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/mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi.patch
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@xxxxxxxxxx>
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@xxxxxxxxxx
Fixes: ba76149f47d8 ("thp: khugepaged")
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxx 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
