Re: [patch] Proposal: move getmntopts(3) into libutil

On Tue, Feb 26, 2013 at 3:39 AM, Sergey Kandaurov <pluknet_at_gmail.com> wrote:

> Hi.
>
>
> External mount-like utilities may also have difficulties with building
> to get getmntopts.c source as this requires /usr/src presence which is
> in sync with installed world. Look how mount_fusefs from ports compiles:
> # mount_fusefs needs mntopts.h and getmntopts.c from src/sbin/mount/
>

I have no object in moving getmntopts.c to libutil.

I'll give some history to some of this stuff, to the best of my ability.
A few years ago, phk_at_ made a big change by introducing the nmount() system
call to replace mount().
Look at all mount-related commits around this time:
http://lists.freebsd.org/pipermail/cvs-src/2004-December/author.html#36373

This required changing every file system, and for old file systems which
supported the "classic mount" cmount(),
in each file system, the cmount() call had to internally call the nmount()
code.

In addition, phk made a pass to clean up all the userland mount programs to
use nmount().  There was a lot
of duplicated ("copy and pasted") code in various mount programs.  I helped
in the effort to clean up some of the userland mount() programs.

pjd_at_ proposed to make the main /sbin/mount load a shared library for each
specific file system,
and each shared library would have file-system specific mount logic.  For
example:

mount -t newfoofs  /dev/blah /mnt

would internally do something like:

dlopen("libmount_newfoofs",.....);


phk_at_ opposed this approach, saying that it could lead to ABI/API problems,
library mismatches, etc.
So we kept the existing approach.  I modified /sbin/mount to by default use
nmount() and only
for certain file systems, exec an external mount program.

phk's ideas for getmntopts.c was always to keep it as a place where
"library-like" functions for mounting
file systems would be kept.  To avoid library mismatch problems, it was
kept has a C file directly compiled
into the mount programs.

I have no problems keeping getmntopts.c in a separate library.  libutil is
fine, or even a separate libmntutil (or whatever).
Just keep in mind the issues that could possibly come up if there is a
mismatch between
the userland mount programs, and the library which contains getmntopts.c

Other than that, you proposal is quite reasonable, and I have no issue with
it.
Thanks!
--
Craig


--
Craig