projects/linux·blob uaccess-cleanups · refs

453 lines · 12.3 KiB

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 ([email protected])
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/namei.h>
13#include <linux/falloc.h>
14#include <trace/events/fscache.h>
15#include "internal.h"
16
17static atomic_t cachefiles_object_debug_id;
18
19/*
20 * Allocate a cache object record.
21 */
22static
23struct cachefiles_object *cachefiles_alloc_object(struct fscache_cookie *cookie)
24{
25 struct fscache_volume *vcookie = cookie->volume;
26 struct cachefiles_volume *volume = vcookie->cache_priv;
27 struct cachefiles_object *object;
28
29 _enter("{%s},%x,", vcookie->key, cookie->debug_id);
30
31 object = kmem_cache_zalloc(cachefiles_object_jar, GFP_KERNEL);
32 if (!object)
33 return NULL;
34
35 refcount_set(&object->ref, 1);
36
37 spin_lock_init(&object->lock);
38 INIT_LIST_HEAD(&object->cache_link);
39 object->volume = volume;
40 object->debug_id = atomic_inc_return(&cachefiles_object_debug_id);
41 object->cookie = fscache_get_cookie(cookie, fscache_cookie_get_attach_object);
42
43 fscache_count_object(vcookie->cache);
44 trace_cachefiles_ref(object->debug_id, cookie->debug_id, 1,
45 cachefiles_obj_new);
46 return object;
47}
48
49/*
50 * Note that an object has been seen.
51 */
52void cachefiles_see_object(struct cachefiles_object *object,
53 enum cachefiles_obj_ref_trace why)
54{
55 trace_cachefiles_ref(object->debug_id, object->cookie->debug_id,
56 refcount_read(&object->ref), why);
57}
58
59/*
60 * Increment the usage count on an object;
61 */
62struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
63 enum cachefiles_obj_ref_trace why)
64{
65 int r;
66
67 __refcount_inc(&object->ref, &r);
68 trace_cachefiles_ref(object->debug_id, object->cookie->debug_id, r, why);
69 return object;
70}
71
72/*
73 * dispose of a reference to an object
74 */
75void cachefiles_put_object(struct cachefiles_object *object,
76 enum cachefiles_obj_ref_trace why)
77{
78 unsigned int object_debug_id = object->debug_id;
79 unsigned int cookie_debug_id = object->cookie->debug_id;
80 struct fscache_cache *cache;
81 bool done;
82 int r;
83
84 done = __refcount_dec_and_test(&object->ref, &r);
85 trace_cachefiles_ref(object_debug_id, cookie_debug_id, r, why);
86 if (done) {
87 _debug("- kill object OBJ%x", object_debug_id);
88
89 ASSERTCMP(object->file, ==, NULL);
90
91 kfree(object->d_name);
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 */
109static 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
154truncate_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 */
172static 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
207fail_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
217fail_put:
218 cachefiles_put_object(object, cachefiles_obj_put_alloc_fail);
219fail:
220 return false;
221}
222
223/*
224 * Shorten the backing object to discard any dirty data and free up
225 * any unused granules.
226 */
227static 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 */
273static 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 */
303static 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 */
322static void cachefiles_clean_up_object(struct cachefiles_object *object,
323 struct cachefiles_cache *cache)
324{
325 struct file *file;
326
327 if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
328 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
329 cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
330 _debug("- inval object OBJ%x", object->debug_id);
331 cachefiles_delete_object(object, FSCACHE_OBJECT_WAS_RETIRED);
332 } else {
333 cachefiles_see_object(object, cachefiles_obj_see_clean_drop_tmp);
334 _debug("- inval object OBJ%x tmpfile", object->debug_id);
335 }
336 } else {
337 cachefiles_see_object(object, cachefiles_obj_see_clean_commit);
338 cachefiles_commit_object(object, cache);
339 }
340
341 cachefiles_unmark_inode_in_use(object, object->file);
342
343 spin_lock(&object->lock);
344 file = object->file;
345 object->file = NULL;
346 spin_unlock(&object->lock);
347
348 if (file)
349 fput(file);
350}
351
352/*
353 * Withdraw caching for a cookie.
354 */
355static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
356{
357 struct cachefiles_object *object = cookie->cache_priv;
358 struct cachefiles_cache *cache = object->volume->cache;
359 const struct cred *saved_cred;
360
361 _enter("o=%x", object->debug_id);
362 cachefiles_see_object(object, cachefiles_obj_see_withdraw_cookie);
363
364 if (!list_empty(&object->cache_link)) {
365 spin_lock(&cache->object_list_lock);
366 cachefiles_see_object(object, cachefiles_obj_see_withdrawal);
367 list_del_init(&object->cache_link);
368 spin_unlock(&cache->object_list_lock);
369 }
370
371 if (object->file) {
372 cachefiles_begin_secure(cache, &saved_cred);
373 cachefiles_clean_up_object(object, cache);
374 cachefiles_end_secure(cache, saved_cred);
375 }
376
377 cookie->cache_priv = NULL;
378 cachefiles_put_object(object, cachefiles_obj_put_detach);
379}
380
381/*
382 * Invalidate the storage associated with a cookie.
383 */
384static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
385{
386 struct cachefiles_object *object = cookie->cache_priv;
387 struct file *new_file, *old_file;
388 bool old_tmpfile;
389
390 _enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size);
391
392 old_tmpfile = test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
393
394 if (!object->file) {
395 fscache_resume_after_invalidation(cookie);
396 _leave(" = t [light]");
397 return true;
398 }
399
400 new_file = cachefiles_create_tmpfile(object);
401 if (IS_ERR(new_file))
402 goto failed;
403
404 /* Substitute the VFS target */
405 _debug("sub");
406 spin_lock(&object->lock);
407
408 old_file = object->file;
409 object->file = new_file;
410 object->content_info = CACHEFILES_CONTENT_NO_DATA;
411 set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
412 set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
413
414 spin_unlock(&object->lock);
415 _debug("subbed");
416
417 /* Allow I/O to take place again */
418 fscache_resume_after_invalidation(cookie);
419
420 if (old_file) {
421 if (!old_tmpfile) {
422 struct cachefiles_volume *volume = object->volume;
423 struct dentry *fan = volume->fanout[(u8)cookie->key_hash];
424 struct dentry *obj;
425
426 obj = start_removing_dentry(fan, old_file->f_path.dentry);
427 if (!IS_ERR(obj))
428 cachefiles_bury_object(volume->cache, object,
429 fan, obj,
430 FSCACHE_OBJECT_INVALIDATED);
431 }
432 fput(old_file);
433 }
434
435 _leave(" = t");
436 return true;
437
438failed:
439 _leave(" = f");
440 return false;
441}
442
443const struct fscache_cache_ops cachefiles_cache_ops = {
444 .name = "cachefiles",
445 .acquire_volume = cachefiles_acquire_volume,
446 .free_volume = cachefiles_free_volume,
447 .lookup_cookie = cachefiles_lookup_cookie,
448 .withdraw_cookie = cachefiles_withdraw_cookie,
449 .invalidate_cookie = cachefiles_invalidate_cookie,
450 .begin_operation = cachefiles_begin_operation,
451 .resize_cookie = cachefiles_resize_cookie,
452 .prepare_to_write = cachefiles_prepare_to_write,
453};