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1/*
2 * fs/kernfs/dir.c - kernfs directory implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
7 *
8 * This file is released under the GPLv2.
9 */
10
11#include <linux/sched.h>
12#include <linux/fs.h>
13#include <linux/namei.h>
14#include <linux/idr.h>
15#include <linux/slab.h>
16#include <linux/security.h>
17#include <linux/hash.h>
18
19#include "kernfs-internal.h"
20
21DEFINE_MUTEX(kernfs_mutex);
22static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
23static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */
24
25#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
26
27static bool kernfs_active(struct kernfs_node *kn)
28{
29 lockdep_assert_held(&kernfs_mutex);
30 return atomic_read(&kn->active) >= 0;
31}
32
33static bool kernfs_lockdep(struct kernfs_node *kn)
34{
35#ifdef CONFIG_DEBUG_LOCK_ALLOC
36 return kn->flags & KERNFS_LOCKDEP;
37#else
38 return false;
39#endif
40}
41
42static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
43{
44 return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
45}
46
47/* kernfs_node_depth - compute depth from @from to @to */
48static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
49{
50 size_t depth = 0;
51
52 while (to->parent && to != from) {
53 depth++;
54 to = to->parent;
55 }
56 return depth;
57}
58
59static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
60 struct kernfs_node *b)
61{
62 size_t da, db;
63 struct kernfs_root *ra = kernfs_root(a), *rb = kernfs_root(b);
64
65 if (ra != rb)
66 return NULL;
67
68 da = kernfs_depth(ra->kn, a);
69 db = kernfs_depth(rb->kn, b);
70
71 while (da > db) {
72 a = a->parent;
73 da--;
74 }
75 while (db > da) {
76 b = b->parent;
77 db--;
78 }
79
80 /* worst case b and a will be the same at root */
81 while (b != a) {
82 b = b->parent;
83 a = a->parent;
84 }
85
86 return a;
87}
88
89/**
90 * kernfs_path_from_node_locked - find a pseudo-absolute path to @kn_to,
91 * where kn_from is treated as root of the path.
92 * @kn_from: kernfs node which should be treated as root for the path
93 * @kn_to: kernfs node to which path is needed
94 * @buf: buffer to copy the path into
95 * @buflen: size of @buf
96 *
97 * We need to handle couple of scenarios here:
98 * [1] when @kn_from is an ancestor of @kn_to at some level
99 * kn_from: /n1/n2/n3
100 * kn_to: /n1/n2/n3/n4/n5
101 * result: /n4/n5
102 *
103 * [2] when @kn_from is on a different hierarchy and we need to find common
104 * ancestor between @kn_from and @kn_to.
105 * kn_from: /n1/n2/n3/n4
106 * kn_to: /n1/n2/n5
107 * result: /../../n5
108 * OR
109 * kn_from: /n1/n2/n3/n4/n5 [depth=5]
110 * kn_to: /n1/n2/n3 [depth=3]
111 * result: /../..
112 *
113 * Returns the length of the full path. If the full length is equal to or
114 * greater than @buflen, @buf contains the truncated path with the trailing
115 * '\0'. On error, -errno is returned.
116 */
117static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
118 struct kernfs_node *kn_from,
119 char *buf, size_t buflen)
120{
121 struct kernfs_node *kn, *common;
122 const char parent_str[] = "/..";
123 size_t depth_from, depth_to, len = 0;
124 int i, j;
125
126 if (!kn_from)
127 kn_from = kernfs_root(kn_to)->kn;
128
129 if (kn_from == kn_to)
130 return strlcpy(buf, "/", buflen);
131
132 common = kernfs_common_ancestor(kn_from, kn_to);
133 if (WARN_ON(!common))
134 return -EINVAL;
135
136 depth_to = kernfs_depth(common, kn_to);
137 depth_from = kernfs_depth(common, kn_from);
138
139 if (buf)
140 buf[0] = '\0';
141
142 for (i = 0; i < depth_from; i++)
143 len += strlcpy(buf + len, parent_str,
144 len < buflen ? buflen - len : 0);
145
146 /* Calculate how many bytes we need for the rest */
147 for (i = depth_to - 1; i >= 0; i--) {
148 for (kn = kn_to, j = 0; j < i; j++)
149 kn = kn->parent;
150 len += strlcpy(buf + len, "/",
151 len < buflen ? buflen - len : 0);
152 len += strlcpy(buf + len, kn->name,
153 len < buflen ? buflen - len : 0);
154 }
155
156 return len;
157}
158
159/**
160 * kernfs_name - obtain the name of a given node
161 * @kn: kernfs_node of interest
162 * @buf: buffer to copy @kn's name into
163 * @buflen: size of @buf
164 *
165 * Copies the name of @kn into @buf of @buflen bytes. The behavior is
166 * similar to strlcpy(). It returns the length of @kn's name and if @buf
167 * isn't long enough, it's filled upto @buflen-1 and nul terminated.
168 *
169 * This function can be called from any context.
170 */
171int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
172{
173 unsigned long flags;
174 int ret;
175
176 spin_lock_irqsave(&kernfs_rename_lock, flags);
177 ret = kernfs_name_locked(kn, buf, buflen);
178 spin_unlock_irqrestore(&kernfs_rename_lock, flags);
179 return ret;
180}
181
182/**
183 * kernfs_path_from_node - build path of node @to relative to @from.
184 * @from: parent kernfs_node relative to which we need to build the path
185 * @to: kernfs_node of interest
186 * @buf: buffer to copy @to's path into
187 * @buflen: size of @buf
188 *
189 * Builds @to's path relative to @from in @buf. @from and @to must
190 * be on the same kernfs-root. If @from is not parent of @to, then a relative
191 * path (which includes '..'s) as needed to reach from @from to @to is
192 * returned.
193 *
194 * Returns the length of the full path. If the full length is equal to or
195 * greater than @buflen, @buf contains the truncated path with the trailing
196 * '\0'. On error, -errno is returned.
197 */
198int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
199 char *buf, size_t buflen)
200{
201 unsigned long flags;
202 int ret;
203
204 spin_lock_irqsave(&kernfs_rename_lock, flags);
205 ret = kernfs_path_from_node_locked(to, from, buf, buflen);
206 spin_unlock_irqrestore(&kernfs_rename_lock, flags);
207 return ret;
208}
209EXPORT_SYMBOL_GPL(kernfs_path_from_node);
210
211/**
212 * pr_cont_kernfs_name - pr_cont name of a kernfs_node
213 * @kn: kernfs_node of interest
214 *
215 * This function can be called from any context.
216 */
217void pr_cont_kernfs_name(struct kernfs_node *kn)
218{
219 unsigned long flags;
220
221 spin_lock_irqsave(&kernfs_rename_lock, flags);
222
223 kernfs_name_locked(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf));
224 pr_cont("%s", kernfs_pr_cont_buf);
225
226 spin_unlock_irqrestore(&kernfs_rename_lock, flags);
227}
228
229/**
230 * pr_cont_kernfs_path - pr_cont path of a kernfs_node
231 * @kn: kernfs_node of interest
232 *
233 * This function can be called from any context.
234 */
235void pr_cont_kernfs_path(struct kernfs_node *kn)
236{
237 unsigned long flags;
238 int sz;
239
240 spin_lock_irqsave(&kernfs_rename_lock, flags);
241
242 sz = kernfs_path_from_node_locked(kn, NULL, kernfs_pr_cont_buf,
243 sizeof(kernfs_pr_cont_buf));
244 if (sz < 0) {
245 pr_cont("(error)");
246 goto out;
247 }
248
249 if (sz >= sizeof(kernfs_pr_cont_buf)) {
250 pr_cont("(name too long)");
251 goto out;
252 }
253
254 pr_cont("%s", kernfs_pr_cont_buf);
255
256out:
257 spin_unlock_irqrestore(&kernfs_rename_lock, flags);
258}
259
260/**
261 * kernfs_get_parent - determine the parent node and pin it
262 * @kn: kernfs_node of interest
263 *
264 * Determines @kn's parent, pins and returns it. This function can be
265 * called from any context.
266 */
267struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
268{
269 struct kernfs_node *parent;
270 unsigned long flags;
271
272 spin_lock_irqsave(&kernfs_rename_lock, flags);
273 parent = kn->parent;
274 kernfs_get(parent);
275 spin_unlock_irqrestore(&kernfs_rename_lock, flags);
276
277 return parent;
278}
279
280/**
281 * kernfs_name_hash
282 * @name: Null terminated string to hash
283 * @ns: Namespace tag to hash
284 *
285 * Returns 31 bit hash of ns + name (so it fits in an off_t )
286 */
287static unsigned int kernfs_name_hash(const char *name, const void *ns)
288{
289 unsigned long hash = init_name_hash(ns);
290 unsigned int len = strlen(name);
291 while (len--)
292 hash = partial_name_hash(*name++, hash);
293 hash = end_name_hash(hash);
294 hash &= 0x7fffffffU;
295 /* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
296 if (hash < 2)
297 hash += 2;
298 if (hash >= INT_MAX)
299 hash = INT_MAX - 1;
300 return hash;
301}
302
303static int kernfs_name_compare(unsigned int hash, const char *name,
304 const void *ns, const struct kernfs_node *kn)
305{
306 if (hash < kn->hash)
307 return -1;
308 if (hash > kn->hash)
309 return 1;
310 if (ns < kn->ns)
311 return -1;
312 if (ns > kn->ns)
313 return 1;
314 return strcmp(name, kn->name);
315}
316
317static int kernfs_sd_compare(const struct kernfs_node *left,
318 const struct kernfs_node *right)
319{
320 return kernfs_name_compare(left->hash, left->name, left->ns, right);
321}
322
323/**
324 * kernfs_link_sibling - link kernfs_node into sibling rbtree
325 * @kn: kernfs_node of interest
326 *
327 * Link @kn into its sibling rbtree which starts from
328 * @kn->parent->dir.children.
329 *
330 * Locking:
331 * mutex_lock(kernfs_mutex)
332 *
333 * RETURNS:
334 * 0 on susccess -EEXIST on failure.
335 */
336static int kernfs_link_sibling(struct kernfs_node *kn)
337{
338 struct rb_node **node = &kn->parent->dir.children.rb_node;
339 struct rb_node *parent = NULL;
340
341 while (*node) {
342 struct kernfs_node *pos;
343 int result;
344
345 pos = rb_to_kn(*node);
346 parent = *node;
347 result = kernfs_sd_compare(kn, pos);
348 if (result < 0)
349 node = &pos->rb.rb_left;
350 else if (result > 0)
351 node = &pos->rb.rb_right;
352 else
353 return -EEXIST;
354 }
355
356 /* add new node and rebalance the tree */
357 rb_link_node(&kn->rb, parent, node);
358 rb_insert_color(&kn->rb, &kn->parent->dir.children);
359
360 /* successfully added, account subdir number */
361 if (kernfs_type(kn) == KERNFS_DIR)
362 kn->parent->dir.subdirs++;
363
364 return 0;
365}
366
367/**
368 * kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
369 * @kn: kernfs_node of interest
370 *
371 * Try to unlink @kn from its sibling rbtree which starts from
372 * kn->parent->dir.children. Returns %true if @kn was actually
373 * removed, %false if @kn wasn't on the rbtree.
374 *
375 * Locking:
376 * mutex_lock(kernfs_mutex)
377 */
378static bool kernfs_unlink_sibling(struct kernfs_node *kn)
379{
380 if (RB_EMPTY_NODE(&kn->rb))
381 return false;
382
383 if (kernfs_type(kn) == KERNFS_DIR)
384 kn->parent->dir.subdirs--;
385
386 rb_erase(&kn->rb, &kn->parent->dir.children);
387 RB_CLEAR_NODE(&kn->rb);
388 return true;
389}
390
391/**
392 * kernfs_get_active - get an active reference to kernfs_node
393 * @kn: kernfs_node to get an active reference to
394 *
395 * Get an active reference of @kn. This function is noop if @kn
396 * is NULL.
397 *
398 * RETURNS:
399 * Pointer to @kn on success, NULL on failure.
400 */
401struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
402{
403 if (unlikely(!kn))
404 return NULL;
405
406 if (!atomic_inc_unless_negative(&kn->active))
407 return NULL;
408
409 if (kernfs_lockdep(kn))
410 rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
411 return kn;
412}
413
414/**
415 * kernfs_put_active - put an active reference to kernfs_node
416 * @kn: kernfs_node to put an active reference to
417 *
418 * Put an active reference to @kn. This function is noop if @kn
419 * is NULL.
420 */
421void kernfs_put_active(struct kernfs_node *kn)
422{
423 struct kernfs_root *root = kernfs_root(kn);
424 int v;
425
426 if (unlikely(!kn))
427 return;
428
429 if (kernfs_lockdep(kn))
430 rwsem_release(&kn->dep_map, 1, _RET_IP_);
431 v = atomic_dec_return(&kn->active);
432 if (likely(v != KN_DEACTIVATED_BIAS))
433 return;
434
435 wake_up_all(&root->deactivate_waitq);
436}
437
438/**
439 * kernfs_drain - drain kernfs_node
440 * @kn: kernfs_node to drain
441 *
442 * Drain existing usages and nuke all existing mmaps of @kn. Mutiple
443 * removers may invoke this function concurrently on @kn and all will
444 * return after draining is complete.
445 */
446static void kernfs_drain(struct kernfs_node *kn)
447 __releases(&kernfs_mutex) __acquires(&kernfs_mutex)
448{
449 struct kernfs_root *root = kernfs_root(kn);
450
451 lockdep_assert_held(&kernfs_mutex);
452 WARN_ON_ONCE(kernfs_active(kn));
453
454 mutex_unlock(&kernfs_mutex);
455
456 if (kernfs_lockdep(kn)) {
457 rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
458 if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
459 lock_contended(&kn->dep_map, _RET_IP_);
460 }
461
462 /* but everyone should wait for draining */
463 wait_event(root->deactivate_waitq,
464 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
465
466 if (kernfs_lockdep(kn)) {
467 lock_acquired(&kn->dep_map, _RET_IP_);
468 rwsem_release(&kn->dep_map, 1, _RET_IP_);
469 }
470
471 kernfs_unmap_bin_file(kn);
472
473 mutex_lock(&kernfs_mutex);
474}
475
476/**
477 * kernfs_get - get a reference count on a kernfs_node
478 * @kn: the target kernfs_node
479 */
480void kernfs_get(struct kernfs_node *kn)
481{
482 if (kn) {
483 WARN_ON(!atomic_read(&kn->count));
484 atomic_inc(&kn->count);
485 }
486}
487EXPORT_SYMBOL_GPL(kernfs_get);
488
489/**
490 * kernfs_put - put a reference count on a kernfs_node
491 * @kn: the target kernfs_node
492 *
493 * Put a reference count of @kn and destroy it if it reached zero.
494 */
495void kernfs_put(struct kernfs_node *kn)
496{
497 struct kernfs_node *parent;
498 struct kernfs_root *root;
499
500 if (!kn || !atomic_dec_and_test(&kn->count))
501 return;
502 root = kernfs_root(kn);
503 repeat:
504 /*
505 * Moving/renaming is always done while holding reference.
506 * kn->parent won't change beneath us.
507 */
508 parent = kn->parent;
509
510 WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
511 "kernfs_put: %s/%s: released with incorrect active_ref %d\n",
512 parent ? parent->name : "", kn->name, atomic_read(&kn->active));
513
514 if (kernfs_type(kn) == KERNFS_LINK)
515 kernfs_put(kn->symlink.target_kn);
516
517 kfree_const(kn->name);
518
519 if (kn->iattr) {
520 if (kn->iattr->ia_secdata)
521 security_release_secctx(kn->iattr->ia_secdata,
522 kn->iattr->ia_secdata_len);
523 simple_xattrs_free(&kn->iattr->xattrs);
524 }
525 kfree(kn->iattr);
526 ida_simple_remove(&root->ino_ida, kn->ino);
527 kmem_cache_free(kernfs_node_cache, kn);
528
529 kn = parent;
530 if (kn) {
531 if (atomic_dec_and_test(&kn->count))
532 goto repeat;
533 } else {
534 /* just released the root kn, free @root too */
535 ida_destroy(&root->ino_ida);
536 kfree(root);
537 }
538}
539EXPORT_SYMBOL_GPL(kernfs_put);
540
541static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
542{
543 struct kernfs_node *kn;
544
545 if (flags & LOOKUP_RCU)
546 return -ECHILD;
547
548 /* Always perform fresh lookup for negatives */
549 if (d_really_is_negative(dentry))
550 goto out_bad_unlocked;
551
552 kn = dentry->d_fsdata;
553 mutex_lock(&kernfs_mutex);
554
555 /* The kernfs node has been deactivated */
556 if (!kernfs_active(kn))
557 goto out_bad;
558
559 /* The kernfs node has been moved? */
560 if (dentry->d_parent->d_fsdata != kn->parent)
561 goto out_bad;
562
563 /* The kernfs node has been renamed */
564 if (strcmp(dentry->d_name.name, kn->name) != 0)
565 goto out_bad;
566
567 /* The kernfs node has been moved to a different namespace */
568 if (kn->parent && kernfs_ns_enabled(kn->parent) &&
569 kernfs_info(dentry->d_sb)->ns != kn->ns)
570 goto out_bad;
571
572 mutex_unlock(&kernfs_mutex);
573 return 1;
574out_bad:
575 mutex_unlock(&kernfs_mutex);
576out_bad_unlocked:
577 return 0;
578}
579
580static void kernfs_dop_release(struct dentry *dentry)
581{
582 kernfs_put(dentry->d_fsdata);
583}
584
585const struct dentry_operations kernfs_dops = {
586 .d_revalidate = kernfs_dop_revalidate,
587 .d_release = kernfs_dop_release,
588};
589
590/**
591 * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
592 * @dentry: the dentry in question
593 *
594 * Return the kernfs_node associated with @dentry. If @dentry is not a
595 * kernfs one, %NULL is returned.
596 *
597 * While the returned kernfs_node will stay accessible as long as @dentry
598 * is accessible, the returned node can be in any state and the caller is
599 * fully responsible for determining what's accessible.
600 */
601struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
602{
603 if (dentry->d_sb->s_op == &kernfs_sops)
604 return dentry->d_fsdata;
605 return NULL;
606}
607
608static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
609 const char *name, umode_t mode,
610 unsigned flags)
611{
612 struct kernfs_node *kn;
613 int ret;
614
615 name = kstrdup_const(name, GFP_KERNEL);
616 if (!name)
617 return NULL;
618
619 kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
620 if (!kn)
621 goto err_out1;
622
623 ret = ida_simple_get(&root->ino_ida, 1, 0, GFP_KERNEL);
624 if (ret < 0)
625 goto err_out2;
626 kn->ino = ret;
627
628 atomic_set(&kn->count, 1);
629 atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
630 RB_CLEAR_NODE(&kn->rb);
631
632 kn->name = name;
633 kn->mode = mode;
634 kn->flags = flags;
635
636 return kn;
637
638 err_out2:
639 kmem_cache_free(kernfs_node_cache, kn);
640 err_out1:
641 kfree_const(name);
642 return NULL;
643}
644
645struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
646 const char *name, umode_t mode,
647 unsigned flags)
648{
649 struct kernfs_node *kn;
650
651 kn = __kernfs_new_node(kernfs_root(parent), name, mode, flags);
652 if (kn) {
653 kernfs_get(parent);
654 kn->parent = parent;
655 }
656 return kn;
657}
658
659/**
660 * kernfs_add_one - add kernfs_node to parent without warning
661 * @kn: kernfs_node to be added
662 *
663 * The caller must already have initialized @kn->parent. This
664 * function increments nlink of the parent's inode if @kn is a
665 * directory and link into the children list of the parent.
666 *
667 * RETURNS:
668 * 0 on success, -EEXIST if entry with the given name already
669 * exists.
670 */
671int kernfs_add_one(struct kernfs_node *kn)
672{
673 struct kernfs_node *parent = kn->parent;
674 struct kernfs_iattrs *ps_iattr;
675 bool has_ns;
676 int ret;
677
678 mutex_lock(&kernfs_mutex);
679
680 ret = -EINVAL;
681 has_ns = kernfs_ns_enabled(parent);
682 if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
683 has_ns ? "required" : "invalid", parent->name, kn->name))
684 goto out_unlock;
685
686 if (kernfs_type(parent) != KERNFS_DIR)
687 goto out_unlock;
688
689 ret = -ENOENT;
690 if (parent->flags & KERNFS_EMPTY_DIR)
691 goto out_unlock;
692
693 if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
694 goto out_unlock;
695
696 kn->hash = kernfs_name_hash(kn->name, kn->ns);
697
698 ret = kernfs_link_sibling(kn);
699 if (ret)
700 goto out_unlock;
701
702 /* Update timestamps on the parent */
703 ps_iattr = parent->iattr;
704 if (ps_iattr) {
705 struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
706 ktime_get_real_ts(&ps_iattrs->ia_ctime);
707 ps_iattrs->ia_mtime = ps_iattrs->ia_ctime;
708 }
709
710 mutex_unlock(&kernfs_mutex);
711
712 /*
713 * Activate the new node unless CREATE_DEACTIVATED is requested.
714 * If not activated here, the kernfs user is responsible for
715 * activating the node with kernfs_activate(). A node which hasn't
716 * been activated is not visible to userland and its removal won't
717 * trigger deactivation.
718 */
719 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
720 kernfs_activate(kn);
721 return 0;
722
723out_unlock:
724 mutex_unlock(&kernfs_mutex);
725 return ret;
726}
727
728/**
729 * kernfs_find_ns - find kernfs_node with the given name
730 * @parent: kernfs_node to search under
731 * @name: name to look for
732 * @ns: the namespace tag to use
733 *
734 * Look for kernfs_node with name @name under @parent. Returns pointer to
735 * the found kernfs_node on success, %NULL on failure.
736 */
737static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
738 const unsigned char *name,
739 const void *ns)
740{
741 struct rb_node *node = parent->dir.children.rb_node;
742 bool has_ns = kernfs_ns_enabled(parent);
743 unsigned int hash;
744
745 lockdep_assert_held(&kernfs_mutex);
746
747 if (has_ns != (bool)ns) {
748 WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
749 has_ns ? "required" : "invalid", parent->name, name);
750 return NULL;
751 }
752
753 hash = kernfs_name_hash(name, ns);
754 while (node) {
755 struct kernfs_node *kn;
756 int result;
757
758 kn = rb_to_kn(node);
759 result = kernfs_name_compare(hash, name, ns, kn);
760 if (result < 0)
761 node = node->rb_left;
762 else if (result > 0)
763 node = node->rb_right;
764 else
765 return kn;
766 }
767 return NULL;
768}
769
770static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
771 const unsigned char *path,
772 const void *ns)
773{
774 size_t len;
775 char *p, *name;
776
777 lockdep_assert_held(&kernfs_mutex);
778
779 /* grab kernfs_rename_lock to piggy back on kernfs_pr_cont_buf */
780 spin_lock_irq(&kernfs_rename_lock);
781
782 len = strlcpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
783
784 if (len >= sizeof(kernfs_pr_cont_buf)) {
785 spin_unlock_irq(&kernfs_rename_lock);
786 return NULL;
787 }
788
789 p = kernfs_pr_cont_buf;
790
791 while ((name = strsep(&p, "/")) && parent) {
792 if (*name == '\0')
793 continue;
794 parent = kernfs_find_ns(parent, name, ns);
795 }
796
797 spin_unlock_irq(&kernfs_rename_lock);
798
799 return parent;
800}
801
802/**
803 * kernfs_find_and_get_ns - find and get kernfs_node with the given name
804 * @parent: kernfs_node to search under
805 * @name: name to look for
806 * @ns: the namespace tag to use
807 *
808 * Look for kernfs_node with name @name under @parent and get a reference
809 * if found. This function may sleep and returns pointer to the found
810 * kernfs_node on success, %NULL on failure.
