The patch titled Subject: mm: thp: fix pmd_present for split_huge_page and PROT_NONE with THP has been added to the -mm tree. Its filename is mm-thp-fix-pmd_present-for-split_huge_page-and-prot_none-with-thp.patch
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/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Andrea Arcangeli <aarca...@redhat.com> Subject: mm: thp: fix pmd_present for split_huge_page and PROT_NONE with THP In many places !pmd_present has been converted to pmd_none. For pmds that's equivalent and pmd_none is quicker so using pmd_none is better. However (unless we delete pmd_present) we should provide an accurate pmd_present too. This will avoid the risk of code thinking the pmd is non present because it's under __split_huge_page_map, see the pmd_mknotpresent there and the comment above it. If the page has been mprotected as PROT_NONE, it would also lead to a pmd_present false negative in the same way as the race with split_huge_page. Because the PSE bit stays on at all times (both during split_huge_page and when the _PAGE_PROTNONE bit get set), we could only check for the PSE bit, but checking the PROTNONE bit too is still good to remember pmd_present must always keep PROT_NONE into account. This explains a not reproducible BUG_ON that was seldom reported on the lists. The same issue is in pmd_large, it would go wrong with both PROT_NONE and if it races with split_huge_page. Signed-off-by: Andrea Arcangeli <aarca...@redhat.com> Cc: Rik van Riel <r...@redhat.com> Cc: Johannes Weiner <jwei...@redhat.com> Cc: Hugh Dickins <hu...@google.com> Cc: Mel Gorman <mgor...@suse.de> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <a...@linux-foundation.org> --- arch/x86/include/asm/pgtable.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff -puN arch/x86/include/asm/pgtable.h~mm-thp-fix-pmd_present-for-split_huge_page-and-prot_none-with-thp arch/x86/include/asm/pgtable.h --- a/arch/x86/include/asm/pgtable.h~mm-thp-fix-pmd_present-for-split_huge_page-and-prot_none-with-thp +++ a/arch/x86/include/asm/pgtable.h @@ -146,8 +146,7 @@ static inline unsigned long pmd_pfn(pmd_ static inline int pmd_large(pmd_t pte) { - return (pmd_flags(pte) & (_PAGE_PSE | _PAGE_PRESENT)) == - (_PAGE_PSE | _PAGE_PRESENT); + return pmd_flags(pte) & _PAGE_PSE; } #ifdef CONFIG_TRANSPARENT_HUGEPAGE @@ -415,7 +414,13 @@ static inline int pte_hidden(pte_t pte) static inline int pmd_present(pmd_t pmd) { - return pmd_flags(pmd) & _PAGE_PRESENT; + /* + * Checking for _PAGE_PSE is needed too because + * split_huge_page will temporarily clear the present bit (but + * the _PAGE_PSE flag will remain set at all times while the + * _PAGE_PRESENT bit is clear). + */ + return pmd_flags(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE | _PAGE_PSE); } static inline int pmd_none(pmd_t pmd) _ Patches currently in -mm which might be from aarca...@redhat.com are mm-thp-fix-pmd_present-for-split_huge_page-and-prot_none-with-thp.patch mm-remove-__gfp_no_kswapd.patch mm-mmu_notifier-fix-inconsistent-memory-between-secondary-mmu-and-host.patch mm-mmu_notifier-fix-inconsistent-memory-between-secondary-mmu-and-host-fix.patch mm-mmu_notifier-have-mmu_notifiers-use-a-global-srcu-so-they-may-safely-schedule.patch mm-mmu_notifier-init-notifier-if-necessary.patch thp-fix-the-count-of-thp_collapse_alloc.patch thp-remove-unnecessary-check-in-start_khugepaged.patch