks;
297
298			cachefiles_begin_secure(cache, &saved_cred);
299			cachefiles_delete_object(cache, object);
300			cachefiles_end_secure(cache, saved_cred);
301		}
302
303		/* close the filesystem stuff attached to the object */
304		if (object->backer != object->dentry)
305			dput(object->backer);
306		object->backer = NULL;
307	}
308
309	/* note that the object is now inactive */
310	if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags))
311		cachefiles_mark_object_inactive(cache, object, i_blocks);
312
313	dput(object->dentry);
314	object->dentry = NULL;
315
316	_leave("");
317}
318
319/*
320 * dispose of a reference to an object
321 */
322void cachefiles_put_object(struct fscache_object *_object,
323			   enum fscache_obj_ref_trace why)
324{
325	struct cachefiles_object *object;
326	struct fscache_cache *cache;
327	int u;
328
329	ASSERT(_object);
330
331	object = container_of(_object, struct cachefiles_object, fscache);
332
333	_enter("{OBJ%x,%d}",
334	       object->fscache.debug_id, atomic_read(&object->usage));
335
336#ifdef CACHEFILES_DEBUG_SLAB
337	ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
338#endif
339
340	ASSERTIFCMP(object->fscache.parent,
341		    object->fscache.parent->n_children, >, 0);
342
343	u = atomic_dec_return(&object->usage);
344	trace_cachefiles_ref(object, _object->cookie,
345			     (enum cachefiles_obj_ref_trace)why, u);
346	ASSERTCMP(u, !=, -1);
347	if (u == 0) {
348		_debug("- kill object OBJ%x", object->fscache.debug_id);
349
350		ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
351		ASSERTCMP(object->fscache.parent, ==, NULL);
352		ASSERTCMP(object->backer, ==, NULL);
353		ASSERTCMP(object->dentry, ==, NULL);
354		ASSERTCMP(object->fscache.n_ops, ==, 0);
355		ASSERTCMP(object->fscache.n_children, ==, 0);
356
357		if (object->lookup_data) {
358			kfree(object->lookup_data->key);
359			kfree(object->lookup_data->auxdata);
360			kfree(object->lookup_data);
361			object->lookup_data = NULL;
362		}
363
364		cache = object->fscache.cache;
365		fscache_object_destroy(&object->fscache);
366		kmem_cache_free(cachefiles_object_jar, object);
367		fscache_object_destroyed(cache);
368	}
369
370	_leave("");
371}
372
373/*
374 * sync a cache
375 */
376static void cachefiles_sync_cache(struct fscache_cache *_cache)
377{
378	struct cachefiles_cache *cache;
379	const struct cred *saved_cred;
380	int ret;
381
382	_enter("%s", _cache->tag->name);
383
384	cache = container_of(_cache, struct cachefiles_cache, cache);
385
386	/* make sure all pages pinned by operations on behalf of the netfs are
387	 * written to disc */
388	cachefiles_begin_secure(cache, &saved_cred);
389	down_read(&cache->mnt->mnt_sb->s_umount);
390	ret = sync_filesystem(cache->mnt->mnt_sb);
391	up_read(&cache->mnt->mnt_sb->s_umount);
392	cachefiles_end_secure(cache, saved_cred);
393
394	if (ret == -EIO)
395		cachefiles_io_error(cache,
396				    "Attempt to sync backing fs superblock"
397				    " returned error %d",
398				    ret);
399}
400
401/*
402 * check if the backing cache is updated to FS-Cache
403 * - called by FS-Cache when evaluates if need to invalidate the cache
404 */
405static int cachefiles_check_consistency(struct fscache_operation *op)
406{
407	struct cachefiles_object *object;
408	struct cachefiles_cache *cache;
409	const struct cred *saved_cred;
410	int ret;
411
412	_enter("{OBJ%x}", op->object->debug_id);
413
414	object = container_of(op->object, struct cachefiles_object, fscache);
415	cache = container_of(object->fscache.cache,
416			     struct cachefiles_cache, cache);
417
418	cachefiles_begin_secure(cache, &saved_cred);
419	ret = cachefiles_check_auxdata(object);
420	cachefiles_end_secure(cache, saved_cred);
421
422	_leave(" = %d", ret);
423	return ret;
424}
425
426/*
427 * notification the attributes on an object have changed
428 * - called with reads/writes excluded by FS-Cache
429 */
430static int cachefiles_attr_changed(struct fscache_object *_object)
431{
432	struct cachefiles_object *object;
433	struct cachefiles_cache *cache;
434	const struct cred *saved_cred;
435	struct iattr newattrs;
436	uint64_t ni_size;
437	loff_t oi_size;
