mm: introduce mm_find_pmd()

Several place need to find the pmd by(mm_struct, address), so introduce a
function to simplify it.

[akpm@linux-foundation.org: fix warning]
Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Ni zhan Chen <nizhan.chen@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 45 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 6f022f505e88..9ae97242aa8d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1146,22 +1146,14 @@ pmd_t *page_check_address_pmd(struct page *page,
 			      unsigned long address,
 			      enum page_check_address_pmd_flag flag)
 {
-	pgd_t *pgd;
-	pud_t *pud;
 	pmd_t *pmd, *ret = NULL;
 
 	if (address & ~HPAGE_PMD_MASK)
 		goto out;
 
-	pgd = pgd_offset(mm, address);
-	if (!pgd_present(*pgd))
+	pmd = mm_find_pmd(mm, address);
+	if (!pmd)
 		goto out;
-
-	pud = pud_offset(pgd, address);
-	if (!pud_present(*pud))
-		goto out;
-
-	pmd = pmd_offset(pud, address);
 	if (pmd_none(*pmd))
 		goto out;
 	if (pmd_page(*pmd) != page)
@@ -1908,8 +1900,6 @@ static void collapse_huge_page(struct mm_struct *mm,
 				   struct vm_area_struct *vma,
 				   int node)
 {
-	pgd_t *pgd;
-	pud_t *pud;
 	pmd_t *pmd, _pmd;
 	pte_t *pte;
 	pgtable_t pgtable;
@@ -1955,17 +1945,10 @@ static void collapse_huge_page(struct mm_struct *mm,
 		goto out;
 	VM_BUG_ON(vma->vm_flags & VM_NO_THP);
 
-	pgd = pgd_offset(mm, address);
-	if (!pgd_present(*pgd))
+	pmd = mm_find_pmd(mm, address);
+	if (!pmd)
 		goto out;
-
-	pud = pud_offset(pgd, address);
-	if (!pud_present(*pud))
-		goto out;
-
-	pmd = pmd_offset(pud, address);
-	/* pmd can't go away or become huge under us */
-	if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
+	if (pmd_trans_huge(*pmd))
 		goto out;
 
 	anon_vma_lock(vma->anon_vma);
@@ -2048,8 +2031,6 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 			       unsigned long address,
 			       struct page **hpage)
 {
-	pgd_t *pgd;
-	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte, *_pte;
 	int ret = 0, referenced = 0, none = 0;
@@ -2060,16 +2041,10 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 
-	pgd = pgd_offset(mm, address);
-	if (!pgd_present(*pgd))
+	pmd = mm_find_pmd(mm, address);
+	if (!pmd)
 		goto out;
-
-	pud = pud_offset(pgd, address);
-	if (!pud_present(*pud))
-		goto out;
-
-	pmd = pmd_offset(pud, address);
-	if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
+	if (pmd_trans_huge(*pmd))
 		goto out;
 
 	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
@@ -2363,22 +2338,12 @@ void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
 static void split_huge_page_address(struct mm_struct *mm,
 				    unsigned long address)
 {
-	pgd_t *pgd;
-	pud_t *pud;
 	pmd_t *pmd;
 
 	VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
 
-	pgd = pgd_offset(mm, address);
-	if (!pgd_present(*pgd))
-		return;
-
-	pud = pud_offset(pgd, address);
-	if (!pud_present(*pud))
-		return;
-
-	pmd = pmd_offset(pud, address);
-	if (!pmd_present(*pmd))
+	pmd = mm_find_pmd(mm, address);
+	if (!pmd)
 		return;
 	/*
 	 * Caller holds the mmap_sem write mode, so a huge pmd cannot