[PATCH 5/6] LBS: fix crashes in vma_address

[Hugh Dickins <hugh@veritas.com>]

vma_address oopsed on mapping_order(page->mapping): because page may now
be a tail page in which page->mapping is NULL.  There's (too!) many ways
to do this, I went for page_cache_page_order(page_cache_head(page)) so
we can also avoid the PageAnon test.   Indeed, use page_cache_page_order
throughout, to simplify those "page_cache_shift(mapping) - PAGE_SHIFT"s.

vma_address bugged on !PageAnon because loops over page_cache_base_pages
may try a component file page outside the range of the vma: just delete
that BUG_ON now it no longer applies.

Signed-off-by: Hugh Dickins <hugh@veritas.com>

--- 2.6.23-rc6-lbs/mm/rmap.c	2007-09-11 20:01:08.000000000 +0100
+++ linux/mm/rmap.c	2007-09-13 21:22:33.000000000 +0100
@@ -191,17 +191,10 @@ vma_address(struct page *page, struct vm
 	pgoff_t pgoff;
 	unsigned long address;
 
-	if (PageAnon(page))
-		pgoff = page->index;
-	else
-		pgoff = page->index << mapping_order(page->mapping);
-
+	pgoff = page->index << page_cache_page_order(page_cache_head(page));
 	address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
-	if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
-		/* page should be within any vma from prio_tree_next */
-		BUG_ON(!PageAnon(page));
+	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
 		return -EFAULT;
-	}
 	return address;
 }
 
@@ -352,7 +345,7 @@ static int page_referenced_file(struct p
 {
 	unsigned int mapcount;
 	struct address_space *mapping = page->mapping;
-	pgoff_t pgoff = page->index << (page_cache_shift(mapping) - PAGE_SHIFT);
+	pgoff_t pgoff = page->index << page_cache_page_order(page);
 	struct vm_area_struct *vma;
 	struct prio_tree_iter iter;
 	int referenced = 0;
@@ -475,7 +468,7 @@ static int page_mkclean_one(struct page 
 
 static int page_mkclean_file(struct address_space *mapping, struct page *page)
 {
-	pgoff_t pgoff = page->index << (page_cache_shift(mapping) - PAGE_SHIFT);
+	pgoff_t pgoff = page->index << page_cache_page_order(page);
 	struct vm_area_struct *vma;
 	struct prio_tree_iter iter;
 	int ret = 0;
@@ -907,7 +900,7 @@ static int try_to_unmap_anon(struct page
 static int try_to_unmap_file(struct page *page, int migration)
 {
 	struct address_space *mapping = page->mapping;
-	pgoff_t pgoff = page->index << (page_cache_shift(mapping) - PAGE_SHIFT);
+	pgoff_t pgoff = page->index << page_cache_page_order(page);
 	struct vm_area_struct *vma;
 	struct prio_tree_iter iter;
 	int ret = SWAP_AGAIN;