ocfs2_dentry_revalidate(): use stable parent inode and name passed by caller

theoretically, ->d_name use in there is a UAF, but only if you are messing with
tracepoints...

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

fs/ocfs2/dcache.c

@@ -45,21 +45,16 @@ static int ocfs2_dentry_revalidate(struct inode *dir, const struct qstr *name,
 	inode = d_inode(dentry);
 	osb = OCFS2_SB(dentry->d_sb);
 
-	trace_ocfs2_dentry_revalidate(dentry, dentry->d_name.len,
-				      dentry->d_name.name);
+	trace_ocfs2_dentry_revalidate(dentry, name->len, name->name);
 
 	/* For a negative dentry -
 	 * check the generation number of the parent and compare with the
 	 * one stored in the inode.
 	 */
 	if (inode == NULL) {
 		unsigned long gen = (unsigned long) dentry->d_fsdata;
-		unsigned long pgen;
-		spin_lock(&dentry->d_lock);
-		pgen = OCFS2_I(d_inode(dentry->d_parent))->ip_dir_lock_gen;
-		spin_unlock(&dentry->d_lock);
-		trace_ocfs2_dentry_revalidate_negative(dentry->d_name.len,
-						       dentry->d_name.name,
+		unsigned long pgen = OCFS2_I(dir)->ip_dir_lock_gen;
+		trace_ocfs2_dentry_revalidate_negative(name->len, name->name,
 						       pgen, gen);
 		if (gen != pgen)
 			goto bail;