vfs: make path_openat take a struct filename pointer

...and fix up the callers. For do_file_open_root, just declare a
struct filename on the stack and fill out the .name field. For
do_filp_open, make it also take a struct filename pointer, and fix up its
callers to call it appropriately.

For filp_open, add a variant that takes a struct filename pointer and turn
filp_open into a wrapper around it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/exec.c b/fs/exec.c
index 4e591e2..8b9011b 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -116,7 +116,7 @@
 	if (IS_ERR(tmp))
 		goto out;
 
-	file = do_filp_open(AT_FDCWD, tmp->name, &uselib_flags, LOOKUP_FOLLOW);
+	file = do_filp_open(AT_FDCWD, tmp, &uselib_flags, LOOKUP_FOLLOW);
 	putname(tmp);
 	error = PTR_ERR(file);
 	if (IS_ERR(file))
@@ -751,13 +751,14 @@
 {
 	struct file *file;
 	int err;
+	struct filename tmp = { .name = name };
 	static const struct open_flags open_exec_flags = {
 		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 		.acc_mode = MAY_EXEC | MAY_OPEN,
 		.intent = LOOKUP_OPEN
 	};
 
-	file = do_filp_open(AT_FDCWD, name, &open_exec_flags, LOOKUP_FOLLOW);
+	file = do_filp_open(AT_FDCWD, &tmp, &open_exec_flags, LOOKUP_FOLLOW);
 	if (IS_ERR(file))
 		goto out;