On Mon, Oct 04, 2021 at 04:07:04PM +0100, Stefan Hajnoczi wrote:
> On Thu, Sep 30, 2021 at 11:30:36AM -0400, Vivek Goyal wrote:
> > As of now we don't support fcntl(F_SETLKW) and if we see one, we return
> > -EOPNOTSUPP.
> >
> > Change that by accepting these requests and returning a reply
> > immediately asking caller to wait. Once lock is available, send a
> > notification to the waiter indicating lock is available.
> >
> > In response to lock request, we are returning error value as "1", which
> > signals to client to queue the lock request internally and later client
> > will get a notification which will signal lock is taken (or error). And
> > then fuse client should wake up the guest process.
> >
> > Signed-off-by: Vivek Goyal <vgo...@redhat.com>
> > Signed-off-by: Ioannis Angelakopoulos <iange...@redhat.com>
> > ---
> > tools/virtiofsd/fuse_lowlevel.c | 37 ++++++++++++++++-
> > tools/virtiofsd/fuse_lowlevel.h | 26 ++++++++++++
> > tools/virtiofsd/fuse_virtio.c | 50 ++++++++++++++++++++---
> > tools/virtiofsd/passthrough_ll.c | 70 ++++++++++++++++++++++++++++----
> > 4 files changed, 167 insertions(+), 16 deletions(-)
> >
> > diff --git a/tools/virtiofsd/fuse_lowlevel.c
> > b/tools/virtiofsd/fuse_lowlevel.c
> > index e4679c73ab..2e7f4b786d 100644
> > --- a/tools/virtiofsd/fuse_lowlevel.c
> > +++ b/tools/virtiofsd/fuse_lowlevel.c
> > @@ -179,8 +179,8 @@ int fuse_send_reply_iov_nofree(fuse_req_t req, int
> > error, struct iovec *iov,
> > .unique = req->unique,
> > .error = error,
> > };
> > -
> > - if (error <= -1000 || error > 0) {
> > + /* error = 1 has been used to signal client to wait for notificaiton */
>
> s/notificaiton/notification/
Will fix. I have made too many spelling mistakes. :-(
>
> > + if (error <= -1000 || error > 1) {
> > fuse_log(FUSE_LOG_ERR, "fuse: bad error value: %i\n", error);
> > out.error = -ERANGE;
> > }
> > @@ -290,6 +290,11 @@ int fuse_reply_err(fuse_req_t req, int err)
> > return send_reply(req, -err, NULL, 0);
> > }
> >
> > +int fuse_reply_wait(fuse_req_t req)
> > +{
> > + return send_reply(req, 1, NULL, 0);
> > +}
> > +
> > void fuse_reply_none(fuse_req_t req)
> > {
> > fuse_free_req(req);
> > @@ -2165,6 +2170,34 @@ static void do_destroy(fuse_req_t req, fuse_ino_t
> > nodeid,
> > send_reply_ok(req, NULL, 0);
> > }
> >
> > +static int send_notify_iov(struct fuse_session *se, int notify_code,
> > + struct iovec *iov, int count)
> > +{
> > + struct fuse_out_header out;
> > + if (!se->got_init) {
> > + return -ENOTCONN;
> > + }
> > + out.unique = 0;
> > + out.error = notify_code;
>
> Please fully initialize all fuse_out_header fields so it's obvious that
> there is no accidental information leak from virtiofsd to the guest:
>
> struct fuse_out_header out = {
> .error = notify_code,
> };
>
> The host must not expose uninitialized memory to the guest (just like
> the kernel vs userspace). fuse_send_msg() initializes out.len later, but
> to be on the safe side I think we should be explicit here.
Agreed. Its better to be explicit here and initialize fuse_out_header
fully. Will do.
Vivek
