xref: /linux/fs/cachefiles/namei.c (revision a6021aa24f6417416d93318bbfa022ab229c33c8)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* CacheFiles path walking and related routines
3  *
4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  */
7 
8 #include <linux/fs.h>
9 #include <linux/namei.h>
10 #include "internal.h"
11 
12 /*
13  * Mark the backing file as being a cache file if it's not already in use.  The
14  * mark tells the culling request command that it's not allowed to cull the
15  * file or directory.  The caller must hold the inode lock.
16  */
17 static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
18 					   struct inode *inode)
19 {
20 	bool can_use = false;
21 
22 	if (!(inode->i_flags & S_KERNEL_FILE)) {
23 		inode->i_flags |= S_KERNEL_FILE;
24 		trace_cachefiles_mark_active(object, inode);
25 		can_use = true;
26 	} else {
27 		trace_cachefiles_mark_failed(object, inode);
28 	}
29 
30 	return can_use;
31 }
32 
33 static bool cachefiles_mark_inode_in_use(struct cachefiles_object *object,
34 					 struct inode *inode)
35 {
36 	bool can_use;
37 
38 	inode_lock(inode);
39 	can_use = __cachefiles_mark_inode_in_use(object, inode);
40 	inode_unlock(inode);
41 	return can_use;
42 }
43 
44 /*
45  * Unmark a backing inode.  The caller must hold the inode lock.
46  */
47 static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
48 					     struct inode *inode)
49 {
50 	inode->i_flags &= ~S_KERNEL_FILE;
51 	trace_cachefiles_mark_inactive(object, inode);
52 }
53 
54 static void cachefiles_do_unmark_inode_in_use(struct cachefiles_object *object,
55 					      struct inode *inode)
56 {
57 	inode_lock(inode);
58 	__cachefiles_unmark_inode_in_use(object, inode);
59 	inode_unlock(inode);
60 }
61 
62 /*
63  * Unmark a backing inode and tell cachefilesd that there's something that can
64  * be culled.
65  */
66 void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
67 				    struct file *file)
68 {
69 	struct cachefiles_cache *cache = object->volume->cache;
70 	struct inode *inode = file_inode(file);
71 
72 	cachefiles_do_unmark_inode_in_use(object, inode);
73 
74 	if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
75 		atomic_long_add(inode->i_blocks, &cache->b_released);
76 		if (atomic_inc_return(&cache->f_released))
77 			cachefiles_state_changed(cache);
78 	}
79 }
80 
81 /*
82  * get a subdirectory
83  */
84 struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
85 					struct dentry *dir,
86 					const char *dirname,
87 					bool *_is_new)
88 {
89 	struct dentry *subdir;
90 	struct path path;
91 	int ret;
92 
93 	_enter(",,%s", dirname);
94 
95 	/* search the current directory for the element name */
96 	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
97 
98 retry:
99 	ret = cachefiles_inject_read_error();
100 	if (ret == 0)
101 		subdir = lookup_one_len(dirname, dir, strlen(dirname));
102 	else
103 		subdir = ERR_PTR(ret);
104 	trace_cachefiles_lookup(NULL, dir, subdir);
105 	if (IS_ERR(subdir)) {
106 		trace_cachefiles_vfs_error(NULL, d_backing_inode(dir),
107 					   PTR_ERR(subdir),
108 					   cachefiles_trace_lookup_error);
109 		if (PTR_ERR(subdir) == -ENOMEM)
110 			goto nomem_d_alloc;
111 		goto lookup_error;
