New helper - current_umask()

current->fs->umask is what most of fs_struct users are doing.
Put that into a helper function.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 1d53b62..7fdd184 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -256,7 +256,7 @@
 		}
 
 		if (!acl)
-			inode->i_mode &= ~current->fs->umask;
+			inode->i_mode &= ~current_umask();
 	}
 
 	if (IS_POSIXACL(dir) && acl) {