Where are these buffer_xxx macros/fucntion defined?

Hi, I see that a lot of FS code is using buffer_invalidate(), buffer_req() etc, but I could not find the definition of these anywhere in the tree. What am i missing? For example, see ext3 code using buffer_invalidate() here[1]. For building cscope and tags database, I invoke the following command from the top of the tree: $ make cscope tags [1] http://lxr.linux.no/#linux+v3.10/fs/ext3/namei.c#L926 Thanks, Amit