path: root/fs/sysfs/dir.c

/*
 * fs/sysfs/dir.c - sysfs core and dir operation implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
 *
 * This file is released under the GPLv2.
 *
 * Please see Documentation/filesystems/sysfs.txt for more information.
 */

#undef DEBUG

#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/idr.h>
#include <linux/completion.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/hash.h>
#include "sysfs.h"

DEFINE_MUTEX(sysfs_mutex);
DEFINE_SPINLOCK(sysfs_assoc_lock);

#define to_sysfs_dirent(X) rb_entry((X), struct sysfs_dirent, s_rb);

static DEFINE_SPINLOCK(sysfs_ino_lock);
static DEFINE_IDA(sysfs_ino_ida);

/**
 *	sysfs_name_hash
 *	@ns:   Namespace tag to hash
 *	@name: Null terminated string to hash
 *
 *	Returns 31 bit hash of ns + name (so it fits in an off_t )
 */
static unsigned int sysfs_name_hash(const void *ns, const char *name)
{
	unsigned long hash = init_name_hash();
	unsigned int len = strlen(name);
	while (len--)
		hash = partial_name_hash(*name++, hash);
	hash = ( end_name_hash(hash) ^ hash_ptr( (void *)ns, 31 ) );
	hash &= 0x7fffffffU;
	/* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
	if (hash < 1)
		hash += 2;
	if (hash >= INT_MAX)
		hash = INT_MAX - 1;
	return hash;
}

static int sysfs_name_compare(unsigned int hash, const void *ns,
	const char *name, const struct sysfs_dirent *sd)
{
	if (hash != sd->s_hash)
		return hash - sd->s_hash;
	if (ns != sd->s_ns)
		return ns - sd->s_ns;
	return strcmp(name, sd->s_name);
}

static int sysfs_sd_compare(const struct sysfs_dirent *left,
			    const struct sysfs_dirent *right)
{
	return sysfs_name_compare(left->s_hash, left->s_ns, left->s_name,
				  right);
}

/**
 *	sysfs_link_subling - link sysfs_dirent into sibling rbtree
 *	@sd: sysfs_dirent of interest
 *
 *	Link @sd into its sibling rbtree which starts from
 *	sd->s_parent->s_dir.children.
 *
 *	Locking:
 *	mutex_lock(sysfs_mutex)
 *
 *	RETURNS:
 *	0 on susccess -EEXIST on failure.
 */
static int sysfs_link_sibling(struct sysfs_dirent *sd)
{
	struct rb_node **node = &sd->s_parent->s_dir.children.rb_node;
	struct rb_node *parent = NULL;

	if (sysfs_type(sd) == SYSFS_DIR)
		sd->s_parent->s_dir.subdirs++;

	while (*node) {
		struct sysfs_dirent *pos;
		int result;

		pos = to_sysfs_dirent(*node);
		parent = *node;
		result = sysfs_sd_compare(sd, pos);
		if (result < 0)
			node = &pos->s_rb.rb_left;
		else if (result > 0)
			node = &pos->s_rb.rb_right;
		else
			return -EEXIST;
	}
	/* add new node and rebalance the tree */
	rb_link_node(&sd->s_rb, parent, node);
	rb_insert_color(&sd->s_rb, &sd->s_parent->s_dir.children);
	return 0;
}

/**
 *	sysfs_unlink_sibling - unlink sysfs_dirent from sibling rbtree
 *	@sd: sysfs_dirent of interest
 *
 *	Unlink @sd from its sibling rbtree which starts from
 *	sd->s_parent->s_dir.children.
 *
 *	Locking:
 *	mutex_lock(sysfs_mutex)
 */
static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
{
	if (sysfs_type(sd) == SYSFS_DIR)
		sd->s_parent->s_dir.subdirs--;

	rb_erase(&sd->s_rb, &sd->s_parent->s_dir.children);
}

#ifdef CONFIG_DEBUG_LOCK_ALLOC

/* Test for attributes that want to ignore lockdep for read-locking */
static bool ignore_lockdep(struct sysfs_dirent *sd)
{
	return sysfs_type(sd) == SYSFS_KOBJ_ATTR &&
			sd->s_attr