Re: [PATCH 066/104] virtiofsd: passthrough_ll: add renameat2 support

[Dr. David Alan Gilbert]

* Dr. David Alan Gilbert (address@hidden) wrote:
> * Daniel P. Berrangé (address@hidden) wrote:
> > On Thu, Dec 12, 2019 at 04:38:26PM +0000, Dr. David Alan Gilbert (git) 
> > wrote:
> > > From: Miklos Szeredi <address@hidden>
> > > 
> > > No glibc support yet, so use syscall().
> > 
> > It exists in glibc in my Fedora 31 install.
> > 
> > Presumably this is related to an older version
> > 
> > > Signed-off-by: Miklos Szeredi <address@hidden>
> > > ---
> > >  tools/virtiofsd/passthrough_ll.c | 10 ++++++++++
> > >  1 file changed, 10 insertions(+)
> > > 
> > > diff --git a/tools/virtiofsd/passthrough_ll.c 
> > > b/tools/virtiofsd/passthrough_ll.c
> > > index 91d3120033..bed2270141 100644
> > > --- a/tools/virtiofsd/passthrough_ll.c
> > > +++ b/tools/virtiofsd/passthrough_ll.c
> > > @@ -1083,7 +1083,17 @@ static void lo_rename(fuse_req_t req, fuse_ino_t 
> > > parent, const char *name,
> > >      }
> > >  
> > >      if (flags) {
> > > +#ifndef SYS_renameat2
> > >          fuse_reply_err(req, EINVAL);
> > > +#else
> > > +        res = syscall(SYS_renameat2, lo_fd(req, parent), name,
> > > +                      lo_fd(req, newparent), newname, flags);
> > > +        if (res == -1 && errno == ENOSYS) {
> > > +            fuse_reply_err(req, EINVAL);
> > > +        } else {
> > > +            fuse_reply_err(req, res == -1 ? errno : 0);
> > > +        }
> > > +#endif
> > 
> > We should use the formal API if available as first choice
> 
> OK, done - I've kept the 'ifndef SYS_renameat2' that drops back to an
> error for truly ancient cases; although I doubt everything else will
> build on something that old.

Hmm, and this breaks on middle age distros;  older distros don't have it
at all, new ones have both the syscall and the wrapper; but for the
middle age ones they have the syscall but not the wrapper.

Dan: What's your preference here; should I add a config fragment to
detect the wrapper - it seems overkill rather than just reverting it
until it becomes common.

Dave

> Dave
> 
> > 
> > Regards,
> > Daniel
> > -- 
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> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK