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kernfs: define kernfs_node_dentry 

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

Signed-off-by: Aditya Kali <adityakali@google.com>
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
hifive-unleashed-5.1
Aditya Kali 2016-01-29 02:54:08 -06:00 committed by Tejun Heo
parent a0530e087e
commit fb3c831565
2 changed files with 71 additions and 0 deletions
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69
fs/kernfs/mount.c
View File

@ -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);

2
include/linux/kernfs.h
View File

@ -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);