[PATCH] mm,do_huge_pmd_numa_page: remove unnecessary TLB flushing code

From: Huang Ying
Date: Tue Jul 20 2021 - 02:56:55 EST

Before the commit c5b5a3dd2c1f ("mm: thp: refactor NUMA fault
handling"), the TLB flushing is done in do_huge_pmd_numa_page() itself
via flush_tlb_range().

But after commit c5b5a3dd2c1f ("mm: thp: refactor NUMA fault
handling"), the TLB flushing is done in migrate_pages() as in the
following code path anyway.


So now, the TLB flushing code in do_huge_pmd_numa_page() becomes
unnecessary. So the code is deleted in this patch to simplify the
code. This is only code cleanup, there's no visible performance

Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
mm/huge_memory.c | 26 --------------------------
1 file changed, 26 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index afff3ac87067..9f21e44c9030 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1440,32 +1440,6 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
goto out;

- /*
- * Since we took the NUMA fault, we must have observed the !accessible
- * bit. Make sure all other CPUs agree with that, to avoid them
- * modifying the page we're about to migrate.
- *
- * Must be done under PTL such that we'll observe the relevant
- * inc_tlb_flush_pending().
- *
- * We are not sure a pending tlb flush here is for a huge page
- * mapping or not. Hence use the tlb range variant
- */
- if (mm_tlb_flush_pending(vma->vm_mm)) {
- flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
- /*
- * change_huge_pmd() released the pmd lock before
- * invalidating the secondary MMUs sharing the primary
- * MMU pagetables (with ->invalidate_range()). The
- * mmu_notifier_invalidate_range_end() (which
- * internally calls ->invalidate_range()) in
- * change_pmd_range() will run after us, so we can't
- * rely on it here and we need an explicit invalidate.
- */
- mmu_notifier_invalidate_range(vma->vm_mm, haddr,
- haddr + HPAGE_PMD_SIZE);
- }
pmd = pmd_modify(oldpmd, vma->vm_page_prot);
page = vm_normal_page_pmd(vma, haddr, pmd);
if (!page)