linux-kernel - [PATCH 3.16 104/131] mm/pagewalk: remove pgd_entry() and pud

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Message-ID: <lsq.1538257387.319902689@decadent.org.uk>
Date:   Sat, 29 Sep 2018 22:43:07 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Naoya Horiguchi" <n-horiguchi@...jp.nec.com>,
        "Cyrill Gorcunov" <gorcunov@...nvz.org>,
        "Pavel Emelyanov" <xemul@...allels.com>,
        "Dave Hansen" <dave.hansen@...el.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Benjamin Herrenschmidt" <benh@...nel.crashing.org>,
        "Andrea Arcangeli" <aarcange@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 3.16 104/131] mm/pagewalk: remove pgd_entry() and pud_entry()

3.16.59-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>

commit 0b1fbfe50006c41014cc25660c0e735d21c34939 upstream.

Currently no user of page table walker sets ->pgd_entry() or
->pud_entry(), so checking their existence in each loop is just wasting
CPU cycle.  So let's remove it to reduce overhead.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Cyrill Gorcunov <gorcunov@...nvz.org>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Pavel Emelyanov <xemul@...allels.com>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[bwh: Backported to 3.16 as dependency of L1TF mitigation]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/linux/mm.h | 6 ------
 mm/pagewalk.c      | 9 ++-------
 2 files changed, 2 insertions(+), 13 deletions(-)

--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1114,8 +1114,6 @@ void unmap_vmas(struct mmu_gather *tlb,
 
 /**
  * mm_walk - callbacks for walk_page_range
- * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
- * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
  * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
  *	       this handler is required to be able to handle
  *	       pmd_trans_huge() pmds.  They may simply choose to
@@ -1129,10 +1127,6 @@ void unmap_vmas(struct mmu_gather *tlb,
  * (see walk_page_range for more details)
  */
 struct mm_walk {
-	int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
-			 unsigned long next, struct mm_walk *walk);
-	int (*pud_entry)(pud_t *pud, unsigned long addr,
-	                 unsigned long next, struct mm_walk *walk);
 	int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
 			 unsigned long next, struct mm_walk *walk);
 	int (*pte_entry)(pte_t *pte, unsigned long addr,
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -86,9 +86,7 @@ static int walk_pud_range(pgd_t *pgd, un
 				break;
 			continue;
 		}
-		if (walk->pud_entry)
-			err = walk->pud_entry(pud, addr, next, walk);
-		if (!err && (walk->pmd_entry || walk->pte_entry))
+		if (walk->pmd_entry || walk->pte_entry)
 			err = walk_pmd_range(pud, addr, next, walk);
 		if (err)
 			break;
@@ -237,10 +235,7 @@ int walk_page_range(unsigned long addr,
 			pgd++;
 			continue;
 		}
-		if (walk->pgd_entry)
-			err = walk->pgd_entry(pgd, addr, next, walk);
-		if (!err &&
-		    (walk->pud_entry || walk->pmd_entry || walk->pte_entry))
+		if (walk->pmd_entry || walk->pte_entry)
 			err = walk_pud_range(pgd, addr, next, walk);
 		if (err)
 			break;