Re: [PATCH 0/8] btrfs-progs: add subvol list options for sane path behavior

[Omar Sandoval <osandov@osandov.com>]

On Tue, Jun 25, 2024 at 05:34:38PM +0200, David Sterba wrote:
> On Fri, Jun 21, 2024 at 11:53:29AM -0700, Omar Sandoval wrote:
> > From: Omar Sandoval <osandov@fb.com>
> > 
> > Hello,
> > 
> > btrfs subvol list's path handling has been a constant source of
> > confusion for users. None of -o, -a, or the default do what users
> > expect. This has been broken for a decade; see [1].
> > 
> > This series adds two new options, -O and -A, which do what users
> > actually want: list subvolumes below a path, or list all subvolumes,
> > with minimal path shenanigans. This approach is conservative and tries
> > to maintain backwards compatibility, but it's worth discussing whether
> > we should instead fix the existing options/default, or more noisily
> > deprecate the existing options.
> 
> I'm working on a replacement command of 'subvolume list', there seems to
> be no other sane way around that.

I love this idea. Do you have a work in progress anywhere?

> The command line options are indeed
> confusing and the output is maybe easy to parse but not nice to read.
> Changing meaning of the options would break too many things as everybody
> got used to the bad UI and output.
> 
> We can add the two new options but I'd rather do that only in the new
> command so we can let everybody migrate there.
> 
> > One additional benefit of this is that -O can be used by unprivileged
> > users.
> 
> This should be the default (and is supposed to be in the new command).
> 
> > Patch 1 fixes a libbtrfsutil bug I encountered while testing this.
> > Patches 2 and 3 fix libbtrfsutil's privilege checks to work in user
> > namespaces. Patches 4 and 5 remove some unused subvol list code. Patch 6
> > documents and tests the current, insane behavior. Patch 7 converts
> > subvol list to use libbtrfsutil. This is a revival of one of my old
> > patches [2], but is much easier now that libbtrfs has been pared down.
> > Patch 8 adds the new options, including documentation and tests.
> > 
> > Thanks!
> > Omar
> > 
> > 1: https://lore.kernel.org/all/bdd9af61-b408-c8d2-6697-84230b0bcf89@gmail.com/
> > 2: https://lore.kernel.org/all/6492726d6e89bf792627e4431f7ba7691f09c3d2.1518720598.git.osandov@fb.com/
> > 
> > Omar Sandoval (8):
> >   libbtrfsutil: fix accidentally closing fd passed to subvolume iterator
> 
> I've picked this patch now as it's a fix.

Patches 2 and 3 are also fixes, so those would be nice to have, too, if
you don't mind.

My real motivation for this series is so that some internal workloads in
user namespaces can use subvol list. I'd love for the unprivileged use
case to be unblocked in the short term. Would it be better to add just
the -O option without -A and all of the big documentation changes? (This
still requires the libbtrfsutil rework.)

Thanks,
Omar