vop setattr and secure levels

[Luca Ferrari]

Hi all,
I'm trying to undertsand the path to some low level file operations,
with particular regard to where and when the secure level is checked.
While digging the code I found that there is an operation in the vop
operation structure that is named vop_setattr which is often referred
to an operation that will be called by a lot of syscalls related to
file system operations. I'd like to understand when and how such
operation is called, since I cannot find any direct reference in, for
instance, the ufs implementation. I suspect it is a general routine
called by the kernel itself somewhere I cannot find.

I've tried to post the same question on the freebsd forums, but
without any reply, so I believe that this mailing list can give me
some hints.

Thanks,
Luca