squashfs: use a folio throughout squashfs_read_folio()

Use modern folio APIs where they exist and convert back to struct
page for the internal functions.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Cc: Phillip Lougher <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

fs/squashfs/file.c

···
 
 static int squashfs_read_folio(struct file *file, struct folio *folio)
 {
-	struct page *page = &folio->page;
-	struct inode *inode = page->mapping->host;
+	struct inode *inode = folio->mapping->host;
 	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
-	int index = page->index >> (msblk->block_log - PAGE_SHIFT);
+	int index = folio->index >> (msblk->block_log - PAGE_SHIFT);
 	int file_end = i_size_read(inode) >> msblk->block_log;
 	int expected = index == file_end ?
 			(i_size_read(inode) & (msblk->block_size - 1)) :
 			 msblk->block_size;
 	int res = 0;
-	void *pageaddr;
 
 	TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
-				page->index, squashfs_i(inode)->start);
+				folio->index, squashfs_i(inode)->start);
 
-	if (page->index >= ((i_size_read(inode) + PAGE_SIZE - 1) >>
+	if (folio->index >= ((i_size_read(inode) + PAGE_SIZE - 1) >>
 					PAGE_SHIFT))
 		goto out;
 
···
 			goto out;
 
 		if (res == 0)
-			res = squashfs_readpage_sparse(page, expected);
+			res = squashfs_readpage_sparse(&folio->page, expected);
 		else
-			res = squashfs_readpage_block(page, block, res, expected);
+			res = squashfs_readpage_block(&folio->page, block, res, expected);
 	} else
-		res = squashfs_readpage_fragment(page, expected);
+		res = squashfs_readpage_fragment(&folio->page, expected);
 
 	if (!res)
 		return 0;
 
 out:
-	pageaddr = kmap_atomic(page);
-	memset(pageaddr, 0, PAGE_SIZE);
-	kunmap_atomic(pageaddr);
-	flush_dcache_page(page);
-	if (res == 0)
-		SetPageUptodate(page);
-	unlock_page(page);
+	folio_zero_segment(folio, 0, folio_size(folio));
+	folio_end_read(folio, res == 0);
 
 	return res;
 }