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/namei.h>
13 #include <linux/falloc.h>
14 #include <trace/events/fscache.h>
15 #include "internal.h"
16
17 static atomic_t cachefiles_object_debug_id;
18
19 /*
20 * Allocate a cache object record.
21 */
22 static
cachefiles_alloc_object(struct fscache_cookie * cookie)23 struct 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 */
cachefiles_see_object(struct cachefiles_object * object,enum cachefiles_obj_ref_trace why)52 void 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 */
cachefiles_grab_object(struct cachefiles_object * object,enum cachefiles_obj_ref_trace why)62 struct 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 */
cachefiles_put_object(struct cachefiles_object * object,enum cachefiles_obj_ref_trace why)75 void 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 * Attempt to look up the nominated node in this cache
104 */
cachefiles_lookup_cookie(struct fscache_cookie * cookie)105 static bool cachefiles_lookup_cookie(struct fscache_cookie *cookie)
106 {
107 struct cachefiles_object *object;
108 struct cachefiles_cache *cache = cookie->volume->cache->cache_priv;
109 const struct cred *saved_cred;
110 bool success;
111
112 object = cachefiles_alloc_object(cookie);
113 if (!object)
114 goto fail;
115
116 _enter("{OBJ%x}", object->debug_id);
117
118 if (!cachefiles_cook_key(object))
119 goto fail_put;
120
121 cookie->cache_priv = object;
122
123 cachefiles_begin_secure(cache, &saved_cred);
124
125 success = cachefiles_look_up_object(object);
126 if (!success)
127 goto fail_withdraw;
128
129 cachefiles_see_object(object, cachefiles_obj_see_lookup_cookie);
130
131 spin_lock(&cache->object_list_lock);
132 list_add(&object->cache_link, &cache->object_list);
133 spin_unlock(&cache->object_list_lock);
134
135 cachefiles_end_secure(cache, saved_cred);
136 _leave(" = t");
137 return true;
138
139 fail_withdraw:
140 cachefiles_end_secure(cache, saved_cred);
141 cachefiles_see_object(object, cachefiles_obj_see_lookup_failed);
142 fscache_caching_failed(cookie);
143 _debug("failed c=%08x o=%08x", cookie->debug_id, object->debug_id);
144 /* The caller holds an access count on the cookie, so we need them to
145 * drop it before we can withdraw the object.
146 */
147 return false;
148
149 fail_put:
150 cachefiles_put_object(object, cachefiles_obj_put_alloc_fail);
151 fail:
152 return false;
153 }
154
155 /*
156 * Shorten the backing object to discard any dirty data and free up
157 * any unused granules.
158 */
cachefiles_shorten_object(struct cachefiles_object * object,struct file * file,uoff_t new_size)159 static bool cachefiles_shorten_object(struct cachefiles_object *object,
160 struct file *file, uoff_t new_size)
161 {
162 struct cachefiles_cache *cache = object->volume->cache;
163 struct inode *inode = file_inode(file);
164 uoff_t i_size, dio_size;
165 int ret;
166
167 dio_size = round_up(new_size, cache->bsize);
168 i_size = i_size_read(inode);
169
170 trace_cachefiles_trunc(object, inode, i_size, dio_size,
171 cachefiles_trunc_shrink);
172 ret = cachefiles_inject_remove_error();
173 if (ret == 0)
174 ret = vfs_truncate(&file->f_path, dio_size);
175 if (ret < 0) {
176 trace_cachefiles_io_error(object, file_inode(file), ret,
177 cachefiles_trace_trunc_error);
178 cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret);
179 cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
180 return false;
181 }
182
183 if (new_size < dio_size) {
184 trace_cachefiles_trunc(object, inode, dio_size, new_size,
185 cachefiles_trunc_dio_adjust);
186 ret = cachefiles_inject_write_error();
187 if (ret == 0)
188 ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
189 new_size, dio_size - new_size);
190 if (ret < 0) {
191 trace_cachefiles_io_error(object, file_inode(file), ret,
192 cachefiles_trace_fallocate_error);
193 cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret);
194 cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
195 return false;
196 }
197 }
198
199 object->object_size = new_size;
200 return true;
201 }
202
203 /*
204 * Resize the backing object.
205 */
cachefiles_resize_cookie(struct netfs_cache_resources * cres,uoff_t new_size,bool shrank)206 static void cachefiles_resize_cookie(struct netfs_cache_resources *cres,
207 uoff_t new_size, bool shrank)
208 {
209 struct cachefiles_object *object = cachefiles_cres_object(cres);
210 struct cachefiles_cache *cache = object->volume->cache;
211 struct fscache_cookie *cookie = object->cookie;
212 const struct cred *saved_cred;
213 struct file *file = cachefiles_cres_file(cres);
214 uoff_t i_size = i_size_read(file_inode(file));
215
216 _enter("%llu->%llu", object->object_size, new_size);
217
218 /* If the file shrank, we need to downsize the backing file and clear
219 * the end of the final block.
220 */
221 if (shrank) {
222 if (new_size >= i_size)
223 goto out;
224 cachefiles_begin_secure(cache, &saved_cred);
225 cachefiles_shorten_object(object, file, new_size);
226 cachefiles_end_secure(cache, saved_cred);
227 object->cookie->object_size = new_size;
228 if (new_size == 0)
229 object->content_info = CACHEFILES_CONTENT_NO_DATA;
230 return;
231 }
232
233 /* The file is being expanded. We don't need to do anything
234 * particularly. The tail of the last block should have been cleared
235 * both when it is written and when it is shrunk.
