From fb3c8315650f89a1993fb3ae3e74e9c7e4a1c9c0 Mon Sep 17 00:00:00 2001 From: Aditya Kali Date: Fri, 29 Jan 2016 02:54:08 -0600 Subject: 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 Signed-off-by: Serge E. Hallyn Acked-by: Greg Kroah-Hartman Signed-off-by: Tejun Heo --- fs/kernfs/mount.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) (limited to 'fs/kernfs') diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index 8eaf417187f1..b67dbccdaf88 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -14,6 +14,7 @@ #include #include #include +#include #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); -- cgit v1.2.3