1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * fs/kernfs/dir.c - kernfs directory implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 */
9
10 #include <linux/sched.h>
11 #include <linux/fs.h>
12 #include <linux/namei.h>
13 #include <linux/idr.h>
14 #include <linux/slab.h>
15 #include <linux/security.h>
16 #include <linux/hash.h>
17
18 #include "kernfs-internal.h"
19
20 static DEFINE_RWLOCK(kernfs_rename_lock); /* kn->parent and ->name */
21 /*
22 * Don't use rename_lock to piggy back on pr_cont_buf. We don't want to
23 * call pr_cont() while holding rename_lock. Because sometimes pr_cont()
24 * will perform wakeups when releasing console_sem. Holding rename_lock
25 * will introduce deadlock if the scheduler reads the kernfs_name in the
26 * wakeup path.
27 */
28 static DEFINE_SPINLOCK(kernfs_pr_cont_lock);
29 static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by pr_cont_lock */
30 static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
31
32 #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
33
__kernfs_active(struct kernfs_node * kn)34 static bool __kernfs_active(struct kernfs_node *kn)
35 {
36 return atomic_read(&kn->active) >= 0;
37 }
38
kernfs_active(struct kernfs_node * kn)39 static bool kernfs_active(struct kernfs_node *kn)
40 {
41 lockdep_assert_held(&kernfs_root(kn)->kernfs_rwsem);
42 return __kernfs_active(kn);
43 }
44
kernfs_lockdep(struct kernfs_node * kn)45 static bool kernfs_lockdep(struct kernfs_node *kn)
46 {
47 #ifdef CONFIG_DEBUG_LOCK_ALLOC
48 return kn->flags & KERNFS_LOCKDEP;
49 #else
50 return false;
51 #endif
52 }
53
kernfs_name_locked(struct kernfs_node * kn,char * buf,size_t buflen)54 static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
55 {
56 if (!kn)
57 return strlcpy(buf, "(null)", buflen);
58
59 return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
60 }
61
62 /* kernfs_node_depth - compute depth from @from to @to */
kernfs_depth(struct kernfs_node * from,struct kernfs_node * to)63 static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
64 {
65 size_t depth = 0;
66
67 while (to->parent && to != from) {
68 depth++;
69 to = to->parent;
70 }
71 return depth;
72 }
73
kernfs_common_ancestor(struct kernfs_node * a,struct kernfs_node * b)74 static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
75 struct kernfs_node *b)
76 {
77 size_t da, db;
78 struct kernfs_root *ra = kernfs_root(a), *rb = kernfs_root(b);
79
80 if (ra != rb)
81 return NULL;
82
83 da = kernfs_depth(ra->kn, a);
84 db = kernfs_depth(rb->kn, b);
85
86 while (da > db) {
87 a = a->parent;
88 da--;
89 }
90 while (db > da) {
91 b = b->parent;
92 db--;
93 }
94
95 /* worst case b and a will be the same at root */
96 while (b != a) {
97 b = b->parent;
98 a = a->parent;
99 }
100
101 return a;
102 }
103
104 /**
105 * kernfs_path_from_node_locked - find a pseudo-absolute path to @kn_to,
106 * where kn_from is treated as root of the path.
107 * @kn_from: kernfs node which should be treated as root for the path
108 * @kn_to: kernfs node to which path is needed
109 * @buf: buffer to copy the path into
110 * @buflen: size of @buf
111 *
112 * We need to handle couple of scenarios here:
113 * [1] when @kn_from is an ancestor of @kn_to at some level
114 * kn_from: /n1/n2/n3
115 * kn_to: /n1/n2/n3/n4/n5
116 * result: /n4/n5
117 *
118 * [2] when @kn_from is on a different hierarchy and we need to find common
119 * ancestor between @kn_from and @kn_to.
120 * kn_from: /n1/n2/n3/n4
121 * kn_to: /n1/n2/n5
122 * result: /../../n5
123 * OR
124 * kn_from: /n1/n2/n3/n4/n5 [depth=5]
125 * kn_to: /n1/n2/n3 [depth=3]
126 * result: /../..
127 *
128 * [3] when @kn_to is %NULL result will be "(null)"
129 *
130 * Return: the length of the full path. If the full length is equal to or
131 * greater than @buflen, @buf contains the truncated path with the trailing
132 * '\0'. On error, -errno is returned.
133 */
kernfs_path_from_node_locked(struct kernfs_node * kn_to,struct kernfs_node * kn_from,char * buf,size_t buflen)134 static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
135 struct kernfs_node *kn_from,
136 char *buf, size_t buflen)
137 {
138 struct kernfs_node *kn, *common;
139 const char parent_str[] = "/..";
140 size_t depth_from, depth_to, len = 0;
141 int i, j;
142
143 if (!kn_to)
144 return strlcpy(buf, "(null)", buflen);
145
146 if (!kn_from)
147 kn_from = kernfs_root(kn_to)->kn;
148
149 if (kn_from == kn_to)
150 return strlcpy(buf, "/", buflen);
151
152 common = kernfs_common_ancestor(kn_from, kn_to);
153 if (WARN_ON(!common))
154 return -EINVAL;
155
156 depth_to = kernfs_depth(common, kn_to);
157 depth_from = kernfs_depth(common, kn_from);
158
159 buf[0] = '\0';
160
161 for (i = 0; i < depth_from; i++)
162 len += strlcpy(buf + len, parent_str,
163 len < buflen ? buflen - len : 0);
164
165 /* Calculate how many bytes we need for the rest */
166 for (i = depth_to - 1; i >= 0; i--) {
167 for (kn = kn_to, j = 0; j < i; j++)
168 kn = kn->parent;
169 len += strlcpy(buf + len, "/",
170 len < buflen ? buflen - len : 0);
171 len += strlcpy(buf + len, kn->name,
172 len < buflen ? buflen - len : 0);
173 }
174
175 return len;
176 }
177
178 /**
179 * kernfs_name - obtain the name of a given node
180 * @kn: kernfs_node of interest
181 * @buf: buffer to copy @kn's name into
182 * @buflen: size of @buf
183 *
184 * Copies the name of @kn into @buf of @buflen bytes. The behavior is
185 * similar to strlcpy().
186 *
187 * Fills buffer with "(null)" if @kn is %NULL.
188 *
189 * Return: the length of @kn's name and if @buf isn't long enough,
190 * it's filled up to @buflen-1 and nul terminated.
191 *
192 * This function can be called from any context.
193 */
kernfs_name(struct kernfs_node * kn,char * buf,size_t buflen)194 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
195 {
196 unsigned long flags;
197 int ret;
198
199 read_lock_irqsave(&kernfs_rename_lock, flags);
200 ret = kernfs_name_locked(kn, buf, buflen);
201 read_unlock_irqrestore(&kernfs_rename_lock, flags);
202 return ret;
203 }
204
205 /**
206 * kernfs_path_from_node - build path of node @to relative to @from.
207 * @from: parent kernfs_node relative to which we need to build the path
208 * @to: kernfs_node of interest
209 * @buf: buffer to copy @to's path into
210 * @buflen: size of @buf
211 *
212 * Builds @to's path relative to @from in @buf. @from and @to must
213 * be on the same kernfs-root. If @from is not parent of @to, then a relative
214 * path (which includes '..'s) as needed to reach from @from to @to is
215 * returned.
216 *
217 * Return: the length of the full path. If the full length is equal to or
218 * greater than @buflen, @buf contains the truncated path with the trailing
219 * '\0'. On error, -errno is returned.
220 */
kernfs_path_from_node(struct kernfs_node * to,struct kernfs_node * from,char * buf,size_t buflen)221 int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
222 char *buf, size_t buflen)
223 {
224 unsigned long flags;
225 int ret;
226
227 read_lock_irqsave(&kernfs_rename_lock, flags);
228 ret = kernfs_path_from_node_locked(to, from, buf, buflen);
229 read_unlock_irqrestore(&kernfs_rename_lock, flags);
230 return ret;
231 }
232 EXPORT_SYMBOL_GPL(kernfs_path_from_node);
233
234 /**
235 * pr_cont_kernfs_name - pr_cont name of a kernfs_node
236 * @kn: kernfs_node of interest
237 *
238 * This function can be called from any context.
239 */
pr_cont_kernfs_name(struct kernfs_node * kn)240 void pr_cont_kernfs_name(struct kernfs_node *kn)
241 {
242 unsigned long flags;
243
244 spin_lock_irqsave(&kernfs_pr_cont_lock, flags);
245
246 kernfs_name(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf));
247 pr_cont("%s", kernfs_pr_cont_buf);
248
249 spin_unlock_irqrestore(&kernfs_pr_cont_lock, flags);
250 }
251
252 /**
253 * pr_cont_kernfs_path - pr_cont path of a kernfs_node
254 * @kn: kernfs_node of interest
255 *
256 * This function can be called from any context.
