[systemd-devel] [RFC] link against util-linux for fstab parsing

Lennart Poettering lennart at poettering.net
Mon Feb 20 07:03:43 PST 2012

On Mon, 20.02.12 09:50, Dave Reisner (d at falconindy.com) wrote:

> On Mon, Feb 20, 2012 at 03:31:01PM +0100, Lennart Poettering wrote:
> > On Fri, 17.02.12 16:47, Dave Reisner (d at falconindy.com) wrote:
> > 
> > > Based on the premise that we shouldn't develop a case of NIH, link
> > > against a library whose sole purpose in life is parsing tab files.
> > 
> > Hmmm, using the glibc api setmntent() is hardly NIH, is it?
> > 
> > I am not strictly against this, but I'd like to have good reasons for
> > this. Right now I see on the side against this:
> > 
> > - adds another dependency
> > - code isn't really any shorter than right now
> > 
> > On the pro side:
> Well, it does get shorter if you keep going with it (there's code in
> umount that can be replaced). replacing the mountinfo sscanf parsing
> with libmount seems like more of a win to me. My working tree is
> currently looking like +172/-219 and replaces code in
> src/{,u}mount.c and src/cryptsetup/cryptsetup-generator.c

OK, this sounds not too bad. But I need more on the "pro" side.

> Rewriting remount-api-vfs purely with libmount almost works, but then
> doesn't if you want to be able to fork for each mount call. Karel, maybe
> I missed something... mnt_context_next_mount() doesn't seem to let you
> filter in the way sd's mount_point_is_api() does (filtering on target),
> but you can't fork internally for mount(2) if you don't use that call.

I'd prefer keeping the mounts out of process here. (Why? well, NSS calls
make me suspicious, like they might be required for the gid=xxx param
for devtmpfs, and suchlike).

> > > Curious if something like this is wanted -- it's 90% complete, but there's no
> > > sense in finishing it up if it's not interesting. I'd like to be able to get
> > > rid of the fstab_node_to_udev_node() function but that would likely require
> > > linking against libblkid in cryptsetup-generator.
> > 
> > I am not sure about this? What's wrong with fstab_node_to_udev_node()?
> Nothing's wrong with it. I was a bit hasty in assuming it could be
> ditched -- the value of it is that it always creates a "resolved" path
> for LABEL and UUID tags without actually checking for existance. Trying
> to resolve LABEL=foo via mnt_resolve_spec() for a crypto volume before
> its unlocked of course leads to Bad Things, as I found out in testing.

Yes, we need to be able to resolve LABEL= and UUID= without actually
having the disks arounds.


Lennart Poettering - Red Hat, Inc.

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