On Thu, Mar 08, 2007 at 03:14:38PM +0900, Doi.Tsunehisa@xxxxxxxxxxxxxx wrote:
> >> +
> >> guest_physmap_remove_page(d, gpfn, mfn);
> >> +
> >> + /* post-set PGC_allocated flag */
> >> + do {
> >> + x = mfn_to_page(mfn)->count_info;
> >> + if ((x & PGC_count_mask) == 0)
> >> + goto out;
> >> + nx = x | PGC_allocated;
> >> + } while (cmpxchg_acq(&mfn_to_page(mfn)->count_info, x, nx)
> >> != x);
> >> + }
> >
> > checking == 0 is non-sense because we incremented it.
> > Probably you want to
> > if (!test_and_set_bit(page->count_info, _PGC_allocated)) {
> > put_page(page);
> > goto out;
> > }
>
> guest_physmap_remove_page() unsets PGC_allocated flag, thus
> this test_and_set_bit() returns zero allways, I think.
Sorry, I was somewhat confused.
Probably it should looks like the following.
if (page->count_info != 1) { /* no one but us is using this page */
put_page(page);
goto out;
}
__set_bit(&page->count_info, _PGC_allocated);
> In this code, I assumed that hypervisor might be destructing the
> domain. In this case, the page counter might be zero.
Such case doesn't occur because we called get_page().
It is the reason that the page reference counter exists for, isn't it?
--
yamahata
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