Messages in this thread | | | Date | Tue, 12 Jan 2021 11:48:23 +0100 | From | Oscar Salvador <> | Subject | Re: [PATCH v2 2/5] mm: Teach pfn_to_online_page() to consider subsection validity |
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On Tue, Jan 12, 2021 at 10:53:17AM +0100, David Hildenbrand wrote: > That's not sufficient for alternative implementations of pfn_valid(). > > You still need some kind of pfn_valid(pfn) for alternative versions of > pfn_valid(). Consider arm64 memory holes in the memmap. See their > current (yet to be fixed/reworked) pfn_valid() implementation. > (pfn_valid_within() is implicitly active on arm64) > > Actually, I think we should add something like the following, to make > this clearer (pfn_valid_within() is confusing) > > #ifdef CONFIG_HAVE_ARCH_PFN_VALID > /* We might have to check for holes inside the memmap. */ > if (!pfn_valid()) > return NULL; > #endif
I have to confess that I was a bit confused by pfn_valid_within + HOLES_IN_ZONES + HAVE_ARCH_PFN_VALID.
At first I thought that we should stick with pfn_valid_within, as we also depend on HOLES_IN_ZONES, so it could be that
if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID)) ...
would to too much work, as if CONFIG_HOLES_IN_ZONES was not set but an arch pfn_valid was provided, we would perform unedeed checks. But on a closer look, CONFIG_HOLES_IN_ZONES is set by default on arm64, and on ia64 when SPARSEMEM is set, so looks fine.
-- Oscar Salvador SUSE L3
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