811 */
812struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
813 const char *name, const void *ns)
814{
815 struct kernfs_node *kn;
816
817 mutex_lock(&kernfs_mutex);
818 kn = kernfs_find_ns(parent, name, ns);
819 kernfs_get(kn);
820 mutex_unlock(&kernfs_mutex);
821
822 return kn;
823}
824EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
825
826/**
827 * kernfs_walk_and_get_ns - find and get kernfs_node with the given path
828 * @parent: kernfs_node to search under
829 * @path: path to look for
830 * @ns: the namespace tag to use
831 *
832 * Look for kernfs_node with path @path under @parent and get a reference
833 * if found. This function may sleep and returns pointer to the found
834 * kernfs_node on success, %NULL on failure.
835 */
836struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
837 const char *path, const void *ns)
838{
839 struct kernfs_node *kn;
840
841 mutex_lock(&kernfs_mutex);
842 kn = kernfs_walk_ns(parent, path, ns);
843 kernfs_get(kn);
844 mutex_unlock(&kernfs_mutex);
845
846 return kn;
847}
848
849/**
850 * kernfs_create_root - create a new kernfs hierarchy
851 * @scops: optional syscall operations for the hierarchy
852 * @flags: KERNFS_ROOT_* flags
853 * @priv: opaque data associated with the new directory
854 *
855 * Returns the root of the new hierarchy on success, ERR_PTR() value on
856 * failure.
857 */
858struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
859 unsigned int flags, void *priv)
860{
861 struct kernfs_root *root;
862 struct kernfs_node *kn;
863
864 root = kzalloc(sizeof(*root), GFP_KERNEL);
865 if (!root)
866 return ERR_PTR(-ENOMEM);
867
868 ida_init(&root->ino_ida);
869 INIT_LIST_HEAD(&root->supers);
870
871 kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO,
872 KERNFS_DIR);
873 if (!kn) {
874 ida_destroy(&root->ino_ida);
875 kfree(root);
876 return ERR_PTR(-ENOMEM);
877 }
878
879 kn->priv = priv;
880 kn->dir.root = root;
881
882 root->syscall_ops = scops;
883 root->flags = flags;
884 root->kn = kn;
885 init_waitqueue_head(&root->deactivate_waitq);
886
887 if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
888 kernfs_activate(kn);
889
890 return root;
891}
892
893/**
894 * kernfs_destroy_root - destroy a kernfs hierarchy
895 * @root: root of the hierarchy to destroy
896 *
897 * Destroy the hierarchy anchored at @root by removing all existing
898 * directories and destroying @root.
899 */
900void kernfs_destroy_root(struct kernfs_root *root)
901{
902 kernfs_remove(root->kn); /* will also free @root */
903}
904
905/**
906 * kernfs_create_dir_ns - create a directory
907 * @parent: parent in which to create a new directory
908 * @name: name of the new directory
909 * @mode: mode of the new directory
910 * @priv: opaque data associated with the new directory
911 * @ns: optional namespace tag of the directory
912 *
913 * Returns the created node on success, ERR_PTR() value on failure.
914 */
915struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
916 const char *name, umode_t mode,
917 void *priv, const void *ns)
918{
919 struct kernfs_node *kn;
920 int rc;
921
922 /* allocate */
923 kn = kernfs_new_node(parent, name, mode | S_IFDIR, KERNFS_DIR);
924 if (!kn)
925 return ERR_PTR(-ENOMEM);
926
927 kn->dir.root = parent->dir.root;
928 kn->ns = ns;
929 kn->priv = priv;
930
931 /* link in */
932 rc = kernfs_add_one(kn);
933 if (!rc)
934 return kn;
935
936 kernfs_put(kn);
937 return ERR_PTR(rc);
938}
939
940/**
941 * kernfs_create_empty_dir - create an always empty directory
942 * @parent: parent in which to create a new directory
943 * @name: name of the new directory
944 *
945 * Returns the created node on success, ERR_PTR() value on failure.
946 */
947struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
948 const char *name)
949{
950 struct kernfs_node *kn;
951 int rc;
952
953 /* allocate */
954 kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR, KERNFS_DIR);
955 if (!kn)
956 return ERR_PTR(-ENOMEM);
957
958 kn->flags |= KERNFS_EMPTY_DIR;
959 kn->dir.root = parent->dir.root;
960 kn->ns = NULL;
961 kn->priv = NULL;
962
963 /* link in */
964 rc = kernfs_add_one(kn);
965 if (!rc)
966 return kn;
967
968 kernfs_put(kn);
969 return ERR_PTR(rc);
970}
971
972static struct dentry *kernfs_iop_lookup(struct inode *dir,
973 struct dentry *dentry,
974 unsigned int flags)
975{
976 struct dentry *ret;
977 struct kernfs_node *parent = dentry->d_parent->d_fsdata;
978 struct kernfs_node *kn;
979 struct inode *inode;
980 const void *ns = NULL;
981
982 mutex_lock(&kernfs_mutex);
983
984 if (kernfs_ns_enabled(parent))
985 ns = kernfs_info(dir->i_sb)->ns;
986
987 kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
988
989 /* no such entry */
990 if (!kn || !kernfs_active(kn)) {
991 ret = NULL;
992 goto out_unlock;
993 }
994 kernfs_get(kn);
995 dentry->d_fsdata = kn;
996
997 /* attach dentry and inode */
998 inode = kernfs_get_inode(dir->i_sb, kn);
999 if (!inode) {
1000 ret = ERR_PTR(-ENOMEM);
1001 goto out_unlock;
1002 }
1003
1004 /* instantiate and hash dentry */
1005 ret = d_splice_alias(inode, dentry);
1006 out_unlock:
1007 mutex_unlock(&kernfs_mutex);
1008 return ret;
1009}
1010
1011static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
1012 umode_t mode)
1013{
1014 struct kernfs_node *parent = dir->i_private;
1015 struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
1016 int ret;
1017
1018 if (!scops || !scops->mkdir)
1019 return -EPERM;
1020
1021 if (!kernfs_get_active(parent))
1022 return -ENODEV;
1023
1024 ret = scops->mkdir(parent, dentry->d_name.name, mode);
1025
1026 kernfs_put_active(parent);
1027 return ret;
1028}
1029
1030static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
1031{
1032 struct kernfs_node *kn = dentry->d_fsdata;
1033 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
1034 int ret;
1035
1036 if (!scops || !scops->rmdir)
1037 return -EPERM;
1038
1039 if (!kernfs_get_active(kn))
1040 return -ENODEV;
1041
1042 ret = scops->rmdir(kn);
1043
1044 kernfs_put_active(kn);
1045 return ret;
1046}
1047
1048static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
1049 struct inode *new_dir, struct dentry *new_dentry,
1050 unsigned int flags)
1051{
1052 struct kernfs_node *kn = old_dentry->d_fsdata;
1053 struct kernfs_node *new_parent = new_dir->i_private;
1054 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
1055 int ret;
1056
1057 if (flags)
1058 return -EINVAL;
1059
1060 if (!scops || !scops->rename)
1061 return -EPERM;
1062
1063 if (!kernfs_get_active(kn))
1064 return -ENODEV;
1065
1066 if (!kernfs_get_active(new_parent)) {
1067 kernfs_put_active(kn);
1068 return -ENODEV;
1069 }
1070
1071 ret = scops->rename(kn, new_parent, new_dentry->d_name.name);
1072
1073 kernfs_put_active(new_parent);
1074 kernfs_put_active(kn);
1075 return ret;
1076}
1077
1078const struct inode_operations kernfs_dir_iops = {
1079 .lookup = kernfs_iop_lookup,
1080 .permission = kernfs_iop_permission,
1081 .setattr = kernfs_iop_setattr,
1082 .getattr = kernfs_iop_getattr,
1083 .listxattr = kernfs_iop_listxattr,
1084
1085 .mkdir = kernfs_iop_mkdir,
1086 .rmdir = kernfs_iop_rmdir,
1087 .rename = kernfs_iop_rename,
1088};
1089
1090static struct kernfs_node *kernfs_leftmost_descendant(struct kernfs_node *pos)
1091{
1092 struct kernfs_node *last;
1093
1094 while (true) {
1095 struct rb_node *rbn;
1096
1097 last = pos;
1098
1099 if (kernfs_type(pos) != KERNFS_DIR)
1100 break;
1101
1102 rbn = rb_first(&pos->dir.children);
1103 if (!rbn)
1104 break;
1105
1106 pos = rb_to_kn(rbn);
1107 }
1108
1109 return last;
1110}
1111
1112/**
1113 * kernfs_next_descendant_post - find the next descendant for post-order walk
1114 * @pos: the current position (%NULL to initiate traversal)
1115 * @root: kernfs_node whose descendants to walk
1116 *
1117 * Find the next descendant to visit for post-order traversal of @root's
1118 * descendants. @root is included in the iteration and the last node to be
1119 * visited.
1120 */
1121static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
1122 struct kernfs_node *root)
1123{
1124 struct rb_node *rbn;
1125
1126 lockdep_assert_held(&kernfs_mutex);
1127
1128 /* if first iteration, visit leftmost descendant which may be root */
1129 if (!pos)
1130 return kernfs_leftmost_descendant(root);
1131
1132 /* if we visited @root, we're done */
1133 if (pos == root)
1134 return NULL;
1135
1136 /* if there's an unvisited sibling, visit its leftmost descendant */
1137 rbn = rb_next(&pos->rb);
1138 if (rbn)
1139 return kernfs_leftmost_descendant(rb_to_kn(rbn));
1140
1141 /* no sibling left, visit parent */
1142 return pos->parent;
1143}
1144
1145/**
1146 * kernfs_activate - activate a node which started deactivated
1147 * @kn: kernfs_node whose subtree is to be activated
1148 *
1149 * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
1150 * needs to be explicitly activated. A node which hasn't been activated
1151 * isn't visible to userland and deactivation is skipped during its
1152 * removal. This is useful to construct atomic init sequences where
1153 * creation of multiple nodes should either succeed or fail atomically.
1154 *
1155 * The caller is responsible for ensuring that this function is not called
1156 * after kernfs_remove*() is invoked on @kn.
1157 */
1158void kernfs_activate(struct kernfs_node *kn)
1159{
1160 struct kernfs_node *pos;
1161
1162 mutex_lock(&kernfs_mutex);
1163
1164 pos = NULL;
1165 while ((pos = kernfs_next_descendant_post(pos, kn))) {
1166 if (!pos || (pos->flags & KERNFS_ACTIVATED))
1167 continue;
1168
1169 WARN_ON_ONCE(pos->parent && RB_EMPTY_NODE(&pos->rb));
1170 WARN_ON_ONCE(atomic_read(&pos->active) != KN_DEACTIVATED_BIAS);
1171
1172 atomic_sub(KN_DEACTIVATED_BIAS, &pos->active);
1173 pos->flags |= KERNFS_ACTIVATED;
1174 }
1175
1176 mutex_unlock(&kernfs_mutex);
1177}
1178
1179static void __kernfs_remove(struct kernfs_node *kn)
1180{
1181 struct kernfs_node *pos;
1182
1183 lockdep_assert_held(&kernfs_mutex);
1184
1185 /*
1186 * Short-circuit if non-root @kn has already finished removal.
