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 if (cachefiles_ondemand_init_obj_info(obj: object, volume)) {
35 kmem_cache_free(s: cachefiles_object_jar, objp: object);
36 return NULL;
37 }
38
39 refcount_set(r: &object->ref, n: 1);
40
41 spin_lock_init(&object->lock);
42 INIT_LIST_HEAD(list: &object->cache_link);
43 object->volume = volume;
44 object->debug_id = atomic_inc_return(v: &cachefiles_object_debug_id);
45 object->cookie = fscache_get_cookie(cookie, where: fscache_cookie_get_attach_object);
46
47 fscache_count_object(cache: vcookie->cache);
48 trace_cachefiles_ref(object_debug_id: object->debug_id, cookie_debug_id: cookie->debug_id, usage: 1,
49 why: cachefiles_obj_new);
50 return object;
51}
52
53/*
54 * Note that an object has been seen.
55 */
56void cachefiles_see_object(struct cachefiles_object *object,
57 enum cachefiles_obj_ref_trace why)
58{
59 trace_cachefiles_ref(object_debug_id: object->debug_id, cookie_debug_id: object->cookie->debug_id,
60 usage: refcount_read(r: &object->ref), why);
61}
62
63/*
64 * Increment the usage count on an object;
65 */
66struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
67 enum cachefiles_obj_ref_trace why)
68{
69 int r;
70
71 __refcount_inc(r: &object->ref, oldp: &r);
72 trace_cachefiles_ref(object_debug_id: object->debug_id, cookie_debug_id: object->cookie->debug_id, usage: r, why);
73 return object;
74}
75
76/*
77 * dispose of a reference to an object
78 */
79void cachefiles_put_object(struct cachefiles_object *object,
80 enum cachefiles_obj_ref_trace why)
81{
82 unsigned int object_debug_id = object->debug_id;
83 unsigned int cookie_debug_id = object->cookie->debug_id;
84 struct fscache_cache *cache;
85 bool done;
86 int r;
87
88 done = __refcount_dec_and_test(r: &object->ref, oldp: &r);
89 trace_cachefiles_ref(object_debug_id, cookie_debug_id, usage: r, why);
90 if (done) {
91 _debug("- kill object OBJ%x", object_debug_id);
92
93 ASSERTCMP(object->file, ==, NULL);
94
95 kfree(objp: object->d_name);
96 cachefiles_ondemand_deinit_obj_info(obj: object);
97 cache = object->volume->cache->cache;
98 fscache_put_cookie(cookie: object->cookie, where: fscache_cookie_put_object);
99 object->cookie = NULL;
100 kmem_cache_free(s: cachefiles_object_jar, objp: object);
101 fscache_uncount_object(cache);
102 }
103
104 _leave("");
105}
106
107/*
108 * Adjust the size of a cache file if necessary to match the DIO size. We keep
109 * the EOF marker a multiple of DIO blocks so that we don't fall back to doing
110 * non-DIO for a partial block straddling the EOF, but we also have to be
111 * careful of someone expanding the file and accidentally accreting the
112 * padding.
113 */
114static int cachefiles_adjust_size(struct cachefiles_object *object)
115{
116 struct iattr newattrs;
117 struct file *file = object->file;
118 uint64_t ni_size;
119 loff_t oi_size;
120 int ret;
121
122 ni_size = object->cookie->object_size;
123 ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);
124
125 _enter("{OBJ%x},[%llu]",
126 object->debug_id, (unsigned long long) ni_size);
127
128 if (!file)
129 return -ENOBUFS;
130
131 oi_size = i_size_read(inode: file_inode(f: file));
132 if (oi_size == ni_size)
133 return 0;
134
135 inode_lock(inode: file_inode(f: file));
136
137 /* if there's an extension to a partial page at the end of the backing
138 * file, we need to discard the partial page so that we pick up new
139 * data after it */
140 if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
141 _debug("discard tail %llx", oi_size);
142 newattrs.ia_valid = ATTR_SIZE;
143 newattrs.ia_size = oi_size & PAGE_MASK;
144 ret = cachefiles_inject_remove_error();
145 if (ret == 0)
146 ret = notify_change(&nop_mnt_idmap, file->f_path.dentry,
147 &newattrs, NULL);
148 if (ret < 0)
149 goto truncate_failed;
150 }
151
152 newattrs.ia_valid = ATTR_SIZE;
153 newattrs.ia_size = ni_size;
154 ret = cachefiles_inject_write_error();
155 if (ret == 0)
156 ret = notify_change(&nop_mnt_idmap, file->f_path.dentry,
157 &newattrs, NULL);
158
159truncate_failed:
160 inode_unlock(inode: file_inode(f: file));
161
162 if (ret < 0)
163 trace_cachefiles_io_error(NULL, backer: file_inode(f: file), error: ret,
164 where: cachefiles_trace_notify_change_error);
165 if (ret == -EIO) {
166 cachefiles_io_error_obj(object, "Size set failed");
167 ret = -ENOBUFS;
168 }
169
170 _leave(" = %d", ret);
171 return ret;
