[CRIU] [PATCH] btrfs: Don't fail if we meet non-subvolume mountpoint

[Cyrill Gorcunov]

On Thu, Dec 05, 2013 at 03:10:01PM +0400, Pavel Emelyanov wrote:
> >  
> > -	if (stat(m->mountpoint, &st)) {
> > -		pr_perror("Can't get stat on %s", m->mountpoint);
> > +	if (st.st_ino != BTRFS_FIRST_FREE_OBJECTID)
> > +		return ERR_PTR(-ENOENT);
> > +
> > +	fd = open(m->mountpoint, O_RDONLY);
> > +	if (fd < 0) {
> > +		pr_perror("Can't open %s", m->mountpoint);
> 
> Don't do start + open. Do open + fstat.

How it's different? If we hit non BTRFS_FIRST_FREE_OBJECTID we exit earlier.

> >  
> >  int btrfs_parse_mountinfo(struct mount_info *m)
> >  {
> > -	return btrfs_parse_volume(m) ? 0 : -1;
> > +	struct btrfs_subvol_root *r;
> > +
> > +	r = btrfs_parse_volume(m);
> > +	if (IS_ERR(r)) {
> > +		if (PTR_ERR(r) == -ENOENT)
> > +			return 0;
> > +		return -1;
> > +	}
> > +	return r ? 0 : -1;
> 
> This looks tricky. Why not make btrfs_parse_volume() return int and
> decide when to report error and when not itself?
> 

I think I'll need to use this btrfs_subvol_root returned pointer for
lazy scheme (the patch in current stat become smaller in size, that's
the only idea I carried for now).