1187 * This is for kernfs_remove_self() which plays with active ref
1188 * after removal.
1189 */
1190 if (!kn || (kn->parent && RB_EMPTY_NODE(&kn->rb)))
1191 return;
1192
1193 pr_debug("kernfs %s: removing\n", kn->name);
1194
1195 /* prevent any new usage under @kn by deactivating all nodes */
1196 pos = NULL;
1197 while ((pos = kernfs_next_descendant_post(pos, kn)))
1198 if (kernfs_active(pos))
1199 atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
1200
1201 /* deactivate and unlink the subtree node-by-node */
1202 do {
1203 pos = kernfs_leftmost_descendant(kn);
1204
1205 /*
1206 * kernfs_drain() drops kernfs_mutex temporarily and @pos's
1207 * base ref could have been put by someone else by the time
1208 * the function returns. Make sure it doesn't go away
1209 * underneath us.
1210 */
1211 kernfs_get(pos);
1212
1213 /*
1214 * Drain iff @kn was activated. This avoids draining and
1215 * its lockdep annotations for nodes which have never been
1216 * activated and allows embedding kernfs_remove() in create
1217 * error paths without worrying about draining.
1218 */
1219 if (kn->flags & KERNFS_ACTIVATED)
1220 kernfs_drain(pos);
1221 else
1222 WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
1223
1224 /*
1225 * kernfs_unlink_sibling() succeeds once per node. Use it
1226 * to decide who's responsible for cleanups.
1227 */
1228 if (!pos->parent || kernfs_unlink_sibling(pos)) {
1229 struct kernfs_iattrs *ps_iattr =
1230 pos->parent ? pos->parent->iattr : NULL;
1231
1232 /* update timestamps on the parent */
1233 if (ps_iattr) {
1234 ktime_get_real_ts(&ps_iattr->ia_iattr.ia_ctime);
1235 ps_iattr->ia_iattr.ia_mtime =
1236 ps_iattr->ia_iattr.ia_ctime;
1237 }
1238
1239 kernfs_put(pos);
1240 }
1241
1242 kernfs_put(pos);
1243 } while (pos != kn);
1244}
1245
1246/**
1247 * kernfs_remove - remove a kernfs_node recursively
1248 * @kn: the kernfs_node to remove
1249 *
1250 * Remove @kn along with all its subdirectories and files.
1251 */
1252void kernfs_remove(struct kernfs_node *kn)
1253{
1254 mutex_lock(&kernfs_mutex);
1255 __kernfs_remove(kn);
1256 mutex_unlock(&kernfs_mutex);
1257}
1258
1259/**
1260 * kernfs_break_active_protection - break out of active protection
1261 * @kn: the self kernfs_node
1262 *
1263 * The caller must be running off of a kernfs operation which is invoked
1264 * with an active reference - e.g. one of kernfs_ops. Each invocation of
1265 * this function must also be matched with an invocation of
1266 * kernfs_unbreak_active_protection().
1267 *
1268 * This function releases the active reference of @kn the caller is
1269 * holding. Once this function is called, @kn may be removed at any point
1270 * and the caller is solely responsible for ensuring that the objects it
1271 * dereferences are accessible.
1272 */
1273void kernfs_break_active_protection(struct kernfs_node *kn)
1274{
1275 /*
1276 * Take out ourself out of the active ref dependency chain. If
1277 * we're called without an active ref, lockdep will complain.
1278 */
1279 kernfs_put_active(kn);
1280}
1281
1282/**
1283 * kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
1284 * @kn: the self kernfs_node
1285 *
1286 * If kernfs_break_active_protection() was called, this function must be
1287 * invoked before finishing the kernfs operation. Note that while this
1288 * function restores the active reference, it doesn't and can't actually
1289 * restore the active protection - @kn may already or be in the process of
1290 * being removed. Once kernfs_break_active_protection() is invoked, that
1291 * protection is irreversibly gone for the kernfs operation instance.
1292 *
1293 * While this function may be called at any point after
1294 * kernfs_break_active_protection() is invoked, its most useful location
1295 * would be right before the enclosing kernfs operation returns.
1296 */
1297void kernfs_unbreak_active_protection(struct kernfs_node *kn)
1298{
1299 /*
1300 * @kn->active could be in any state; however, the increment we do
1301 * here will be undone as soon as the enclosing kernfs operation
1302 * finishes and this temporary bump can't break anything. If @kn
1303 * is alive, nothing changes. If @kn is being deactivated, the
1304 * soon-to-follow put will either finish deactivation or restore
1305 * deactivated state. If @kn is already removed, the temporary
1306 * bump is guaranteed to be gone before @kn is released.
1307 */
1308 atomic_inc(&kn->active);
1309 if (kernfs_lockdep(kn))
1310 rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
1311}
1312
1313/**
1314 * kernfs_remove_self - remove a kernfs_node from its own method
1315 * @kn: the self kernfs_node to remove
1316 *
1317 * The caller must be running off of a kernfs operation which is invoked
1318 * with an active reference - e.g. one of kernfs_ops. This can be used to
1319 * implement a file operation which deletes itself.
1320 *
1321 * For example, the "delete" file for a sysfs device directory can be
1322 * implemented by invoking kernfs_remove_self() on the "delete" file
1323 * itself. This function breaks the circular dependency of trying to
1324 * deactivate self while holding an active ref itself. It isn't necessary
1325 * to modify the usual removal path to use kernfs_remove_self(). The
1326 * "delete" implementation can simply invoke kernfs_remove_self() on self
1327 * before proceeding with the usual removal path. kernfs will ignore later
1328 * kernfs_remove() on self.
1329 *
1330 * kernfs_remove_self() can be called multiple times concurrently on the
1331 * same kernfs_node. Only the first one actually performs removal and
1332 * returns %true. All others will wait until the kernfs operation which
1333 * won self-removal finishes and return %false. Note that the losers wait
1334 * for the completion of not only the winning kernfs_remove_self() but also
1335 * the whole kernfs_ops which won the arbitration. This can be used to
1336 * guarantee, for example, all concurrent writes to a "delete" file to
1337 * finish only after the whole operation is complete.
1338 */
1339bool kernfs_remove_self(struct kernfs_node *kn)
1340{
1341 bool ret;
1342
1343 mutex_lock(&kernfs_mutex);
1344 kernfs_break_active_protection(kn);
1345
1346 /*
1347 * SUICIDAL is used to arbitrate among competing invocations. Only
1348 * the first one will actually perform removal. When the removal
1349 * is complete, SUICIDED is set and the active ref is restored
1350 * while holding kernfs_mutex. The ones which lost arbitration
1351 * waits for SUICDED && drained which can happen only after the
1352 * enclosing kernfs operation which executed the winning instance
1353 * of kernfs_remove_self() finished.
1354 */
1355 if (!(kn->flags & KERNFS_SUICIDAL)) {
1356 kn->flags |= KERNFS_SUICIDAL;
1357 __kernfs_remove(kn);
1358 kn->flags |= KERNFS_SUICIDED;
1359 ret = true;
1360 } else {
1361 wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
1362 DEFINE_WAIT(wait);
1363
1364 while (true) {
1365 prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
1366
1367 if ((kn->flags & KERNFS_SUICIDED) &&
1368 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
1369 break;
1370
1371 mutex_unlock(&kernfs_mutex);
1372 schedule();
1373 mutex_lock(&kernfs_mutex);
1374 }
1375 finish_wait(waitq, &wait);
1376 WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
1377 ret = false;
1378 }
1379
1380 /*
1381 * This must be done while holding kernfs_mutex; otherwise, waiting
1382 * for SUICIDED && deactivated could finish prematurely.
1383 */
1384 kernfs_unbreak_active_protection(kn);
1385
1386 mutex_unlock(&kernfs_mutex);
1387 return ret;
1388}
1389
1390/**
1391 * kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
1392 * @parent: parent of the target
1393 * @name: name of the kernfs_node to remove
1394 * @ns: namespace tag of the kernfs_node to remove
1395 *
1396 * Look for the kernfs_node with @name and @ns under @parent and remove it.
1397 * Returns 0 on success, -ENOENT if such entry doesn't exist.
1398 */
1399int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
1400 const void *ns)
1401{
1402 struct kernfs_node *kn;
1403
1404 if (!parent) {
1405 WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
1406 name);
1407 return -ENOENT;
1408 }
1409
1410 mutex_lock(&kernfs_mutex);
1411
1412 kn = kernfs_find_ns(parent, name, ns);
1413 if (kn)
1414 __kernfs_remove(kn);
1415
1416 mutex_unlock(&kernfs_mutex);
1417
1418 if (kn)
1419 return 0;
1420 else
1421 return -ENOENT;
1422}
1423
1424/**
1425 * kernfs_rename_ns - move and rename a kernfs_node
1426 * @kn: target node
1427 * @new_parent: new parent to put @sd under
1428 * @new_name: new name
1429 * @new_ns: new namespace tag
1430 */
1431int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
1432 const char *new_name, const void *new_ns)
1433{
1434 struct kernfs_node *old_parent;
1435 const char *old_name = NULL;
1436 int error;
1437
1438 /* can't move or rename root */
1439 if (!kn->parent)
1440 return -EINVAL;
1441
1442 mutex_lock(&kernfs_mutex);
1443
1444 error = -ENOENT;
1445 if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
1446 (new_parent->flags & KERNFS_EMPTY_DIR))
1447 goto out;
1448
1449 error = 0;
1450 if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
1451 (strcmp(kn->name, new_name) == 0))
1452 goto out; /* nothing to rename */
1453
1454 error = -EEXIST;
1455 if (kernfs_find_ns(new_parent, new_name, new_ns))
1456 goto out;
1457
1458 /* rename kernfs_node */
1459 if (strcmp(kn->name, new_name) != 0) {
1460 error = -ENOMEM;
1461 new_name = kstrdup_const(new_name, GFP_KERNEL);
1462 if (!new_name)
1463 goto out;
1464 } else {
1465 new_name = NULL;
1466 }
1467
1468 /*
1469 * Move to the appropriate place in the appropriate directories rbtree.
