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