+ mmdo_huge_pmd_numa_page-remove-unnecessary-tlb-flushing-code.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm,do_huge_pmd_numa_page: remove unnecessary TLB flushing code
has been added to the -mm tree.  Its filename is
     mmdo_huge_pmd_numa_page-remove-unnecessary-tlb-flushing-code.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mmdo_huge_pmd_numa_page-remove-unnecessary-tlb-flushing-code.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mmdo_huge_pmd_numa_page-remove-unnecessary-tlb-flushing-code.patch

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------------------------------------------------------
From: Huang Ying <ying.huang@intel.com>
Subject: mm,do_huge_pmd_numa_page: remove unnecessary TLB flushing code

Before 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.

do_huge_pmd_numa_page
  migrate_misplaced_page
    migrate_pages

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 difference.

Link: https://lkml.kernel.org/r/20210720065529.716031-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |   26 --------------------------
 1 file changed, 26 deletions(-)

--- a/mm/huge_memory.c~mmdo_huge_pmd_numa_page-remove-unnecessary-tlb-flushing-code
+++ a/mm/huge_memory.c
@@ -1440,32 +1440,6 @@ vm_fault_t do_huge_pmd_numa_page(struct
 		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)
_

Patches currently in -mm which might be from ying.huang@intel.com are

mmdo_huge_pmd_numa_page-remove-unnecessary-tlb-flushing-code.patch
mm-migrate-add-sysfs-interface-to-enable-reclaim-migration.patch