The patch titled Subject: mm/khugepaged: fix GUP-fast interaction by sending IPI has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Jann Horn jannh@google.com Subject: mm/khugepaged: fix GUP-fast interaction by sending IPI Date: Fri, 25 Nov 2022 22:37:13 +0100
Since commit 70cbc3cc78a99 ("mm: gup: fix the fast GUP race against THP collapse"), the lockless_pages_from_mm() fastpath rechecks the pmd_t to ensure that the page table was not removed by khugepaged in between.
However, lockless_pages_from_mm() still requires that the page table is not concurrently freed. Fix it by sending IPIs (if the architecture uses semi-RCU-style page table freeing) before freeing/reusing page tables.
Link: https://lkml.kernel.org/r/20221125213714.4115729-2-jannh@google.com Fixes: ba76149f47d8 ("thp: khugepaged") Signed-off-by: Jann Horn jannh@google.com Cc: David Hildenbrand david@redhat.com Cc: John Hubbard jhubbard@nvidia.com Cc: Peter Xu peterx@redhat.com Cc: Yang Shi shy828301@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/asm-generic/tlb.h | 4 ++++ mm/khugepaged.c | 2 ++ mm/mmu_gather.c | 4 +--- 3 files changed, 7 insertions(+), 3 deletions(-)
--- a/include/asm-generic/tlb.h~mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi +++ a/include/asm-generic/tlb.h @@ -222,12 +222,16 @@ extern void tlb_remove_table(struct mmu_ #define tlb_needs_table_invalidate() (true) #endif
+void tlb_remove_table_sync_one(void); + #else
#ifdef tlb_needs_table_invalidate #error tlb_needs_table_invalidate() requires MMU_GATHER_RCU_TABLE_FREE #endif
+static inline void tlb_remove_table_sync_one(void) { } + #endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */
--- a/mm/khugepaged.c~mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi +++ a/mm/khugepaged.c @@ -1051,6 +1051,7 @@ static int collapse_huge_page(struct mm_ _pmd = pmdp_collapse_flush(vma, address, pmd); spin_unlock(pmd_ptl); mmu_notifier_invalidate_range_end(&range); + tlb_remove_table_sync_one();
spin_lock(pte_ptl); result = __collapse_huge_page_isolate(vma, address, pte, cc, @@ -1410,6 +1411,7 @@ static void collapse_and_free_pmd(struct lockdep_assert_held_write(&vma->anon_vma->root->rwsem);
pmd = pmdp_collapse_flush(vma, addr, pmdp); + tlb_remove_table_sync_one(); mm_dec_nr_ptes(mm); page_table_check_pte_clear_range(mm, addr, pmd); pte_free(mm, pmd_pgtable(pmd)); --- a/mm/mmu_gather.c~mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi +++ a/mm/mmu_gather.c @@ -153,7 +153,7 @@ static void tlb_remove_table_smp_sync(vo /* Simply deliver the interrupt */ }
-static void tlb_remove_table_sync_one(void) +void tlb_remove_table_sync_one(void) { /* * This isn't an RCU grace period and hence the page-tables cannot be @@ -177,8 +177,6 @@ static void tlb_remove_table_free(struct
#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */
-static void tlb_remove_table_sync_one(void) { } - static void tlb_remove_table_free(struct mmu_table_batch *batch) { __tlb_remove_table_free(batch); _
Patches currently in -mm which might be from jannh@google.com are
mm-khugepaged-take-the-right-locks-for-page-table-retraction.patch mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi.patch mm-khugepaged-invoke-mmu-notifiers-in-shmem-file-collapse-paths.patch