1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * fs/kernfs/dir.c - kernfs directory implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 */
9
10 #include <linux/sched.h>
11 #include <linux/fs.h>
12 #include <linux/namei.h>
13 #include <linux/idr.h>
14 #include <linux/slab.h>
15 #include <linux/security.h>
16 #include <linux/hash.h>
17
18 #include "kernfs-internal.h"
19
20 static DEFINE_RWLOCK(kernfs_rename_lock); /* kn->parent and ->name */
21 /*
22 * Don't use rename_lock to piggy back on pr_cont_buf. We don't want to
23 * call pr_cont() while holding rename_lock. Because sometimes pr_cont()
24 * will perform wakeups when releasing console_sem. Holding rename_lock
25 * will introduce deadlock if the scheduler reads the kernfs_name in the
26 * wakeup path.
27 */
28 static DEFINE_SPINLOCK(kernfs_pr_cont_lock);
29 static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by pr_cont_lock */
30 static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
31
32 #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
33
34 static bool __kernfs_active(struct kernfs_node *kn)
35 {
36 return atomic_read(&kn->active) >= 0;
37 }
38
39 static bool kernfs_active(struct kernfs_node *kn)
40 {
41 lockdep_assert_held(&kernfs_root(kn)->kernfs_rwsem);
42 return __kernfs_active(kn);
43 }
44
45 static bool kernfs_lockdep(struct kernfs_node *kn)
46 {
47 #ifdef CONFIG_DEBUG_LOCK_ALLOC
48 return kn->flags & KERNFS_LOCKDEP;
49 #else
50 return false;
51 #endif
52 }
53
54 static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
55 {
56 if (!kn)
57 return strscpy(buf, "(null)", buflen);
58
59 return strscpy(buf, kn->parent ? kn->name : "/", buflen);
60 }
61
62 /* kernfs_node_depth - compute depth from @from to @to */
63 static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
64 {
65 size_t depth = 0;
66
67 while (to->parent && to != from) {
68 depth++;
69 to = to->parent;
70 }
71 return depth;
72 }
73
74 static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
75 struct kernfs_node *b)
76 {
77 size_t da, db;
78 struct kernfs_root *ra = kernfs_root(a), *rb = kernfs_root(b);
79
80 if (ra != rb)
81 return NULL;
82
83 da = kernfs_depth(ra->kn, a);
84 db = kernfs_depth(rb->kn, b);
85
86 while (da > db) {
87 a = a->parent;
88 da--;
89 }
90 while (db > da) {
91 b = b->parent;
92 db--;
93 }
94
95 /* worst case b and a will be the same at root */
96 while (b != a) {
97 b = b->parent;
98 a = a->parent;
99 }
100
101 return a;
102 }
103
104 /**
105 * kernfs_path_from_node_locked - find a pseudo-absolute path to @kn_to,
106 * where kn_from is treated as root of the path.
107 * @kn_from: kernfs node which should be treated as root for the path
108 * @kn_to: kernfs node to which path is needed
109 * @buf: buffer to copy the path into
110 * @buflen: size of @buf
111 *
112 * We need to handle couple of scenarios here:
113 * [1] when @kn_from is an ancestor of @kn_to at some level
114 * kn_from: /n1/n2/n3
115 * kn_to: /n1/n2/n3/n4/n5
116 * result: /n4/n5
117 *
118 * [2] when @kn_from is on a different hierarchy and we need to find common
119 * ancestor between @kn_from and @kn_to.
120 * kn_from: /n1/n2/n3/n4
121 * kn_to: /n1/n2/n5
122 * result: /../../n5
123 * OR
124 * kn_from: /n1/n2/n3/n4/n5 [depth=5]
125 * kn_to: /n1/n2/n3 [depth=3]
126 * result: /../..
127 *
128 * [3] when @kn_to is %NULL result will be "(null)"
129 *
130 * Return: the length of the constructed path. If the path would have been
131 * greater than @buflen, @buf contains the truncated path with the trailing
132 * '\0'. On error, -errno is returned.
133 */
134 static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
135 struct kernfs_node *kn_from,
136 char *buf, size_t buflen)
137 {
138 struct kernfs_node *kn, *common;
139 const char parent_str[] = "/..";
140 size_t depth_from, depth_to, len = 0;
141 ssize_t copied;
142 int i, j;
143
144 if (!kn_to)
145 return strscpy(buf, "(null)", buflen);
146
147 if (!kn_from)
148 kn_from = kernfs_root(kn_to)->kn;
149
150 if (kn_from == kn_to)
151 return strscpy(buf, "/", buflen);
152
153 common = kernfs_common_ancestor(kn_from, kn_to);
154 if (WARN_ON(!common))
155 return -EINVAL;
156
157 depth_to = kernfs_depth(common, kn_to);
158 depth_from = kernfs_depth(common, kn_from);
159
160 buf[0] = '\0';
161
162 for (i = 0; i < depth_from; i++) {
163 copied = strscpy(buf + len, parent_str, buflen - len);
164 if (copied < 0)
165 return copied;
166 len += copied;
167 }
168
169 /* Calculate how many bytes we need for the rest */
170 for (i = depth_to - 1; i >= 0; i--) {
171 for (kn = kn_to, j = 0; j < i; j++)
172 kn = kn->parent;
173
174 len += scnprintf(buf + len, buflen - len, "/%s", kn->name);
175 }
176
177 return len;
178 }
179
180 /**
181 * kernfs_name - obtain the name of a given node
182 * @kn: kernfs_node of interest
183 * @buf: buffer to copy @kn's name into
184 * @buflen: size of @buf
185 *
186 * Copies the name of @kn into @buf of @buflen bytes. The behavior is
187 * similar to strscpy().
188 *
189 * Fills buffer with "(null)" if @kn is %NULL.
190 *
191 * Return: the resulting length of @buf. If @buf isn't long enough,
192 * it's filled up to @buflen-1 and nul terminated, and returns -E2BIG.
193 *
194 * This function can be called from any context.
195 */
196 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
197 {
198 unsigned long flags;
199 int ret;
200
201 read_lock_irqsave(&kernfs_rename_lock, flags);
202 ret = kernfs_name_locked(kn, buf, buflen);
203 read_unlock_irqrestore(&kernfs_rename_lock, flags);
204 return ret;
205 }
206
207 /**
208 * kernfs_path_from_node - build path of node @to relative to @from.
209 * @from: parent kernfs_node relative to which we need to build the path
210 * @to: kernfs_node of interest
211 * @buf: buffer to copy @to's path into
212 * @buflen: size of @buf
213 *
214 * Builds @to's path relative to @from in @buf. @from and @to must
215 * be on the same kernfs-root. If @from is not parent of @to, then a relative
216 * path (which includes '..'s) as needed to reach from @from to @to is
217 * returned.
218 *
219 * Return: the length of the constructed path. If the path would have been
220 * greater than @buflen, @buf contains the truncated path with the trailing
221 * '\0'. On error, -errno is returned.
222 */
223 int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
224 char *buf, size_t buflen)
225 {
226 unsigned long flags;
227 int ret;
228
229 read_lock_irqsave(&kernfs_rename_lock, flags);
230 ret = kernfs_path_from_node_locked(to, from, buf, buflen);
231 read_unlock_irqrestore(&kernfs_rename_lock, flags);
232 return ret;
233 }
234 EXPORT_SYMBOL_GPL(kernfs_path_from_node);
235
236 /**
237 * pr_cont_kernfs_name - pr_cont name of a kernfs_node
238 * @kn: kernfs_node of interest
239 *
240 * This function can be called from any context.
