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

From: Anshuman Khandual
Date: Wed Aug 23 2017 - 04:29:03 EST


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@xxxxxxxxxxxxxxxxxx>
---
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