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/20221129154730.2274278-2-jannh@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20221128180252.1684965-2-jannh@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20221125213714.4115729-2-jannh@xxxxxxxxxx
Fixes: ba76149f47d8 ("thp: khugepaged")
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
[manual backport: two of the three places in khugepaged that can free
ptes were refactored into a common helper between 5.15 and 6.0;
TLB flushing was refactored between 5.4 and 5.10;
TLB flushing was refactored between 4.19 and 5.4;
pmd collapse for PTE-mapped THP was only added in 5.4;
ugly hack for s390 and arm in <=4.19]
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
---
include/asm-generic/tlb.h | 6 ++++++
mm/khugepaged.c | 15 +++++++++++++++
mm/memory.c | 5 +++++
3 files changed, 26 insertions(+)
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 5e7e4aaf36c5..43409a047480 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -60,6 +60,12 @@ struct mmu_table_batch {
extern void tlb_table_flush(struct mmu_gather *tlb);
extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
+void tlb_remove_table_sync_one(void);
+
+#else
+
+static inline void tlb_remove_table_sync_one(void) { }
+
#endif
/*
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index f426d42d629d..6f8a1b423538 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -23,6 +23,19 @@
#include <asm/pgalloc.h>
#include "internal.h"
+/* gross hack for <=4.19 stable */
+#if defined(CONFIG_S390) || defined(CONFIG_ARM)
+static void tlb_remove_table_smp_sync(void *arg)
+{
+ /* Simply deliver the interrupt */
+}
+
+static void tlb_remove_table_sync_one(void)
+{
+ smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
+}
+#endif
+
enum scan_result {
SCAN_FAIL,
SCAN_SUCCEED,
@@ -1046,6 +1059,7 @@ static void collapse_huge_page(struct mm_struct *mm,
_pmd = pmdp_collapse_flush(vma, address, pmd);
spin_unlock(pmd_ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
+ tlb_remove_table_sync_one();
spin_lock(pte_ptl);
isolated = __collapse_huge_page_isolate(vma, address, pte);
@@ -1295,6 +1309,7 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
_pmd = pmdp_collapse_flush(vma, addr, pmd);
spin_unlock(ptl);
atomic_long_dec(&mm->nr_ptes);
+ tlb_remove_table_sync_one();
pte_free(mm, pmd_pgtable(_pmd));
}
up_write(&mm->mmap_sem);
diff --git a/mm/memory.c b/mm/memory.c
index 615cb3fe763d..0136af15ba18 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -373,6 +373,11 @@ static void tlb_remove_table_smp_sync(void *arg)
/* Simply deliver the interrupt */
}
+void tlb_remove_table_sync_one(void)
+{
+ smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
+}
+
static void tlb_remove_table_one(void *table)
{
/*
base-commit: 179ef7fe86775fe32bd1bfe791887d1994ddcfb0
--
2.39.0.314.g84b9a713c41-goog
