The quilt patch titled Subject: mm/hugetlb: pre-allocate pgtable pages for uffd wr-protects has been removed from the -mm tree. Its filename was mm-hugetlb-pre-allocate-pgtable-pages-for-uffd-wr-protects.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------ From: Peter Xu peterx@redhat.com Subject: mm/hugetlb: pre-allocate pgtable pages for uffd wr-protects Date: Wed, 4 Jan 2023 17:52:05 -0500
Userfaultfd-wp uses pte markers to mark wr-protected pages for both shmem and hugetlb. Shmem has pre-allocation ready for markers, but hugetlb path was overlooked.
Doing so by calling huge_pte_alloc() if the initial pgtable walk fails to find the huge ptep. It's possible that huge_pte_alloc() can fail with high memory pressure, in that case stop the loop immediately and fail silently. This is not the most ideal solution but it matches with what we do with shmem meanwhile it avoids the splat in dmesg.
Link: https://lkml.kernel.org/r/20230104225207.1066932-2-peterx@redhat.com Fixes: 60dfaad65aa9 ("mm/hugetlb: allow uffd wr-protect none ptes") Signed-off-by: Peter Xu peterx@redhat.com Reported-by: James Houghton jthoughton@google.com Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Acked-by: David Hildenbrand david@redhat.com Acked-by: James Houghton jthoughton@google.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Axel Rasmussen axelrasmussen@google.com Cc: Muchun Song songmuchun@bytedance.com Cc: Nadav Amit nadav.amit@gmail.com Cc: stable@vger.kernel.org [5.19+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/hugetlb.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-pre-allocate-pgtable-pages-for-uffd-wr-protects +++ a/mm/hugetlb.c @@ -6660,8 +6660,17 @@ unsigned long hugetlb_change_protection( spinlock_t *ptl; ptep = huge_pte_offset(mm, address, psize); if (!ptep) { - address |= last_addr_mask; - continue; + if (!uffd_wp) { + address |= last_addr_mask; + continue; + } + /* + * Userfaultfd wr-protect requires pgtable + * pre-allocations to install pte markers. + */ + ptep = huge_pte_alloc(mm, vma, address, psize); + if (!ptep) + break; } ptl = huge_pte_lock(h, mm, ptep); if (huge_pmd_unshare(mm, vma, address, ptep)) { _
Patches currently in -mm which might be from peterx@redhat.com are
mm-uffd-fix-pte-marker-when-fork-without-fork-event.patch mm-fix-a-few-rare-cases-of-using-swapin-error-pte-marker.patch mm-uffd-always-wr-protect-pte-in-ptepmd_mkuffd_wp.patch mm-hugetlb-let-vma_offset_start-to-return-start.patch mm-hugetlb-dont-wait-for-migration-entry-during-follow-page.patch mm-hugetlb-document-huge_pte_offset-usage.patch mm-hugetlb-move-swap-entry-handling-into-vma-lock-when-faulted.patch mm-hugetlb-make-userfaultfd_huge_must_wait-safe-to-pmd-unshare.patch mm-hugetlb-make-hugetlb_follow_page_mask-safe-to-pmd-unshare.patch mm-hugetlb-make-follow_hugetlb_page-safe-to-pmd-unshare.patch mm-hugetlb-make-walk_hugetlb_range-safe-to-pmd-unshare.patch mm-hugetlb-introduce-hugetlb_walk.patch mm-mprotect-use-long-for-page-accountings-and-retval.patch mm-uffd-detect-pgtable-allocation-failures.patch