Re: [Xen-devel] [PATCH v5 03/10] IOMMU/MMU: enhance the call trees of IOMMU unmapping and mapping

["Xu, Quan" <quan.xu@xxxxxxxxx>]

On May 26, 2016 12:02 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> >>> On 25.05.16 at 17:34, <quan.xu@xxxxxxxxx> wrote:
> > On May 23, 2016 10:19 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> >> >>> On 18.05.16 at 10:08, <quan.xu@xxxxxxxxx> wrote:
> >> > +                                        unsigned long type,
> >> > +                                        int preemptible)
> >> >  {
> >> >      unsigned long nx, x, y = page->u.inuse.type_info;
> >> > -    int rc = 0;
> >> > +    int rc = 0, ret = 0;
> >> >
> >> >      ASSERT(!(type & ~(PGT_type_mask | PGT_pae_xen_l2)));
> >> >
> >> > @@ -2578,11 +2579,11 @@ static int __get_page_type(struct page_info
> >> *page, unsigned long type,
> >> >          if ( d && is_pv_domain(d) && unlikely(need_iommu(d)) )
> >> >          {
> >> >              if ( (x & PGT_type_mask) == PGT_writable_page )
> >> > -                iommu_unmap_page(d, mfn_to_gmfn(d, page_to_mfn(page)));
> >> > +                ret = iommu_unmap_page(d, mfn_to_gmfn(d,
> >> > + page_to_mfn(page)));
> >> >              else if ( type == PGT_writable_page )
> >> > -                iommu_map_page(d, mfn_to_gmfn(d, page_to_mfn(page)),
> >> > -                               page_to_mfn(page),
> >> > -                               IOMMUF_readable|IOMMUF_writable);
> >> > +                ret = iommu_map_page(d, mfn_to_gmfn(d,
> page_to_mfn(page)),
> >> > +                                     page_to_mfn(page),
> >> > +
> >> > + IOMMUF_readable|IOMMUF_writable);
> >> >          }
> >> >      }
> >> >
> >> > @@ -2599,6 +2600,9 @@ static int __get_page_type(struct page_info
> >> *page, unsigned long type,
> >> >      if ( (x & PGT_partial) && !(nx & PGT_partial) )
> >> >          put_page(page);
> >> >
> >> > +    if ( !rc )
> >> > +        rc = ret;
> >>
> >> I know I've seen this a couple of time already, but with the special
> >> purpose of "ret" I really wonder whether a more specific name
> >> wouldn't be warranted - e.g. "iommu_rc" or "iommu_ret".
> >
> >
> > rc is return value for this function, and no directly association with
> > IOMMU related code ( rc is only for alloc_page_type() ).
> > So the rc cannot be "iommu_rc"..
> >
> > ret can be "iommu_ret", but I think the pair 'rc' / 'ret' may look good.
> 
> Well, I'm not entirely opposed to keeping the names, but I continue to think
> that while at the call sites the shorter name is reasonable, it is quite a 
> bit less
> clear at the point where you conditionally update rc.
> 

I am open to it. What about 'rc' / 'iommu_ret' ?

Quan

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