1470 */
1471 kernfs_unlink_sibling(kn);
1472 kernfs_get(new_parent);
1473
1474 /* rename_lock protects ->parent and ->name accessors */
1475 spin_lock_irq(&kernfs_rename_lock);
1476
1477 old_parent = kn->parent;
1478 kn->parent = new_parent;
1479
1480 kn->ns = new_ns;
1481 if (new_name) {
1482 old_name = kn->name;
1483 kn->name = new_name;
1484 }
1485
1486 spin_unlock_irq(&kernfs_rename_lock);
1487
1488 kn->hash = kernfs_name_hash(kn->name, kn->ns);
1489 kernfs_link_sibling(kn);
1490
1491 kernfs_put(old_parent);
1492 kfree_const(old_name);
1493
1494 error = 0;
1495 out:
1496 mutex_unlock(&kernfs_mutex);
1497 return error;
1498}
1499
1500/* Relationship between s_mode and the DT_xxx types */
1501static inline unsigned char dt_type(struct kernfs_node *kn)
1502{
1503 return (kn->mode >> 12) & 15;
1504}
1505
1506static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
1507{
1508 kernfs_put(filp->private_data);
1509 return 0;
1510}
1511
1512static struct kernfs_node *kernfs_dir_pos(const void *ns,
1513 struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
1514{
1515 if (pos) {
1516 int valid = kernfs_active(pos) &&
1517 pos->parent == parent && hash == pos->hash;
1518 kernfs_put(pos);
1519 if (!valid)
1520 pos = NULL;
1521 }
1522 if (!pos && (hash > 1) && (hash < INT_MAX)) {
1523 struct rb_node *node = parent->dir.children.rb_node;
1524 while (node) {
1525 pos = rb_to_kn(node);
1526
1527 if (hash < pos->hash)
1528 node = node->rb_left;
1529 else if (hash > pos->hash)
1530 node = node->rb_right;
1531 else
1532 break;
1533 }
1534 }
1535 /* Skip over entries which are dying/dead or in the wrong namespace */
1536 while (pos && (!kernfs_active(pos) || pos->ns != ns)) {
1537 struct rb_node *node = rb_next(&pos->rb);
1538 if (!node)
1539 pos = NULL;
1540 else
1541 pos = rb_to_kn(node);
1542 }
1543 return pos;
1544}
1545
1546static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
1547 struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
1548{
1549 pos = kernfs_dir_pos(ns, parent, ino, pos);
1550 if (pos) {
1551 do {
1552 struct rb_node *node = rb_next(&pos->rb);
1553 if (!node)
1554 pos = NULL;
1555 else
1556 pos = rb_to_kn(node);
1557 } while (pos && (!kernfs_active(pos) || pos->ns != ns));
1558 }
1559 return pos;
1560}
1561
1562static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
1563{
1564 struct dentry *dentry = file->f_path.dentry;
1565 struct kernfs_node *parent = dentry->d_fsdata;
1566 struct kernfs_node *pos = file->private_data;
1567 const void *ns = NULL;
1568
1569 if (!dir_emit_dots(file, ctx))
1570 return 0;
1571 mutex_lock(&kernfs_mutex);
1572
1573 if (kernfs_ns_enabled(parent))
1574 ns = kernfs_info(dentry->d_sb)->ns;
1575
1576 for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
1577 pos;
1578 pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
1579 const char *name = pos->name;
1580 unsigned int type = dt_type(pos);
1581 int len = strlen(name);
1582 ino_t ino = pos->ino;
1583
1584 ctx->pos = pos->hash;
1585 file->private_data = pos;
1586 kernfs_get(pos);
1587
1588 mutex_unlock(&kernfs_mutex);
1589 if (!dir_emit(ctx, name, len, ino, type))
1590 return 0;
1591 mutex_lock(&kernfs_mutex);
1592 }
1593 mutex_unlock(&kernfs_mutex);
1594 file->private_data = NULL;
1595 ctx->pos = INT_MAX;
1596 return 0;
1597}
1598
1599const struct file_operations kernfs_dir_fops = {
1600 .read = generic_read_dir,
1601 .iterate_shared = kernfs_fop_readdir,
1602 .release = kernfs_dir_fop_release,
1603 .llseek = generic_file_llseek,
1604};
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
20static 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 */
28static DEFINE_SPINLOCK(kernfs_pr_cont_lock);
29static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by pr_cont_lock */
30static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
31
32#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
33
34static bool __kernfs_active(struct kernfs_node *kn)
35{
36 return atomic_read(&kn->active) >= 0;
37}
38
39static bool kernfs_active(struct kernfs_node *kn)
40{
41 lockdep_assert_held(&kernfs_root(kn)->kernfs_rwsem);
42 return __kernfs_active(kn);
43}
44
45static 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
54static 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 */
63static 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
74static 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 */
134static 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 */
196int 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 */
223int 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}
234EXPORT_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 */
242void 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 */
260void 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
279out:
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 */
292struct 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 */
312static 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
328static 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
342static 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 */
361static 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 */
408static 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 */
434struct 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 */
454void 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 */
478static 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 */
523void kernfs_get(struct kernfs_node *kn)
524{
525 if (kn) {
526 WARN_ON(!atomic_read(&kn->count));
527 atomic_inc(&kn->count);
528 }
529}
530EXPORT_SYMBOL_GPL(kernfs_get);
531
532/**
533 * kernfs_put - put a reference count on a kernfs_node
534 * @kn: the target kernfs_node
535 *
536 * Put a reference count of @kn and destroy it if it reached zero.
537 */
538void kernfs_put(struct kernfs_node *kn)
539{
540 struct kernfs_node *parent;
541 struct kernfs_root *root;
542
543 if (!kn || !atomic_dec_and_test(&kn->count))
544 return;
545 root = kernfs_root(kn);
546 repeat:
547 /*
548 * Moving/renaming is always done while holding reference.
549 * kn->parent won't change beneath us.
550 */
551 parent = kn->parent;
552
553 WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
554 "kernfs_put: %s/%s: released with incorrect active_ref %d\n",
555 parent ? parent->name : "", kn->name, atomic_read(&kn->active));
556
557 if (kernfs_type(kn) == KERNFS_LINK)
558 kernfs_put(kn->symlink.target_kn);
559
560 kfree_const(kn->name);
561
562 if (kn->iattr) {
563 simple_xattrs_free(&kn->iattr->xattrs, NULL);
564 kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
565 }
566 spin_lock(&kernfs_idr_lock);
567 idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
568 spin_unlock(&kernfs_idr_lock);
569 kmem_cache_free(kernfs_node_cache, kn);
570
571 kn = parent;
572 if (kn) {
573 if (atomic_dec_and_test(&kn->count))
574 goto repeat;
575 } else {
576 /* just released the root kn, free @root too */
577 idr_destroy(&root->ino_idr);
578 kfree(root);
579 }
580}
581EXPORT_SYMBOL_GPL(kernfs_put);
582
583/**
584 * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
585 * @dentry: the dentry in question
586 *
587 * Return: the kernfs_node associated with @dentry. If @dentry is not a
588 * kernfs one, %NULL is returned.
589 *
590 * While the returned kernfs_node will stay accessible as long as @dentry
591 * is accessible, the returned node can be in any state and the caller is
592 * fully responsible for determining what's accessible.
593 */
594struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
595{
596 if (dentry->d_sb->s_op == &kernfs_sops)
597 return kernfs_dentry_node(dentry);
598 return NULL;
599}
600
601static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
602 struct kernfs_node *parent,
603 const char *name, umode_t mode,
604 kuid_t uid, kgid_t gid,
605 unsigned flags)
606{
607 struct kernfs_node *kn;
608 u32 id_highbits;
609 int ret;
610
611 name = kstrdup_const(name, GFP_KERNEL);
612 if (!name)
613 return NULL;
614
615 kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
616 if (!kn)
617 goto err_out1;
618
619 idr_preload(GFP_KERNEL);
620 spin_lock(&kernfs_idr_lock);
621 ret = idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
622 if (ret >= 0 && ret < root->last_id_lowbits)
623 root->id_highbits++;
624 id_highbits = root->id_highbits;
625 root->last_id_lowbits = ret;
626 spin_unlock(&kernfs_idr_lock);
627 idr_preload_end();
628 if (ret < 0)
629 goto err_out2;
630
631 kn->id = (u64)id_highbits << 32 | ret;
632
633 atomic_set(&kn->count, 1);
634 atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
635 RB_CLEAR_NODE(&kn->rb);
636
637 kn->name = name;
638 kn->mode = mode;
639 kn->flags = flags;
640
641 if (!uid_eq(uid, GLOBAL_ROOT_UID) || !gid_eq(gid, GLOBAL_ROOT_GID)) {
642 struct iattr iattr = {
643 .ia_valid = ATTR_UID | ATTR_GID,
644 .ia_uid = uid,
645 .ia_gid = gid,
646 };
647
648 ret = __kernfs_setattr(kn, &iattr);
649 if (ret < 0)
650 goto err_out3;
651 }
652
653 if (parent) {
654 ret = security_kernfs_init_security(parent, kn);
655 if (ret)
656 goto err_out3;
657 }
658
659 return kn;
660
661 err_out3:
662 spin_lock(&kernfs_idr_lock);
663 idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
664 spin_unlock(&kernfs_idr_lock);
665 err_out2:
666 kmem_cache_free(kernfs_node_cache, kn);
667 err_out1:
668 kfree_const(name);
669 return NULL;
670}
671
672struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
673 const char *name, umode_t mode,
674 kuid_t uid, kgid_t gid,
675 unsigned flags)
676{
677 struct kernfs_node *kn;
678
679 if (parent->mode & S_ISGID) {
680 /* this code block imitates inode_init_owner() for
681 * kernfs
682 */
683
684 if (parent->iattr)
685 gid = parent->iattr->ia_gid;
686
687 if (flags & KERNFS_DIR)
688 mode |= S_ISGID;
689 }
690
691 kn = __kernfs_new_node(kernfs_root(parent), parent,
692 name, mode, uid, gid, flags);
693 if (kn) {
694 kernfs_get(parent);
695 kn->parent = parent;
696 }
697 return kn;
698}
699
700/*
701 * kernfs_find_and_get_node_by_id - get kernfs_node from node id
702 * @root: the kernfs root
703 * @id: the target node id
704 *
705 * @id's lower 32bits encode ino and upper gen. If the gen portion is
706 * zero, all generations are matched.
707 *
708 * Return: %NULL on failure,
709 * otherwise a kernfs node with reference counter incremented.
710 */
711struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
712 u64 id)
713{
714 struct kernfs_node *kn;
715 ino_t ino = kernfs_id_ino(id);
716 u32 gen = kernfs_id_gen(id);
717
718 spin_lock(&kernfs_idr_lock);
719
720 kn = idr_find(&root->ino_idr, (u32)ino);
721 if (!kn)
722 goto err_unlock;
723
724 if (sizeof(ino_t) >= sizeof(u64)) {
725 /* we looked up with the low 32bits, compare the whole */
726 if (kernfs_ino(kn) != ino)
727 goto err_unlock;
728 } else {
729 /* 0 matches all generations */
730 if (unlikely(gen && kernfs_gen(kn) != gen))
731 goto err_unlock;
732 }
733
734 /*
735 * We should fail if @kn has never been activated and guarantee success
736 * if the caller knows that @kn is active. Both can be achieved by
737 * __kernfs_active() which tests @kn->active without kernfs_rwsem.
738 */
739 if (unlikely(!__kernfs_active(kn) || !atomic_inc_not_zero(&kn->count)))
740 goto err_unlock;
741
742 spin_unlock(&kernfs_idr_lock);
743 return kn;
744err_unlock:
745 spin_unlock(&kernfs_idr_lock);
746 return NULL;
747}
748
749/**
750 * kernfs_add_one - add kernfs_node to parent without warning
751 * @kn: kernfs_node to be added
752 *
753 * The caller must already have initialized @kn->parent. This
754 * function increments nlink of the parent's inode if @kn is a
755 * directory and link into the children list of the parent.
756 *
757 * Return:
758 * %0 on success, -EEXIST if entry with the given name already
759 * exists.
760 */
761int kernfs_add_one(struct kernfs_node *kn)
762{
763 struct kernfs_node *parent = kn->parent;
764 struct kernfs_root *root = kernfs_root(parent);
765 struct kernfs_iattrs *ps_iattr;
766 bool has_ns;
767 int ret;
768
769 down_write(&root->kernfs_rwsem);
770
771 ret = -EINVAL;
772 has_ns = kernfs_ns_enabled(parent);
773 if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
774 has_ns ? "required" : "invalid", parent->name, kn->name))
775 goto out_unlock;
776
777 if (kernfs_type(parent) != KERNFS_DIR)
778 goto out_unlock;
779
780 ret = -ENOENT;
781 if (parent->flags & (KERNFS_REMOVING | KERNFS_EMPTY_DIR))
782 goto out_unlock;
783
784 kn->hash = kernfs_name_hash(kn->name, kn->ns);
785
786 ret = kernfs_link_sibling(kn);
787 if (ret)
788 goto out_unlock;
789
790 /* Update timestamps on the parent */
791 down_write(&root->kernfs_iattr_rwsem);
792
793 ps_iattr = parent->iattr;
794 if (ps_iattr) {
795 ktime_get_real_ts64(&ps_iattr->ia_ctime);
796 ps_iattr->ia_mtime = ps_iattr->ia_ctime;
797 }
798
799 up_write(&root->kernfs_iattr_rwsem);
800 up_write(&root->kernfs_rwsem);
801
802 /*
803 * Activate the new node unless CREATE_DEACTIVATED is requested.
