mm: cleanup size checks in filemap_fault() and filemap_map_pages()

Minor cleanups:
 - 'size' variable is now in bytes, not pages;
 - use round_up(): it should be easier to read.

Signed-off-by: Kirill A. Shutemov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Ning Qu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/filemap.c

@@ -1953,11 +1953,11 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	struct inode *inode = mapping->host;
 	pgoff_t offset = vmf->pgoff;
 	struct page *page;
-	pgoff_t size;
+	loff_t size;
 	int ret = 0;
 
-	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-	if (offset >= size)
+	size = round_up(i_size_read(inode), PAGE_CACHE_SIZE);
+	if (offset >= size >> PAGE_CACHE_SHIFT)
 		return VM_FAULT_SIGBUS;
 
 	/*
@@ -2006,8 +2006,8 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	 * Found the page and have a reference on it.
 	 * We must recheck i_size under page lock.
 	 */
-	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-	if (unlikely(offset >= size)) {
+	size = round_up(i_size_read(inode), PAGE_CACHE_SIZE);
+	if (unlikely(offset >= size >> PAGE_CACHE_SHIFT)) {
 		unlock_page(page);
 		page_cache_release(page);
 		return VM_FAULT_SIGBUS;
@@ -2111,8 +2111,8 @@ void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf)
 		if (page->mapping != mapping || !PageUptodate(page))
 			goto unlock;
 
-		size = i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1;
-		if (page->index >= size	>> PAGE_CACHE_SHIFT)
+		size = round_up(i_size_read(mapping->host), PAGE_CACHE_SIZE);
+		if (page->index >= size >> PAGE_CACHE_SHIFT)
 			goto unlock;
 
 		pte = vmf->pte + page->index - vmf->pgoff;