241 */
242 void pr_cont_kernfs_name(struct kernfs_node *kn)
243 {
244 unsigned long flags;
245
246 spin_lock_irqsave(&kernfs_pr_cont_lock, flags);
247
248 kernfs_name(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf));
249 pr_cont("%s", kernfs_pr_cont_buf);
250
251 spin_unlock_irqrestore(&kernfs_pr_cont_lock, flags);
252 }
253
254 /**
255 * pr_cont_kernfs_path - pr_cont path of a kernfs_node
256 * @kn: kernfs_node of interest
257 *
258 * This function can be called from any context.
259 */
260 void pr_cont_kernfs_path(struct kernfs_node *kn)
261 {
262 unsigned long flags;
263 int sz;
264
265 spin_lock_irqsave(&kernfs_pr_cont_lock, flags);
266
267 sz = kernfs_path_from_node(kn, NULL, kernfs_pr_cont_buf,
268 sizeof(kernfs_pr_cont_buf));
269 if (sz < 0) {
270 if (sz == -E2BIG)
271 pr_cont("(name too long)");
272 else
273 pr_cont("(error)");
274 goto out;
275 }
276
277 pr_cont("%s", kernfs_pr_cont_buf);
278
279 out:
280 spin_unlock_irqrestore(&kernfs_pr_cont_lock, flags);
281 }
282
283 /**
284 * kernfs_get_parent - determine the parent node and pin it
285 * @kn: kernfs_node of interest
286 *
287 * Determines @kn's parent, pins and returns it. This function can be
288 * called from any context.
289 *
290 * Return: parent node of @kn
291 */
292 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
293 {
294 struct kernfs_node *parent;
295 unsigned long flags;
296
297 read_lock_irqsave(&kernfs_rename_lock, flags);
298 parent = kn->parent;
299 kernfs_get(parent);
300 read_unlock_irqrestore(&kernfs_rename_lock, flags);
301
302 return parent;
303 }
304
305 /**
306 * kernfs_name_hash - calculate hash of @ns + @name
307 * @name: Null terminated string to hash
308 * @ns: Namespace tag to hash
309 *
310 * Return: 31-bit hash of ns + name (so it fits in an off_t)
311 */
312 static unsigned int kernfs_name_hash(const char *name, const void *ns)
313 {
314 unsigned long hash = init_name_hash(ns);
315 unsigned int len = strlen(name);
316 while (len--)
317 hash = partial_name_hash(*name++, hash);
318 hash = end_name_hash(hash);
319 hash &= 0x7fffffffU;
320 /* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
321 if (hash < 2)
322 hash += 2;
323 if (hash >= INT_MAX)
324 hash = INT_MAX - 1;
325 return hash;
326 }
327
328 static int kernfs_name_compare(unsigned int hash, const char *name,
329 const void *ns, const struct kernfs_node *kn)
330 {
331 if (hash < kn->hash)
332 return -1;
333 if (hash > kn->hash)
334 return 1;
335 if (ns < kn->ns)
336 return -1;
337 if (ns > kn->ns)
338 return 1;
339 return strcmp(name, kn->name);
340 }
341
342 static int kernfs_sd_compare(const struct kernfs_node *left,
343 const struct kernfs_node *right)
344 {
345 return kernfs_name_compare(left->hash, left->name, left->ns, right);
346 }
347
348 /**
349 * kernfs_link_sibling - link kernfs_node into sibling rbtree
350 * @kn: kernfs_node of interest
351 *
352 * Link @kn into its sibling rbtree which starts from
353 * @kn->parent->dir.children.
354 *
355 * Locking:
356 * kernfs_rwsem held exclusive
357 *
358 * Return:
359 * %0 on success, -EEXIST on failure.
360 */
361 static int kernfs_link_sibling(struct kernfs_node *kn)
362 {
363 struct rb_node **node = &kn->parent->dir.children.rb_node;
364 struct rb_node *parent = NULL;
365
366 while (*node) {
367 struct kernfs_node *pos;
368 int result;
369
370 pos = rb_to_kn(*node);
371 parent = *node;
372 result = kernfs_sd_compare(kn, pos);
373 if (result < 0)
374 node = &pos->rb.rb_left;
375 else if (result > 0)
376 node = &pos->rb.rb_right;
377 else
378 return -EEXIST;
379 }
380
381 /* add new node and rebalance the tree */
382 rb_link_node(&kn->rb, parent, node);
383 rb_insert_color(&kn->rb, &kn->parent->dir.children);
384
385 /* successfully added, account subdir number */
386 down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
387 if (kernfs_type(kn) == KERNFS_DIR)
388 kn->parent->dir.subdirs++;
389 kernfs_inc_rev(kn->parent);
390 up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
391
392 return 0;
393 }
394
395 /**
396 * kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
397 * @kn: kernfs_node of interest
398 *
399 * Try to unlink @kn from its sibling rbtree which starts from
400 * kn->parent->dir.children.
401 *
402 * Return: %true if @kn was actually removed,
403 * %false if @kn wasn't on the rbtree.
404 *
405 * Locking:
406 * kernfs_rwsem held exclusive
407 */
408 static bool kernfs_unlink_sibling(struct kernfs_node *kn)
409 {
410 if (RB_EMPTY_NODE(&kn->rb))
411 return false;
412
413 down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
414 if (kernfs_type(kn) == KERNFS_DIR)
415 kn->parent->dir.subdirs--;
416 kernfs_inc_rev(kn->parent);
417 up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
418
419 rb_erase(&kn->rb, &kn->parent->dir.children);
420 RB_CLEAR_NODE(&kn->rb);
421 return true;
422 }
423
424 /**
425 * kernfs_get_active - get an active reference to kernfs_node
426 * @kn: kernfs_node to get an active reference to
427 *
428 * Get an active reference of @kn. This function is noop if @kn
429 * is %NULL.
430 *
431 * Return:
432 * Pointer to @kn on success, %NULL on failure.
433 */
434 struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
435 {
436 if (unlikely(!kn))
437 return NULL;
438
439 if (!atomic_inc_unless_negative(&kn->active))
440 return NULL;
441
442 if (kernfs_lockdep(kn))
443 rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
444 return kn;
445 }
446
447 /**
448 * kernfs_put_active - put an active reference to kernfs_node
449 * @kn: kernfs_node to put an active reference to
450 *
451 * Put an active reference to @kn. This function is noop if @kn
452 * is %NULL.
453 */
454 void kernfs_put_active(struct kernfs_node *kn)
455 {
456 int v;
457
458 if (unlikely(!kn))
459 return;
460
461 if (kernfs_lockdep(kn))
462 rwsem_release(&kn->dep_map, _RET_IP_);
463 v = atomic_dec_return(&kn->active);
464 if (likely(v != KN_DEACTIVATED_BIAS))
465 return;
466
467 wake_up_all(&kernfs_root(kn)->deactivate_waitq);
468 }
469
470 /**
471 * kernfs_drain - drain kernfs_node
472 * @kn: kernfs_node to drain
473 *
474 * Drain existing usages and nuke all existing mmaps of @kn. Multiple
475 * removers may invoke this function concurrently on @kn and all will
476 * return after draining is complete.
477 */
478 static void kernfs_drain(struct kernfs_node *kn)
479 __releases(&kernfs_root(kn)->kernfs_rwsem)
480 __acquires(&kernfs_root(kn)->kernfs_rwsem)
481 {
482 struct kernfs_root *root = kernfs_root(kn);
483
484 lockdep_assert_held_write(&root->kernfs_rwsem);
485 WARN_ON_ONCE(kernfs_active(kn));
486
487 /*
488 * Skip draining if already fully drained. This avoids draining and its
489 * lockdep annotations for nodes which have never been activated
490 * allowing embedding kernfs_remove() in create error paths without
491 * worrying about draining.
