Re: [PATCH 2.5.63] Teach page_mapped about the anon flag

Andrew Morton
2003-03-03T21:29:06Z

Dave McCracken <dmccr@us.ibm.com> wrote:
>
>
> --On Monday, March 03, 2003 13:12:10 -0800 Andrew Morton <akpm@digeo.com>
> wrote:
>
> > It is. All callers which need to be 100% accurate are under
> > pte_chain_lock().
>
> Hmm, good point. Some places may not need perfect accuracy. Also, if it
> gives a false positive it means someone else is doing an atomic op on it,
> so it's likely to be in transition to/from true anyway.
>
> Ok, you've convinced me. Please ignore the patch. I'll hang onto it in
> case we get proved wrong at some point.

We do need a patch I think. page_mapped() is still assuming that an
all-bits-zero atomic_t corresponds to a zero-value atomic_t.

This does appear to be true for all supported architectures, but it's a bit
grubby.