804 * If not activated here, the kernfs user is responsible for
805 * activating the node with kernfs_activate(). A node which hasn't
806 * been activated is not visible to userland and its removal won't
807 * trigger deactivation.
808 */
809 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
810 kernfs_activate(kn);
811 return 0;
812
813out_unlock:
814 up_write(&root->kernfs_rwsem);
815 return ret;
816}
817
818/**
819 * kernfs_find_ns - find kernfs_node with the given name
820 * @parent: kernfs_node to search under
821 * @name: name to look for
822 * @ns: the namespace tag to use
823 *
824 * Look for kernfs_node with name @name under @parent.
825 *
826 * Return: pointer to the found kernfs_node on success, %NULL on failure.
827 */
828static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
829 const unsigned char *name,
830 const void *ns)
831{
832 struct rb_node *node = parent->dir.children.rb_node;
833 bool has_ns = kernfs_ns_enabled(parent);
834 unsigned int hash;
835
836 lockdep_assert_held(&kernfs_root(parent)->kernfs_rwsem);
837
838 if (has_ns != (bool)ns) {
839 WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
840 has_ns ? "required" : "invalid", parent->name, name);
841 return NULL;
842 }
843
844 hash = kernfs_name_hash(name, ns);
845 while (node) {
846 struct kernfs_node *kn;
847 int result;
848
849 kn = rb_to_kn(node);
850 result = kernfs_name_compare(hash, name, ns, kn);
851 if (result < 0)
852 node = node->rb_left;
853 else if (result > 0)
854 node = node->rb_right;
855 else
856 return kn;
857 }
858 return NULL;
859}
860
861static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
862 const unsigned char *path,
863 const void *ns)
864{
865 ssize_t len;
866 char *p, *name;
867
868 lockdep_assert_held_read(&kernfs_root(parent)->kernfs_rwsem);
869
870 spin_lock_irq(&kernfs_pr_cont_lock);
871
872 len = strscpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
873
874 if (len < 0) {
875 spin_unlock_irq(&kernfs_pr_cont_lock);
876 return NULL;
877 }
878
879 p = kernfs_pr_cont_buf;
880
881 while ((name = strsep(&p, "/")) && parent) {
882 if (*name == '\0')
883 continue;
884 parent = kernfs_find_ns(parent, name, ns);
885 }
886
887 spin_unlock_irq(&kernfs_pr_cont_lock);
888
889 return parent;
890}
891
892/**
893 * kernfs_find_and_get_ns - find and get kernfs_node with the given name
894 * @parent: kernfs_node to search under
895 * @name: name to look for
896 * @ns: the namespace tag to use
897 *
898 * Look for kernfs_node with name @name under @parent and get a reference
899 * if found. This function may sleep.
900 *
901 * Return: pointer to the found kernfs_node on success, %NULL on failure.
902 */
903struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
904 const char *name, const void *ns)
905{
906 struct kernfs_node *kn;
907 struct kernfs_root *root = kernfs_root(parent);
908
909 down_read(&root->kernfs_rwsem);
910 kn = kernfs_find_ns(parent, name, ns);
911 kernfs_get(kn);
912 up_read(&root->kernfs_rwsem);
913
914 return kn;
915}
916EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
917
918/**
919 * kernfs_walk_and_get_ns - find and get kernfs_node with the given path
920 * @parent: kernfs_node to search under
921 * @path: path to look for
922 * @ns: the namespace tag to use
923 *
924 * Look for kernfs_node with path @path under @parent and get a reference
925 * if found. This function may sleep.
926 *
927 * Return: pointer to the found kernfs_node on success, %NULL on failure.
928 */
929struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
930 const char *path, const void *ns)
931{
932 struct kernfs_node *kn;
933 struct kernfs_root *root = kernfs_root(parent);
934
935 down_read(&root->kernfs_rwsem);
936 kn = kernfs_walk_ns(parent, path, ns);
937 kernfs_get(kn);
938 up_read(&root->kernfs_rwsem);
939
940 return kn;
941}
942
943/**
944 * kernfs_create_root - create a new kernfs hierarchy
945 * @scops: optional syscall operations for the hierarchy
946 * @flags: KERNFS_ROOT_* flags
947 * @priv: opaque data associated with the new directory
948 *
949 * Return: the root of the new hierarchy on success, ERR_PTR() value on
950 * failure.
951 */
952struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
953 unsigned int flags, void *priv)
954{
955 struct kernfs_root *root;
956 struct kernfs_node *kn;
957
958 root = kzalloc(sizeof(*root), GFP_KERNEL);
959 if (!root)
960 return ERR_PTR(-ENOMEM);
961
962 idr_init(&root->ino_idr);
963 init_rwsem(&root->kernfs_rwsem);
964 init_rwsem(&root->kernfs_iattr_rwsem);
965 init_rwsem(&root->kernfs_supers_rwsem);
966 INIT_LIST_HEAD(&root->supers);
967
968 /*
969 * On 64bit ino setups, id is ino. On 32bit, low 32bits are ino.
970 * High bits generation. The starting value for both ino and
971 * genenration is 1. Initialize upper 32bit allocation
972 * accordingly.
973 */
974 if (sizeof(ino_t) >= sizeof(u64))
975 root->id_highbits = 0;
976 else
977 root->id_highbits = 1;
978
979 kn = __kernfs_new_node(root, NULL, "", S_IFDIR | S_IRUGO | S_IXUGO,
980 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
981 KERNFS_DIR);
982 if (!kn) {
983 idr_destroy(&root->ino_idr);
984 kfree(root);
985 return ERR_PTR(-ENOMEM);
986 }
987
988 kn->priv = priv;
989 kn->dir.root = root;
990
991 root->syscall_ops = scops;
992 root->flags = flags;
993 root->kn = kn;
994 init_waitqueue_head(&root->deactivate_waitq);
995
996 if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
997 kernfs_activate(kn);
998
999 return root;
1000}
1001
1002/**
1003 * kernfs_destroy_root - destroy a kernfs hierarchy
1004 * @root: root of the hierarchy to destroy
1005 *
1006 * Destroy the hierarchy anchored at @root by removing all existing
1007 * directories and destroying @root.
1008 */
1009void kernfs_destroy_root(struct kernfs_root *root)
1010{
1011 /*
1012 * kernfs_remove holds kernfs_rwsem from the root so the root
1013 * shouldn't be freed during the operation.
1014 */
1015 kernfs_get(root->kn);
1016 kernfs_remove(root->kn);
1017 kernfs_put(root->kn); /* will also free @root */
1018}
1019
1020/**
1021 * kernfs_root_to_node - return the kernfs_node associated with a kernfs_root
1022 * @root: root to use to lookup
1023 *
1024 * Return: @root's kernfs_node
1025 */
1026struct kernfs_node *kernfs_root_to_node(struct kernfs_root *root)
1027{
1028 return root->kn;
1029}
1030
1031/**
1032 * kernfs_create_dir_ns - create a directory
1033 * @parent: parent in which to create a new directory
1034 * @name: name of the new directory
1035 * @mode: mode of the new directory
1036 * @uid: uid of the new directory
1037 * @gid: gid of the new directory
1038 * @priv: opaque data associated with the new directory
1039 * @ns: optional namespace tag of the directory
1040 *
1041 * Return: the created node on success, ERR_PTR() value on failure.
1042 */
1043struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
1044 const char *name, umode_t mode,
1045 kuid_t uid, kgid_t gid,
1046 void *priv, const void *ns)
1047{
1048 struct kernfs_node *kn;
1049 int rc;
1050
1051 /* allocate */
1052 kn = kernfs_new_node(parent, name, mode | S_IFDIR,
1053 uid, gid, KERNFS_DIR);
1054 if (!kn)
1055 return ERR_PTR(-ENOMEM);
1056
1057 kn->dir.root = parent->dir.root;
1058 kn->ns = ns;
1059 kn->priv = priv;
1060
1061 /* link in */
1062 rc = kernfs_add_one(kn);
1063 if (!rc)
1064 return kn;
1065
1066 kernfs_put(kn);
1067 return ERR_PTR(rc);
1068}
1069
1070/**
1071 * kernfs_create_empty_dir - create an always empty directory
1072 * @parent: parent in which to create a new directory
1073 * @name: name of the new directory
1074 *
1075 * Return: the created node on success, ERR_PTR() value on failure.
1076 */
1077struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
1078 const char *name)
1079{
1080 struct kernfs_node *kn;
1081 int rc;
1082
1083 /* allocate */
1084 kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR,
1085 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, KERNFS_DIR);
1086 if (!kn)
1087 return ERR_PTR(-ENOMEM);
1088
1089 kn->flags |= KERNFS_EMPTY_DIR;
1090 kn->dir.root = parent->dir.root;
1091 kn->ns = NULL;
1092 kn->priv = NULL;
1093
1094 /* link in */
1095 rc = kernfs_add_one(kn);
1096 if (!rc)
1097 return kn;
1098
1099 kernfs_put(kn);
1100 return ERR_PTR(rc);
1101}
1102
1103static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
1104{
1105 struct kernfs_node *kn;
1106 struct kernfs_root *root;
1107
1108 if (flags & LOOKUP_RCU)
1109 return -ECHILD;
1110
1111 /* Negative hashed dentry? */
1112 if (d_really_is_negative(dentry)) {
1113 struct kernfs_node *parent;
1114
1115 /* If the kernfs parent node has changed discard and
1116 * proceed to ->lookup.
1117 *
1118 * There's nothing special needed here when getting the
1119 * dentry parent, even if a concurrent rename is in
1120 * progress. That's because the dentry is negative so
1121 * it can only be the target of the rename and it will
1122 * be doing a d_move() not a replace. Consequently the
1123 * dentry d_parent won't change over the d_move().
1124 *
1125 * Also kernfs negative dentries transitioning from
1126 * negative to positive during revalidate won't happen
1127 * because they are invalidated on containing directory
1128 * changes and the lookup re-done so that a new positive
1129 * dentry can be properly created.
1130 */
1131 root = kernfs_root_from_sb(dentry->d_sb);
1132 down_read(&root->kernfs_rwsem);
1133 parent = kernfs_dentry_node(dentry->d_parent);
1134 if (parent) {
1135 if (kernfs_dir_changed(parent, dentry)) {
1136 up_read(&root->kernfs_rwsem);
1137 return 0;
1138 }
1139 }
1140 up_read(&root->kernfs_rwsem);
1141
1142 /* The kernfs parent node hasn't changed, leave the
1143 * dentry negative and return success.
1144 */
1145 return 1;
1146 }
1147
1148 kn = kernfs_dentry_node(dentry);
1149 root = kernfs_root(kn);
1150 down_read(&root->kernfs_rwsem);
1151
1152 /* The kernfs node has been deactivated */
1153 if (!kernfs_active(kn))
1154 goto out_bad;
1155
1156 /* The kernfs node has been moved? */
1157 if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
1158 goto out_bad;
1159
1160 /* The kernfs node has been renamed */
1161 if (strcmp(dentry->d_name.name, kn->name) != 0)
1162 goto out_bad;
1163
1164 /* The kernfs node has been moved to a different namespace */
1165 if (kn->parent && kernfs_ns_enabled(kn->parent) &&
1166 kernfs_info(dentry->d_sb)->ns != kn->ns)
1167 goto out_bad;
1168
1169 up_read(&root->kernfs_rwsem);
1170 return 1;
1171out_bad:
1172 up_read(&root->kernfs_rwsem);
1173 return 0;
1174}
1175
1176const struct dentry_operations kernfs_dops = {
1177 .d_revalidate = kernfs_dop_revalidate,
1178};
1179
1180static struct dentry *kernfs_iop_lookup(struct inode *dir,
1181 struct dentry *dentry,
1182 unsigned int flags)
1183{
1184 struct kernfs_node *parent = dir->i_private;
1185 struct kernfs_node *kn;
1186 struct kernfs_root *root;
1187 struct inode *inode = NULL;
1188 const void *ns = NULL;
1189
1190 root = kernfs_root(parent);
1191 down_read(&root->kernfs_rwsem);
1192 if (kernfs_ns_enabled(parent))
1193 ns = kernfs_info(dir->i_sb)->ns;
1194
1195 kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
1196 /* attach dentry and inode */
1197 if (kn) {
1198 /* Inactive nodes are invisible to the VFS so don't
1199 * create a negative.