492 */
493 if (atomic_read(&kn->active) == KN_DEACTIVATED_BIAS &&
494 !kernfs_should_drain_open_files(kn))
495 return;
496
497 up_write(&root->kernfs_rwsem);
498
499 if (kernfs_lockdep(kn)) {
500 rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
501 if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
502 lock_contended(&kn->dep_map, _RET_IP_);
503 }
504
505 wait_event(root->deactivate_waitq,
506 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
507
508 if (kernfs_lockdep(kn)) {
509 lock_acquired(&kn->dep_map, _RET_IP_);
510 rwsem_release(&kn->dep_map, _RET_IP_);
511 }
512
513 if (kernfs_should_drain_open_files(kn))
514 kernfs_drain_open_files(kn);
515
516 down_write(&root->kernfs_rwsem);
517 }
518
519 /**
520 * kernfs_get - get a reference count on a kernfs_node
521 * @kn: the target kernfs_node
522 */
523 void kernfs_get(struct kernfs_node *kn)
524 {
525 if (kn) {
526 WARN_ON(!atomic_read(&kn->count));
527 atomic_inc(&kn->count);
528 }
529 }
530 EXPORT_SYMBOL_GPL(kernfs_get);
531
532 static void kernfs_free_rcu(struct rcu_head *rcu)
533 {
534 struct kernfs_node *kn = container_of(rcu, struct kernfs_node, rcu);
535
536 kfree_const(kn->name);
537
538 if (kn->iattr) {
539 simple_xattrs_free(&kn->iattr->xattrs, NULL);
540 kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
541 }
542
543 kmem_cache_free(kernfs_node_cache, kn);
544 }
545
546 /**
547 * kernfs_put - put a reference count on a kernfs_node
548 * @kn: the target kernfs_node
549 *
550 * Put a reference count of @kn and destroy it if it reached zero.
551 */
552 void kernfs_put(struct kernfs_node *kn)
553 {
554 struct kernfs_node *parent;
555 struct kernfs_root *root;
556
557 if (!kn || !atomic_dec_and_test(&kn->count))
558 return;
559 root = kernfs_root(kn);
560 repeat:
561 /*
562 * Moving/renaming is always done while holding reference.
563 * kn->parent won't change beneath us.
564 */
565 parent = kn->parent;
566
567 WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
568 "kernfs_put: %s/%s: released with incorrect active_ref %d\n",
569 parent ? parent->name : "", kn->name, atomic_read(&kn->active));
570
571 if (kernfs_type(kn) == KERNFS_LINK)
572 kernfs_put(kn->symlink.target_kn);
573
574 spin_lock(&kernfs_idr_lock);
575 idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
576 spin_unlock(&kernfs_idr_lock);
577
578 call_rcu(&kn->rcu, kernfs_free_rcu);
579
580 kn = parent;
581 if (kn) {
582 if (atomic_dec_and_test(&kn->count))
583 goto repeat;
584 } else {
585 /* just released the root kn, free @root too */
586 idr_destroy(&root->ino_idr);
587 kfree_rcu(root, rcu);
588 }
589 }
590 EXPORT_SYMBOL_GPL(kernfs_put);
591
592 /**
593 * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
594 * @dentry: the dentry in question
595 *
596 * Return: the kernfs_node associated with @dentry. If @dentry is not a
597 * kernfs one, %NULL is returned.
598 *
599 * While the returned kernfs_node will stay accessible as long as @dentry
600 * is accessible, the returned node can be in any state and the caller is
601 * fully responsible for determining what's accessible.
602 */
603 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
604 {
605 if (dentry->d_sb->s_op == &kernfs_sops)
606 return kernfs_dentry_node(dentry);
607 return NULL;
608 }
609
610 static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
611 struct kernfs_node *parent,
612 const char *name, umode_t mode,
613 kuid_t uid, kgid_t gid,
614 unsigned flags)
615 {
616 struct kernfs_node *kn;
617 u32 id_highbits;
618 int ret;
619
620 name = kstrdup_const(name, GFP_KERNEL);
621 if (!name)
622 return NULL;
623
624 kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
625 if (!kn)
626 goto err_out1;
627
628 idr_preload(GFP_KERNEL);
629 spin_lock(&kernfs_idr_lock);
630 ret = idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
631 if (ret >= 0 && ret < root->last_id_lowbits)
632 root->id_highbits++;
633 id_highbits = root->id_highbits;
634 root->last_id_lowbits = ret;
635 spin_unlock(&kernfs_idr_lock);
636 idr_preload_end();
637 if (ret < 0)
638 goto err_out2;
639
640 kn->id = (u64)id_highbits << 32 | ret;
641
642 atomic_set(&kn->count, 1);
643 atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
644 RB_CLEAR_NODE(&kn->rb);
645
646 kn->name = name;
647 kn->mode = mode;
648 kn->flags = flags;
649
650 if (!uid_eq(uid, GLOBAL_ROOT_UID) || !gid_eq(gid, GLOBAL_ROOT_GID)) {
651 struct iattr iattr = {
652 .ia_valid = ATTR_UID | ATTR_GID,
653 .ia_uid = uid,
654 .ia_gid = gid,
655 };
656
657 ret = __kernfs_setattr(kn, &iattr);
658 if (ret < 0)
659 goto err_out3;
660 }
661
662 if (parent) {
663 ret = security_kernfs_init_security(parent, kn);
664 if (ret)
665 goto err_out3;
666 }
667
668 return kn;
669
670 err_out3:
671 spin_lock(&kernfs_idr_lock);
672 idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
673 spin_unlock(&kernfs_idr_lock);
674 err_out2:
675 kmem_cache_free(kernfs_node_cache, kn);
676 err_out1:
677 kfree_const(name);
678 return NULL;
679 }
680
681 struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
682 const char *name, umode_t mode,
683 kuid_t uid, kgid_t gid,
684 unsigned flags)
685 {
686 struct kernfs_node *kn;
687
688 if (parent->mode & S_ISGID) {
689 /* this code block imitates inode_init_owner() for
690 * kernfs
691 */
692
693 if (parent->iattr)
694 gid = parent->iattr->ia_gid;
695
696 if (flags & KERNFS_DIR)
697 mode |= S_ISGID;
698 }
699
700 kn = __kernfs_new_node(kernfs_root(parent), parent,
701 name, mode, uid, gid, flags);
702 if (kn) {
703 kernfs_get(parent);
704 kn->parent = parent;
705 }
706 return kn;
707 }
708
709 /*
710 * kernfs_find_and_get_node_by_id - get kernfs_node from node id
711 * @root: the kernfs root
712 * @id: the target node id
713 *
714 * @id's lower 32bits encode ino and upper gen. If the gen portion is
715 * zero, all generations are matched.
716 *
717 * Return: %NULL on failure,
718 * otherwise a kernfs node with reference counter incremented.
719 */
720 struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
721 u64 id)
722 {
723 struct kernfs_node *kn;
724 ino_t ino = kernfs_id_ino(id);
725 u32 gen = kernfs_id_gen(id);
726
727 rcu_read_lock();
728
729 kn = idr_find(&root->ino_idr, (u32)ino);
730 if (!kn)
731 goto err_unlock;
732
733 if (sizeof(ino_t) >= sizeof(u64)) {
734 /* we looked up with the low 32bits, compare the whole */
735 if (kernfs_ino(kn) != ino)
736 goto err_unlock;
737 } else {
738 /* 0 matches all generations */
739 if (unlikely(gen && kernfs_gen(kn) != gen))
740 goto err_unlock;
741 }
742
743 /*
744 * We should fail if @kn has never been activated and guarantee success
745 * if the caller knows that @kn is active. Both can be achieved by
746 * __kernfs_active() which tests @kn->active without kernfs_rwsem.
