Where are these buffer_xxx macros/fucntion defined?

[Kumar amit mehta]

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