112 	}
113 
114 	_debug("subdir -> %pd %s",
115 	       subdir, d_backing_inode(subdir) ? "positive" : "negative");
116 
117 	/* we need to create the subdir if it doesn't exist yet */
118 	if (d_is_negative(subdir)) {
119 		ret = cachefiles_has_space(cache, 1, 0,
120 					   cachefiles_has_space_for_create);
121 		if (ret < 0)
122 			goto mkdir_error;
123 
124 		_debug("attempt mkdir");
125 
126 		path.mnt = cache->mnt;
127 		path.dentry = dir;
128 		ret = security_path_mkdir(&path, subdir, 0700);
129 		if (ret < 0)
130 			goto mkdir_error;
131 		ret = cachefiles_inject_write_error();
132 		if (ret == 0)
133 			ret = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), subdir, 0700);
134 		if (ret < 0) {
135 			trace_cachefiles_vfs_error(NULL, d_inode(dir), ret,
136 						   cachefiles_trace_mkdir_error);
137 			goto mkdir_error;
138 		}
139 		trace_cachefiles_mkdir(dir, subdir);
140 
141 		if (unlikely(d_unhashed(subdir))) {
142 			cachefiles_put_directory(subdir);
143 			goto retry;
144 		}
145 		ASSERT(d_backing_inode(subdir));
146 
147 		_debug("mkdir -> %pd{ino=%lu}",
148 		       subdir, d_backing_inode(subdir)->i_ino);
149 		if (_is_new)
150 			*_is_new = true;
151 	}
152 
153 	/* Tell rmdir() it's not allowed to delete the subdir */
154 	inode_lock(d_inode(subdir));
155 	inode_unlock(d_inode(dir));
156 
157 	if (!__cachefiles_mark_inode_in_use(NULL, d_inode(subdir))) {
158 		pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
159 			  subdir, d_inode(subdir)->i_ino);
160 		goto mark_error;
161 	}
162 
163 	inode_unlock(d_inode(subdir));
164 
165 	/* we need to make sure the subdir is a directory */
166 	ASSERT(d_backing_inode(subdir));
167 
168 	if (!d_can_lookup(subdir)) {
169 		pr_err("%s is not a directory\n", dirname);
170 		ret = -EIO;
171 		goto check_error;
172 	}
173 
174 	ret = -EPERM;
175 	if (!(d_backing_inode(subdir)->i_opflags & IOP_XATTR) ||
176 	    !d_backing_inode(subdir)->i_op->lookup ||
177 	    !d_backing_inode(subdir)->i_op->mkdir ||
178 	    !d_backing_inode(subdir)->i_op->rename ||
179 	    !d_backing_inode(subdir)->i_op->rmdir ||
180 	    !d_backing_inode(subdir)->i_op->unlink)
181 		goto check_error;
182 
183 	_leave(" = [%lu]", d_backing_inode(subdir)->i_ino);
184 	return subdir;
185 
186 check_error:
187 	cachefiles_put_directory(subdir);
188 	_leave(" = %d [check]", ret);
189 	return ERR_PTR(ret);
190 
191 mark_error:
192 	inode_unlock(d_inode(subdir));
193 	dput(subdir);
194 	return ERR_PTR(-EBUSY);
195 
196 mkdir_error:
197 	inode_unlock(d_inode(dir));
198 	dput(subdir);
199 	pr_err("mkdir %s failed with error %d\n", dirname, ret);
200 	return ERR_PTR(ret);
201 
202 lookup_error:
203 	inode_unlock(d_inode(dir));
204 	ret = PTR_ERR(subdir);
205 	pr_err("Lookup %s failed with error %d\n", dirname, ret);
206 	return ERR_PTR(ret);
207 
208 nomem_d_alloc:
209 	inode_unlock(d_inode(dir));
210 	_leave(" = -ENOMEM");
211 	return ERR_PTR(-ENOMEM);
212 }
213 
214 /*
215  * Put a subdirectory.
216  */
217 void cachefiles_put_directory(struct dentry *dir)
218 {
219 	if (dir) {
220 		cachefiles_do_unmark_inode_in_use(NULL, d_inode(dir));
221 		dput(dir);
222 	}
223 }
224 
225 /*
226  * Remove a regular file from the cache.