172}
173
174/*
175 * Attempt to look up the nominated node in this cache
176 */
177static bool cachefiles_lookup_cookie(struct fscache_cookie *cookie)
178{
179 struct cachefiles_object *object;
180 struct cachefiles_cache *cache = cookie->volume->cache->cache_priv;
181 const struct cred *saved_cred;
182 bool success;
183
184 object = cachefiles_alloc_object(cookie);
185 if (!object)
186 goto fail;
187
188 _enter("{OBJ%x}", object->debug_id);
189
190 if (!cachefiles_cook_key(object))
191 goto fail_put;
192
193 cookie->cache_priv = object;
194
195 cachefiles_begin_secure(cache, saved_cred: &saved_cred);
196
197 success = cachefiles_look_up_object(object);
198 if (!success)
199 goto fail_withdraw;
200
201 cachefiles_see_object(object, why: cachefiles_obj_see_lookup_cookie);
202
203 spin_lock(lock: &cache->object_list_lock);
204 list_add(new: &object->cache_link, head: &cache->object_list);
205 spin_unlock(lock: &cache->object_list_lock);
206 cachefiles_adjust_size(object);
207
208 cachefiles_end_secure(cache, saved_cred);
209 _leave(" = t");
210 return true;
211
212fail_withdraw:
213 cachefiles_end_secure(cache, saved_cred);
214 cachefiles_see_object(object, why: cachefiles_obj_see_lookup_failed);
215 fscache_caching_failed(cookie);
216 _debug("failed c=%08x o=%08x", cookie->debug_id, object->debug_id);
217 /* The caller holds an access count on the cookie, so we need them to
218 * drop it before we can withdraw the object.
219 */
220 return false;
221
222fail_put:
223 cachefiles_put_object(object, why: cachefiles_obj_put_alloc_fail);
224fail:
225 return false;
226}
227
228/*
229 * Shorten the backing object to discard any dirty data and free up
230 * any unused granules.
231 */
232static bool cachefiles_shorten_object(struct cachefiles_object *object,
233 struct file *file, loff_t new_size)
234{
235 struct cachefiles_cache *cache = object->volume->cache;
236 struct inode *inode = file_inode(f: file);
237 loff_t i_size, dio_size;
238 int ret;
239
240 dio_size = round_up(new_size, CACHEFILES_DIO_BLOCK_SIZE);
241 i_size = i_size_read(inode);
242
243 trace_cachefiles_trunc(obj: object, backer: inode, from: i_size, to: dio_size,
244 why: cachefiles_trunc_shrink);
245 ret = cachefiles_inject_remove_error();
246 if (ret == 0)
247 ret = vfs_truncate(&file->f_path, dio_size);
248 if (ret < 0) {
249 trace_cachefiles_io_error(obj: object, backer: file_inode(f: file), error: ret,
250 where: cachefiles_trace_trunc_error);
251 cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret);
252 cachefiles_remove_object_xattr(cache, object, dentry: file->f_path.dentry);
253 return false;
254 }
255
256 if (new_size < dio_size) {
257 trace_cachefiles_trunc(obj: object, backer: inode, from: dio_size, to: new_size,
258 why: cachefiles_trunc_dio_adjust);
259 ret = cachefiles_inject_write_error();
260 if (ret == 0)
261 ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
262 offset: new_size, len: dio_size - new_size);
263 if (ret < 0) {
264 trace_cachefiles_io_error(obj: object, backer: file_inode(f: file), error: ret,
265 where: cachefiles_trace_fallocate_error);
266 cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret);
267 cachefiles_remove_object_xattr(cache, object, dentry: file->f_path.dentry);
268 return false;
269 }
270 }
271
272 return true;
273}
274
275/*
276 * Resize the backing object.
277 */
278static void cachefiles_resize_cookie(struct netfs_cache_resources *cres,
279 loff_t new_size)
280{
281 struct cachefiles_object *object = cachefiles_cres_object(cres);
282 struct cachefiles_cache *cache = object->volume->cache;
283 struct fscache_cookie *cookie = object->cookie;
284 const struct cred *saved_cred;
285 struct file *file = cachefiles_cres_file(cres);
286 loff_t old_size = cookie->object_size;
287
288 _enter("%llu->%llu", old_size, new_size);
289
290 if (new_size < old_size) {
291 cachefiles_begin_secure(cache, saved_cred: &saved_cred);
292 cachefiles_shorten_object(object, file, new_size);
293 cachefiles_end_secure(cache, saved_cred);
294 object->cookie->object_size = new_size;
295 return;
296 }
297
298 /* The file is being expanded. We don't need to do anything
299 * particularly. cookie->initial_size doesn't change and so the point
300 * at which we have to download before doesn't change.
301 */
302 cookie->object_size = new_size;
303}
304
305/*
306 * Commit changes to the object as we drop it.
