On 12/22/22 21:55, David Hildenbrand wrote:
We have to update the uffd-wp SWP PTE bit independent of the type of migration entry. Currently, if we're unlucky and we want to install/clear the uffd-wp bit just while we're migrating a read-only mapped hugetlb page, we would miss to set/clear the uffd-wp bit.
Further, if we're processing a readable-exclusive migration entry and neither want to set or clear the uffd-wp bit, we could currently end up losing the uffd-wp bit. Note that the same would hold for writable migrating entries, however, having a writable migration entry with the uffd-wp bit set would already mean that something went wrong.
Note that the change from !is_readable_migration_entry -> writable_migration_entry is harmless and actually cleaner, as raised by Miaohe Lin and discussed in [1].
[1] https://lkml.kernel.org/r/90dd6a93-4500-e0de-2bf0-bf522c311b0c@huawei.com
Fixes: 60dfaad65aa9 ("mm/hugetlb: allow uffd wr-protect none ptes") Cc: stable@vger.kernel.org Signed-off-by: David Hildenbrand david@redhat.com
mm/hugetlb.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)
Thanks,
Reviewed-by: Mike Kravetz mike.kravetz@oracle.com