vfs: add rcu argument to ->get_acl() callback

Add a rcu argument to the ->get_acl() callback to allow
get_cached_acl_rcu() to call the ->get_acl() method in the next patch.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c
index 9165d70..734d1f0 100644
--- a/fs/gfs2/acl.c
+++ b/fs/gfs2/acl.c
@@ -57,13 +57,16 @@ static struct posix_acl *__gfs2_get_acl(struct inode *inode, int type)
 	return acl;
 }
 
-struct posix_acl *gfs2_get_acl(struct inode *inode, int type)
+struct posix_acl *gfs2_get_acl(struct inode *inode, int type, bool rcu)
 {
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_holder gh;
 	bool need_unlock = false;
 	struct posix_acl *acl;
 
+	if (rcu)
+		return ERR_PTR(-ECHILD);
+
 	if (!gfs2_glock_is_locked_by_me(ip->i_gl)) {
 		int ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED,
 					     LM_FLAG_ANY, &gh);