227  */
228 static int cachefiles_unlink(struct cachefiles_cache *cache,
229 			     struct cachefiles_object *object,
230 			     struct dentry *dir, struct dentry *dentry,
231 			     enum fscache_why_object_killed why)
232 {
233 	struct path path = {
234 		.mnt	= cache->mnt,
235 		.dentry	= dir,
236 	};
237 	int ret;
238 
239 	trace_cachefiles_unlink(object, d_inode(dentry)->i_ino, why);
240 	ret = security_path_unlink(&path, dentry);
241 	if (ret < 0) {
242 		cachefiles_io_error(cache, "Unlink security error");
243 		return ret;
244 	}
245 
246 	ret = cachefiles_inject_remove_error();
247 	if (ret == 0) {
248 		ret = vfs_unlink(&nop_mnt_idmap, d_backing_inode(dir), dentry, NULL);
249 		if (ret == -EIO)
250 			cachefiles_io_error(cache, "Unlink failed");
251 	}
252 	if (ret != 0)
253 		trace_cachefiles_vfs_error(object, d_backing_inode(dir), ret,
254 					   cachefiles_trace_unlink_error);
255 	return ret;
256 }
257 
258 /*
259  * Delete an object representation from the cache
260  * - File backed objects are unlinked
261  * - Directory backed objects are stuffed into the graveyard for userspace to
262  *   delete
263  */
264 int cachefiles_bury_object(struct cachefiles_cache *cache,
265 			   struct cachefiles_object *object,
266 			   struct dentry *dir,
267 			   struct dentry *rep,
268 			   enum fscache_why_object_killed why)
269 {
270 	struct dentry *grave, *trap;
271 	struct path path, path_to_graveyard;
272 	char nbuffer[8 + 8 + 1];
273 	int ret;
274 
275 	_enter(",'%pd','%pd'", dir, rep);
276 
277 	if (rep->d_parent != dir) {
278 		inode_unlock(d_inode(dir));
279 		_leave(" = -ESTALE");
280 		return -ESTALE;
281 	}
282 
283 	/* non-directories can just be unlinked */
284 	if (!d_is_dir(rep)) {
285 		dget(rep); /* Stop the dentry being negated if it's only pinned
286 			    * by a file struct.
287 			    */
288 		ret = cachefiles_unlink(cache, object, dir, rep, why);
289 		dput(rep);
290 
291 		inode_unlock(d_inode(dir));
292 		_leave(" = %d", ret);
293 		return ret;
294 	}
295 
296 	/* directories have to be moved to the graveyard */
297 	_debug("move stale object to graveyard");
298 	inode_unlock(d_inode(dir));
299 
300 try_again:
301 	/* first step is to make up a grave dentry in the graveyard */
302 	sprintf(nbuffer, "%08x%08x",
303 		(uint32_t) ktime_get_real_seconds(),
304 		(uint32_t) atomic_inc_return(&cache->gravecounter));
305 
306 	/* do the multiway lock magic */
307 	trap = lock_rename(cache->graveyard, dir);
308 	if (IS_ERR(trap))
309 		return PTR_ERR(trap);
310 
311 	/* do some checks before getting the grave dentry */
312 	if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
313 		/* the entry was probably culled when we dropped the parent dir
314 		 * lock */
315 		unlock_rename(cache->graveyard, dir);
316 		_leave(" = 0 [culled?]");
317 		return 0;
318 	}
319 
320 	if (!d_can_lookup(cache->graveyard)) {
321 		unlock_rename(cache->graveyard, dir);
322 		cachefiles_io_error(cache, "Graveyard no longer a directory");
323 		return -EIO;
324 	}
325 
326 	if (trap == rep) {
327 		unlock_rename(cache->graveyard, dir);
328 		cachefiles_io_error(cache, "May not make directory loop");
329 		return -EIO;
330 	}
331 
332 	if (d_mountpoint(rep)) {
333 		unlock_rename(cache->graveyard, dir);
334 		cachefiles_io_error(cache, "Mountpoint in cache");
335 		return -EIO;
336 	}
337 
338 	grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
339 	if (IS_ERR(grave)) {
340 		unlock_rename(cache->graveyard, dir);
341 		trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
342 					   PTR_ERR(grave),
343 					   cachefiles_trace_lookup_error);
344 
345 		if (PTR_ERR(grave) == -ENOMEM) {
346 			_leave(" = -ENOMEM");
347 			return -ENOMEM;
348 		}
349 
350 		cachefiles_io_error(cache, "Lookup error %ld", PTR_ERR(grave));
