Re: [Qemu-devel] [PATCH] [RESEND-try-3] hw/9pfs: fix P9_STATS_GEN handling

[Kirill A. Shutemov]

Michael S. Tsirkin wrote:
> On Tue, Jan 28, 2014 at 12:55:51PM +0200, Kirill A. Shutemov wrote:
> > Currently we have few issues with P9_STATS_GEN:
> > 
> >  - We don't try to read st_gen anything except files or directories, but
> >    still set P9_STATS_GEN bit in st_result_mask. It may mislead client:
> >    we present garbage as valid st_gen.
> > 
> >  - If we failed to get valid st_gen with ENOTTY, we ignore error, but
> >    still set P9_STATS_GEN bit in st_result_mask.
> > 
> >  - If we failed to get valid st_gen with any other errno, we fail
> >    getattr altogether. It's excessive: we block valid client use-cases,
> >    like chdir(2) to non-readable directory with execution bit set.
> > 
> > The patch fixes these issues and cleanup code a bit.
> > 
> > Signed-off-by: Kirill A. Shutemov <address@hidden>
> > Reviewed-by: Daniel P. Berrange <address@hidden>
> > Reviewed-by: Aneesh Kumar K.V <address@hidden>
> 
> Would be better to split unrelated issues out to separate patches.

They are not totally unrelated: they all unbreak P9_STATS_GEN.

But yes, I can split if it needed.

> > diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
> > index 8cbb8ae32a03..3e51fcd152f8 100644
> > --- a/hw/9pfs/virtio-9p.c
> > +++ b/hw/9pfs/virtio-9p.c
> > @@ -1080,10 +1080,18 @@ static void v9fs_getattr(void *opaque)
> >      /*  fill st_gen if requested and supported by underlying fs */
> >      if (request_mask & P9_STATS_GEN) {
> >          retval = v9fs_co_st_gen(pdu, &fidp->path, stbuf.st_mode, 
> > &v9stat_dotl);
> > -        if (retval < 0) {
> > +        switch (retval) {
> > +        case 0:
> > +            /* we have valid st_gen: update result mask */
> > +            v9stat_dotl.st_result_mask |= P9_STATS_GEN;
> > +            break;
> > +        case -EINTR:
> > +            /* request cancelled */
> >              goto out;
> 
> Shouldn't EINTR be retried?

No. It could be canceled by client (with Tflush) on purpose and client can
retry if needed.

-- 
 Kirill A. Shutemov