236 */
237 out:
238 object->object_size = new_size;
239 cookie->object_size = new_size;
240 }
241
242 /*
243 * Commit changes to the object as we drop it.
244 */
cachefiles_commit_object(struct cachefiles_object * object,struct cachefiles_cache * cache)245 static void cachefiles_commit_object(struct cachefiles_object *object,
246 struct cachefiles_cache *cache)
247 {
248 bool update = false;
249
250 if (test_and_clear_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
251 update = true;
252 if (test_and_clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags))
253 update = true;
254 if (update)
255 cachefiles_set_object_xattr(object);
256
257 if (test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags))
258 cachefiles_commit_tmpfile(cache, object);
259 }
260
261 /*
262 * Finalise and object and close the VFS structs that we have.
263 */
cachefiles_clean_up_object(struct cachefiles_object * object,struct cachefiles_cache * cache)264 static void cachefiles_clean_up_object(struct cachefiles_object *object,
265 struct cachefiles_cache *cache)
266 {
267 struct file *file;
268
269 if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
270 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
271 cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
272 _debug("- inval object OBJ%x", object->debug_id);
273 cachefiles_delete_object(object, FSCACHE_OBJECT_WAS_RETIRED);
274 } else {
275 cachefiles_see_object(object, cachefiles_obj_see_clean_drop_tmp);
276 _debug("- inval object OBJ%x tmpfile", object->debug_id);
277 }
278 } else {
279 cachefiles_see_object(object, cachefiles_obj_see_clean_commit);
280 cachefiles_commit_object(object, cache);
281 }
282
283 cachefiles_unmark_inode_in_use(object, object->file);
284
285 spin_lock(&object->lock);
286 file = object->file;
287 object->file = NULL;
288 spin_unlock(&object->lock);
289
290 if (file)
291 fput(file);
292 }
293
294 /*
295 * Withdraw caching for a cookie.
296 */
cachefiles_withdraw_cookie(struct fscache_cookie * cookie)297 static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
298 {
299 struct cachefiles_object *object = cookie->cache_priv;
300 struct cachefiles_cache *cache = object->volume->cache;
301 const struct cred *saved_cred;
302
303 _enter("o=%x", object->debug_id);
304 cachefiles_see_object(object, cachefiles_obj_see_withdraw_cookie);
305
306 if (!list_empty(&object->cache_link)) {
307 spin_lock(&cache->object_list_lock);
308 cachefiles_see_object(object, cachefiles_obj_see_withdrawal);
309 list_del_init(&object->cache_link);
310 spin_unlock(&cache->object_list_lock);
311 }
312
313 if (object->file) {
314 cachefiles_begin_secure(cache, &saved_cred);
315 cachefiles_clean_up_object(object, cache);
316 cachefiles_end_secure(cache, saved_cred);
317 }
318
319 cookie->cache_priv = NULL;
320 cachefiles_put_object(object, cachefiles_obj_put_detach);
321 }
322
323 /*
324 * Invalidate the storage associated with a cookie.
325 */
cachefiles_invalidate_cookie(struct fscache_cookie * cookie)326 static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
327 {
328 struct cachefiles_object *object = cookie->cache_priv;
329 struct file *new_file, *old_file;
330 bool old_tmpfile;
331
332 _enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size);
333
334 old_tmpfile = test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
335
336 if (!object->file) {
337 fscache_resume_after_invalidation(cookie);
338 _leave(" = t [light]");
339 return true;
340 }
341
342 new_file = cachefiles_create_tmpfile(object);
343 if (IS_ERR(new_file))
344 goto failed;
345
346 /* Substitute the VFS target */
347 _debug("sub");
348 spin_lock(&object->lock);
349
350 old_file = object->file;
351 object->file = new_file;
352 object->content_info = CACHEFILES_CONTENT_NO_DATA;
353 set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
354 set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
355
356 spin_unlock(&object->lock);
357 _debug("subbed");
358
359 /* Allow I/O to take place again */
360 fscache_resume_after_invalidation(cookie);
361
362 if (old_file) {
363 if (!old_tmpfile) {
364 struct cachefiles_volume *volume = object->volume;
365 struct dentry *fan = volume->fanout[(u8)cookie->key_hash];
366 struct dentry *obj;
367
368 obj = start_removing_dentry(fan, old_file->f_path.dentry);
369 if (!IS_ERR(obj))
370 cachefiles_bury_object(volume->cache, object,
371 fan, obj,
372 FSCACHE_OBJECT_INVALIDATED);
373 }
374 fput(old_file);
375 }
376
377 _leave(" = t");
378 return true;
379
380 failed:
381 _leave(" = f");
382 return false;
383 }
384
385 const struct fscache_cache_ops cachefiles_cache_ops = {
386 .name = "cachefiles",
387 .acquire_volume = cachefiles_acquire_volume,
388 .free_volume = cachefiles_free_volume,
389 .lookup_cookie = cachefiles_lookup_cookie,
390 .withdraw_cookie = cachefiles_withdraw_cookie,
391 .invalidate_cookie = cachefiles_invalidate_cookie,
392 .begin_operation = cachefiles_begin_operation,
393 .resize_cookie = cachefiles_resize_cookie,
394 .prepare_to_write = cachefiles_prepare_to_write,
395 };
396