The patch titled Subject: mm/khugepaged: check compound_order() in collapse_pte_mapped_thp() has been added to the -mm mm-unstable branch. Its filename is mm-khugepaged-check-compound_order-in-collapse_pte_mapped_thp.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-check-compound_order-in-collapse_pte_mapped_thp.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: "Zach O'Keefe" <zokeefe@xxxxxxxxxx> Subject: mm/khugepaged: check compound_order() in collapse_pte_mapped_thp() Date: Thu, 22 Sep 2022 15:27:31 -0700 By the time we lock a page in collapse_pte_mapped_thp(), the page mapped by the address pushed onto the slot's .pte_mapped_thp[] array might have changed arbitrarily since we last looked at it. We revalidate that the page is still the head of a compound page, but we don't revalidate if the compound page is of order HPAGE_PMD_ORDER before applying rmap and page table updates. Since the kernel now supports large folios of arbitrary order, and since replacing page's pte mappings by a pmd mapping only makes sense for compound pages of order HPAGE_PMD_ORDER, revalidate that the compound order is indeed of order HPAGE_PMD_ORDER before proceeding. Link: https://lore.kernel.org/linux-mm/CAHbLzkon+2ky8v9ywGcsTUgXM_B35jt5NThYqQKXW2YV_GUacw@xxxxxxxxxxxxxx/ Link: https://lkml.kernel.org/r/20220922222731.1124481-1-zokeefe@xxxxxxxxxx Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx> Suggested-by: Yang Shi <shy828301@xxxxxxxxx> Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx> Cc: Chris Kennelly <ckennelly@xxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: James Houghton <jthoughton@xxxxxxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx> Cc: Peter Xu <peterx@xxxxxxxxxx> Cc: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx> Cc: SeongJae Park <sj@xxxxxxxxxx> Cc: Song Liu <songliubraving@xxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- --- a/mm/khugepaged.c~mm-khugepaged-check-compound_order-in-collapse_pte_mapped_thp +++ a/mm/khugepaged.c @@ -1399,6 +1399,9 @@ void collapse_pte_mapped_thp(struct mm_s if (!PageHead(hpage)) goto drop_hpage; + if (compound_order(hpage) != HPAGE_PMD_ORDER) + goto drop_hpage; + if (find_pmd_or_thp_or_none(mm, haddr, &pmd) != SCAN_SUCCEED) goto drop_hpage; _ Patches currently in -mm which might be from zokeefe@xxxxxxxxxx are mm-khugepaged-check-compound_order-in-collapse_pte_mapped_thp.patch mm-madvise-madv_collapse-return-eagain-when-page-cannot-be-isolated.patch selftests-vm-retry-on-eagain-for-madv_collapse-selftest.patch mm-shmem-add-flag-to-enforce-shmem-thp-in-hugepage_vma_check.patch mm-khugepaged-attempt-to-map-file-shmem-backed-pte-mapped-thps-by-pmds.patch mm-madvise-add-file-and-shmem-support-to-madv_collapse.patch mm-khugepaged-add-tracepoint-to-hpage_collapse_scan_file.patch selftests-vm-dedup-thp-helpers.patch selftests-vm-modularize-thp-collapse-memory-operations.patch selftests-vm-add-thp-collapse-file-and-tmpfs-testing.patch selftests-vm-add-thp-collapse-shmem-testing.patch selftests-vm-add-file-shmem-madv_collapse-selftest-for-cleared-pmd.patch selftests-vm-add-selftest-for-madv_collapse-of-uffd-minor-memory.patch