747 */
748 if (unlikely(!__kernfs_active(kn) || !atomic_inc_not_zero(&kn->count)))
749 goto err_unlock;
750
751 rcu_read_unlock();
752 return kn;
753 err_unlock:
754 rcu_read_unlock();
755 return NULL;
756 }
757
758 /**
759 * kernfs_add_one - add kernfs_node to parent without warning
760 * @kn: kernfs_node to be added
761 *
762 * The caller must already have initialized @kn->parent. This
763 * function increments nlink of the parent's inode if @kn is a
764 * directory and link into the children list of the parent.
765 *
766 * Return:
767 * %0 on success, -EEXIST if entry with the given name already
768 * exists.
769 */
770 int kernfs_add_one(struct kernfs_node *kn)
771 {
772 struct kernfs_node *parent = kn->parent;
773 struct kernfs_root *root = kernfs_root(parent);
774 struct kernfs_iattrs *ps_iattr;
775 bool has_ns;
776 int ret;
777
778 down_write(&root->kernfs_rwsem);
779
780 ret = -EINVAL;
781 has_ns = kernfs_ns_enabled(parent);
782 if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
783 has_ns ? "required" : "invalid", parent->name, kn->name))
784 goto out_unlock;
785
786 if (kernfs_type(parent) != KERNFS_DIR)
787 goto out_unlock;
788
789 ret = -ENOENT;
790 if (parent->flags & (KERNFS_REMOVING | KERNFS_EMPTY_DIR))
791 goto out_unlock;
792
793 kn->hash = kernfs_name_hash(kn->name, kn->ns);
794
795 ret = kernfs_link_sibling(kn);
796 if (ret)
797 goto out_unlock;
798
799 /* Update timestamps on the parent */
800 down_write(&root->kernfs_iattr_rwsem);
801
802 ps_iattr = parent->iattr;
803 if (ps_iattr) {
804 ktime_get_real_ts64(&ps_iattr->ia_ctime);
805 ps_iattr->ia_mtime = ps_iattr->ia_ctime;
806 }
807
808 up_write(&root->kernfs_iattr_rwsem);
809 up_write(&root->kernfs_rwsem);
810
811 /*
812 * Activate the new node unless CREATE_DEACTIVATED is requested.
813 * If not activated here, the kernfs user is responsible for
814 * activating the node with kernfs_activate(). A node which hasn't
815 * been activated is not visible to userland and its removal won't
816 * trigger deactivation.
817 */
818 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
819 kernfs_activate(kn);
820 return 0;
821
822 out_unlock:
823 up_write(&root->kernfs_rwsem);
824 return ret;
825 }
826
827 /**
828 * kernfs_find_ns - find kernfs_node with the given name
829 * @parent: kernfs_node to search under
830 * @name: name to look for
831 * @ns: the namespace tag to use
832 *
833 * Look for kernfs_node with name @name under @parent.
834 *
835 * Return: pointer to the found kernfs_node on success, %NULL on failure.
836 */
837 static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
838 const unsigned char *name,
839 const void *ns)
840 {
841 struct rb_node *node = parent->dir.children.rb_node;
842 bool has_ns = kernfs_ns_enabled(parent);
843 unsigned int hash;
844
845 lockdep_assert_held(&kernfs_root(parent)->kernfs_rwsem);
846
847 if (has_ns != (bool)ns) {
848 WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
849 has_ns ? "required" : "invalid", parent->name, name);
850 return NULL;
851 }
852
853 hash = kernfs_name_hash(name, ns);
854 while (node) {
855 struct kernfs_node *kn;
856 int result;
857
858 kn = rb_to_kn(node);
859 result = kernfs_name_compare(hash, name, ns, kn);
860 if (result < 0)
861 node = node->rb_left;
862 else if (result > 0)
863 node = node->rb_right;
864 else
865 return kn;
866 }
867 return NULL;
868 }
869
870 static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
871 const unsigned char *path,
872 const void *ns)
873 {
874 ssize_t len;
875 char *p, *name;
876
877 lockdep_assert_held_read(&kernfs_root(parent)->kernfs_rwsem);
878
879 spin_lock_irq(&kernfs_pr_cont_lock);
880
881 len = strscpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
882
883 if (len < 0) {
884 spin_unlock_irq(&kernfs_pr_cont_lock);
885 return NULL;
886 }
887
888 p = kernfs_pr_cont_buf;
889
890 while ((name = strsep(&p, "/")) && parent) {
891 if (*name == '\0')
892 continue;
893 parent = kernfs_find_ns(parent, name, ns);
894 }
895
896 spin_unlock_irq(&kernfs_pr_cont_lock);
897
898 return parent;
899 }
900
901 /**
902 * kernfs_find_and_get_ns - find and get kernfs_node with the given name
903 * @parent: kernfs_node to search under
904 * @name: name to look for
905 * @ns: the namespace tag to use
906 *
907 * Look for kernfs_node with name @name under @parent and get a reference
908 * if found. This function may sleep.
909 *
910 * Return: pointer to the found kernfs_node on success, %NULL on failure.
911 */
912 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
913 const char *name, const void *ns)
914 {
915 struct kernfs_node *kn;
916 struct kernfs_root *root = kernfs_root(parent);
917
918 down_read(&root->kernfs_rwsem);
919 kn = kernfs_find_ns(parent, name, ns);
920 kernfs_get(kn);
921 up_read(&root->kernfs_rwsem);
922
923 return kn;
924 }
925 EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
926
927 /**
928 * kernfs_walk_and_get_ns - find and get kernfs_node with the given path
929 * @parent: kernfs_node to search under
930 * @path: path to look for
931 * @ns: the namespace tag to use
932 *
933 * Look for kernfs_node with path @path under @parent and get a reference
934 * if found. This function may sleep.
935 *
936 * Return: pointer to the found kernfs_node on success, %NULL on failure.
937 */
938 struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
939 const char *path, const void *ns)
940 {
941 struct kernfs_node *kn;
942 struct kernfs_root *root = kernfs_root(parent);
943
944 down_read(&root->kernfs_rwsem);
945 kn = kernfs_walk_ns(parent, path, ns);
946 kernfs_get(kn);
947 up_read(&root->kernfs_rwsem);
948
949 return kn;
950 }
951
952 /**
953 * kernfs_create_root - create a new kernfs hierarchy
954 * @scops: optional syscall operations for the hierarchy
955 * @flags: KERNFS_ROOT_* flags
956 * @priv: opaque data associated with the new directory
957 *
958 * Return: the root of the new hierarchy on success, ERR_PTR() value on
959 * failure.
960 */
961 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
962 unsigned int flags, void *priv)
963 {
964 struct kernfs_root *root;
965 struct kernfs_node *kn;
966
967 root = kzalloc(sizeof(*root), GFP_KERNEL);
968 if (!root)
969 return ERR_PTR(-ENOMEM);
970
971 idr_init(&root->ino_idr);
972 init_rwsem(&root->kernfs_rwsem);
973 init_rwsem(&root->kernfs_iattr_rwsem);
974 init_rwsem(&root->kernfs_supers_rwsem);
975 INIT_LIST_HEAD(&root->supers);
976
977 /*
978 * On 64bit ino setups, id is ino. On 32bit, low 32bits are ino.
979 * High bits generation. The starting value for both ino and
980 * genenration is 1. Initialize upper 32bit allocation
981 * accordingly.
