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>

5 files changed, 44 insertions, 92 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 6f022f505e8..9ae97242aa8 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
diff --git a/mm/internal.h b/mm/internal.h
index a4fa284f6bc..52d1fa95719 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -92,6 +92,11 @@ 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
  */
 extern void __free_pages_bootmem(struct page *page, unsigned int order);
diff --git a/mm/ksm.c b/mm/ksm.c
index ae539f0b8aa..31ae5ea1eac 100644
--- a/mm/ksm.c
+++ b/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;
diff --git a/mm/migrate.c b/mm/migrate.c
index 77ed2d77370..1dc4598d251 100644
--- a/mm/migrate.c
+++ b/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);
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 2ee1ef0f317..46823fb0e80 100644
--- a/mm/rmap.c
+++ b/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;