xref: /openbmc/linux/fs/cachefiles/interface.c (revision f4356947)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* FS-Cache interface to CacheFiles
3  *
4  * Copyright (C) 2021 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 <linux/xattr.h>
11 #include <linux/file.h>
12 #include <linux/falloc.h>
13 #include <trace/events/fscache.h>
14 #include "internal.h"
15 
16 static atomic_t cachefiles_object_debug_id;
17 
18 /*
19  * Allocate a cache object record.
20  */
21 static
22 struct cachefiles_object *cachefiles_alloc_object(struct fscache_cookie *cookie)
23 {
24 	struct fscache_volume *vcookie = cookie->volume;
25 	struct cachefiles_volume *volume = vcookie->cache_priv;
26 	struct cachefiles_object *object;
27 
28 	_enter("{%s},%x,", vcookie->key, cookie->debug_id);
29 
30 	object = kmem_cache_zalloc(cachefiles_object_jar, GFP_KERNEL);
31 	if (!object)
32 		return NULL;
33 
34 	refcount_set(&object->ref, 1);
35 
36 	spin_lock_init(&object->lock);
37 	INIT_LIST_HEAD(&object->cache_link);
38 	object->volume = volume;
39 	object->debug_id = atomic_inc_return(&cachefiles_object_debug_id);
40 	object->cookie = fscache_get_cookie(cookie, fscache_cookie_get_attach_object);
41 
42 	fscache_count_object(vcookie->cache);
43 	trace_cachefiles_ref(object->debug_id, cookie->debug_id, 1,
44 			     cachefiles_obj_new);
45 	return object;
46 }
47 
48 /*
49  * Note that an object has been seen.
50  */
51 void cachefiles_see_object(struct cachefiles_object *object,
52 			   enum cachefiles_obj_ref_trace why)
53 {
54 	trace_cachefiles_ref(object->debug_id, object->cookie->debug_id,
55 			     refcount_read(&object->ref), why);
56 }
57 
58 /*
59  * Increment the usage count on an object;
60  */
61 struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
62 						 enum cachefiles_obj_ref_trace why)
63 {
64 	int r;
65 
66 	__refcount_inc(&object->ref, &r);
67 	trace_cachefiles_ref(object->debug_id, object->cookie->debug_id, r, why);
68 	return object;
69 }
70 
71 /*
72  * dispose of a reference to an object
73  */
74 void cachefiles_put_object(struct cachefiles_object *object,
75 			   enum cachefiles_obj_ref_trace why)
76 {
77 	unsigned int object_debug_id = object->debug_id;
78 	unsigned int cookie_debug_id = object->cookie->debug_id;
79 	struct fscache_cache *cache;
80 	bool done;
81 	int r;
82 
83 	done = __refcount_dec_and_test(&object->ref, &r);
84 	trace_cachefiles_ref(object_debug_id, cookie_debug_id, r, why);
85 	if (done) {
86 		_debug("- kill object OBJ%x", object_debug_id);
87 
88 		ASSERTCMP(object->file, ==, NULL);
89 
90 		kfree(object->d_name);
91 
92 		cache = object->volume->cache->cache;
93 		fscache_put_cookie(object->cookie, fscache_cookie_put_object);
94 		object->cookie = NULL;
95 		kmem_cache_free(cachefiles_object_jar, object);
96 		fscache_uncount_object(cache);
97 	}
98 
99 	_leave("");
100 }
101 
102 /*
103  * Adjust the size of a cache file if necessary to match the DIO size.  We keep
104  * the EOF marker a multiple of DIO blocks so that we don't fall back to doing
105  * non-DIO for a partial block straddling the EOF, but we also have to be
106  * careful of someone expanding the file and accidentally accreting the
107  * padding.