982 */
983 if (sizeof(ino_t) >= sizeof(u64))
984 root->id_highbits = 0;
985 else
986 root->id_highbits = 1;
987
988 kn = __kernfs_new_node(root, NULL, "", S_IFDIR | S_IRUGO | S_IXUGO,
989 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
990 KERNFS_DIR);
991 if (!kn) {
992 idr_destroy(&root->ino_idr);
993 kfree(root);
994 return ERR_PTR(-ENOMEM);
995 }
996
997 kn->priv = priv;
998 kn->dir.root = root;
999
1000 root->syscall_ops = scops;
1001 root->flags = flags;
1002 root->kn = kn;
1003 init_waitqueue_head(&root->deactivate_waitq);
1004
1005 if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
1006 kernfs_activate(kn);
1007
1008 return root;
1009 }
1010
1011 /**
1012 * kernfs_destroy_root - destroy a kernfs hierarchy
1013 * @root: root of the hierarchy to destroy
1014 *
1015 * Destroy the hierarchy anchored at @root by removing all existing
1016 * directories and destroying @root.
1017 */
1018 void kernfs_destroy_root(struct kernfs_root *root)
1019 {
1020 /*
1021 * kernfs_remove holds kernfs_rwsem from the root so the root
1022 * shouldn't be freed during the operation.
1023 */
1024 kernfs_get(root->kn);
1025 kernfs_remove(root->kn);
1026 kernfs_put(root->kn); /* will also free @root */
1027 }
1028
1029 /**
1030 * kernfs_root_to_node - return the kernfs_node associated with a kernfs_root
1031 * @root: root to use to lookup
1032 *
1033 * Return: @root's kernfs_node
1034 */
1035 struct kernfs_node *kernfs_root_to_node(struct kernfs_root *root)
1036 {
1037 return root->kn;
1038 }
1039
1040 /**
1041 * kernfs_create_dir_ns - create a directory
1042 * @parent: parent in which to create a new directory
1043 * @name: name of the new directory
1044 * @mode: mode of the new directory
1045 * @uid: uid of the new directory
1046 * @gid: gid of the new directory
1047 * @priv: opaque data associated with the new directory
1048 * @ns: optional namespace tag of the directory
1049 *
1050 * Return: the created node on success, ERR_PTR() value on failure.
1051 */
1052 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
1053 const char *name, umode_t mode,
1054 kuid_t uid, kgid_t gid,
1055 void *priv, const void *ns)
1056 {
1057 struct kernfs_node *kn;
1058 int rc;
1059
1060 /* allocate */
1061 kn = kernfs_new_node(parent, name, mode | S_IFDIR,
1062 uid, gid, KERNFS_DIR);
1063 if (!kn)
1064 return ERR_PTR(-ENOMEM);
1065
1066 kn->dir.root = parent->dir.root;
1067 kn->ns = ns;
1068 kn->priv = priv;
1069
1070 /* link in */
1071 rc = kernfs_add_one(kn);
1072 if (!rc)
1073 return kn;
1074
1075 kernfs_put(kn);
1076 return ERR_PTR(rc);
1077 }
1078
1079 /**
1080 * kernfs_create_empty_dir - create an always empty directory
1081 * @parent: parent in which to create a new directory
1082 * @name: name of the new directory
1083 *
1084 * Return: the created node on success, ERR_PTR() value on failure.
1085 */
1086 struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
1087 const char *name)
1088 {
1089 struct kernfs_node *kn;
1090 int rc;
1091
1092 /* allocate */
1093 kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR,
1094 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, KERNFS_DIR);
1095 if (!kn)
1096 return ERR_PTR(-ENOMEM);
1097
1098 kn->flags |= KERNFS_EMPTY_DIR;
1099 kn->dir.root = parent->dir.root;
1100 kn->ns = NULL;
1101 kn->priv = NULL;
1102
1103 /* link in */
1104 rc = kernfs_add_one(kn);
1105 if (!rc)
1106 return kn;
1107
1108 kernfs_put(kn);
1109 return ERR_PTR(rc);
1110 }
1111
1112 static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
1113 {
1114 struct kernfs_node *kn;
1115 struct kernfs_root *root;
1116
1117 if (flags & LOOKUP_RCU)
1118 return -ECHILD;
1119
1120 /* Negative hashed dentry? */
1121 if (d_really_is_negative(dentry)) {
1122 struct kernfs_node *parent;
1123
1124 /* If the kernfs parent node has changed discard and
1125 * proceed to ->lookup.
1126 *
1127 * There's nothing special needed here when getting the
1128 * dentry parent, even if a concurrent rename is in
1129 * progress. That's because the dentry is negative so
1130 * it can only be the target of the rename and it will
1131 * be doing a d_move() not a replace. Consequently the
1132 * dentry d_parent won't change over the d_move().
1133 *
1134 * Also kernfs negative dentries transitioning from
1135 * negative to positive during revalidate won't happen
1136 * because they are invalidated on containing directory
1137 * changes and the lookup re-done so that a new positive
1138 * dentry can be properly created.
1139 */
1140 root = kernfs_root_from_sb(dentry->d_sb);
1141 down_read(&root->kernfs_rwsem);
1142 parent = kernfs_dentry_node(dentry->d_parent);
1143 if (parent) {
1144 if (kernfs_dir_changed(parent, dentry)) {
1145 up_read(&root->kernfs_rwsem);
1146 return 0;
1147 }
1148 }
1149 up_read(&root->kernfs_rwsem);
1150
1151 /* The kernfs parent node hasn't changed, leave the
1152 * dentry negative and return success.
1153 */
1154 return 1;
1155 }
1156
1157 kn = kernfs_dentry_node(dentry);
1158 root = kernfs_root(kn);
1159 down_read(&root->kernfs_rwsem);
1160
1161 /* The kernfs node has been deactivated */
1162 if (!kernfs_active(kn))
1163 goto out_bad;
1164
1165 /* The kernfs node has been moved? */
1166 if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
1167 goto out_bad;
1168
1169 /* The kernfs node has been renamed */
1170 if (strcmp(dentry->d_name.name, kn->name) != 0)
1171 goto out_bad;
1172
1173 /* The kernfs node has been moved to a different namespace */
1174 if (kn->parent && kernfs_ns_enabled(kn->parent) &&
1175 kernfs_info(dentry->d_sb)->ns != kn->ns)
1176 goto out_bad;
1177
1178 up_read(&root->kernfs_rwsem);
1179 return 1;
1180 out_bad:
1181 up_read(&root->kernfs_rwsem);
1182 return 0;
1183 }
1184
1185 const struct dentry_operations kernfs_dops = {
1186 .d_revalidate = kernfs_dop_revalidate,
1187 };
1188
1189 static struct dentry *kernfs_iop_lookup(struct inode *dir,
1190 struct dentry *dentry,
1191 unsigned int flags)
1192 {
1193 struct kernfs_node *parent = dir->i_private;
1194 struct kernfs_node *kn;
1195 struct kernfs_root *root;
1196 struct inode *inode = NULL;
1197 const void *ns = NULL;
1198
1199 root = kernfs_root(parent);
1200 down_read(&root->kernfs_rwsem);
1201 if (kernfs_ns_enabled(parent))
1202 ns = kernfs_info(dir->i_sb)->ns;
1203
1204 kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
1205 /* attach dentry and inode */
1206 if (kn) {
1207 /* Inactive nodes are invisible to the VFS so don't
1208 * create a negative.
1209 */
1210 if (!kernfs_active(kn)) {
1211 up_read(&root->kernfs_rwsem);
1212 return NULL;
1213 }
1214 inode = kernfs_get_inode(dir->i_sb, kn);
1215 if (!inode)
1216 inode = ERR_PTR(-ENOMEM);
1217 }
1218 /*
1219 * Needed for negative dentry validation.