351 		return -EIO;
352 	}
353 
354 	if (d_is_positive(grave)) {
355 		unlock_rename(cache->graveyard, dir);
356 		dput(grave);
357 		grave = NULL;
358 		cond_resched();
359 		goto try_again;
360 	}
361 
362 	if (d_mountpoint(grave)) {
363 		unlock_rename(cache->graveyard, dir);
364 		dput(grave);
365 		cachefiles_io_error(cache, "Mountpoint in graveyard");
366 		return -EIO;
367 	}
368 
369 	/* target should not be an ancestor of source */
370 	if (trap == grave) {
371 		unlock_rename(cache->graveyard, dir);
372 		dput(grave);
373 		cachefiles_io_error(cache, "May not make directory loop");
374 		return -EIO;
375 	}
376 
377 	/* attempt the rename */
378 	path.mnt = cache->mnt;
379 	path.dentry = dir;
380 	path_to_graveyard.mnt = cache->mnt;
381 	path_to_graveyard.dentry = cache->graveyard;
382 	ret = security_path_rename(&path, rep, &path_to_graveyard, grave, 0);
383 	if (ret < 0) {
384 		cachefiles_io_error(cache, "Rename security error %d", ret);
385 	} else {
386 		struct renamedata rd = {
387 			.old_mnt_idmap	= &nop_mnt_idmap,
388 			.old_dir	= d_inode(dir),
389 			.old_dentry	= rep,
390 			.new_mnt_idmap	= &nop_mnt_idmap,
391 			.new_dir	= d_inode(cache->graveyard),
392 			.new_dentry	= grave,
393 		};
394 		trace_cachefiles_rename(object, d_inode(rep)->i_ino, why);
395 		ret = cachefiles_inject_read_error();
396 		if (ret == 0)
397 			ret = vfs_rename(&rd);
398 		if (ret != 0)
399 			trace_cachefiles_vfs_error(object, d_inode(dir), ret,
400 						   cachefiles_trace_rename_error);
401 		if (ret != 0 && ret != -ENOMEM)
402 			cachefiles_io_error(cache,
403 					    "Rename failed with error %d", ret);
404 	}
405 
406 	__cachefiles_unmark_inode_in_use(object, d_inode(rep));
407 	unlock_rename(cache->graveyard, dir);
408 	dput(grave);
409 	_leave(" = 0");
410 	return 0;
411 }
412 
413 /*
414  * Delete a cache file.
415  */
416 int cachefiles_delete_object(struct cachefiles_object *object,
417 			     enum fscache_why_object_killed why)
418 {
419 	struct cachefiles_volume *volume = object->volume;
420 	struct dentry *dentry = object->file->f_path.dentry;
421 	struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash];
422 	int ret;
423 
424 	_enter(",OBJ%x{%pD}", object->debug_id, object->file);
425 
426 	/* Stop the dentry being negated if it's only pinned by a file struct. */
427 	dget(dentry);
428 
429 	inode_lock_nested(d_backing_inode(fan), I_MUTEX_PARENT);
430 	ret = cachefiles_unlink(volume->cache, object, fan, dentry, why);
431 	inode_unlock(d_backing_inode(fan));
432 	dput(dentry);
433 	return ret;
434 }
435 
436 /*
437  * Create a temporary file and leave it unattached and un-xattr'd until the
438  * time comes to discard the object from memory.
439  */
440 struct file *cachefiles_create_tmpfile(struct cachefiles_object *object)
441 {
442 	struct cachefiles_volume *volume = object->volume;
443 	struct cachefiles_cache *cache = volume->cache;
444 	const struct cred *saved_cred;
445 	struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash];
446 	struct file *file;
447 	const struct path parentpath = { .mnt = cache->mnt, .dentry = fan };
448 	uint64_t ni_size;
449 	long ret;
450 
451 
452 	cachefiles_begin_secure(cache, &saved_cred);
453 
454 	ret = cachefiles_inject_write_error();
455 	if (ret == 0) {
456 		file = kernel_tmpfile_open(&nop_mnt_idmap, &parentpath,
457 					   S_IFREG | 0600,
458 					   O_RDWR | O_LARGEFILE | O_DIRECT,
459 					   cache->cache_cred);
460 		ret = PTR_ERR_OR_ZERO(file);
461 	}
462 	if (ret) {
463 		trace_cachefiles_vfs_error(object, d_inode(fan), ret,
464 					   cachefiles_trace_tmpfile_error);
465 		if (ret == -EIO)
466 			cachefiles_io_error_obj(object, "Failed to create tmpfile");
467 		goto err;
468 	}
469 
470 	trace_cachefiles_tmpfile(object, file_inode(file));
471 
