[Virtio-fs] [PATCH] virtiofsd: Show submounts

[Daniel P. Berrangé]

On Mon, Apr 27, 2020 at 06:59:02PM +0100, Dr. David Alan Gilbert wrote:
> * Max Reitz (mreitz at redhat.com) wrote:
> > Currently, setup_mounts() bind-mounts the shared directory without
> > MS_REC.  This makes all submounts disappear.
> > 
> > Pass MS_REC so that the guest can see submounts again.
> 
> Thanks!
> 
> > Fixes: 3ca8a2b1c83eb185c232a4e87abbb65495263756
> 
> Should this actually be 5baa3b8e95064c2434bd9e2f312edd5e9ae275dc ?
> 
> > Signed-off-by: Max Reitz <mreitz at redhat.com>
> > ---
> >  tools/virtiofsd/passthrough_ll.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> > index 4c35c95b25..9d7f863e66 100644
> > --- a/tools/virtiofsd/passthrough_ll.c
> > +++ b/tools/virtiofsd/passthrough_ll.c
> > @@ -2643,7 +2643,7 @@ static void setup_mounts(const char *source)
> >      int oldroot;
> >      int newroot;
> >  
> > -    if (mount(source, source, NULL, MS_BIND, NULL) < 0) {
> > +    if (mount(source, source, NULL, MS_BIND | MS_REC, NULL) < 0) {
> >          fuse_log(FUSE_LOG_ERR, "mount(%s, %s, MS_BIND): %m\n", source, source);
> >          exit(1);
> >      }
> 
> Do we want MS_SLAVE to pick up future mounts that might happenf rom the
> host?

I think that probably makes sense to have MS_SLAVE by default, as that
means the set of files exposed to the guest is consistent across a QEMU
restart. Without MS_SLAVE new mounts aren't visible until after QEMU
is restarted which is likely surprising/undesirable to admins.


Regards,
Daniel
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