438	int ret;
439
440	ni_size = _object->store_limit_l;
441
442	_enter("{OBJ%x},[%llu]",
443	       _object->debug_id, (unsigned long long) ni_size);
444
445	object = container_of(_object, struct cachefiles_object, fscache);
446	cache = container_of(object->fscache.cache,
447			     struct cachefiles_cache, cache);
448
449	if (ni_size == object->i_size)
450		return 0;
451
452	if (!object->backer)
453		return -ENOBUFS;
454
455	ASSERT(d_is_reg(object->backer));
456
457	fscache_set_store_limit(&object->fscache, ni_size);
458
459	oi_size = i_size_read(d_backing_inode(object->backer));
460	if (oi_size == ni_size)
461		return 0;
462
463	cachefiles_begin_secure(cache, &saved_cred);
464	inode_lock(d_inode(object->backer));
465
466	/* if there's an extension to a partial page at the end of the backing
467	 * file, we need to discard the partial page so that we pick up new
468	 * data after it */
469	if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
470		_debug("discard tail %llx", oi_size);
471		newattrs.ia_valid = ATTR_SIZE;
472		newattrs.ia_size = oi_size & PAGE_MASK;
473		ret = notify_change(&init_user_ns, object->backer, &newattrs, NULL);
474		if (ret < 0)
475			goto truncate_failed;
476	}
477
478	newattrs.ia_valid = ATTR_SIZE;
479	newattrs.ia_size = ni_size;
480	ret = notify_change(&init_user_ns, object->backer, &newattrs, NULL);
481
482truncate_failed:
483	inode_unlock(d_inode(object->backer));
484	cachefiles_end_secure(cache, saved_cred);
485
486	if (ret == -EIO) {
487		fscache_set_store_limit(&object->fscache, 0);
488		cachefiles_io_error_obj(object, "Size set failed");
489		ret = -ENOBUFS;
490	}
491
492	_leave(" = %d", ret);
493	return ret;
494}
495
496/*
497 * Invalidate an object
498 */
499static void cachefiles_invalidate_object(struct fscache_operation *op)
500{
501	struct cachefiles_object *object;
502	struct cachefiles_cache *cache;
503	const struct cred *saved_cred;
504	struct path path;
505	uint64_t ni_size;
506	int ret;
507
508	object = container_of(op->object, struct cachefiles_object, fscache);
509	cache = container_of(object->fscache.cache,
510			     struct cachefiles_cache, cache);
511
512	ni_size = op->object->store_limit_l;
513
514	_enter("{OBJ%x},[%llu]",
515	       op->object->debug_id, (unsigned long long)ni_size);
516
517	if (object->backer) {
518		ASSERT(d_is_reg(object->backer));
519
520		fscache_set_store_limit(&object->fscache, ni_size);
521
522		path.dentry = object->backer;
523		path.mnt = cache->mnt;
524
525		cachefiles_begin_secure(cache, &saved_cred);
526		ret = vfs_truncate(&path, 0);
527		if (ret == 0)
528			ret = vfs_truncate(&path, ni_size);
529		cachefiles_end_secure(cache, saved_cred);
530
531		if (ret != 0) {
532			fscache_set_store_limit(&object->fscache, 0);
533			if (ret == -EIO)
534				cachefiles_io_error_obj(object,
535							"Invalidate failed");
536		}
537	}
538
539	fscache_op_complete(op, true);
540	_leave("");
541}
542
543/*
544 * dissociate a cache from all the pages it was backing
545 */
546static void cachefiles_dissociate_pages(struct fscache_cache *cache)
547{
548	_enter("");
549}
550
551const struct fscache_cache_ops cachefiles_cache_ops = {
552	.name			= "cachefiles",
553	.alloc_object		= cachefiles_alloc_object,
554	.lookup_object		= cachefiles_lookup_object,
555	.lookup_complete	= cachefiles_lookup_complete,
556	.grab_object		= cachefiles_grab_object,
557	.update_object		= cachefiles_update_object,
558	.invalidate_object	= cachefiles_invalidate_object,
559	.drop_object		= cachefiles_drop_object,
560	.put_object		= cachefiles_put_object,
561	.sync_cache		= cachefiles_sync_cache,
562	.attr_changed		= cachefiles_attr_changed,
563	.read_or_alloc_page	= cachefiles_read_or_alloc_page,
564	.read_or_alloc_pages	= cachefiles_read_or_alloc_pages,
565	.allocate_page		= cachefiles_allocate_page,
566	.allocate_pages		= cachefiles_allocate_pages,
567	.write_page		= cachefiles_write_page,
568	.uncache_page		= cachefiles_uncache_page,
569	.dissociate_pages	= cachefiles_dissociate_pages,
570	.check_consistency	= cachefiles_check_consistency,
571	.begin_read_operation	= cachefiles_begin_read_operation,
572};
573