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Commit fb3c8315 authored by Aditya Kali's avatar Aditya Kali Committed by Tejun Heo
Browse files

kernfs: define kernfs_node_dentry 



Add a new kernfs api is added to lookup the dentry for a particular
kernfs path.

Signed-off-by: default avatarAditya Kali <adityakali@google.com>
Signed-off-by: default avatarSerge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent a0530e08

fs/kernfs/mount.c

+69 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/magic.h>

#include <linux/slab.h>

#include <linux/pagemap.h>

#include <linux/namei.h>



#include "kernfs-internal.h"
@@ -62,6 +63,74 @@ struct kernfs_root *kernfs_root_from_sb(struct super_block *sb) 
	return NULL;

}



/*

 * find the next ancestor in the path down to @child, where @parent was the

 * ancestor whose descendant we want to find.

 *

 * Say the path is /a/b/c/d.  @child is d, @parent is NULL.  We return the root

 * node.  If @parent is b, then we return the node for c.

 * Passing in d as @parent is not ok.

 */

static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,

					      struct kernfs_node *parent)

{

	if (child == parent) {

		pr_crit_once("BUG in find_next_ancestor: called with parent == child");

		return NULL;

	}



	while (child->parent != parent) {

		if (!child->parent)

			return NULL;

		child = child->parent;

	}



	return child;

}



/**

 * kernfs_node_dentry - get a dentry for the given kernfs_node

 * @kn: kernfs_node for which a dentry is needed

 * @sb: the kernfs super_block

 */

struct dentry *kernfs_node_dentry(struct kernfs_node *kn,

				  struct super_block *sb)

{

	struct dentry *dentry;

	struct kernfs_node *knparent = NULL;



	BUG_ON(sb->s_op != &kernfs_sops);



	dentry = dget(sb->s_root);



	/* Check if this is the root kernfs_node */

	if (!kn->parent)

		return dentry;



	knparent = find_next_ancestor(kn, NULL);

	if (WARN_ON(!knparent))

		return ERR_PTR(-EINVAL);



	do {

		struct dentry *dtmp;

		struct kernfs_node *kntmp;



		if (kn == knparent)

			return dentry;

		kntmp = find_next_ancestor(kn, knparent);

		if (WARN_ON(!kntmp))

			return ERR_PTR(-EINVAL);

		mutex_lock(&d_inode(dentry)->i_mutex);

		dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));

		mutex_unlock(&d_inode(dentry)->i_mutex);

		dput(dentry);

		if (IS_ERR(dtmp))

			return dtmp;

		knparent = kntmp;

		dentry = dtmp;

	} while (true);

}



static int kernfs_fill_super(struct super_block *sb, unsigned long magic)

{

	struct kernfs_super_info *info = kernfs_info(sb);

include/linux/kernfs.h

+2 −0
Original line number Diff line number Diff line
@@ -284,6 +284,8 @@ struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry); 
struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);

struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);



struct dentry *kernfs_node_dentry(struct kernfs_node *kn,

				  struct super_block *sb);

struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,

				       unsigned int flags, void *priv);

void kernfs_destroy_root(struct kernfs_root *root);