472 	/* This is a newly created file with no other possible user */
473 	if (!cachefiles_mark_inode_in_use(object, file_inode(file)))
474 		WARN_ON(1);
475 
476 	ret = cachefiles_ondemand_init_object(object);
477 	if (ret < 0)
478 		goto err_unuse;
479 
480 	ni_size = object->cookie->object_size;
481 	ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);
482 
483 	if (ni_size > 0) {
484 		trace_cachefiles_trunc(object, file_inode(file), 0, ni_size,
485 				       cachefiles_trunc_expand_tmpfile);
486 		ret = cachefiles_inject_write_error();
487 		if (ret == 0)
488 			ret = vfs_truncate(&file->f_path, ni_size);
489 		if (ret < 0) {
490 			trace_cachefiles_vfs_error(
491 				object, file_inode(file), ret,
492 				cachefiles_trace_trunc_error);
493 			goto err_unuse;
494 		}
495 	}
496 
497 	ret = -EINVAL;
498 	if (unlikely(!file->f_op->read_iter) ||
499 	    unlikely(!file->f_op->write_iter)) {
500 		fput(file);
501 		pr_notice("Cache does not support read_iter and write_iter\n");
502 		goto err_unuse;
503 	}
504 out:
505 	cachefiles_end_secure(cache, saved_cred);
506 	return file;
507 
508 err_unuse:
509 	cachefiles_do_unmark_inode_in_use(object, file_inode(file));
510 	fput(file);
511 err:
512 	file = ERR_PTR(ret);
513 	goto out;
514 }
515 
516 /*
517  * Create a new file.
518  */
519 static bool cachefiles_create_file(struct cachefiles_object *object)
520 {
521 	struct file *file;
522 	int ret;
523 
524 	ret = cachefiles_has_space(object->volume->cache, 1, 0,
525 				   cachefiles_has_space_for_create);
526 	if (ret < 0)
527 		return false;
528 
529 	file = cachefiles_create_tmpfile(object);
530 	if (IS_ERR(file))
531 		return false;
532 
533 	set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
534 	set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
535 	_debug("create -> %pD{ino=%lu}", file, file_inode(file)->i_ino);
536 	object->file = file;
537 	return true;
538 }
539 
540 /*
541  * Open an existing file, checking its attributes and replacing it if it is
542  * stale.
543  */
544 static bool cachefiles_open_file(struct cachefiles_object *object,
545 				 struct dentry *dentry)
546 {
547 	struct cachefiles_cache *cache = object->volume->cache;
548 	struct file *file;
549 	struct path path;
550 	int ret;
551 
552 	_enter("%pd", dentry);
553 
554 	if (!cachefiles_mark_inode_in_use(object, d_inode(dentry))) {
555 		pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
556 			  dentry, d_inode(dentry)->i_ino);
557 		return false;
558 	}
559 
560 	/* We need to open a file interface onto a data file now as we can't do
561 	 * it on demand because writeback called from do_exit() sees
562 	 * current->fs == NULL - which breaks d_path() called from ext4 open.
563 	 */
564 	path.mnt = cache->mnt;
565 	path.dentry = dentry;
566 	file = kernel_file_open(&path, O_RDWR | O_LARGEFILE | O_DIRECT, cache->cache_cred);
567 	if (IS_ERR(file)) {
568 		trace_cachefiles_vfs_error(object, d_backing_inode(dentry),
569 					   PTR_ERR(file),
570 					   cachefiles_trace_open_error);
571 		goto error;
572 	}
573 
574 	if (unlikely(!file->f_op->read_iter) ||
575 	    unlikely(!file->f_op->write_iter)) {
576 		pr_notice("Cache does not support read_iter and write_iter\n");
577 		goto error_fput;
578 	}
579 	_debug("file -> %pd positive", dentry);
580 
581 	ret = cachefiles_ondemand_init_object(object);
582 	if (ret < 0)
583 		goto error_fput;
584 
585 	ret = cachefiles_check_auxdata(object, file);
586 	if (ret < 0)
587 		goto check_failed;
588 
589 	clear_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &object->cookie->flags);
590 
591 	object->file = file;
592 
593 	/* Always update the atime on an object we've just looked up (this is
594 	 * used to keep track of culling, and atimes are only updated by read,
595 	 * write and readdir but not lookup or open).
