[Virtio-fs] [Qemu-devel] [PATCH] virtiofsd: fix compile error if 'F_OFD_GETLK' not defined
Dr. David Alan Gilbert
dgilbert at redhat.com
Thu Aug 1 14:20:16 UTC 2019
* Eric Blake (eblake at redhat.com) wrote:
> On 7/29/19 7:27 PM, piaojun wrote:
> > Use F_GETLK for fcntl when F_OFD_GETLK not defined.
>
> Which system are you hitting this problem on?
>
> The problem with F_GETLK is that it is NOT as safe as F_OFD_GETLK.
>
> We already have fcntl_op_getlk and qemu_probe_lock_ops() in util/osdep.c
> to not only determine which form to use, but also to emit a warning to
> the end user if we had to fall back to the unsafe F_GETLK. Why is your
> code not reusing that logic?
>
> >
> > Signed-off-by: Jun Piao <piaojun at huawei.com>
> > ---
> > contrib/virtiofsd/passthrough_ll.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c
> > index 9ae1381..757785b 100644
> > --- a/contrib/virtiofsd/passthrough_ll.c
> > +++ b/contrib/virtiofsd/passthrough_ll.c
> > @@ -1619,7 +1619,11 @@ static void lo_getlk(fuse_req_t req, fuse_ino_t ino,
> > return;
> > }
> >
> > +#ifdef F_OFD_GETLK
> > ret = fcntl(plock->fd, F_OFD_GETLK, lock);
> > +#else
> > + ret = fcntl(plock->fd, F_GETLK, lock);
> > +#endif
>
> Hmm. Since this is in contrib, you are trying to compile something that
> is independent of util/osdep.c (at least, I assume that's the case, as
> contrib/virtiofsd/ is not even part of qemu.git master yet - in which
> case, why is this not being squashed in to the patch introducing that
> file, rather than sent standalone). On the other hand, that raises the
> question - who is trying to use virtiofsd on a kernel that is too old to
> provid F_OFD_GETLK? Isn't the whole point of virtiofsd to be speeding
> up modern usage, at which point an old kernel is just gumming up the
> works? It seems like you are better off letting compilation fail on a
> system that is too old to support decent F_OFD_GETLK, rather than
> silently falling back to something that is unsafe.
It is, but I guess the answer here is someone wanted to build on RHEL7.
Dave
>
> --
> Eric Blake, Principal Software Engineer
> Red Hat, Inc. +1-919-301-3226
> Virtualization: qemu.org | libvirt.org
>
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--
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK
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