Re: [PATCH 2/2] shmem: allow reporting fanotify events with file handles on tmpfs

[Hugh Dickins <hughd@google.com>]

On Fri, 16 Apr 2021, Amir Goldstein wrote:
> On Thu, Mar 25, 2021 at 5:00 PM Jan Kara <jack@suse.cz> wrote:
> >
> > On Mon 22-03-21 19:39:44, Amir Goldstein wrote:
> > > Since kernel v5.1, fanotify_init(2) supports the flag FAN_REPORT_FID
> > > for identifying objects using file handle and fsid in events.
> > >
> > > fanotify_mark(2) fails with -ENODEV when trying to set a mark on
> > > filesystems that report null f_fsid in stasfs(2).
> > >
> > > Use the digest of uuid as f_fsid for tmpfs to uniquely identify tmpfs
> > > objects as best as possible and allow setting an fanotify mark that
> > > reports events with file handles on tmpfs.
> > >
> > > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> >
> > Hugh, any opinion on this patch?
> >
> >                                                                 Honza
> >
> > > ---
> > >  mm/shmem.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/mm/shmem.c b/mm/shmem.c
> > > index b2db4ed0fbc7..162d8f8993bb 100644
> > > --- a/mm/shmem.c
> > > +++ b/mm/shmem.c
> > > @@ -2846,6 +2846,9 @@ static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
> > >               buf->f_ffree = sbinfo->free_inodes;
> > >       }
> > >       /* else leave those fields 0 like simple_statfs */
> > > +
> > > +     buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
> > > +
> > >       return 0;
> > >  }
> > >
> 
> 
> Ping.
> 
> Hugh, are you ok with this change?
> 
> Thanks,
> Amir.

Yes, apologies for my delay to you, Amir and Jan:
sure I'm ok with this change, and thank you for taking care of tmpfs.

Acked-by: Hugh Dickins <hughd@google.com>

But you have more valuable acks on this little series already,
so don't bother rebasing some tree to add mine in now.  I don't yet
see the uuid_to_fsid() 1/2 which this depends on in linux-next, and
fear that's my fault for holding you back: sorry, please go ahead now.

Hugh