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};