path: root/fs/sysfs/dir.c

/*
 * dir.c - Operations for sysfs directories.
 */

#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 "sysfs.h"

DEFINE_MUTEX(sysfs_mutex);
spinlock_t sysfs_assoc_lock = SPIN_LOCK_UNLOCKED;

static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED;
static DEFINE_IDA(sysfs_ino_ida);

/**
 *	sysfs_link_sibling - link sysfs_dirent into sibling list
 *	@sd: sysfs_dirent of interest
 *
 *	Link @sd into its sibling list which starts from
 *	sd->s_parent->s_children.
 *
 *	Locking:
 *	mutex_lock(sysfs_mutex)
 */
static void sysfs_link_sibling(struct sysfs_dirent *sd)
{
	struct sysfs_dirent *parent_sd = sd->s_parent;

	BUG_ON(sd->s_sibling);
	sd->s_sibling = parent_sd->s_children;
	parent_sd->s_children = sd;
}

/**
 *	sysfs_unlink_sibling - unlink sysfs_dirent from sibling list
 *	@sd: sysfs_dirent of interest
 *
 *	Unlink @sd from its sibling list which starts from
 *	sd->s_parent->s_children.
 *
 *	Locking:
 *	mutex_lock(sysfs_mutex)
 */
static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
{
	struct sysfs_dirent **pos;

	for (pos = &sd->s_parent->s_children; *pos; pos = &(*pos)->s_sibling) {
		if (*pos == sd) {
			*pos = sd->s_sibling;
			sd->s_sibling = NULL;
			break;
		}
	}
}

/**
 *	sysfs_get_dentry - get dentry for the given sysfs_dirent
 *	@sd: sysfs_dirent of interest
 *
 *	Get dentry for @sd.  Dentry is looked up if currently not
 *	present.  This function climbs sysfs_dirent tree till it
 *	reaches a sysfs_dirent with valid dentry attached and descends
 *	down from there looking up dentry for each step.
 *
 *	LOCKING:
 *	Kernel thread context (may sleep)
 *
 *	RETURNS:
 *	Pointer to found dentry on success, ERR_PTR() value on error.
 */
struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd)
{
	struct sysfs_dirent *cur;
	struct dentry *parent_dentry, *dentry;
	int i, depth;

	/* Find the first parent which has valid s_dentry and get the
	 * dentry.
	 */
	mutex_lock(&sysfs_mutex);
 restart0:
	spin_lock(&sysfs_assoc_lock);
 restart1:
	spin_lock(&dcache_lock);

	dentry = NULL;
	depth = 0;
	cur = sd;
	while (!cur->s_dentry || !cur->s_dentry->d_inode) {
		if (cur->s_flags & SYSFS_FLAG_REMOVED) {
			dentry = ERR_PTR(-ENOENT);
			depth = 0;
			break;
		}
		cur = cur->s_parent;
		depth++;
	}
	if (!IS_ERR(dentry))
		dentry = dget_locked(cur->s_dentry);

	spin_unlock(&dcache_lock);
	spin_unlock(&sysfs_assoc_lock);

	/* from the found dentry, look up depth times */
	while (depth--) {
		/* find and get depth'th ancestor */
		for (cur = sd, i = 0; cur && i < depth; i++)
			cur = cur->s_parent;

		/* This can happen if tree structure was modified due
		 * to move/rename.  Restart.
		 */
		if (i != depth) {
			dput(dentry);
			goto restart0;
		}

		sysfs_get(cur);

		mutex_unlock(&sysfs_mutex);

		/* look it up */
		parent_dentry = dentry;
		mutex_lock(&parent_dentry->d_inode->i_mutex);
		dentry = lookup_one_len_kern(cur->s_name, parent_dentry,
					     strlen(cur->s_name));
		mutex_unlock(&parent_dentry->d_inode->i_mutex);
		dput(parent_dentry);

		if (IS_ERR(dentry)) {
			sysfs_put(cur);
			return dentry;
		}

		mutex_lock(&sysfs_mutex);
		spin_lock(&sysfs_assoc_lock);

		/* This, again, can happen if tree structure has
		 * changed and we looked up the wrong thing.  Restart.
		 */
		if (cur->s_dentry