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.

The mmu_notifier_invalidate_range() in do_huge_pmd_numa_page() is
deleted too.  Because migrate_pages() takes care of that too when CPU
TLB is flushed.

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 890fb73..5e9ef0f 100644 (file)
--- 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)