VM: add common helper function to create the page tables

This logic was duplicated four times, for no good reason.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/exec.c

@@ -306,9 +306,6 @@ void install_arg_page(struct vm_area_struct *vma,
 			struct page *page, unsigned long address)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	pgd_t * pgd;
-	pud_t * pud;
-	pmd_t * pmd;
 	pte_t * pte;
 	spinlock_t *ptl;
 
@@ -316,14 +313,7 @@ void install_arg_page(struct vm_area_struct *vma,
 		goto out;
 
 	flush_dcache_page(page);
-	pgd = pgd_offset(mm, address);
+	pte = get_locked_pte(mm, address, &ptl);
-	pud = pud_alloc(mm, pgd, address);
-	if (!pud)
-		goto out;
-	pmd = pmd_alloc(mm, pud, address);
-	if (!pmd)
-		goto out;
-	pte = pte_alloc_map_lock(mm, pmd, address, &ptl);
 	if (!pte)
 		goto out;
 	if (!pte_none(*pte)) {

include/linux/mm.h

@@ -742,6 +742,8 @@ struct shrinker;
 extern struct shrinker *set_shrinker(int, shrinker_t);
 extern void remove_shrinker(struct shrinker *shrinker);
 
+extern pte_t *FASTCALL(get_locked_pte(struct mm_struct *mm, unsigned long addr, spinlock_t **ptl));
+
 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address);
 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address);
 int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address);

mm/fremap.c

@@ -55,20 +55,10 @@ int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	pgoff_t size;
 	int err = -ENOMEM;
 	pte_t *pte;
-	pmd_t *pmd;
-	pud_t *pud;
-	pgd_t *pgd;
 	pte_t pte_val;
 	spinlock_t *ptl;
 
-	pgd = pgd_offset(mm, addr);
+	pte = get_locked_pte(mm, addr, &ptl);
-	pud = pud_alloc(mm, pgd, addr);
-	if (!pud)
-		goto out;
-	pmd = pmd_alloc(mm, pud, addr);
-	if (!pmd)
-		goto out;
-	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
 	if (!pte)
 		goto out;
 
@@ -110,20 +100,10 @@ int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
 {
 	int err = -ENOMEM;
 	pte_t *pte;
-	pmd_t *pmd;
-	pud_t *pud;
-	pgd_t *pgd;
 	pte_t pte_val;
 	spinlock_t *ptl;
 
-	pgd = pgd_offset(mm, addr);
+	pte = get_locked_pte(mm, addr, &ptl);
-	pud = pud_alloc(mm, pgd, addr);
-	if (!pud)
-		goto out;
-	pmd = pmd_alloc(mm, pud, addr);
-	if (!pmd)
-		goto out;
-	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
 	if (!pte)
 		goto out;
 

mm/memory.c

@@ -1146,6 +1146,18 @@ int zeromap_page_range(struct vm_area_struct *vma,
 	return err;
 }
 
+pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr, spinlock_t **ptl)
+{
+	pgd_t * pgd = pgd_offset(mm, addr);
+	pud_t * pud = pud_alloc(mm, pgd, addr);
+	if (pud) {
+		pmd_t * pmd = pmd_alloc(mm, pgd, addr);
+		if (pmd)
+			return pte_alloc_map_lock(mm, pmd, addr, ptl);
+	}
+	return NULL;
+}
+
 /*
  * This is the old fallback for page remapping.
  *
@@ -1156,9 +1168,6 @@ int zeromap_page_range(struct vm_area_struct *vma,
 static int insert_page(struct mm_struct *mm, unsigned long addr, struct page *page, pgprot_t prot)
 {
 	int retval;
-	pgd_t * pgd;
-	pud_t * pud;
-	pmd_t * pmd;  
 	pte_t *pte;
 	spinlock_t *ptl;  
 
@@ -1167,14 +1176,7 @@ static int insert_page(struct mm_struct *mm, unsigned long addr, struct page *pa
 		goto out;
 	retval = -ENOMEM;
 	flush_dcache_page(page);
-	pgd = pgd_offset(mm, addr);
+	pte = get_locked_pte(mm, addr, &ptl);
-	pud = pud_alloc(mm, pgd, addr);
-	if (!pud)
-		goto out;
-	pmd = pmd_alloc(mm, pud, addr);
-	if (!pmd)
-		goto out;
-	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
 	if (!pte)
 		goto out;
 	retval = -EBUSY;