596 	 */
597 	touch_atime(&file->f_path);
598 	return true;
599 
600 check_failed:
601 	fscache_cookie_lookup_negative(object->cookie);
602 	cachefiles_unmark_inode_in_use(object, file);
603 	fput(file);
604 	if (ret == -ESTALE)
605 		return cachefiles_create_file(object);
606 	return false;
607 
608 error_fput:
609 	fput(file);
610 error:
611 	cachefiles_do_unmark_inode_in_use(object, d_inode(dentry));
612 	return false;
613 }
614 
615 /*
616  * walk from the parent object to the child object through the backing
617  * filesystem, creating directories as we go
618  */
619 bool cachefiles_look_up_object(struct cachefiles_object *object)
620 {
621 	struct cachefiles_volume *volume = object->volume;
622 	struct dentry *dentry, *fan = volume->fanout[(u8)object->cookie->key_hash];
623 	int ret;
624 
625 	_enter("OBJ%x,%s,", object->debug_id, object->d_name);
626 
627 	/* Look up path "cache/vol/fanout/file". */
628 	ret = cachefiles_inject_read_error();
629 	if (ret == 0)
630 		dentry = lookup_positive_unlocked(object->d_name, fan,
631 						  object->d_name_len);
632 	else
633 		dentry = ERR_PTR(ret);
634 	trace_cachefiles_lookup(object, fan, dentry);
635 	if (IS_ERR(dentry)) {
636 		if (dentry == ERR_PTR(-ENOENT))
637 			goto new_file;
638 		if (dentry == ERR_PTR(-EIO))
639 			cachefiles_io_error_obj(object, "Lookup failed");
640 		return false;
641 	}
642 
643 	if (!d_is_reg(dentry)) {
644 		pr_err("%pd is not a file\n", dentry);
645 		inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
646 		ret = cachefiles_bury_object(volume->cache, object, fan, dentry,
647 					     FSCACHE_OBJECT_IS_WEIRD);
648 		dput(dentry);
649 		if (ret < 0)
650 			return false;
651 		goto new_file;
652 	}
653 
654 	ret = cachefiles_open_file(object, dentry);
655 	dput(dentry);
656 	if (!ret)
657 		return false;
658 
659 	_leave(" = t [%lu]", file_inode(object->file)->i_ino);
660 	return true;
661 
662 new_file:
663 	fscache_cookie_lookup_negative(object->cookie);
664 	return cachefiles_create_file(object);
665 }
666 
667 /*
668  * Attempt to link a temporary file into its rightful place in the cache.
669  */
670 bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
671 			       struct cachefiles_object *object)
672 {
673 	struct cachefiles_volume *volume = object->volume;
674 	struct dentry *dentry, *fan = volume->fanout[(u8)object->cookie->key_hash];
675 	bool success = false;
676 	int ret;
677 
678 	_enter(",%pD", object->file);
679 
680 	inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
681 	ret = cachefiles_inject_read_error();
682 	if (ret == 0)
683 		dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
684 	else
685 		dentry = ERR_PTR(ret);
686 	if (IS_ERR(dentry)) {
687 		trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
688 					   cachefiles_trace_lookup_error);
689 		_debug("lookup fail %ld", PTR_ERR(dentry));
690 		goto out_unlock;
691 	}
692 
693 	if (!d_is_negative(dentry)) {
694 		if (d_backing_inode(dentry) == file_inode(object->file)) {
695 			success = true;
696 			goto out_dput;
697 		}
698 
699 		ret = cachefiles_unlink(volume->cache, object, fan, dentry,
700 					FSCACHE_OBJECT_IS_STALE);
701 		if (ret < 0)
702 			goto out_dput;
703 
704 		dput(dentry);
705 		ret = cachefiles_inject_read_error();
706 		if (ret == 0)
707 			dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
708 		else
709 			dentry = ERR_PTR(ret);
710 		if (IS_ERR(dentry)) {
711 			trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
712 						   cachefiles_trace_lookup_error);
713 			_debug("lookup fail %ld", PTR_ERR(dentry));
714 			goto out_unlock;
715 		}
716 	}
717 
718 	ret = cachefiles_inject_read_error();
719 	if (ret == 0)
720 		ret = vfs_link(object->file->f_path.dentry, &nop_mnt_idmap,
721 			       d_inode(fan), dentry, NULL);
722 	if (ret < 0) {
723 		trace_cachefiles_vfs_error(object, d_inode(fan), ret,
724 					   cachefiles_trace_link_error);
725 		_debug("link fail %d", ret);
726 	} else {
727 		trace_cachefiles_link(object, file_inode(object->file));
728 		spin_lock(&object->lock);
729 		/* TODO: Do we want to switch the file pointer to the new dentry? */
730 		clear_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
731 		spin_unlock(&object->lock);
732 		success = true;
733 	}
734 
735 out_dput:
736 	dput(dentry);
737 out_unlock:
738 	inode_unlock(d_inode(fan));
739 	_leave(" = %u", success);
740 	return success;
741 }
742 
743 /*
744  * Look up an inode to be checked or culled.  Return -EBUSY if the inode is
745  * marked in use.