1220 * The negative dentry can be created in kernfs_iop_lookup()
1221 * or transforms from positive dentry in dentry_unlink_inode()
1222 * called from vfs_rmdir().
1223 */
1224 if (!IS_ERR(inode))
1225 kernfs_set_rev(parent, dentry);
1226 up_read(&root->kernfs_rwsem);
1227
1228 /* instantiate and hash (possibly negative) dentry */
1229 return d_splice_alias(inode, dentry);
1230 }
1231
1232 static int kernfs_iop_mkdir(struct mnt_idmap *idmap,
1233 struct inode *dir, struct dentry *dentry,
1234 umode_t mode)
1235 {
1236 struct kernfs_node *parent = dir->i_private;
1237 struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
1238 int ret;
1239
1240 if (!scops || !scops->mkdir)
1241 return -EPERM;
1242
1243 if (!kernfs_get_active(parent))
1244 return -ENODEV;
1245
1246 ret = scops->mkdir(parent, dentry->d_name.name, mode);
1247
1248 kernfs_put_active(parent);
1249 return ret;
1250 }
1251
1252 static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
1253 {
1254 struct kernfs_node *kn = kernfs_dentry_node(dentry);
1255 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
1256 int ret;
1257
1258 if (!scops || !scops->rmdir)
1259 return -EPERM;
1260
1261 if (!kernfs_get_active(kn))
1262 return -ENODEV;
1263
1264 ret = scops->rmdir(kn);
1265
1266 kernfs_put_active(kn);
1267 return ret;
1268 }
1269
1270 static int kernfs_iop_rename(struct mnt_idmap *idmap,
1271 struct inode *old_dir, struct dentry *old_dentry,
1272 struct inode *new_dir, struct dentry *new_dentry,
1273 unsigned int flags)
1274 {
1275 struct kernfs_node *kn = kernfs_dentry_node(old_dentry);
1276 struct kernfs_node *new_parent = new_dir->i_private;
1277 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
1278 int ret;
1279
1280 if (flags)
1281 return -EINVAL;
1282
1283 if (!scops || !scops->rename)
1284 return -EPERM;
1285
1286 if (!kernfs_get_active(kn))
1287 return -ENODEV;
1288
1289 if (!kernfs_get_active(new_parent)) {
1290 kernfs_put_active(kn);
1291 return -ENODEV;
1292 }
1293
1294 ret = scops->rename(kn, new_parent, new_dentry->d_name.name);
1295
1296 kernfs_put_active(new_parent);
1297 kernfs_put_active(kn);
1298 return ret;
1299 }
1300
1301 const struct inode_operations kernfs_dir_iops = {
1302 .lookup = kernfs_iop_lookup,
1303 .permission = kernfs_iop_permission,
1304 .setattr = kernfs_iop_setattr,
1305 .getattr = kernfs_iop_getattr,
1306 .listxattr = kernfs_iop_listxattr,
1307
1308 .mkdir = kernfs_iop_mkdir,
1309 .rmdir = kernfs_iop_rmdir,
1310 .rename = kernfs_iop_rename,
1311 };
1312
1313 static struct kernfs_node *kernfs_leftmost_descendant(struct kernfs_node *pos)
1314 {
1315 struct kernfs_node *last;
1316
1317 while (true) {
1318 struct rb_node *rbn;
1319
1320 last = pos;
1321
1322 if (kernfs_type(pos) != KERNFS_DIR)
1323 break;
1324
1325 rbn = rb_first(&pos->dir.children);
1326 if (!rbn)
1327 break;
1328
1329 pos = rb_to_kn(rbn);
1330 }
1331
1332 return last;
1333 }
1334
1335 /**
1336 * kernfs_next_descendant_post - find the next descendant for post-order walk
1337 * @pos: the current position (%NULL to initiate traversal)
1338 * @root: kernfs_node whose descendants to walk
1339 *
1340 * Find the next descendant to visit for post-order traversal of @root's
1341 * descendants. @root is included in the iteration and the last node to be
1342 * visited.
1343 *
1344 * Return: the next descendant to visit or %NULL when done.
1345 */
1346 static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
1347 struct kernfs_node *root)
1348 {
1349 struct rb_node *rbn;
1350
1351 lockdep_assert_held_write(&kernfs_root(root)->kernfs_rwsem);
1352
1353 /* if first iteration, visit leftmost descendant which may be root */
1354 if (!pos)
1355 return kernfs_leftmost_descendant(root);
1356
1357 /* if we visited @root, we're done */
1358 if (pos == root)
1359 return NULL;
1360
1361 /* if there's an unvisited sibling, visit its leftmost descendant */
1362 rbn = rb_next(&pos->rb);
1363 if (rbn)
1364 return kernfs_leftmost_descendant(rb_to_kn(rbn));
1365
1366 /* no sibling left, visit parent */
1367 return pos->parent;
1368 }
1369
1370 static void kernfs_activate_one(struct kernfs_node *kn)
1371 {
1372 lockdep_assert_held_write(&kernfs_root(kn)->kernfs_rwsem);
1373
1374 kn->flags |= KERNFS_ACTIVATED;
1375
1376 if (kernfs_active(kn) || (kn->flags & (KERNFS_HIDDEN | KERNFS_REMOVING)))
1377 return;
1378
1379 WARN_ON_ONCE(kn->parent && RB_EMPTY_NODE(&kn->rb));
1380 WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
1381
1382 atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
1383 }
1384
1385 /**
1386 * kernfs_activate - activate a node which started deactivated
1387 * @kn: kernfs_node whose subtree is to be activated
1388 *
1389 * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
1390 * needs to be explicitly activated. A node which hasn't been activated
1391 * isn't visible to userland and deactivation is skipped during its
1392 * removal. This is useful to construct atomic init sequences where
1393 * creation of multiple nodes should either succeed or fail atomically.
1394 *
1395 * The caller is responsible for ensuring that this function is not called
1396 * after kernfs_remove*() is invoked on @kn.
1397 */
1398 void kernfs_activate(struct kernfs_node *kn)
1399 {
1400 struct kernfs_node *pos;
1401 struct kernfs_root *root = kernfs_root(kn);
1402
1403 down_write(&root->kernfs_rwsem);
1404
1405 pos = NULL;
1406 while ((pos = kernfs_next_descendant_post(pos, kn)))
1407 kernfs_activate_one(pos);
1408
1409 up_write(&root->kernfs_rwsem);
1410 }
1411
1412 /**
1413 * kernfs_show - show or hide a node
1414 * @kn: kernfs_node to show or hide
1415 * @show: whether to show or hide
1416 *
1417 * If @show is %false, @kn is marked hidden and deactivated. A hidden node is
1418 * ignored in future activaitons. If %true, the mark is removed and activation
1419 * state is restored. This function won't implicitly activate a new node in a
1420 * %KERNFS_ROOT_CREATE_DEACTIVATED root which hasn't been activated yet.
1421 *
1422 * To avoid recursion complexities, directories aren't supported for now.
