[PATCH] hugetlbfs i_size fix

Growing i_size in hugetlbfs_prefault() isn't right - if we run out of pages,
do_mmap_pgoff() will chop the partially-instantiated pages off again.

So update i_size in hugetlbfs_file_mmap() if the whole mmap attempt was
successful.

arch/i386/mm/hugetlbpage.c

@@ -296,7 +296,6 @@ zap_hugepage_range(struct vm_area_struct *vma,
 int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
 {
 	struct mm_struct *mm = current->mm;
-	struct inode *inode = mapping->host;
 	unsigned long addr;
 	int ret = 0;
 
@@ -320,7 +319,6 @@ int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
 			+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 		page = find_get_page(mapping, idx);
 		if (!page) {
-			loff_t i_size;
 			page = alloc_hugetlb_page();
 			if (!page) {
 				ret = -ENOMEM;
@@ -332,9 +330,6 @@ int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
 				free_huge_page(page);
 				goto out;
 			}
-			i_size = (loff_t)(idx + 1) * HPAGE_SIZE;
-			if (i_size > inode->i_size)
-				inode->i_size = i_size;
 		}
 		set_huge_pte(mm, vma, page, pte, vma->vm_flags & VM_WRITE);
 	}

arch/x86_64/mm/hugetlbpage.c

@@ -245,7 +245,6 @@ void zap_hugepage_range(struct vm_area_struct *vma, unsigned long start, unsigne
 int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
 {
 	struct mm_struct *mm = current->mm;
-	struct inode *inode = mapping->host;
 	unsigned long addr;
 	int ret = 0;
 
@@ -269,7 +268,6 @@ int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
 			+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
 		page = find_get_page(mapping, idx);
 		if (!page) {
-			loff_t i_size;
 
 			page = alloc_hugetlb_page();
 			if (!page) {
@@ -282,9 +280,6 @@ int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
 				free_huge_page(page);
 				goto out;
 			}
-			i_size = (loff_t)(idx + 1) * HPAGE_SIZE;
-			if (i_size > inode->i_size)
-				inode->i_size = i_size;
 		}
 		set_huge_pte(mm, vma, page, pte, vma->vm_flags & VM_WRITE);
 	}

fs/hugetlbfs/inode.c

@@ -45,6 +45,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct inode *inode =file->f_dentry->d_inode;
 	struct address_space *mapping = inode->i_mapping;
+	loff_t len;
 	int ret;
 
 	if (!capable(CAP_IPC_LOCK))
@@ -65,6 +66,10 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
 	vma->vm_flags |= VM_HUGETLB | VM_RESERVED;
 	vma->vm_ops = &hugetlb_vm_ops;
 	ret = hugetlb_prefault(mapping, vma);
+	len = (loff_t)(vma->vm_end - vma->vm_start) +
+			((loff_t)vma->vm_pgoff << PAGE_SHIFT);
+	if (ret == 0 && inode->i_size < len)
+		inode->i_size = len;
 	up(&inode->i_sem);
 	return ret;
 }