257 */
pr_cont_kernfs_path(struct kernfs_node * kn)258 void pr_cont_kernfs_path(struct kernfs_node *kn)
259 {
260 unsigned long flags;
261 int sz;
262
263 spin_lock_irqsave(&kernfs_pr_cont_lock, flags);
264
265 sz = kernfs_path_from_node(kn, NULL, kernfs_pr_cont_buf,
266 sizeof(kernfs_pr_cont_buf));
267 if (sz < 0) {
268 pr_cont("(error)");
269 goto out;
270 }
271
272 if (sz >= sizeof(kernfs_pr_cont_buf)) {
273 pr_cont("(name too long)");
274 goto out;
275 }
276
277 pr_cont("%s", kernfs_pr_cont_buf);
278
279 out:
280 spin_unlock_irqrestore(&kernfs_pr_cont_lock, flags);
281 }
282
283 /**
284 * kernfs_get_parent - determine the parent node and pin it
285 * @kn: kernfs_node of interest
286 *
287 * Determines @kn's parent, pins and returns it. This function can be
288 * called from any context.
289 *
290 * Return: parent node of @kn
291 */
kernfs_get_parent(struct kernfs_node * kn)292 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
293 {
294 struct kernfs_node *parent;
295 unsigned long flags;
296
297 read_lock_irqsave(&kernfs_rename_lock, flags);
298 parent = kn->parent;
299 kernfs_get(parent);
300 read_unlock_irqrestore(&kernfs_rename_lock, flags);
301
302 return parent;
303 }
304
305 /**
306 * kernfs_name_hash - calculate hash of @ns + @name
307 * @name: Null terminated string to hash
308 * @ns: Namespace tag to hash
309 *
310 * Return: 31-bit hash of ns + name (so it fits in an off_t)
311 */
kernfs_name_hash(const char * name,const void * ns)312 static unsigned int kernfs_name_hash(const char *name, const void *ns)
313 {
314 unsigned long hash = init_name_hash(ns);
315 unsigned int len = strlen(name);
316 while (len--)
317 hash = partial_name_hash(*name++, hash);
318 hash = end_name_hash(hash);
319 hash &= 0x7fffffffU;
320 /* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
321 if (hash < 2)
322 hash += 2;
323 if (hash >= INT_MAX)
324 hash = INT_MAX - 1;
325 return hash;
326 }
327
kernfs_name_compare(unsigned int hash,const char * name,const void * ns,const struct kernfs_node * kn)328 static int kernfs_name_compare(unsigned int hash, const char *name,
329 const void *ns, const struct kernfs_node *kn)
330 {
331 if (hash < kn->hash)
332 return -1;
333 if (hash > kn->hash)
334 return 1;
335 if (ns < kn->ns)
336 return -1;
337 if (ns > kn->ns)
338 return 1;
339 return strcmp(name, kn->name);
340 }
341
kernfs_sd_compare(const struct kernfs_node * left,const struct kernfs_node * right)342 static int kernfs_sd_compare(const struct kernfs_node *left,
343 const struct kernfs_node *right)
344 {
345 return kernfs_name_compare(left->hash, left->name, left->ns, right);
346 }
347
348 /**
349 * kernfs_link_sibling - link kernfs_node into sibling rbtree
350 * @kn: kernfs_node of interest
351 *
352 * Link @kn into its sibling rbtree which starts from
353 * @kn->parent->dir.children.
354 *
355 * Locking:
356 * kernfs_rwsem held exclusive
357 *
358 * Return:
359 * %0 on success, -EEXIST on failure.
360 */
kernfs_link_sibling(struct kernfs_node * kn)361 static int kernfs_link_sibling(struct kernfs_node *kn)
362 {
363 struct rb_node **node = &kn->parent->dir.children.rb_node;
364 struct rb_node *parent = NULL;
365
366 while (*node) {
367 struct kernfs_node *pos;
368 int result;
369
370 pos = rb_to_kn(*node);
371 parent = *node;
372 result = kernfs_sd_compare(kn, pos);
373 if (result < 0)
374 node = &pos->rb.rb_left;
375 else if (result > 0)
376 node = &pos->rb.rb_right;
377 else
378 return -EEXIST;
379 }
380
381 /* add new node and rebalance the tree */
382 rb_link_node(&kn->rb, parent, node);
383 rb_insert_color(&kn->rb, &kn->parent->dir.children);
384
385 /* successfully added, account subdir number */
386 down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
387 if (kernfs_type(kn) == KERNFS_DIR)
388 kn->parent->dir.subdirs++;
389 kernfs_inc_rev(kn->parent);
390 up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
391
392 return 0;
393 }
394
395 /**
396 * kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
397 * @kn: kernfs_node of interest
398 *
399 * Try to unlink @kn from its sibling rbtree which starts from
400 * kn->parent->dir.children.
