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>

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

mm/internal.h

@@ -91,6 +91,11 @@ extern unsigned long highest_memmap_pfn;
 extern int isolate_lru_page(struct page *page);
 extern void putback_lru_page(struct page *page);
 
+/*
+ * in mm/rmap.c:
+ */
+extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
+
 /*
  * in mm/page_alloc.c
  */

mm/ksm.c

@@ -778,8 +778,6 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
 			struct page *kpage, pte_t orig_pte)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	pgd_t *pgd;
-	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *ptep;
 	spinlock_t *ptl;
@@ -792,18 +790,10 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
 	if (addr == -EFAULT)
 		goto out;
 
-	pgd = pgd_offset(mm, addr);
-	if (!pgd_present(*pgd))
+	pmd = mm_find_pmd(mm, addr);
+	if (!pmd)
 		goto out;
-
-	pud = pud_offset(pgd, addr);
-	if (!pud_present(*pud))
-		goto out;
-
-	pmd = pmd_offset(pud, addr);
 	BUG_ON(pmd_trans_huge(*pmd));
-	if (!pmd_present(*pmd))
-		goto out;
 
 	mmun_start = addr;
 	mmun_end   = addr + PAGE_SIZE;

mm/migrate.c

@@ -91,8 +91,6 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
 {
 	struct mm_struct *mm = vma->vm_mm;
 	swp_entry_t entry;
- 	pgd_t *pgd;
- 	pud_t *pud;
  	pmd_t *pmd;
 	pte_t *ptep, pte;
  	spinlock_t *ptl;
@@ -103,19 +101,11 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
 			goto out;
 		ptl = &mm->page_table_lock;
 	} else {
-		pgd = pgd_offset(mm, addr);
-		if (!pgd_present(*pgd))
+		pmd = mm_find_pmd(mm, addr);
+		if (!pmd)
 			goto out;
-
-		pud = pud_offset(pgd, addr);
-		if (!pud_present(*pud))
-			goto out;
-
-		pmd = pmd_offset(pud, addr);
 		if (pmd_trans_huge(*pmd))
 			goto out;
-		if (!pmd_present(*pmd))
-			goto out;
 
 		ptep = pte_offset_map(pmd, addr);
 

mm/rmap.c

@@ -562,6 +562,27 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 	return address;
 }
 
+pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd = NULL;
+
+	pgd = pgd_offset(mm, address);
+	if (!pgd_present(*pgd))
+		goto out;
+
+	pud = pud_offset(pgd, address);
+	if (!pud_present(*pud))
+		goto out;
+
+	pmd = pmd_offset(pud, address);
+	if (!pmd_present(*pmd))
+		pmd = NULL;
+out:
+	return pmd;
+}
+
 /*
  * Check that @page is mapped at @address into @mm.
  *
@@ -574,8 +595,6 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
 			  unsigned long address, spinlock_t **ptlp, int sync)
 {
-	pgd_t *pgd;
-	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
 	spinlock_t *ptl;
@@ -586,17 +605,10 @@ pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
 		goto check;
 	}
 
-	pgd = pgd_offset(mm, address);
-	if (!pgd_present(*pgd))
-		return NULL;
-
-	pud = pud_offset(pgd, address);
-	if (!pud_present(*pud))
+	pmd = mm_find_pmd(mm, address);
+	if (!pmd)
 		return NULL;
 
-	pmd = pmd_offset(pud, address);
-	if (!pmd_present(*pmd))
-		return NULL;
 	if (pmd_trans_huge(*pmd))
 		return NULL;
 
@@ -1345,8 +1357,6 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
 		struct vm_area_struct *vma, struct page *check_page)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	pgd_t *pgd;
-	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
 	pte_t pteval;
@@ -1366,16 +1376,8 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
 	if (end > vma->vm_end)
 		end = vma->vm_end;
 
-	pgd = pgd_offset(mm, address);
-	if (!pgd_present(*pgd))
-		return ret;
-
-	pud = pud_offset(pgd, address);
-	if (!pud_present(*pud))
-		return ret;
-
-	pmd = pmd_offset(pud, address);
-	if (!pmd_present(*pmd))
+	pmd = mm_find_pmd(mm, address);
+	if (!pmd)
 		return ret;
 
 	mmun_start = address;