Re: [PATCH v2 2/2] fs: add the ability for statmount() to report the mount devicename

[Jeff Layton <jlayton@kernel.org>]

On Thu, 2024-11-07 at 14:50 +0100, Miklos Szeredi wrote:
> On Wed, 6 Nov 2024 at 20:53, Jeff Layton <jlayton@kernel.org> wrote:
> > 
> > /proc/self/mountinfo displays the devicename for the mount, but
> > statmount() doesn't yet have a way to return it. Add a new
> > STATMOUNT_MNT_DEVNAME flag, claim the 32-bit __spare1 field to hold the
> > offset into the str[] array. STATMOUNT_MNT_DEVNAME will only be set in
> > the return mask if there is a device string.
> > 
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> >  fs/namespace.c             | 25 ++++++++++++++++++++++++-
> >  include/uapi/linux/mount.h |  3 ++-
> >  2 files changed, 26 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/namespace.c b/fs/namespace.c
> > index 52ab892088f08ad71647eff533dd6f3025bbae03..d4ed2cb5de12c86b4da58626441e072fc109b2ff 100644
> > --- a/fs/namespace.c
> > +++ b/fs/namespace.c
> > @@ -5014,6 +5014,19 @@ static void statmount_fs_subtype(struct kstatmount *s, struct seq_file *seq)
> >                 seq_puts(seq, sb->s_subtype);
> >  }
> > 
> > +static int statmount_mnt_devname(struct kstatmount *s, struct seq_file *seq)
> > +{
> > +       struct super_block *sb = s->mnt->mnt_sb;
> > +       struct mount *r = real_mount(s->mnt);
> > +
> > +       if (sb->s_op->show_devname)
> > +               return sb->s_op->show_devname(seq, s->mnt->mnt_root);
> 
> I think the resulting string should be unescaped just like statmount_mnt_root().
> 
> The same goes for the option strings, which went in last cycle.
> 
> I see no reason to require users of this interface to implement
> unescaping themselves.  Others beside libmount probably won't do it
> and will be surprised when encountering escaped strings because they
> are rare.

Good point. I'll fix that up for the next version.

Thanks,
-- 
Jeff Layton <jlayton@kernel.org>