From 7982d8c3784dd5d83167d7dd59899d5b2b4cbac4 Mon Sep 17 00:00:00 2001
From: Huang Ying <ying.huang@intel.com>
Date: Thu, 2 Sep 2021 14:56:40 -0700
Subject: [PATCH] mm,do_huge_pmd_numa_page: remove unnecessary TLB flushing
 code

References: bsc#1190208 (MM functional and performance backports)
Patch-mainline: v5.15-rc1
Git-commit: f00230ff8411eaecbea1f2e528e205424f3725ba

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>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 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)