vboxsf: Convert vboxsf to read_folio

This is a "weak" conversion which converts straight back to using pages.
A full conversion should be performed at some point, hopefully by
someone familiar with the filesystem.
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>

fs/vboxsf/file.c

@@ -225,8 +225,9 @@ const struct inode_operations vboxsf_reg_iops = {
 	.setattr = vboxsf_setattr
 };
 
-static int vboxsf_readpage(struct file *file, struct page *page)
+static int vboxsf_read_folio(struct file *file, struct folio *folio)
 {
+	struct page *page = &folio->page;
 	struct vboxsf_handle *sf_handle = file->private_data;
 	loff_t off = page_offset(page);
 	u32 nread = PAGE_SIZE;
@@ -352,7 +353,7 @@ static int vboxsf_write_end(struct file *file, struct address_space *mapping,
  * page and it does not call SetPageUptodate for partial writes.
  */
 const struct address_space_operations vboxsf_reg_aops = {
-	.readpage = vboxsf_readpage,
+	.read_folio = vboxsf_read_folio,
 	.writepage = vboxsf_writepage,
 	.dirty_folio = filemap_dirty_folio,
 	.write_begin = simple_write_begin,