thp-move-khugepaged_mutex-out-of-khugepaged.patch thp-remove-unnecessary-khugepaged_thread-check.patch thp-remove-wake_up_interruptible-in-the-exit-path.patch thp-remove-some-code-depend-on-config_numa.patch thp-merge-page-pre-alloc-in-khugepaged_loop-into-khugepaged_do_scan.patch thp-release-page-in-page-pre-alloc-path.patch thp-introduce-khugepaged_prealloc_page-and-khugepaged_alloc_page.patch thp-remove-khugepaged_loop.patch thp-use-khugepaged_enabled-to-remove-duplicate-code.patch thp-remove-unnecessary-set_recommended_min_free_kbytes.patch mm-fix-potential-anon_vma-locking-issue-in-mprotect.patch thp-x86-introduce-have_arch_transparent_hugepage.patch thp-remove-assumptions-on-pgtable_t-type.patch thp-introduce-pmdp_invalidate.patch thp-make-madv_hugepage-check-for-mm-def_flags.patch thp-s390-thp-splitting-backend-for-s390.patch thp-s390-thp-pagetable-pre-allocation-for-s390.patch thp-s390-disable-thp-for-kvm-host-on-s390.patch thp-s390-architecture-backend-for-thp-on-s390.patch rbtree-reference-documentation-rbtreetxt-for-usage-instructions.patch rbtree-empty-nodes-have-no-color.patch rbtree-fix-incorrect-rbtree-node-insertion-in-fs-proc-proc_sysctlc.patch rbtree-move-some-implementation-details-from-rbtreeh-to-rbtreec.patch rbtree-performance-and-correctness-test.patch rbtree-break-out-of-rb_insert_color-loop-after-tree-rotation.patch rbtree-adjust-root-color-in-rb_insert_color-only-when-necessary.patch rbtree-low-level-optimizations-in-rb_insert_color.patch rbtree-adjust-node-color-in-__rb_erase_color-only-when-necessary.patch rbtree-optimize-case-selection-logic-in-__rb_erase_color.patch rbtree-low-level-optimizations-in-__rb_erase_color.patch rbtree-coding-style-adjustments.patch rbtree-optimize-fetching-of-sibling-node.patch rbtree-test-fix-sparse-warning-about-64-bit-constant.patch rbtree-add-__rb_change_child-helper-function.patch rbtree-place-easiest-case-first-in-rb_erase.patch rbtree-handle-1-child-recoloring-in-rb_erase-instead-of-rb_erase_color.patch rbtree-low-level-optimizations-in-rb_erase.patch rbtree-augmented-rbtree-test.patch rbtree-faster-augmented-rbtree-manipulation.patch rbtree-remove-prior-augmented-rbtree-implementation.patch rbtree-add-rb_declare_callbacks-macro.patch rbtree-add-prio-tree-and-interval-tree-tests.patch mm-replace-vma-prio_tree-with-an-interval-tree.patch kmemleak-use-rbtree-instead-of-prio-tree.patch prio_tree-remove.patch rbtree-move-augmented-rbtree-functionality-to-rbtree_augmentedh.patch mm-interval-tree-updates.patch mm-anon-rmap-remove-anon_vma_moveto_tail.patch mm-anon-rmap-replace-same_anon_vma-linked-list-with-an-interval-tree.patch mm-rmap-remove-vma_address-check-for-address-inside-vma.patch mm-add-config_debug_vm_rb-build-option.patch mm-avoid-taking-rmap-locks-in-move_ptes.patch mm-mmu_notifier-make-the-mmu_notifier-srcu-static.patch mm-compaction-abort-compaction-loop-if-lock-is-contended-or-run-too-long.patch mm-compaction-abort-compaction-loop-if-lock-is-contended-or-run-too-long-fix.patch mm-compaction-abort-compaction-loop-if-lock-is-contended-or-run-too-long-fix-2.patch thp-khugepaged_prealloc_page-forgot-to-reset-the-page-alloc-indicator.patch mm-compaction-move-fatal-signal-check-out-of-compact_checklock_irqsave.patch mm-thp-fix-the-pmd_clear-arguments-in-pmdp_get_and_clear.patch mm-thp-fix-the-update_mmu_cache-last-argument-passing-in-mm-huge_memoryc.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html