108  */
109 static int cachefiles_adjust_size(struct cachefiles_object *object)
110 {
111 	struct iattr newattrs;
112 	struct file *file = object->file;
113 	uint64_t ni_size;
114 	loff_t oi_size;
115 	int ret;
116 
117 	ni_size = object->cookie->object_size;
118 	ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);
119 
120 	_enter("{OBJ%x},[%llu]",
121 	       object->debug_id, (unsigned long long) ni_size);
122 
123 	if (!file)
124 		return -ENOBUFS;
125 
126 	oi_size = i_size_read(file_inode(file));
127 	if (oi_size == ni_size)
128 		return 0;
129 
130 	inode_lock(file_inode(file));
131 
132 	/* if there's an extension to a partial page at the end of the backing
133 	 * file, we need to discard the partial page so that we pick up new
134 	 * data after it */
135 	if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
136 		_debug("discard tail %llx", oi_size);
137 		newattrs.ia_valid = ATTR_SIZE;
138 		newattrs.ia_size = oi_size & PAGE_MASK;
139 		ret = cachefiles_inject_remove_error();
140 		if (ret == 0)
141 			ret = notify_change(&nop_mnt_idmap, file->f_path.dentry,
142 					    &newattrs, NULL);
143 		if (ret < 0)
144 			goto truncate_failed;
145 	}
146 
147 	newattrs.ia_valid = ATTR_SIZE;
148 	newattrs.ia_size = ni_size;
149 	ret = cachefiles_inject_write_error();
150 	if (ret == 0)
151 		ret = notify_change(&nop_mnt_idmap, file->f_path.dentry,
152 				    &newattrs, NULL);
153 
154 truncate_failed:
155 	inode_unlock(file_inode(file));
156 
157 	if (ret < 0)
158 		trace_cachefiles_io_error(NULL, file_inode(file), ret,
159 					  cachefiles_trace_notify_change_error);
160 	if (ret == -EIO) {
161 		cachefiles_io_error_obj(object, "Size set failed");
162 		ret = -ENOBUFS;
163 	}
164 
165 	_leave(" = %d", ret);
166 	return ret;
167 }
168 
169 /*
170  * Attempt to look up the nominated node in this cache
171  */
172 static bool cachefiles_lookup_cookie(struct fscache_cookie *cookie)
173 {
174 	struct cachefiles_object *object;
175 	struct cachefiles_cache *cache = cookie->volume->cache->cache_priv;
176 	const struct cred *saved_cred;
177 	bool success;
178 
179 	object = cachefiles_alloc_object(cookie);
180 	if (!object)
181 		goto fail;
182 
183 	_enter("{OBJ%x}", object->debug_id);
184 
185 	if (!cachefiles_cook_key(object))
186 		goto fail_put;
187 
188 	cookie->cache_priv = object;
189 
190 	cachefiles_begin_secure(cache, &saved_cred);
191 
192 	success = cachefiles_look_up_object(object);
193 	if (!success)
194 		goto fail_withdraw;
195 
196 	cachefiles_see_object(object, cachefiles_obj_see_lookup_cookie);
197 
198 	spin_lock(&cache->object_list_lock);
199 	list_add(&object->cache_link, &cache->object_list);
200 	spin_unlock(&cache->object_list_lock);
201 	cachefiles_adjust_size(object);
202 
203 	cachefiles_end_secure(cache, saved_cred);
204 	_leave(" = t");
205 	return true;
206 
207 fail_withdraw:
208 	cachefiles_end_secure(cache, saved_cred);
209 	cachefiles_see_object(object, cachefiles_obj_see_lookup_failed);
210 	fscache_caching_failed(cookie);
211 	_debug("failed c=%08x o=%08x", cookie->debug_id, object->debug_id);
212 	/* The caller holds an access count on the cookie, so we need them to
213 	 * drop it before we can withdraw the object.
214 	 */
215 	return false;
216 
217 fail_put:
218 	cachefiles_put_object(object, cachefiles_obj_put_alloc_fail);
219 fail:
220 	return false;
221 }
222 
223 /*
224  * Shorten the backing object to discard any dirty data and free up
225  * any unused granules.