1423 */
1424 void kernfs_show(struct kernfs_node *kn, bool show)
1425 {
1426 struct kernfs_root *root = kernfs_root(kn);
1427
1428 if (WARN_ON_ONCE(kernfs_type(kn) == KERNFS_DIR))
1429 return;
1430
1431 down_write(&root->kernfs_rwsem);
1432
1433 if (show) {
1434 kn->flags &= ~KERNFS_HIDDEN;
1435 if (kn->flags & KERNFS_ACTIVATED)
1436 kernfs_activate_one(kn);
1437 } else {
1438 kn->flags |= KERNFS_HIDDEN;
1439 if (kernfs_active(kn))
1440 atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
1441 kernfs_drain(kn);
1442 }
1443
1444 up_write(&root->kernfs_rwsem);
1445 }
1446
1447 static void __kernfs_remove(struct kernfs_node *kn)
1448 {
1449 struct kernfs_node *pos;
1450
1451 /* Short-circuit if non-root @kn has already finished removal. */
1452 if (!kn)
1453 return;
1454
1455 lockdep_assert_held_write(&kernfs_root(kn)->kernfs_rwsem);
1456
1457 /*
1458 * This is for kernfs_remove_self() which plays with active ref
1459 * after removal.
1460 */
1461 if (kn->parent && RB_EMPTY_NODE(&kn->rb))
1462 return;
1463
1464 pr_debug("kernfs %s: removing\n", kn->name);
1465
1466 /* prevent new usage by marking all nodes removing and deactivating */
1467 pos = NULL;
1468 while ((pos = kernfs_next_descendant_post(pos, kn))) {
1469 pos->flags |= KERNFS_REMOVING;
1470 if (kernfs_active(pos))
1471 atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
1472 }
1473
1474 /* deactivate and unlink the subtree node-by-node */
1475 do {
1476 pos = kernfs_leftmost_descendant(kn);
1477
1478 /*
1479 * kernfs_drain() may drop kernfs_rwsem temporarily and @pos's
1480 * base ref could have been put by someone else by the time
1481 * the function returns. Make sure it doesn't go away
1482 * underneath us.
1483 */
1484 kernfs_get(pos);
1485
1486 kernfs_drain(pos);
1487
1488 /*
1489 * kernfs_unlink_sibling() succeeds once per node. Use it
1490 * to decide who's responsible for cleanups.
1491 */
1492 if (!pos->parent || kernfs_unlink_sibling(pos)) {
1493 struct kernfs_iattrs *ps_iattr =
1494 pos->parent ? pos->parent->iattr : NULL;
1495
1496 /* update timestamps on the parent */
1497 down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
1498
1499 if (ps_iattr) {
1500 ktime_get_real_ts64(&ps_iattr->ia_ctime);
1501 ps_iattr->ia_mtime = ps_iattr->ia_ctime;
1502 }
1503
1504 up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
1505 kernfs_put(pos);
1506 }
1507
1508 kernfs_put(pos);
1509 } while (pos != kn);
1510 }
1511
1512 /**
1513 * kernfs_remove - remove a kernfs_node recursively
1514 * @kn: the kernfs_node to remove
1515 *
1516 * Remove @kn along with all its subdirectories and files.
1517 */
1518 void kernfs_remove(struct kernfs_node *kn)
1519 {
1520 struct kernfs_root *root;
1521
1522 if (!kn)
1523 return;
1524
1525 root = kernfs_root(kn);
1526
1527 down_write(&root->kernfs_rwsem);
1528 __kernfs_remove(kn);
1529 up_write(&root->kernfs_rwsem);
1530 }
1531
1532 /**
1533 * kernfs_break_active_protection - break out of active protection
1534 * @kn: the self kernfs_node
1535 *
1536 * The caller must be running off of a kernfs operation which is invoked
1537 * with an active reference - e.g. one of kernfs_ops. Each invocation of
1538 * this function must also be matched with an invocation of
1539 * kernfs_unbreak_active_protection().
1540 *
1541 * This function releases the active reference of @kn the caller is
1542 * holding. Once this function is called, @kn may be removed at any point
1543 * and the caller is solely responsible for ensuring that the objects it
1544 * dereferences are accessible.
1545 */
1546 void kernfs_break_active_protection(struct kernfs_node *kn)
1547 {
1548 /*
1549 * Take out ourself out of the active ref dependency chain. If
1550 * we're called without an active ref, lockdep will complain.
1551 */
1552 kernfs_put_active(kn);
1553 }
1554
1555 /**
1556 * kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
1557 * @kn: the self kernfs_node
1558 *
1559 * If kernfs_break_active_protection() was called, this function must be
1560 * invoked before finishing the kernfs operation. Note that while this
1561 * function restores the active reference, it doesn't and can't actually
1562 * restore the active protection - @kn may already or be in the process of
1563 * being removed. Once kernfs_break_active_protection() is invoked, that
1564 * protection is irreversibly gone for the kernfs operation instance.
1565 *
1566 * While this function may be called at any point after
1567 * kernfs_break_active_protection() is invoked, its most useful location
1568 * would be right before the enclosing kernfs operation returns.
1569 */
1570 void kernfs_unbreak_active_protection(struct kernfs_node *kn)
1571 {
1572 /*
1573 * @kn->active could be in any state; however, the increment we do
1574 * here will be undone as soon as the enclosing kernfs operation
1575 * finishes and this temporary bump can't break anything. If @kn
1576 * is alive, nothing changes. If @kn is being deactivated, the
1577 * soon-to-follow put will either finish deactivation or restore
1578 * deactivated state. If @kn is already removed, the temporary
1579 * bump is guaranteed to be gone before @kn is released.
1580 */
1581 atomic_inc(&kn->active);
1582 if (kernfs_lockdep(kn))
1583 rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
1584 }
1585
1586 /**
1587 * kernfs_remove_self - remove a kernfs_node from its own method
1588 * @kn: the self kernfs_node to remove
1589 *
1590 * The caller must be running off of a kernfs operation which is invoked
1591 * with an active reference - e.g. one of kernfs_ops. This can be used to
1592 * implement a file operation which deletes itself.
1593 *
1594 * For example, the "delete" file for a sysfs device directory can be
1595 * implemented by invoking kernfs_remove_self() on the "delete" file
1596 * itself. This function breaks the circular dependency of trying to
1597 * deactivate self while holding an active ref itself. It isn't necessary
1598 * to modify the usual removal path to use kernfs_remove_self(). The
1599 * "delete" implementation can simply invoke kernfs_remove_self() on self
1600 * before proceeding with the usual removal path. kernfs will ignore later
1601 * kernfs_remove() on self.
1602 *
1603 * kernfs_remove_self() can be called multiple times concurrently on the
1604 * same kernfs_node. Only the first one actually performs removal and
1605 * returns %true. All others will wait until the kernfs operation which
1606 * won self-removal finishes and return %false. Note that the losers wait
1607 * for the completion of not only the winning kernfs_remove_self() but also
1608 * the whole kernfs_ops which won the arbitration. This can be used to
1609 * guarantee, for example, all concurrent writes to a "delete" file to
1610 * finish only after the whole operation is complete.
1611 *
1612 * Return: %true if @kn is removed by this call, otherwise %false.
1613 */
1614 bool kernfs_remove_self(struct kernfs_node *kn)
1615 {
1616 bool ret;
1617 struct kernfs_root *root = kernfs_root(kn);
1618
1619 down_write(&root->kernfs_rwsem);
1620 kernfs_break_active_protection(kn);
1621
1622 /*
1623 * SUICIDAL is used to arbitrate among competing invocations. Only
1624 * the first one will actually perform removal. When the removal
1625 * is complete, SUICIDED is set and the active ref is restored
1626 * while kernfs_rwsem for held exclusive. The ones which lost
1627 * arbitration waits for SUICIDED && drained which can happen only
1628 * after the enclosing kernfs operation which executed the winning
1629 * instance of kernfs_remove_self() finished.
