This is a note to let you know that I've just added the patch titled
mm/khugepaged: fix GUP-fast interaction by sending IPI
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-khugepaged-fix-gup-fast-interaction-by-sending-ip.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 18272dc2c996b123561f4cde7900aeee19d295f8
Author: Jann Horn <jannh@xxxxxxxxxx>
Date: Tue Dec 6 18:16:02 2022 +0100
mm/khugepaged: fix GUP-fast interaction by sending IPI
commit 2ba99c5e08812494bc57f319fb562f527d9bacd8 upstream.
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]
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index e9851100c0f7..4b1c142be08c 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 0f1bdbae45e2..fef0fdc0a981 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1044,6 +1044,7 @@ 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);
@@ -1293,6 +1294,7 @@ 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 36d46e19df96..a93ea671b8f1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -349,6 +349,11 @@ 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)
{
/*
