[PATCH v3 mm 2/2] mm: vm_insert_pages() checks if pte_index defined.

[Arjun Roy <arjunroy.kdev@gmail.com>]

From: Arjun Roy <arjunroy@google.com>

pte_index() is either defined as a macro (e.g. sparc64) or as an
inlined function (e.g. x86). vm_insert_pages() depends on pte_index
but it is not defined on all platforms (e.g. m68k).

To fix compilation of vm_insert_pages() on architectures not providing
pte_index(), we perform the following fix:

0. For platforms where it is meaningful, and defined as a macro, no
   change is needed.
1. For platforms where it is meaningful and defined as an inlined
   function, and we want to use it with vm_insert_pages(), we define
   a degenerate macro of the form:  #define pte_index pte_index
2. vm_insert_pages() checks for the existence of a pte_index macro
   definition. If found, it implements a batched insert. If not found,
   it devolves to calling vm_insert_page() in a loop.

This patch implements step 2.

v3 of this patch fixes a compilation warning for an unused method.
v2 of this patch moved a macro definition to a more readable location.

Signed-off-by: Arjun Roy <arjunroy@google.com>
---
 mm/memory.c | 41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index d6f834f7d145..47b28fcc73c2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1460,18 +1460,6 @@ static int insert_page_into_pte_locked(struct mm_struct *mm, pte_t *pte,
 	return 0;
 }
 
-static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd,
-			unsigned long addr, struct page *page, pgprot_t prot)
-{
-	int err;
-
-	if (!page_count(page))
-		return -EINVAL;
-	err = validate_page_before_insert(page);
-	return err ? err : insert_page_into_pte_locked(
-		mm, pte_offset_map(pmd, addr), addr, page, prot);
-}
-
 /*
  * This is the old fallback for page remapping.
  *
@@ -1500,8 +1488,21 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
 	return retval;
 }
 
+#ifdef pte_index
+static int insert_page_in_batch_locked(struct mm_struct *mm, pmd_t *pmd,
+			unsigned long addr, struct page *page, pgprot_t prot)
+{
+	int err;
+
+	if (!page_count(page))
+		return -EINVAL;
+	err = validate_page_before_insert(page);
+	return err ? err : insert_page_into_pte_locked(
+		mm, pte_offset_map(pmd, addr), addr, page, prot);
+}
+
 /* insert_pages() amortizes the cost of spinlock operations
- * when inserting pages in a loop.
+ * when inserting pages in a loop. Arch *must* define pte_index.
  */
 static int insert_pages(struct vm_area_struct *vma, unsigned long addr,
 			struct page **pages, unsigned long *num, pgprot_t prot)
@@ -1556,6 +1557,7 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr,
 	*num = remaining_pages_total;
 	return ret;
 }
+#endif  /* ifdef pte_index */
 
 /**
  * vm_insert_pages - insert multiple pages into user vma, batching the pmd lock.
@@ -1575,6 +1577,7 @@ static int insert_pages(struct vm_area_struct *vma, unsigned long addr,
 int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
 			struct page **pages, unsigned long *num)
 {
+#ifdef pte_index
 	const unsigned long end_addr = addr + (*num * PAGE_SIZE) - 1;
 
 	if (addr < vma->vm_start || end_addr >= vma->vm_end)
@@ -1586,6 +1589,18 @@ int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
 	}
 	/* Defer page refcount checking till we're about to map that page. */
 	return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
+#else
+	unsigned long idx = 0, pgcount = *num;
+	int err;
+
+	for (; idx < pgcount; ++idx) {
+		err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]);
+		if (err)
+			break;
+	}
+	*num = pgcount - idx;
+	return err;
+#endif  /* ifdef pte_index */
 }
 EXPORT_SYMBOL(vm_insert_pages);
 
-- 
2.25.1.481.gfbce0eb801-goog