1630 */
1631 if (!(kn->flags & KERNFS_SUICIDAL)) {
1632 kn->flags |= KERNFS_SUICIDAL;
1633 __kernfs_remove(kn);
1634 kn->flags |= KERNFS_SUICIDED;
1635 ret = true;
1636 } else {
1637 wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
1638 DEFINE_WAIT(wait);
1639
1640 while (true) {
1641 prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
1642
1643 if ((kn->flags & KERNFS_SUICIDED) &&
1644 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
1645 break;
1646
1647 up_write(&root->kernfs_rwsem);
1648 schedule();
1649 down_write(&root->kernfs_rwsem);
1650 }
1651 finish_wait(waitq, &wait);
1652 WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
1653 ret = false;
1654 }
1655
1656 /*
1657 * This must be done while kernfs_rwsem held exclusive; otherwise,
1658 * waiting for SUICIDED && deactivated could finish prematurely.
1659 */
1660 kernfs_unbreak_active_protection(kn);
1661
1662 up_write(&root->kernfs_rwsem);
1663 return ret;
1664 }
1665
1666 /**
1667 * kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
1668 * @parent: parent of the target
1669 * @name: name of the kernfs_node to remove
1670 * @ns: namespace tag of the kernfs_node to remove
1671 *
1672 * Look for the kernfs_node with @name and @ns under @parent and remove it.
1673 *
1674 * Return: %0 on success, -ENOENT if such entry doesn't exist.
1675 */
1676 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
1677 const void *ns)
1678 {
1679 struct kernfs_node *kn;
1680 struct kernfs_root *root;
1681
1682 if (!parent) {
1683 WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
1684 name);
1685 return -ENOENT;
1686 }
1687
1688 root = kernfs_root(parent);
1689 down_write(&root->kernfs_rwsem);
1690
1691 kn = kernfs_find_ns(parent, name, ns);
1692 if (kn) {
1693 kernfs_get(kn);
1694 __kernfs_remove(kn);
1695 kernfs_put(kn);
1696 }
1697
1698 up_write(&root->kernfs_rwsem);
1699
1700 if (kn)
1701 return 0;
1702 else
1703 return -ENOENT;
1704 }
1705
1706 /**
1707 * kernfs_rename_ns - move and rename a kernfs_node
1708 * @kn: target node
1709 * @new_parent: new parent to put @sd under
1710 * @new_name: new name
1711 * @new_ns: new namespace tag
1712 *
1713 * Return: %0 on success, -errno on failure.
1714 */
1715 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
1716 const char *new_name, const void *new_ns)
1717 {
1718 struct kernfs_node *old_parent;
1719 struct kernfs_root *root;
1720 const char *old_name = NULL;
1721 int error;
1722
1723 /* can't move or rename root */
1724 if (!kn->parent)
1725 return -EINVAL;
1726
1727 root = kernfs_root(kn);
1728 down_write(&root->kernfs_rwsem);
1729
1730 error = -ENOENT;
1731 if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
1732 (new_parent->flags & KERNFS_EMPTY_DIR))
1733 goto out;
1734
1735 error = 0;
1736 if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
1737 (strcmp(kn->name, new_name) == 0))
1738 goto out; /* nothing to rename */
1739
1740 error = -EEXIST;
1741 if (kernfs_find_ns(new_parent, new_name, new_ns))
1742 goto out;
1743
1744 /* rename kernfs_node */
1745 if (strcmp(kn->name, new_name) != 0) {
1746 error = -ENOMEM;
1747 new_name = kstrdup_const(new_name, GFP_KERNEL);
1748 if (!new_name)
1749 goto out;
1750 } else {
1751 new_name = NULL;
1752 }
1753
1754 /*
1755 * Move to the appropriate place in the appropriate directories rbtree.
1756 */
1757 kernfs_unlink_sibling(kn);
1758 kernfs_get(new_parent);
1759
1760 /* rename_lock protects ->parent and ->name accessors */
1761 write_lock_irq(&kernfs_rename_lock);
1762
1763 old_parent = kn->parent;
1764 kn->parent = new_parent;
1765
1766 kn->ns = new_ns;
1767 if (new_name) {
1768 old_name = kn->name;
1769 kn->name = new_name;
1770 }
1771
1772 write_unlock_irq(&kernfs_rename_lock);
1773
1774 kn->hash = kernfs_name_hash(kn->name, kn->ns);
1775 kernfs_link_sibling(kn);
1776
1777 kernfs_put(old_parent);
1778 kfree_const(old_name);
1779
1780 error = 0;
1781 out:
1782 up_write(&root->kernfs_rwsem);
1783 return error;
1784 }
1785
1786 static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
1787 {
1788 kernfs_put(filp->private_data);
1789 return 0;
1790 }
1791
1792 static struct kernfs_node *kernfs_dir_pos(const void *ns,
1793 struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
1794 {
1795 if (pos) {
1796 int valid = kernfs_active(pos) &&
1797 pos->parent == parent && hash == pos->hash;
1798 kernfs_put(pos);
1799 if (!valid)
1800 pos = NULL;
1801 }
1802 if (!pos && (hash > 1) && (hash < INT_MAX)) {
1803 struct rb_node *node = parent->dir.children.rb_node;
1804 while (node) {
1805 pos = rb_to_kn(node);
1806
1807 if (hash < pos->hash)
1808 node = node->rb_left;
1809 else if (hash > pos->hash)
1810 node = node->rb_right;
1811 else
1812 break;
1813 }
1814 }
1815 /* Skip over entries which are dying/dead or in the wrong namespace */
1816 while (pos && (!kernfs_active(pos) || pos->ns != ns)) {
1817 struct rb_node *node = rb_next(&pos->rb);
1818 if (!node)
1819 pos = NULL;
1820 else
1821 pos = rb_to_kn(node);
1822 }
1823 return pos;
1824 }
1825
1826 static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
1827 struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
1828 {
1829 pos = kernfs_dir_pos(ns, parent, ino, pos);
1830 if (pos) {
1831 do {
1832 struct rb_node *node = rb_next(&pos->rb);
1833 if (!node)
1834 pos = NULL;
1835 else
1836 pos = rb_to_kn(node);
1837 } while (pos && (!kernfs_active(pos) || pos->ns != ns));
1838 }
1839 return pos;
1840 }
1841
1842 static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
1843 {
1844 struct dentry *dentry = file->f_path.dentry;
1845 struct kernfs_node *parent = kernfs_dentry_node(dentry);
1846 struct kernfs_node *pos = file->private_data;
1847 struct kernfs_root *root;
1848 const void *ns = NULL;
1849
1850 if (!dir_emit_dots(file, ctx))
1851 return 0;
1852
1853 root = kernfs_root(parent);
1854 down_read(&root->kernfs_rwsem);
1855
1856 if (kernfs_ns_enabled(parent))
1857 ns = kernfs_info(dentry->d_sb)->ns;
1858
1859 for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
1860 pos;
1861 pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
1862 const char *name = pos->name;
1863 unsigned int type = fs_umode_to_dtype(pos->mode);
1864 int len = strlen(name);
1865 ino_t ino = kernfs_ino(pos);
1866
1867 ctx->pos = pos->hash;
1868 file->private_data = pos;
1869 kernfs_get(pos);
1870
1871 up_read(&root->kernfs_rwsem);
1872 if (!dir_emit(ctx, name, len, ino, type))
1873 return 0;
1874 down_read(&root->kernfs_rwsem);
1875 }
1876 up_read(&root->kernfs_rwsem);
1877 file->private_data = NULL;
1878 ctx->pos = INT_MAX;
1879 return 0;
1880 }
1881
1882 const struct file_operations kernfs_dir_fops = {
1883 .read = generic_read_dir,
1884 .iterate_shared = kernfs_fop_readdir,
1885 .release = kernfs_dir_fop_release,
1886 .llseek = generic_file_llseek,
1887 };
1888
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