linux-kernel - [PATCH] mm/page_fault: Remove reduntant check for write access

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Date:   Wed, 23 Aug 2017 13:58:39 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     akpm@...ux-foundation.org
Subject: [PATCH] mm/page_fault: Remove reduntant check for write access

Flags argument has been copied into vmf.flags and it does not
seem to have changed in between. Hence a single write access
check can be used for both PUD and PMD.

Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
---
 mm/memory.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index fe2fba2..c62236d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3802,6 +3802,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 		.pgoff = linear_page_index(vma, address),
 		.gfp_mask = __get_fault_gfp_mask(vma),
 	};
+	unsigned int dirty = flags & FAULT_FLAG_WRITE;
 	struct mm_struct *mm = vma->vm_mm;
 	pgd_t *pgd;
 	p4d_t *p4d;
@@ -3824,7 +3825,6 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 
 		barrier();
 		if (pud_trans_huge(orig_pud) || pud_devmap(orig_pud)) {
-			unsigned int dirty = flags & FAULT_FLAG_WRITE;
 
 			/* NUMA case for anonymous PUDs would go here */
 
@@ -3854,8 +3854,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 			if (pmd_protnone(orig_pmd) && vma_is_accessible(vma))
 				return do_huge_pmd_numa_page(&vmf, orig_pmd);
 
-			if ((vmf.flags & FAULT_FLAG_WRITE) &&
-					!pmd_write(orig_pmd)) {
+			if (dirty && !pmd_write(orig_pmd)) {
 				ret = wp_huge_pmd(&vmf, orig_pmd);
 				if (!(ret & VM_FAULT_FALLBACK))
 					return ret;
-- 
1.8.5.2