307 */
308static void cachefiles_commit_object(struct cachefiles_object *object,
309 struct cachefiles_cache *cache)
310{
311 bool update = false;
312
313 if (test_and_clear_bit(FSCACHE_COOKIE_LOCAL_WRITE, addr: &object->cookie->flags))
314 update = true;
315 if (test_and_clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, addr: &object->cookie->flags))
316 update = true;
317 if (update)
318 cachefiles_set_object_xattr(object);
319
320 if (test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags))
321 cachefiles_commit_tmpfile(cache, object);
322}
323
324/*
325 * Finalise and object and close the VFS structs that we have.
326 */
327static void cachefiles_clean_up_object(struct cachefiles_object *object,
328 struct cachefiles_cache *cache)
329{
330 if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
331 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
332 cachefiles_see_object(object, why: cachefiles_obj_see_clean_delete);
333 _debug("- inval object OBJ%x", object->debug_id);
334 cachefiles_delete_object(object, why: FSCACHE_OBJECT_WAS_RETIRED);
335 } else {
336 cachefiles_see_object(object, why: cachefiles_obj_see_clean_drop_tmp);
337 _debug("- inval object OBJ%x tmpfile", object->debug_id);
338 }
339 } else {
340 cachefiles_see_object(object, why: cachefiles_obj_see_clean_commit);
341 cachefiles_commit_object(object, cache);
342 }
343
344 cachefiles_unmark_inode_in_use(object, file: object->file);
345 if (object->file) {
346 fput(object->file);
347 object->file = NULL;
348 }
349}
350
351/*
352 * Withdraw caching for a cookie.
353 */
354static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
355{
356 struct cachefiles_object *object = cookie->cache_priv;
357 struct cachefiles_cache *cache = object->volume->cache;
358 const struct cred *saved_cred;
359
360 _enter("o=%x", object->debug_id);
361 cachefiles_see_object(object, why: cachefiles_obj_see_withdraw_cookie);
362
363 if (!list_empty(head: &object->cache_link)) {
364 spin_lock(lock: &cache->object_list_lock);
365 cachefiles_see_object(object, why: cachefiles_obj_see_withdrawal);
366 list_del_init(entry: &object->cache_link);
367 spin_unlock(lock: &cache->object_list_lock);
368 }
369
370 cachefiles_ondemand_clean_object(object);
371
372 if (object->file) {
373 cachefiles_begin_secure(cache, saved_cred: &saved_cred);
374 cachefiles_clean_up_object(object, cache);
375 cachefiles_end_secure(cache, saved_cred);
376 }
377
378 cookie->cache_priv = NULL;
379 cachefiles_put_object(object, why: cachefiles_obj_put_detach);
380}
381
382/*
383 * Invalidate the storage associated with a cookie.
384 */
385static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
386{
387 struct cachefiles_object *object = cookie->cache_priv;
388 struct file *new_file, *old_file;
389 bool old_tmpfile;
390
391 _enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size);
392
393 old_tmpfile = test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
394
395 if (!object->file) {
396 fscache_resume_after_invalidation(cookie);
397 _leave(" = t [light]");
398 return true;
399 }
400
401 new_file = cachefiles_create_tmpfile(object);
402 if (IS_ERR(ptr: new_file))
403 goto failed;
404
405 /* Substitute the VFS target */
406 _debug("sub");
407 spin_lock(lock: &object->lock);
408
409 old_file = object->file;
410 object->file = new_file;
411 object->content_info = CACHEFILES_CONTENT_NO_DATA;
412 set_bit(CACHEFILES_OBJECT_USING_TMPFILE, addr: &object->flags);
413 set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, addr: &object->cookie->flags);
414
415 spin_unlock(lock: &object->lock);
416 _debug("subbed");
417
418 /* Allow I/O to take place again */
419 fscache_resume_after_invalidation(cookie);
420
421 if (old_file) {
422 if (!old_tmpfile) {
423 struct cachefiles_volume *volume = object->volume;
424 struct dentry *fan = volume->fanout[(u8)cookie->key_hash];
425
426 inode_lock_nested(inode: d_inode(dentry: fan), subclass: I_MUTEX_PARENT);
427 cachefiles_bury_object(cache: volume->cache, object, dir: fan,
428 rep: old_file->f_path.dentry,
429 why: FSCACHE_OBJECT_INVALIDATED);
430 }
431 fput(old_file);
432 }
433
434 _leave(" = t");
435 return true;
436
437failed:
438 _leave(" = f");
439 return false;
440}
441
442const struct fscache_cache_ops cachefiles_cache_ops = {
443 .name = "cachefiles",
444 .acquire_volume = cachefiles_acquire_volume,
445 .free_volume = cachefiles_free_volume,
446 .lookup_cookie = cachefiles_lookup_cookie,
447 .withdraw_cookie = cachefiles_withdraw_cookie,
448 .invalidate_cookie = cachefiles_invalidate_cookie,
449 .begin_operation = cachefiles_begin_operation,
450 .resize_cookie = cachefiles_resize_cookie,
451 .prepare_to_write = cachefiles_prepare_to_write,
452};
453

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