746  */
747 static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache,
748 						 struct dentry *dir,
749 						 char *filename)
750 {
751 	struct dentry *victim;
752 	int ret = -ENOENT;
753 
754 	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
755 
756 	victim = lookup_one_len(filename, dir, strlen(filename));
757 	if (IS_ERR(victim))
758 		goto lookup_error;
759 	if (d_is_negative(victim))
760 		goto lookup_put;
761 	if (d_inode(victim)->i_flags & S_KERNEL_FILE)
762 		goto lookup_busy;
763 	return victim;
764 
765 lookup_busy:
766 	ret = -EBUSY;
767 lookup_put:
768 	inode_unlock(d_inode(dir));
769 	dput(victim);
770 	return ERR_PTR(ret);
771 
772 lookup_error:
773 	inode_unlock(d_inode(dir));
774 	ret = PTR_ERR(victim);
775 	if (ret == -ENOENT)
776 		return ERR_PTR(-ESTALE); /* Probably got retired by the netfs */
777 
778 	if (ret == -EIO) {
779 		cachefiles_io_error(cache, "Lookup failed");
780 	} else if (ret != -ENOMEM) {
781 		pr_err("Internal error: %d\n", ret);
782 		ret = -EIO;
783 	}
784 
785 	return ERR_PTR(ret);
786 }
787 
788 /*
789  * Cull an object if it's not in use
790  * - called only by cache manager daemon
791  */
792 int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
793 		    char *filename)
794 {
795 	struct dentry *victim;
796 	struct inode *inode;
797 	int ret;
798 
799 	_enter(",%pd/,%s", dir, filename);
800 
801 	victim = cachefiles_lookup_for_cull(cache, dir, filename);
802 	if (IS_ERR(victim))
803 		return PTR_ERR(victim);
804 
805 	/* check to see if someone is using this object */
806 	inode = d_inode(victim);
807 	inode_lock(inode);
808 	if (inode->i_flags & S_KERNEL_FILE) {
809 		ret = -EBUSY;
810 	} else {
811 		/* Stop the cache from picking it back up */
812 		inode->i_flags |= S_KERNEL_FILE;
813 		ret = 0;
814 	}
815 	inode_unlock(inode);
816 	if (ret < 0)
817 		goto error_unlock;
818 
819 	ret = cachefiles_bury_object(cache, NULL, dir, victim,
820 				     FSCACHE_OBJECT_WAS_CULLED);
821 	if (ret < 0)
822 		goto error;
823 
824 	fscache_count_culled();
825 	dput(victim);
826 	_leave(" = 0");
827 	return 0;
828 
829 error_unlock:
830 	inode_unlock(d_inode(dir));
831 error:
832 	dput(victim);
833 	if (ret == -ENOENT)
834 		return -ESTALE; /* Probably got retired by the netfs */
835 
836 	if (ret != -ENOMEM) {
837 		pr_err("Internal error: %d\n", ret);
838 		ret = -EIO;
839 	}
840 
841 	_leave(" = %d", ret);
842 	return ret;
843 }
844 
845 /*
846  * Find out if an object is in use or not
847  * - called only by cache manager daemon
848  * - returns -EBUSY or 0 to indicate whether an object is in use or not
849  */
850 int cachefiles_check_in_use(struct cachefiles_cache *cache, struct dentry *dir,
851 			    char *filename)
852 {
853 	struct dentry *victim;
854 	int ret = 0;
855 
856 	victim = cachefiles_lookup_for_cull(cache, dir, filename);
857 	if (IS_ERR(victim))
858 		return PTR_ERR(victim);
859 
860 	inode_unlock(d_inode(dir));
861 	dput(victim);
862 	return ret;
863 }
864