Re: [RFC PATCH] network fs notification

[Jan Kara <jack@suse.cz>]

On Thu 02-05-19 11:08:41, Amir Goldstein wrote:
> On Thu, May 2, 2019 at 10:39 AM Jan Kara <jack@suse.cz> wrote:
> >
> > On Wed 01-05-19 16:55:41, Miklos Szeredi wrote:
> > > This is a really really trivial first iteration, but I think it's enough to
> > > try out CIFS notification support.  Doesn't deal with mark deletion, but
> > > that's best effort anyway: fsnotify() will filter out unneeded events.
> > >
> > > Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> > > ---
> > >  fs/notify/fanotify/fanotify_user.c |    6 +++++-
> > >  fs/notify/inotify/inotify_user.c   |    2 ++
> > >  include/linux/fs.h                 |    1 +
> > >  3 files changed, 8 insertions(+), 1 deletion(-)
> > >
> > > --- a/fs/notify/fanotify/fanotify_user.c
> > > +++ b/fs/notify/fanotify/fanotify_user.c
> > > @@ -1041,9 +1041,13 @@ static int do_fanotify_mark(int fanotify
> > >               else if (mark_type == FAN_MARK_FILESYSTEM)
> > >                       ret = fanotify_add_sb_mark(group, mnt->mnt_sb, mask,
> > >                                                  flags, fsid);
> > > -             else
> > > +             else {
> > >                       ret = fanotify_add_inode_mark(group, inode, mask,
> > >                                                     flags, fsid);
> > > +
> > > +                     if (!ret && inode->i_op->notify_update)
> > > +                             inode->i_op->notify_update(inode);
> > > +             }
> >
> > Yeah, so I had something like this in mind but I wanted to inform the
> > filesystem about superblock and mountpoint marks as well. And I'd pass the
> > 'mask' as well as presumably filesystem could behave differently depending
> > on whether we are looking for create vs unlink vs file change events etc...
> >
> 
> It probably wouldn't hurt to update fs about mount marks,
> but in the context of "remote" fs, the changes are most certainly
> being done on a different mount, a different machine most likely...

I agree. I guess I'm missing your point :) What I understood from Steve is
that e.g. cifs could ask the server to provide the notifications. E.g. FUSE
could propagate this information to userspace daemon which could place
appropriate fsnotify marks on underlying objects and then transform the
events to events on the FUSE filesystem? At least that's what I was
imagining, didn't think too much about it.

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR