huge page private reservation review cleanups

Create some new accessors for vma private data to cut down on and contain
the casts.  Encapsulates the huge and small page offset calculations.
Also adds a couple of VM_BUG_ONs for consistency.

[akpm@linux-foundation.org: Make things static]
Signed-off-by: NAndy Whitcroft <apw@shadowen.org>
Acked-by: NMel Gorman <mel@csn.ul.ie>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Johannes Weiner <hannes@saeurebad.de>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: William Lee Irwin III <wli@holomorphy.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -40,6 +40,28 @@ static int hugetlb_next_nid;
  */
 static DEFINE_SPINLOCK(hugetlb_lock);
 
+/*
+ * Convert the address within this vma to the page offset within
+ * the mapping, in base page units.
+ */
+static pgoff_t vma_page_offset(struct vm_area_struct *vma,
+				unsigned long address)
+{
+	return ((address - vma->vm_start) >> PAGE_SHIFT) +
+					(vma->vm_pgoff >> PAGE_SHIFT);
+}
+
+/*
+ * Convert the address within this vma to the page offset within
+ * the mapping, in pagecache page units; huge pages here.
+ */
+static pgoff_t vma_pagecache_offset(struct vm_area_struct *vma,
+					unsigned long address)
+{
+	return ((address - vma->vm_start) >> HPAGE_SHIFT) +
+			(vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
+}
+
 #define HPAGE_RESV_OWNER    (1UL << (BITS_PER_LONG - 1))
 #define HPAGE_RESV_UNMAPPED (1UL << (BITS_PER_LONG - 2))
 #define HPAGE_RESV_MASK (HPAGE_RESV_OWNER | HPAGE_RESV_UNMAPPED)
@@ -53,36 +75,48 @@ static DEFINE_SPINLOCK(hugetlb_lock);
  * to reset the VMA at fork() time as it is not in use yet and there is no
  * chance of the global counters getting corrupted as a result of the values.
  */
+static unsigned long get_vma_private_data(struct vm_area_struct *vma)
+{
+	return (unsigned long)vma->vm_private_data;
+}
+
+static void set_vma_private_data(struct vm_area_struct *vma,
+							unsigned long value)
+{
+	vma->vm_private_data = (void *)value;
+}
+
 static unsigned long vma_resv_huge_pages(struct vm_area_struct *vma)
 {
 	VM_BUG_ON(!is_vm_hugetlb_page(vma));
 	if (!(vma->vm_flags & VM_SHARED))
-		return (unsigned long)vma->vm_private_data & ~HPAGE_RESV_MASK;
+		return get_vma_private_data(vma) & ~HPAGE_RESV_MASK;
 	return 0;
 }
 
 static void set_vma_resv_huge_pages(struct vm_area_struct *vma,
 							unsigned long reserve)
 {
-	unsigned long flags;
 	VM_BUG_ON(!is_vm_hugetlb_page(vma));
 	VM_BUG_ON(vma->vm_flags & VM_SHARED);
 
-	flags = (unsigned long)vma->vm_private_data & HPAGE_RESV_MASK;
-	vma->vm_private_data = (void *)(reserve | flags);
+	set_vma_private_data(vma,
+		(get_vma_private_data(vma) & HPAGE_RESV_MASK) | reserve);
 }
 
 static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
 {
-	unsigned long reserveflags = (unsigned long)vma->vm_private_data;
 	VM_BUG_ON(!is_vm_hugetlb_page(vma));
-	vma->vm_private_data = (void *)(reserveflags | flags);
+	VM_BUG_ON(vma->vm_flags & VM_SHARED);
+
+	set_vma_private_data(vma, get_vma_private_data(vma) | flags);
 }
 
 static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
 {
 	VM_BUG_ON(!is_vm_hugetlb_page(vma));
-	return ((unsigned long)vma->vm_private_data & flag) != 0;
+
+	return (get_vma_private_data(vma) & flag) != 0;
 }
 
 /* Decrement the reserved pages in the hugepage pool by one */
@@ -1151,11 +1185,10 @@ static struct page *hugetlbfs_pagecache_page(struct vm_area_struct *vma,
 			unsigned long address)
 {
 	struct address_space *mapping;
-	unsigned long idx;
+	pgoff_t idx;
 
 	mapping = vma->vm_file->f_mapping;
-	idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
-		+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
+	idx = vma_pagecache_offset(vma, address);
 
 	return find_lock_page(mapping, idx);
 }
@@ -1164,7 +1197,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, pte_t *ptep, int write_access)
 {
 	int ret = VM_FAULT_SIGBUS;
-	unsigned long idx;
+	pgoff_t idx;
 	unsigned long size;
 	struct page *page;
 	struct address_space *mapping;
@@ -1183,8 +1216,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	}
 
 	mapping = vma->vm_file->f_mapping;
-	idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
-		+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
+	idx = vma_pagecache_offset(vma, address);
 
 	/*
 	 * Use page lock to guard against racing truncation