[Virtio-fs] [PATCH] virtiofsd/passthrough_ll: Pass errno to fuse_reply_err()

[Dr. David Alan Gilbert]

* Niels de Vos (ndevos at redhat.com) wrote:
> On Thu, Jan 02, 2020 at 06:55:40PM +0000, Dr. David Alan Gilbert wrote:
> > * Xiao Yang (yangx.jy at cn.fujitsu.com) wrote:
> > > lo_copy_file_range() passes -errno to fuse_reply_err() and then fuse_reply_err()
> > > changes it to errno again, so that subsequent fuse_send_reply_iov_nofree() catches
> > > the wrong errno.(i.e. reports "fuse: bad error value: ...").
> > > 
> > > Make fuse_send_reply_iov_nofree() accept the correct -errno by passing errno
> > > directly in lo_copy_file_range().
> > > 
> > > Signed-off-by: Xiao Yang <yangx.jy at cn.fujitsu.com>
> > 
> > Yes, I think you're right - FUSE does use +ve errno's for some things,
> > normally the failure of the fuse channel itself; but in this case it
> > looks like 'errno' is consistent with the other calls; this comes
> > straight from upstream libfuse commit 2548c4b8, so lets cc in Niels.
> 
> Indeed, setting a negative errno is a mistake. Could you send the fix to
> https://github.com/libfuse/libfuse (example/passthrough_ll.c) as well? I
> am happy to do so if you prefer, just let me know.

I'll do a pull with Xiao Yang's fix.

Dave

> Thanks,
> Niels
> 
> > 
> > I'll take it into virtiofsd for the moment; thanks!
> > 
> > Dave
> > 
> > > ---
> > >  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 83dd0084b4..a77bed655e 100644
> > > --- a/tools/virtiofsd/passthrough_ll.c
> > > +++ b/tools/virtiofsd/passthrough_ll.c
> > > @@ -2615,7 +2615,7 @@ static void lo_copy_file_range(fuse_req_t req, fuse_ino_t ino_in, off_t off_in,
> > >  
> > >      res = copy_file_range(in_fd, &off_in, out_fd, &off_out, len, flags);
> > >      if (res < 0) {
> > > -        fuse_reply_err(req, -errno);
> > > +        fuse_reply_err(req, errno);
> > >      } else {
> > >          fuse_reply_write(req, res);
> > >      }
> > > -- 
> > > 2.21.0
> > > 
> > > 
> > > 
> > > 
> > > _______________________________________________
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> > > Virtio-fs at redhat.com
> > > https://www.redhat.com/mailman/listinfo/virtio-fs
> > --
> > Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK