ext4: convert ext4_da_do_write_end() to take a folio

There's nothing page-specific happening in ext4_da_do_write_end();
it's merely used for its refcount & lock, both of which are folio
properties.  Saves four calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20231214053035.1018876-1-willy@infradead.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: Matthew Wilcox (Oracle)

fs/ext4/inode.c

@@ -2947,7 +2947,7 @@ static int ext4_da_should_update_i_disksize(struct folio *folio,
 
 static int ext4_da_do_write_end(struct address_space *mapping,
 			loff_t pos, unsigned len, unsigned copied,
-			struct page *page)
+			struct folio *folio)
 {
 	struct inode *inode = mapping->host;
 	loff_t old_size = inode->i_size;
@@ -2958,12 +2958,13 @@ static int ext4_da_do_write_end(struct address_space *mapping,
 	 * block_write_end() will mark the inode as dirty with I_DIRTY_PAGES
 	 * flag, which all that's needed to trigger page writeback.
 	 */
-	copied = block_write_end(NULL, mapping, pos, len, copied, page, NULL);
+	copied = block_write_end(NULL, mapping, pos, len, copied,
+			&folio->page, NULL);
 	new_i_size = pos + copied;
 
 	/*
-	 * It's important to update i_size while still holding page lock,
-	 * because page writeout could otherwise come in and zero beyond
+	 * It's important to update i_size while still holding folio lock,
+	 * because folio writeout could otherwise come in and zero beyond
 	 * i_size.
 	 *
 	 * Since we are holding inode lock, we are sure i_disksize <=
@@ -2981,14 +2982,14 @@ static int ext4_da_do_write_end(struct address_space *mapping,
 
 		i_size_write(inode, new_i_size);
 		end = (new_i_size - 1) & (PAGE_SIZE - 1);
-		if (copied && ext4_da_should_update_i_disksize(page_folio(page), end)) {
+		if (copied && ext4_da_should_update_i_disksize(folio, end)) {
 			ext4_update_i_disksize(inode, new_i_size);
 			disksize_changed = true;
 		}
 	}
 
-	unlock_page(page);
-	put_page(page);
+	folio_unlock(folio);
+	folio_put(folio);
 
 	if (old_size < pos)
 		pagecache_isize_extended(inode, old_size, pos);
@@ -3027,10 +3028,10 @@ static int ext4_da_write_end(struct file *file,
 		return ext4_write_inline_data_end(inode, pos, len, copied,
 						  folio);
 
-	if (unlikely(copied < len) && !PageUptodate(page))
+	if (unlikely(copied < len) && !folio_test_uptodate(folio))
 		copied = 0;
 
-	return ext4_da_do_write_end(mapping, pos, len, copied, &folio->page);
+	return ext4_da_do_write_end(mapping, pos, len, copied, folio);
 }
 
 /*