1200 */
1201 if (!kernfs_active(kn)) {
1202 up_read(&root->kernfs_rwsem);
1203 return NULL;
1204 }
1205 inode = kernfs_get_inode(dir->i_sb, kn);
1206 if (!inode)
1207 inode = ERR_PTR(-ENOMEM);
1208 }
1209 /*
1210 * Needed for negative dentry validation.
1211 * The negative dentry can be created in kernfs_iop_lookup()
1212 * or transforms from positive dentry in dentry_unlink_inode()
1213 * called from vfs_rmdir().
1214 */
1215 if (!IS_ERR(inode))
1216 kernfs_set_rev(parent, dentry);
1217 up_read(&root->kernfs_rwsem);
1218
1219 /* instantiate and hash (possibly negative) dentry */
1220 return d_splice_alias(inode, dentry);
1221}
1222
1223static int kernfs_iop_mkdir(struct mnt_idmap *idmap,
1224 struct inode *dir, struct dentry *dentry,
1225 umode_t mode)
1226{
1227 struct kernfs_node *parent = dir->i_private;
1228 struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
1229 int ret;
1230
1231 if (!scops || !scops->mkdir)
1232 return -EPERM;
1233
1234 if (!kernfs_get_active(parent))
1235 return -ENODEV;
1236
1237 ret = scops->mkdir(parent, dentry->d_name.name, mode);
1238
1239 kernfs_put_active(parent);
1240 return ret;
1241}
1242
1243static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
1244{
1245 struct kernfs_node *kn = kernfs_dentry_node(dentry);
1246 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
1247 int ret;
1248
1249 if (!scops || !scops->rmdir)
1250 return -EPERM;
1251
1252 if (!kernfs_get_active(kn))
1253 return -ENODEV;
1254
1255 ret = scops->rmdir(kn);
1256
1257 kernfs_put_active(kn);
1258 return ret;
1259}
1260
1261static int kernfs_iop_rename(struct mnt_idmap *idmap,
1262 struct inode *old_dir, struct dentry *old_dentry,
1263 struct inode *new_dir, struct dentry *new_dentry,
1264 unsigned int flags)
1265{
1266 struct kernfs_node *kn = kernfs_dentry_node(old_dentry);
1267 struct kernfs_node *new_parent = new_dir->i_private;
1268 struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
1269 int ret;
1270
1271 if (flags)
1272 return -EINVAL;
1273
1274 if (!scops || !scops->rename)
1275 return -EPERM;
1276
1277 if (!kernfs_get_active(kn))
1278 return -ENODEV;
1279
1280 if (!kernfs_get_active(new_parent)) {
1281 kernfs_put_active(kn);
1282 return -ENODEV;
1283 }
1284
1285 ret = scops->rename(kn, new_parent, new_dentry->d_name.name);
1286
1287 kernfs_put_active(new_parent);
1288 kernfs_put_active(kn);
1289 return ret;
1290}
1291
1292const struct inode_operations kernfs_dir_iops = {
1293 .lookup = kernfs_iop_lookup,
1294 .permission = kernfs_iop_permission,
1295 .setattr = kernfs_iop_setattr,
1296 .getattr = kernfs_iop_getattr,
1297 .listxattr = kernfs_iop_listxattr,
1298
1299 .mkdir = kernfs_iop_mkdir,
1300 .rmdir = kernfs_iop_rmdir,
1301 .rename = kernfs_iop_rename,
1302};
1303
1304static struct kernfs_node *kernfs_leftmost_descendant(struct kernfs_node *pos)
1305{
1306 struct kernfs_node *last;
1307
1308 while (true) {
1309 struct rb_node *rbn;
1310
1311 last = pos;
1312
1313 if (kernfs_type(pos) != KERNFS_DIR)
1314 break;
1315
1316 rbn = rb_first(&pos->dir.children);
1317 if (!rbn)
1318 break;
1319
1320 pos = rb_to_kn(rbn);
1321 }
1322
1323 return last;
1324}
1325
1326/**
1327 * kernfs_next_descendant_post - find the next descendant for post-order walk
1328 * @pos: the current position (%NULL to initiate traversal)
1329 * @root: kernfs_node whose descendants to walk
1330 *
1331 * Find the next descendant to visit for post-order traversal of @root's
1332 * descendants. @root is included in the iteration and the last node to be
1333 * visited.
1334 *
1335 * Return: the next descendant to visit or %NULL when done.
1336 */
1337static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
1338 struct kernfs_node *root)
1339{
1340 struct rb_node *rbn;
1341
1342 lockdep_assert_held_write(&kernfs_root(root)->kernfs_rwsem);
1343
1344 /* if first iteration, visit leftmost descendant which may be root */
1345 if (!pos)
1346 return kernfs_leftmost_descendant(root);
1347
1348 /* if we visited @root, we're done */
1349 if (pos == root)
1350 return NULL;
1351
1352 /* if there's an unvisited sibling, visit its leftmost descendant */
1353 rbn = rb_next(&pos->rb);
1354 if (rbn)
1355 return kernfs_leftmost_descendant(rb_to_kn(rbn));
1356
1357 /* no sibling left, visit parent */
1358 return pos->parent;
1359}
1360
1361static void kernfs_activate_one(struct kernfs_node *kn)
1362{
1363 lockdep_assert_held_write(&kernfs_root(kn)->kernfs_rwsem);
1364
1365 kn->flags |= KERNFS_ACTIVATED;
1366
1367 if (kernfs_active(kn) || (kn->flags & (KERNFS_HIDDEN | KERNFS_REMOVING)))
1368 return;
1369
1370 WARN_ON_ONCE(kn->parent && RB_EMPTY_NODE(&kn->rb));
1371 WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
1372
1373 atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
1374}
1375
1376/**
1377 * kernfs_activate - activate a node which started deactivated
1378 * @kn: kernfs_node whose subtree is to be activated
1379 *
1380 * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
1381 * needs to be explicitly activated. A node which hasn't been activated
1382 * isn't visible to userland and deactivation is skipped during its
1383 * removal. This is useful to construct atomic init sequences where
1384 * creation of multiple nodes should either succeed or fail atomically.
1385 *
1386 * The caller is responsible for ensuring that this function is not called
1387 * after kernfs_remove*() is invoked on @kn.
1388 */
1389void kernfs_activate(struct kernfs_node *kn)
1390{
1391 struct kernfs_node *pos;
1392 struct kernfs_root *root = kernfs_root(kn);
1393
1394 down_write(&root->kernfs_rwsem);
1395
1396 pos = NULL;
1397 while ((pos = kernfs_next_descendant_post(pos, kn)))
1398 kernfs_activate_one(pos);
1399
1400 up_write(&root->kernfs_rwsem);
1401}
1402
1403/**
1404 * kernfs_show - show or hide a node
1405 * @kn: kernfs_node to show or hide
1406 * @show: whether to show or hide
1407 *
1408 * If @show is %false, @kn is marked hidden and deactivated. A hidden node is
1409 * ignored in future activaitons. If %true, the mark is removed and activation
1410 * state is restored. This function won't implicitly activate a new node in a
1411 * %KERNFS_ROOT_CREATE_DEACTIVATED root which hasn't been activated yet.
1412 *
1413 * To avoid recursion complexities, directories aren't supported for now.
1414 */
1415void kernfs_show(struct kernfs_node *kn, bool show)
1416{
1417 struct kernfs_root *root = kernfs_root(kn);
1418
1419 if (WARN_ON_ONCE(kernfs_type(kn) == KERNFS_DIR))
1420 return;
1421
1422 down_write(&root->kernfs_rwsem);
1423
1424 if (show) {
1425 kn->flags &= ~KERNFS_HIDDEN;
1426 if (kn->flags & KERNFS_ACTIVATED)
1427 kernfs_activate_one(kn);
1428 } else {
1429 kn->flags |= KERNFS_HIDDEN;
1430 if (kernfs_active(kn))
1431 atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
1432 kernfs_drain(kn);
1433 }
1434
1435 up_write(&root->kernfs_rwsem);
1436}
1437
1438static void __kernfs_remove(struct kernfs_node *kn)
1439{
1440 struct kernfs_node *pos;
1441
1442 /* Short-circuit if non-root @kn has already finished removal. */
1443 if (!kn)
1444 return;
1445
1446 lockdep_assert_held_write(&kernfs_root(kn)->kernfs_rwsem);
1447
1448 /*
1449 * This is for kernfs_remove_self() which plays with active ref
1450 * after removal.
1451 */
1452 if (kn->parent && RB_EMPTY_NODE(&kn->rb))
1453 return;
1454
1455 pr_debug("kernfs %s: removing\n", kn->name);
1456
1457 /* prevent new usage by marking all nodes removing and deactivating */
1458 pos = NULL;
1459 while ((pos = kernfs_next_descendant_post(pos, kn))) {
1460 pos->flags |= KERNFS_REMOVING;
1461 if (kernfs_active(pos))
1462 atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
1463 }
1464
1465 /* deactivate and unlink the subtree node-by-node */
1466 do {
1467 pos = kernfs_leftmost_descendant(kn);
1468
1469 /*
1470 * kernfs_drain() may drop kernfs_rwsem temporarily and @pos's
1471 * base ref could have been put by someone else by the time
1472 * the function returns. Make sure it doesn't go away
1473 * underneath us.
1474 */
1475 kernfs_get(pos);
1476
1477 kernfs_drain(pos);
1478
1479 /*
1480 * kernfs_unlink_sibling() succeeds once per node. Use it
1481 * to decide who's responsible for cleanups.
1482 */
1483 if (!pos->parent || kernfs_unlink_sibling(pos)) {
1484 struct kernfs_iattrs *ps_iattr =
1485 pos->parent ? pos->parent->iattr : NULL;
1486
1487 /* update timestamps on the parent */
1488 down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
1489
1490 if (ps_iattr) {
1491 ktime_get_real_ts64(&ps_iattr->ia_ctime);
1492 ps_iattr->ia_mtime = ps_iattr->ia_ctime;
1493 }
1494
1495 up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
1496 kernfs_put(pos);
1497 }
1498
1499 kernfs_put(pos);
1500 } while (pos != kn);
1501}
1502
1503/**
1504 * kernfs_remove - remove a kernfs_node recursively
1505 * @kn: the kernfs_node to remove
1506 *
1507 * Remove @kn along with all its subdirectories and files.
1508 */
1509void kernfs_remove(struct kernfs_node *kn)
1510{
1511 struct kernfs_root *root;
1512
1513 if (!kn)
1514 return;
1515
1516 root = kernfs_root(kn);
1517
1518 down_write(&root->kernfs_rwsem);
1519 __kernfs_remove(kn);
1520 up_write(&root->kernfs_rwsem);
1521}
1522
1523/**
1524 * kernfs_break_active_protection - break out of active protection
1525 * @kn: the self kernfs_node
1526 *
1527 * The caller must be running off of a kernfs operation which is invoked
1528 * with an active reference - e.g. one of kernfs_ops. Each invocation of
1529 * this function must also be matched with an invocation of
1530 * kernfs_unbreak_active_protection().
