On 10.06.24 06:38, Oscar Salvador wrote:
On Fri, Jun 07, 2024 at 02:23:53PM +0200, David Hildenbrand wrote:
Relying on the mapcount for non-present PTEs that reference pages
doesn't make any sense: they are not accounted in the mapcount, so
page_mapcount() == 1 won't return the result we actually want to know.
While we don't check the mapcount for migration entries already, we
could end up checking it for swap, hwpoison, device exclusive, ...
entries, which we really shouldn't.
There is one exception: device private entries, which we consider
fake-present (e.g., incremented the mapcount). But we won't care about
that for now for PM_MMAP_EXCLUSIVE, because indicating PM_SWAP for them
although they are fake-present already sounds suspiciously wrong.
Let's never indicate PM_MMAP_EXCLUSIVE without PM_PRESENT.
Alternatively we could use is_pfn_swap_entry?
It's all weird, because only device private fake swp entries are
fake-present. For these, we might want to use PM_PRESENT, but I don't
care enough about device private entries to handle that here in a better
way :)
Indicating PM_SWAP for something that is not swap (migration/poison/...)
is also a bit weird. But likely nobody cared about that for now: it's
either present (PM_PRESENT), something else (PM_SWAP), or nothing is
there (no bit set).
Thanks!
--
Cheers,
David / dhildenb
