Re: [PATCH v2 04/27] libbtrfsutil: add btrfs_util_is_subvolume() and btrfs_util_subvolume_id()

[Omar Sandoval <osandov@osandov.com>]

On Wed, Feb 21, 2018 at 02:02:02PM +0100, David Sterba wrote:
> On Wed, Feb 21, 2018 at 12:43:07PM +0100, David Sterba wrote:
> > On Thu, Feb 15, 2018 at 11:04:49AM -0800, Omar Sandoval wrote:
> > > --- /dev/null
> > > +++ b/libbtrfsutil/subvolume.c
> > > @@ -0,0 +1,127 @@
> > > +/*
> > > + * Copyright (C) 2018 Facebook
> > > + *
> > > + * This file is part of libbtrfsutil.
> > > + *
> > > + * libbtrfsutil is free software: you can redistribute it and/or modify
> > > + * it under the terms of the GNU Lesser General Public License as published by
> > > + * the Free Software Foundation, either version 3 of the License, or
> > > + * (at your option) any later version.
> > > + *
> > > + * libbtrfsutil is distributed in the hope that it will be useful,
> > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > > + * GNU Lesser General Public License for more details.
> > > + *
> > > + * You should have received a copy of the GNU Lesser General Public License
> > > + * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
> > > + */
> > > +
> > > +#include <errno.h>
> > > +#include <fcntl.h>
> > > +#include <unistd.h>
> > > +#include <sys/ioctl.h>
> > > +#include <sys/stat.h>
> > > +#include <sys/types.h>
> > > +#include <sys/vfs.h>
> > > +#include <linux/btrfs.h>
> > > +#include <linux/btrfs_tree.h>
> > 
> > How is this supposed to work? This pulls the system-wide includes, the
> > travis-ci environment has an old kernel and btrfs_tree.h does not exist
> > there. The missing defines are provided by libbtrfs' btrfs/ctree.h.
> > 
> > We can add a configure-time check to detect the availability of the
> > headers, but I'm not sure if this is right. As libbtrfsutil/subvolume.c
> > is built internally it should use the includes from the btrfs-progs git
> > itself, no?

Dang it, yes, since the lib started out as its own repo I used the
system headers, but when I ported it to btrfs-progs I forgot to sort
this out.

> Oh yeah, the fun has begun.  This will need to be sorted first. ctree.h
> unconditionally pulls kerncompat.h, so it cannot be used instead of the
> linux/btrfs*.h headers, there are warnings about redefined endianity
> conversion macros.
> 
> We can split the headers by type, so ctree.h does not contain
> everything, or copy defines and types to libbtrfsutil header so it is
> completely independent of the git or system headers. Or something else.
> 
> I can now make it compile without including btrfs_tree.h and copying
> parts of ctree.h until it compiles. The type u8 also has to be __u8.

I'll figure something out and send a patch, thanks.