226  */
227 static bool cachefiles_shorten_object(struct cachefiles_object *object,
228 				      struct file *file, loff_t new_size)
229 {
230 	struct cachefiles_cache *cache = object->volume->cache;
231 	struct inode *inode = file_inode(file);
232 	loff_t i_size, dio_size;
233 	int ret;
234 
235 	dio_size = round_up(new_size, CACHEFILES_DIO_BLOCK_SIZE);
236 	i_size = i_size_read(inode);
237 
238 	trace_cachefiles_trunc(object, inode, i_size, dio_size,
239 			       cachefiles_trunc_shrink);
240 	ret = cachefiles_inject_remove_error();
241 	if (ret == 0)
242 		ret = vfs_truncate(&file->f_path, dio_size);
243 	if (ret < 0) {
244 		trace_cachefiles_io_error(object, file_inode(file), ret,
245 					  cachefiles_trace_trunc_error);
246 		cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret);
247 		cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
248 		return false;
249 	}
250 
251 	if (new_size < dio_size) {
252 		trace_cachefiles_trunc(object, inode, dio_size, new_size,
253 				       cachefiles_trunc_dio_adjust);
254 		ret = cachefiles_inject_write_error();
255 		if (ret == 0)
256 			ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
257 					    new_size, dio_size - new_size);
258 		if (ret < 0) {
259 			trace_cachefiles_io_error(object, file_inode(file), ret,
260 						  cachefiles_trace_fallocate_error);
261 			cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret);
262 			cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
263 			return false;
264 		}
265 	}
266 
267 	return true;
268 }
269 
270 /*
271  * Resize the backing object.
272  */
273 static void cachefiles_resize_cookie(struct netfs_cache_resources *cres,
274 				     loff_t new_size)
275 {
276 	struct cachefiles_object *object = cachefiles_cres_object(cres);
277 	struct cachefiles_cache *cache = object->volume->cache;
278 	struct fscache_cookie *cookie = object->cookie;
279 	const struct cred *saved_cred;
280 	struct file *file = cachefiles_cres_file(cres);
281 	loff_t old_size = cookie->object_size;
282 
283 	_enter("%llu->%llu", old_size, new_size);
284 
285 	if (new_size < old_size) {
286 		cachefiles_begin_secure(cache, &saved_cred);
287 		cachefiles_shorten_object(object, file, new_size);
288 		cachefiles_end_secure(cache, saved_cred);
289 		object->cookie->object_size = new_size;
290 		return;
291 	}
292 
293 	/* The file is being expanded.  We don't need to do anything
294 	 * particularly.  cookie->initial_size doesn't change and so the point
295 	 * at which we have to download before doesn't change.
296 	 */
297 	cookie->object_size = new_size;
298 }
299 
300 /*
301  * Commit changes to the object as we drop it.
302  */
303 static void cachefiles_commit_object(struct cachefiles_object *object,
304 				     struct cachefiles_cache *cache)
305 {
306 	bool update = false;
307 
308 	if (test_and_clear_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
309 		update = true;
310 	if (test_and_clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags))
311 		update = true;
312 	if (update)
313 		cachefiles_set_object_xattr(object);
314 
315 	if (test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags))
316 		cachefiles_commit_tmpfile(cache, object);
317 }
318 
319 /*
320  * Finalise and object and close the VFS structs that we have.
321  */
322 static void cachefiles_clean_up_object(struct cachefiles_object *object,
323 				       struct cachefiles_cache *cache)
324 {
325 	if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
326 		if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
327 			cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
328 			_debug("- inval object OBJ%x", object->debug_id);
329 			cachefiles_delete_object(object, FSCACHE_OBJECT_WAS_RETIRED);
330 		} else {
331 			cachefiles_see_object(object, cachefiles_obj_see_clean_drop_tmp);
332 			_debug("- inval object OBJ%x tmpfile", object->debug_id);
333 		}
334 	} else {
335 		cachefiles_see_object(object, cachefiles_obj_see_clean_commit);
336 		cachefiles_commit_object(object, cache);
337 	}
338 
339 	cachefiles_unmark_inode_in_use(object, object->file);
340 	if (object->file) {
341 		fput(object->file);
342 		object->file = NULL;
343 	}
344 }
345 
346 /*
347  * Withdraw caching for a cookie.
