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
16static atomic_t cachefiles_object_debug_id;
17
18/*
19 * Allocate a cache object record.
20 */
21static
22struct 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(k: cachefiles_object_jar, GFP_KERNEL);
31 if (!object)
32 return NULL;
33
34 refcount_set(r: &object->ref, n: 1);
35
36 spin_lock_init(&object->lock);
37 INIT_LIST_HEAD(list: &object->cache_link);
38 object->volume = volume;
39 object->debug_id = atomic_inc_return(v: &cachefiles_object_debug_id);
40 object->cookie = fscache_get_cookie(cookie, where: fscache_cookie_get_attach_object);
41
42 fscache_count_object(cache: vcookie->cache);
43 trace_cachefiles_ref(object_debug_id: object->debug_id, cookie_debug_id: cookie->debug_id, usage: 1,
44 why: cachefiles_obj_new);
45 return object;
46}
47
48/*
49 * Note that an object has been seen.
50 */
51void cachefiles_see_object(struct cachefiles_object *object,
52 enum cachefiles_obj_ref_trace why)
53{
54 trace_cachefiles_ref(object_debug_id: object->debug_id, cookie_debug_id: object->cookie->debug_id,
55 usage: refcount_read(r: &object->ref), why);
56}
57
58/*
59 * Increment the usage count on an object;
60 */
61struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
62 enum cachefiles_obj_ref_trace why)
63{
64 int r;
65
66 __refcount_inc(r: &object->ref, oldp: &r);
67 trace_cachefiles_ref(object_debug_id: object->debug_id, cookie_debug_id: object->cookie->debug_id, usage: r, why);
68 return object;
69}
70
71/*
72 * dispose of a reference to an object
73 */
74void 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(r: &object->ref, oldp: &r);
84 trace_cachefiles_ref(object_debug_id, cookie_debug_id, usage: r, why);
85 if (done) {
86 _debug("- kill object OBJ%x", object_debug_id);
87
88 ASSERTCMP(object->file, ==, NULL);
89
90 kfree(objp: object->d_name);
91
92 cache = object->volume->cache->cache;
93 fscache_put_cookie(cookie: object->cookie, where: fscache_cookie_put_object);
94 object->cookie = NULL;
95 kmem_cache_free(s: cachefiles_object_jar, objp: 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(inode: file_inode(f: file));
127 if (oi_size == ni_size)
128 return 0;
129
130 inode_lock(inode: file_inode(f: 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(inode: file_inode(f: file));
156
157 if (ret < 0)
158 trace_cachefiles_io_error(NULL, backer: file_inode(f: file), error: ret,
159 where: 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: &saved_cred);
191
192 success = cachefiles_look_up_object(object);
193 if (!success)
194 goto fail_withdraw;
195
196 cachefiles_see_object(object, why: cachefiles_obj_see_lookup_cookie);
197
198 spin_lock(lock: &cache->object_list_lock);
199 list_add(new: &object->cache_link, head: &cache->object_list);
200 spin_unlock(lock: &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, why: 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, why: 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(f: 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(obj: object, backer: inode, from: i_size, to: dio_size,
239 why: 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(obj: object, backer: file_inode(f: file), error: ret,
245 where: cachefiles_trace_trunc_error);
246 cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret);
247 cachefiles_remove_object_xattr(cache, object, dentry: file->f_path.dentry);
248 return false;
249 }
250
251 if (new_size < dio_size) {
252 trace_cachefiles_trunc(obj: object, backer: inode, from: dio_size, to: new_size,
253 why: cachefiles_trunc_dio_adjust);
254 ret = cachefiles_inject_write_error();
255 if (ret == 0)
256 ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
257 offset: new_size, len: dio_size - new_size);
258 if (ret < 0) {
259 trace_cachefiles_io_error(obj: object, backer: file_inode(f: file), error: ret,
260 where: cachefiles_trace_fallocate_error);
261 cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret);
262 cachefiles_remove_object_xattr(cache, object, dentry: 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: &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, addr: &object->cookie->flags))
309 update = true;
310 if (test_and_clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, addr: &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 if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
326 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
327 cachefiles_see_object(object, why: cachefiles_obj_see_clean_delete);
328 _debug("- inval object OBJ%x", object->debug_id);
329 cachefiles_delete_object(object, why: FSCACHE_OBJECT_WAS_RETIRED);
330 } else {
331 cachefiles_see_object(object, why: cachefiles_obj_see_clean_drop_tmp);
332 _debug("- inval object OBJ%x tmpfile", object->debug_id);
333 }
334 } else {
335 cachefiles_see_object(object, why: cachefiles_obj_see_clean_commit);
336 cachefiles_commit_object(object, cache);
337 }
338
339 cachefiles_unmark_inode_in_use(object, file: 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 */
349static 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, why: cachefiles_obj_see_withdraw_cookie);
357
358 if (!list_empty(head: &object->cache_link)) {
359 spin_lock(lock: &cache->object_list_lock);
360 cachefiles_see_object(object, why: cachefiles_obj_see_withdrawal);
361 list_del_init(entry: &object->cache_link);
362 spin_unlock(lock: &cache->object_list_lock);
363 }
364
365 cachefiles_ondemand_clean_object(object);
366
367 if (object->file) {
368 cachefiles_begin_secure(cache, saved_cred: &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, why: cachefiles_obj_put_detach);
375}
376
377/*
378 * Invalidate the storage associated with a cookie.
379 */
380static 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(ptr: new_file))
398 goto failed;
399
400 /* Substitute the VFS target */
401 _debug("sub");
402 spin_lock(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, addr: &object->flags);
408 set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, addr: &object->cookie->flags);
409
410 spin_unlock(lock: &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(inode: d_inode(dentry: fan), subclass: I_MUTEX_PARENT);
422 cachefiles_bury_object(cache: volume->cache, object, dir: fan,
423 rep: old_file->f_path.dentry,
424 why: FSCACHE_OBJECT_INVALIDATED);
425 }
426 fput(old_file);
427 }
428
429 _leave(" = t");
430 return true;
431
432failed:
433 _leave(" = f");
434 return false;
435}
436
437const 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

source code of linux/fs/cachefiles/interface.c