Quoting Tejun Heo (tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org):

Hello, Serge.

On Thu, Dec 03, 2015 at 04:47:06PM -0600, Serge E. Hallyn wrote:
...

quoted

+	dentry = dget(sb->s_root);
+	if (!kn->parent) // this is the root
+		return dentry;
+
+	knparent = find_kn_ancestor_below(kn, NULL);
+	BUG_ON(!knparent);

Doing WARN_ON() and returning failure is better, I think.  Failing ns
mount is an okay failure mode and a lot better than crashing the
system.

Ok - this shouldn't be user-triggerable, so if it happens it really
is a bug in our code, but I'll change it,

Also, how about find_next_ancestor() for the name of the
function?

Yeah it's static anyway :)

will change, squash, and resend the set.

quoted

+	do {
+		struct dentry *dtmp;
+		struct kernfs_node *kntmp;
+
+		if (kn == knparent)
+			return dentry;
+		kntmp = find_kn_ancestor_below(kn, knparent);
+		BUG_ON(!kntmp);
+		dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
+		dput(dentry);
+		if (IS_ERR(dtmp))
+			return dtmp;
+		knparent = kntmp;
+		dentry = dtmp;
+	} while (1);

Other than the nitpicks, looks good to me.

Thanks.

-- 
tejun