401 *
402 * Return: %true if @kn was actually removed,
403 * %false if @kn wasn't on the rbtree.
404 *
405 * Locking:
406 * kernfs_rwsem held exclusive
407 */
kernfs_unlink_sibling(struct kernfs_node * kn)408 static bool kernfs_unlink_sibling(struct kernfs_node *kn)
409 {
410 if (RB_EMPTY_NODE(&kn->rb))
411 return false;
412
413 down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
414 if (kernfs_type(kn) == KERNFS_DIR)
415 kn->parent->dir.subdirs--;
416 kernfs_inc_rev(kn->parent);
417 up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);
418
419 rb_erase(&kn->rb, &kn->parent->dir.children);
420 RB_CLEAR_NODE(&kn->rb);
421 return true;
422 }
423
424 /**
425 * kernfs_get_active - get an active reference to kernfs_node
426 * @kn: kernfs_node to get an active reference to
427 *
428 * Get an active reference of @kn. This function is noop if @kn
429 * is %NULL.
430 *
431 * Return:
432 * Pointer to @kn on success, %NULL on failure.
433 */
kernfs_get_active(struct kernfs_node * kn)434 struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
435 {
436 if (unlikely(!kn))
437 return NULL;
438
439 if (!atomic_inc_unless_negative(&kn->active))
440 return NULL;
441
442 if (kernfs_lockdep(kn))
443 rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
444 return kn;
445 }
446
447 /**
448 * kernfs_put_active - put an active reference to kernfs_node
449 * @kn: kernfs_node to put an active reference to
450 *
451 * Put an active reference to @kn. This function is noop if @kn
452 * is %NULL.
453 */
kernfs_put_active(struct kernfs_node * kn)454 void kernfs_put_active(struct kernfs_node *kn)
455 {
456 int v;
457
458 if (unlikely(!kn))
459 return;
460
461 if (kernfs_lockdep(kn))
462 rwsem_release(&kn->dep_map, _RET_IP_);
463 v = atomic_dec_return(&kn->active);
464 if (likely(v != KN_DEACTIVATED_BIAS))
465 return;
466
467 wake_up_all(&kernfs_root(kn)->deactivate_waitq);
468 }
469
470 /**
471 * kernfs_drain - drain kernfs_node
472 * @kn: kernfs_node to drain
473 *
474 * Drain existing usages and nuke all existing mmaps of @kn. Multiple
475 * removers may invoke this function concurrently on @kn and all will
476 * return after draining is complete.
477 */
kernfs_drain(struct kernfs_node * kn)478 static void kernfs_drain(struct kernfs_node *kn)
479 __releases(&kernfs_root(kn)->kernfs_rwsem)
480 __acquires(&kernfs_root(kn)->kernfs_rwsem)
481 {
482 struct kernfs_root *root = kernfs_root(kn);
483
484 lockdep_assert_held_write(&root->kernfs_rwsem);
485 WARN_ON_ONCE(kernfs_active(kn));
486
487 /*
488 * Skip draining if already fully drained. This avoids draining and its
489 * lockdep annotations for nodes which have never been activated
490 * allowing embedding kernfs_remove() in create error paths without
491 * worrying about draining.
