On 10.06.24 06:49, 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.
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Forgot to comment on something:
@@ -1517,14 +1514,13 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
if (pmd_swp_uffd_wp(pmd))
flags |= PM_UFFD_WP;
VM_BUG_ON(!is_pmd_migration_entry(pmd));
- migration = is_migration_entry(entry);
page = pfn_swap_entry_to_page(entry);
We do not really need to get the page anymore here as that is the non-present
part.
Then we could get away without checking the flags as only page != NULL
would mean a present pmd.
Not that we gain much as this is far from being a hot-path, but just
saying..
I *think* we still want that for indicating PM_FILE after patch #1.
--
Cheers,
David / dhildenb
