*at family of syscalls in FreeBSD

[Eric Lemar]

Ok, I'll get together a rough patch of what we are doing.  Strict Posix conformance wasn't a top priority and it's currently in a FreeBSD 6ish branch, so I'm sure it will require at least a small amount of work to be useful.  Unfortunately there's a bit of other code to untangle this from and (as always) other stuff to keep me from spending time untangling, so it will probably be a few days before I get a chance to put it together...
 
thanks,
Eric Lemar

________________________________

From: Kostik Belousov [mailto:kostikbel at gmail.com]
Sent: Wed 6/6/2007 1:03 AM
To: Roman Divacky
Cc: Eric Lemar; arch at freebsd.org
Subject: Re: *at family of syscalls in FreeBSD



On Wed, Jun 06, 2007 at 09:44:29AM +0200, Roman Divacky wrote:
> On Tue, Jun 05, 2007 at 06:17:40PM -0700, Eric Lemar wrote:
> > I'm definitely a fan of this API.  Aside from the general thread-related
> > utility of this API, it provides a reasonable API for accessing
> > windows-style ADS streams (subfiles) on a filesystem that supports them
> > and is becoming reasonably cross-platform.  This lets you handle things
> > like ADS hanging off directories in a comparatively sane manner.
> >
> > We've actually implemented a subset of these syscalls in-house (Isilon)
> > for use with our filesystem, largely for the ADS-related functionality.
> > Generally speaking, in our tree most of the traditional non-'at' syscalls
> > are just small kernel wrappers around the 'at' interfaces.  Overall ends
> > up looking fairly clean and we've ended up using them even in places
> > where we don't need the ADS functionality just because they are so
> > convenient.
> >
> > If you're interested in implementing this API I'd be happy to talk about
> > our implementation and see whether the relevant parts of our implementation
> > would be useful for the general community.
>
> my current patch is at: www.vlakno.cz/~rdivacky/linux_at.patch
>
> it does not implement the native fbsd syscalls, only the linuxulator ones
> but adding those is a matter of minutes. I asked for a review by pjd and/or
> rwatson and hopefully this will get commited soon..

I think it would be very useful to look at Isilon implementation, and possibly
merge your and their patch. In particular, it could give an insight of what
real uses for the API/KPI are.