GNU Linux-libre 5.19-rc6-gnu
[releases.git] / fs / cachefiles / interface.c
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(&init_user_ns, 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(&init_user_ns, 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 };