1531 *
1532 * This function releases the active reference of @kn the caller is
1533 * holding. Once this function is called, @kn may be removed at any point
1534 * and the caller is solely responsible for ensuring that the objects it
1535 * dereferences are accessible.
1536 */
1537void kernfs_break_active_protection(struct kernfs_node *kn)
1538{
1539 /*
1540 * Take out ourself out of the active ref dependency chain. If
1541 * we're called without an active ref, lockdep will complain.
1542 */
1543 kernfs_put_active(kn);
1544}
1545
1546/**
1547 * kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
1548 * @kn: the self kernfs_node
1549 *
1550 * If kernfs_break_active_protection() was called, this function must be
1551 * invoked before finishing the kernfs operation. Note that while this
1552 * function restores the active reference, it doesn't and can't actually
1553 * restore the active protection - @kn may already or be in the process of
1554 * being removed. Once kernfs_break_active_protection() is invoked, that
1555 * protection is irreversibly gone for the kernfs operation instance.
1556 *
1557 * While this function may be called at any point after
1558 * kernfs_break_active_protection() is invoked, its most useful location
1559 * would be right before the enclosing kernfs operation returns.
1560 */
1561void kernfs_unbreak_active_protection(struct kernfs_node *kn)
1562{
1563 /*
1564 * @kn->active could be in any state; however, the increment we do
1565 * here will be undone as soon as the enclosing kernfs operation
1566 * finishes and this temporary bump can't break anything. If @kn
1567 * is alive, nothing changes. If @kn is being deactivated, the
1568 * soon-to-follow put will either finish deactivation or restore
1569 * deactivated state. If @kn is already removed, the temporary
1570 * bump is guaranteed to be gone before @kn is released.
1571 */
1572 atomic_inc(&kn->active);
1573 if (kernfs_lockdep(kn))
1574 rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
1575}
1576
1577/**
1578 * kernfs_remove_self - remove a kernfs_node from its own method
1579 * @kn: the self kernfs_node to remove
1580 *
1581 * The caller must be running off of a kernfs operation which is invoked
1582 * with an active reference - e.g. one of kernfs_ops. This can be used to
1583 * implement a file operation which deletes itself.
1584 *
1585 * For example, the "delete" file for a sysfs device directory can be
1586 * implemented by invoking kernfs_remove_self() on the "delete" file
1587 * itself. This function breaks the circular dependency of trying to
1588 * deactivate self while holding an active ref itself. It isn't necessary
1589 * to modify the usual removal path to use kernfs_remove_self(). The
1590 * "delete" implementation can simply invoke kernfs_remove_self() on self
1591 * before proceeding with the usual removal path. kernfs will ignore later
1592 * kernfs_remove() on self.
1593 *
1594 * kernfs_remove_self() can be called multiple times concurrently on the
1595 * same kernfs_node. Only the first one actually performs removal and
1596 * returns %true. All others will wait until the kernfs operation which
1597 * won self-removal finishes and return %false. Note that the losers wait
1598 * for the completion of not only the winning kernfs_remove_self() but also
1599 * the whole kernfs_ops which won the arbitration. This can be used to
1600 * guarantee, for example, all concurrent writes to a "delete" file to
1601 * finish only after the whole operation is complete.
1602 *
1603 * Return: %true if @kn is removed by this call, otherwise %false.
1604 */
1605bool kernfs_remove_self(struct kernfs_node *kn)
1606{
1607 bool ret;
1608 struct kernfs_root *root = kernfs_root(kn);
1609
1610 down_write(&root->kernfs_rwsem);
1611 kernfs_break_active_protection(kn);
1612
1613 /*
1614 * SUICIDAL is used to arbitrate among competing invocations. Only
1615 * the first one will actually perform removal. When the removal
1616 * is complete, SUICIDED is set and the active ref is restored
1617 * while kernfs_rwsem for held exclusive. The ones which lost
1618 * arbitration waits for SUICIDED && drained which can happen only
1619 * after the enclosing kernfs operation which executed the winning
1620 * instance of kernfs_remove_self() finished.
1621 */
1622 if (!(kn->flags & KERNFS_SUICIDAL)) {
1623 kn->flags |= KERNFS_SUICIDAL;
1624 __kernfs_remove(kn);
1625 kn->flags |= KERNFS_SUICIDED;
1626 ret = true;
1627 } else {
1628 wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
1629 DEFINE_WAIT(wait);
1630
1631 while (true) {
1632 prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
1633
1634 if ((kn->flags & KERNFS_SUICIDED) &&
1635 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
1636 break;
1637
1638 up_write(&root->kernfs_rwsem);
1639 schedule();
1640 down_write(&root->kernfs_rwsem);
1641 }
1642 finish_wait(waitq, &wait);
1643 WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
1644 ret = false;
1645 }
1646
1647 /*
1648 * This must be done while kernfs_rwsem held exclusive; otherwise,
1649 * waiting for SUICIDED && deactivated could finish prematurely.
1650 */
1651 kernfs_unbreak_active_protection(kn);
1652
1653 up_write(&root->kernfs_rwsem);
1654 return ret;
1655}
1656
1657/**
1658 * kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
1659 * @parent: parent of the target
1660 * @name: name of the kernfs_node to remove
1661 * @ns: namespace tag of the kernfs_node to remove
1662 *
1663 * Look for the kernfs_node with @name and @ns under @parent and remove it.
1664 *
1665 * Return: %0 on success, -ENOENT if such entry doesn't exist.
1666 */
1667int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
1668 const void *ns)
1669{
1670 struct kernfs_node *kn;
1671 struct kernfs_root *root;
1672
1673 if (!parent) {
1674 WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
1675 name);
1676 return -ENOENT;
1677 }
1678
1679 root = kernfs_root(parent);
1680 down_write(&root->kernfs_rwsem);
1681
1682 kn = kernfs_find_ns(parent, name, ns);
1683 if (kn) {
1684 kernfs_get(kn);
1685 __kernfs_remove(kn);
1686 kernfs_put(kn);
1687 }
1688
1689 up_write(&root->kernfs_rwsem);
1690
1691 if (kn)
1692 return 0;
1693 else
1694 return -ENOENT;
1695}
1696
1697/**
1698 * kernfs_rename_ns - move and rename a kernfs_node
1699 * @kn: target node
1700 * @new_parent: new parent to put @sd under
1701 * @new_name: new name
1702 * @new_ns: new namespace tag
1703 *
1704 * Return: %0 on success, -errno on failure.
1705 */
1706int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
1707 const char *new_name, const void *new_ns)
1708{
1709 struct kernfs_node *old_parent;
1710 struct kernfs_root *root;
1711 const char *old_name = NULL;
1712 int error;
1713
1714 /* can't move or rename root */
1715 if (!kn->parent)
1716 return -EINVAL;
1717
1718 root = kernfs_root(kn);
1719 down_write(&root->kernfs_rwsem);
1720
1721 error = -ENOENT;
1722 if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
1723 (new_parent->flags & KERNFS_EMPTY_DIR))
1724 goto out;
1725
1726 error = 0;
1727 if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
1728 (strcmp(kn->name, new_name) == 0))
1729 goto out; /* nothing to rename */
1730
1731 error = -EEXIST;
1732 if (kernfs_find_ns(new_parent, new_name, new_ns))
1733 goto out;
1734
1735 /* rename kernfs_node */
1736 if (strcmp(kn->name, new_name) != 0) {
1737 error = -ENOMEM;
1738 new_name = kstrdup_const(new_name, GFP_KERNEL);
1739 if (!new_name)
1740 goto out;
1741 } else {
1742 new_name = NULL;
1743 }
1744
1745 /*
1746 * Move to the appropriate place in the appropriate directories rbtree.
1747 */
1748 kernfs_unlink_sibling(kn);
1749 kernfs_get(new_parent);
1750
1751 /* rename_lock protects ->parent and ->name accessors */
1752 write_lock_irq(&kernfs_rename_lock);
1753
1754 old_parent = kn->parent;
1755 kn->parent = new_parent;
1756
1757 kn->ns = new_ns;
1758 if (new_name) {
1759 old_name = kn->name;
1760 kn->name = new_name;
1761 }
1762
1763 write_unlock_irq(&kernfs_rename_lock);
1764
1765 kn->hash = kernfs_name_hash(kn->name, kn->ns);
1766 kernfs_link_sibling(kn);
1767
1768 kernfs_put(old_parent);
1769 kfree_const(old_name);
1770
1771 error = 0;
1772 out:
1773 up_write(&root->kernfs_rwsem);
1774 return error;
1775}
1776
1777static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
1778{
1779 kernfs_put(filp->private_data);
1780 return 0;
1781}
1782
1783static struct kernfs_node *kernfs_dir_pos(const void *ns,
1784 struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
1785{
1786 if (pos) {
1787 int valid = kernfs_active(pos) &&
1788 pos->parent == parent && hash == pos->hash;
1789 kernfs_put(pos);
1790 if (!valid)
1791 pos = NULL;
1792 }
1793 if (!pos && (hash > 1) && (hash < INT_MAX)) {
1794 struct rb_node *node = parent->dir.children.rb_node;
1795 while (node) {
1796 pos = rb_to_kn(node);
1797
1798 if (hash < pos->hash)
1799 node = node->rb_left;
1800 else if (hash > pos->hash)
1801 node = node->rb_right;
1802 else
1803 break;
1804 }
1805 }
1806 /* Skip over entries which are dying/dead or in the wrong namespace */
1807 while (pos && (!kernfs_active(pos) || pos->ns != ns)) {
1808 struct rb_node *node = rb_next(&pos->rb);
1809 if (!node)
1810 pos = NULL;
1811 else
1812 pos = rb_to_kn(node);
1813 }
1814 return pos;
1815}
1816
1817static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
1818 struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
1819{
1820 pos = kernfs_dir_pos(ns, parent, ino, pos);
1821 if (pos) {
1822 do {
1823 struct rb_node *node = rb_next(&pos->rb);
1824 if (!node)
1825 pos = NULL;
1826 else
1827 pos = rb_to_kn(node);
1828 } while (pos && (!kernfs_active(pos) || pos->ns != ns));
1829 }
1830 return pos;
1831}
1832
1833static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
1834{
1835 struct dentry *dentry = file->f_path.dentry;
1836 struct kernfs_node *parent = kernfs_dentry_node(dentry);
1837 struct kernfs_node *pos = file->private_data;
1838 struct kernfs_root *root;
1839 const void *ns = NULL;
1840
1841 if (!dir_emit_dots(file, ctx))
1842 return 0;
1843
1844 root = kernfs_root(parent);
1845 down_read(&root->kernfs_rwsem);
1846
1847 if (kernfs_ns_enabled(parent))
1848 ns = kernfs_info(dentry->d_sb)->ns;
1849
1850 for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
1851 pos;
1852 pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
1853 const char *name = pos->name;
1854 unsigned int type = fs_umode_to_dtype(pos->mode);
1855 int len = strlen(name);
1856 ino_t ino = kernfs_ino(pos);
1857
1858 ctx->pos = pos->hash;
1859 file->private_data = pos;
1860 kernfs_get(pos);
1861
1862 up_read(&root->kernfs_rwsem);
1863 if (!dir_emit(ctx, name, len, ino, type))
1864 return 0;
1865 down_read(&root->kernfs_rwsem);
1866 }
1867 up_read(&root->kernfs_rwsem);
1868 file->private_data = NULL;
1869 ctx->pos = INT_MAX;
1870 return 0;
1871}
1872
1873const struct file_operations kernfs_dir_fops = {
1874 .read = generic_read_dir,
1875 .iterate_shared = kernfs_fop_readdir,
1876 .release = kernfs_dir_fop_release,
1877 .llseek = generic_file_llseek,
1878};