348  */
349 static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
350 {
351 	struct cachefiles_object *object = cookie->cache_priv;
352 	struct cachefiles_cache *cache = object->volume->cache;
353 	const struct cred *saved_cred;
354 
355 	_enter("o=%x", object->debug_id);
356 	cachefiles_see_object(object, cachefiles_obj_see_withdraw_cookie);
357 
358 	if (!list_empty(&object->cache_link)) {
359 		spin_lock(&cache->object_list_lock);
360 		cachefiles_see_object(object, cachefiles_obj_see_withdrawal);
361 		list_del_init(&object->cache_link);
362 		spin_unlock(&cache->object_list_lock);
363 	}
364 
365 	cachefiles_ondemand_clean_object(object);
366 
367 	if (object->file) {
368 		cachefiles_begin_secure(cache, &saved_cred);
369 		cachefiles_clean_up_object(object, cache);
370 		cachefiles_end_secure(cache, saved_cred);
371 	}
372 
373 	cookie->cache_priv = NULL;
374 	cachefiles_put_object(object, cachefiles_obj_put_detach);
375 }
376 
377 /*
378  * Invalidate the storage associated with a cookie.
379  */
380 static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
381 {
382 	struct cachefiles_object *object = cookie->cache_priv;
383 	struct file *new_file, *old_file;
384 	bool old_tmpfile;
385 
386 	_enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size);
387 
388 	old_tmpfile = test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
389 
390 	if (!object->file) {
391 		fscache_resume_after_invalidation(cookie);
392 		_leave(" = t [light]");
393 		return true;
394 	}
395 
396 	new_file = cachefiles_create_tmpfile(object);
397 	if (IS_ERR(new_file))
398 		goto failed;
399 
400 	/* Substitute the VFS target */
401 	_debug("sub");
402 	spin_lock(&object->lock);
403 
404 	old_file = object->file;
405 	object->file = new_file;
406 	object->content_info = CACHEFILES_CONTENT_NO_DATA;
407 	set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
408 	set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
409 
410 	spin_unlock(&object->lock);
411 	_debug("subbed");
412 
413 	/* Allow I/O to take place again */
414 	fscache_resume_after_invalidation(cookie);
415 
416 	if (old_file) {
417 		if (!old_tmpfile) {
418 			struct cachefiles_volume *volume = object->volume;
419 			struct dentry *fan = volume->fanout[(u8)cookie->key_hash];
420 
421 			inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
422 			cachefiles_bury_object(volume->cache, object, fan,
423 					       old_file->f_path.dentry,
424 					       FSCACHE_OBJECT_INVALIDATED);
425 		}
426 		fput(old_file);
427 	}
428 
429 	_leave(" = t");
430 	return true;
431 
432 failed:
433 	_leave(" = f");
434 	return false;
435 }
436 
437 const struct fscache_cache_ops cachefiles_cache_ops = {
438 	.name			= "cachefiles",
439 	.acquire_volume		= cachefiles_acquire_volume,
440 	.free_volume		= cachefiles_free_volume,
441 	.lookup_cookie		= cachefiles_lookup_cookie,
442 	.withdraw_cookie	= cachefiles_withdraw_cookie,
443 	.invalidate_cookie	= cachefiles_invalidate_cookie,
444 	.begin_operation	= cachefiles_begin_operation,
445 	.resize_cookie		= cachefiles_resize_cookie,
446 	.prepare_to_write	= cachefiles_prepare_to_write,
447 };
448