492 */
493 if (atomic_read(&kn->active) == KN_DEACTIVATED_BIAS &&
494 !kernfs_should_drain_open_files(kn))
495 return;
496
497 up_write(&root->kernfs_rwsem);
498
499 if (kernfs_lockdep(kn)) {
500 rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
501 if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
502 lock_contended(&kn->dep_map, _RET_IP_);
503 }
504
505 wait_event(root->deactivate_waitq,
506 atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
507
508 if (kernfs_lockdep(kn)) {
509 lock_acquired(&kn->dep_map, _RET_IP_);
510 rwsem_release(&kn->dep_map, _RET_IP_);
511 }
512
513 if (kernfs_should_drain_open_files(kn))
514 kernfs_drain_open_files(kn);
515
516 down_write(&root->kernfs_rwsem);
517 }
518
519 /**
520 * kernfs_get - get a reference count on a kernfs_node
521 * @kn: the target kernfs_node
522 */
kernfs_get(struct kernfs_node * kn)523 void kernfs_get(struct kernfs_node *kn)
524 {
525 if (kn) {
526 WARN_ON(!atomic_read(&kn->count));
527 atomic_inc(&kn->count);
528 }
529 }
530 EXPORT_SYMBOL_GPL(kernfs_get);
531
532 /**
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 */
kernfs_put(struct kernfs_node * kn)538 void 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 }
581 EXPORT_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 */
kernfs_node_from_dentry(struct dentry * dentry)594 struct 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
__kernfs_new_node(struct kernfs_root * root,struct kernfs_node * parent,const char * name,umode_t mode,kuid_t uid,kgid_t gid,unsigned flags)601 static 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
kernfs_new_node(struct kernfs_node * parent,const char * name,umode_t mode,kuid_t uid,kgid_t gid,unsigned flags)672 struct 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 */
kernfs_find_and_get_node_by_id(struct kernfs_root * root,u64 id)711 struct 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;
744 err_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 */
kernfs_add_one(struct kernfs_node * kn)761 int 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
813 out_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 */
kernfs_find_ns(struct kernfs_node * parent,const unsigned char * name,const void * ns)828 static 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
kernfs_walk_ns(struct kernfs_node * parent,const unsigned char * path,const void * ns)861 static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
862 const unsigned char *path,
863 const void *ns)
864 {
865 size_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 = strlcpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
873
874 if (len >= sizeof(kernfs_pr_cont_buf)) {
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 */
kernfs_find_and_get_ns(struct kernfs_node * parent,const char * name,const void * ns)903 struct 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 }
916 EXPORT_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 */
kernfs_walk_and_get_ns(struct kernfs_node * parent,const char * path,const void * ns)929 struct 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 */
kernfs_create_root(struct kernfs_syscall_ops * scops,unsigned int flags,void * priv)952 struct 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 */
kernfs_destroy_root(struct kernfs_root * root)1009 void 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 */
kernfs_root_to_node(struct kernfs_root * root)1026 struct 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 */
kernfs_create_dir_ns(struct kernfs_node * parent,const char * name,umode_t mode,kuid_t uid,kgid_t gid,void * priv,const void * ns)1043 struct 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 */
kernfs_create_empty_dir(struct kernfs_node * parent,const char * name)1077 struct 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
kernfs_dop_revalidate(struct dentry * dentry,unsigned int flags)1103 static 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;
1171 out_bad:
1172 up_read(&root->kernfs_rwsem);
1173 return 0;
1174 }
1175
1176 const struct dentry_operations kernfs_dops = {
1177 .d_revalidate = kernfs_dop_revalidate,
1178 };
1179
kernfs_iop_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)1180 static 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
kernfs_iop_mkdir(struct mnt_idmap * idmap,struct inode * dir,struct dentry * dentry,umode_t mode)1223 static 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
kernfs_iop_rmdir(struct inode * dir,struct dentry * dentry)1243 static 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
kernfs_iop_rename(struct mnt_idmap * idmap,struct inode * old_dir,struct dentry * old_dentry,struct inode * new_dir,struct dentry * new_dentry,unsigned int flags)1261 static 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
1292 const 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
kernfs_leftmost_descendant(struct kernfs_node * pos)1304 static 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 */
kernfs_next_descendant_post(struct kernfs_node * pos,struct kernfs_node * root)1337 static 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
kernfs_activate_one(struct kernfs_node * kn)1361 static 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 */
kernfs_activate(struct kernfs_node * kn)1389 void 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 */
kernfs_show(struct kernfs_node * kn,bool show)1415 void 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
__kernfs_remove(struct kernfs_node * kn)1438 static 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 */
kernfs_remove(struct kernfs_node * kn)1509 void 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 */
kernfs_break_active_protection(struct kernfs_node * kn)1537 void 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 */
kernfs_unbreak_active_protection(struct kernfs_node * kn)1561 void 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 */
kernfs_remove_self(struct kernfs_node * kn)1605 bool 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 */
kernfs_remove_by_name_ns(struct kernfs_node * parent,const char * name,const void * ns)1667 int 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 */
kernfs_rename_ns(struct kernfs_node * kn,struct kernfs_node * new_parent,const char * new_name,const void * new_ns)1706 int 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
kernfs_dir_fop_release(struct inode * inode,struct file * filp)1777 static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
1778 {
1779 kernfs_put(filp->private_data);
1780 return 0;
1781 }
1782
kernfs_dir_pos(const void * ns,struct kernfs_node * parent,loff_t hash,struct kernfs_node * pos)1783 static 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
kernfs_dir_next_pos(const void * ns,struct kernfs_node * parent,ino_t ino,struct kernfs_node * pos)1817 static 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
kernfs_fop_readdir(struct file * file,struct dir_context * ctx)1833 static 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
1873 const 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 };
1879