diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index c44f1fcc1909..d1dae29a3d01 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -859,6 +859,7 @@ static bool btree_dirty_folio(struct address_space *mapping,
 		struct folio *folio)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(mapping->host->i_sb);
+	struct btrfs_subpage_info *spi = fs_info->subpage_info;
 	struct btrfs_subpage *subpage;
 	struct extent_buffer *eb;
 	int cur_bit = 0;
@@ -872,18 +873,19 @@ static bool btree_dirty_folio(struct address_space *mapping,
 		btrfs_assert_tree_write_locked(eb);
 		return filemap_dirty_folio(mapping, folio);
 	}
+
+	ASSERT(spi);
 	subpage = folio_get_private(folio);
 
-	ASSERT(subpage->dirty_bitmap);
-	while (cur_bit < BTRFS_SUBPAGE_BITMAP_SIZE) {
+	for (cur_bit = spi->dirty_offset;
+	     cur_bit < spi->dirty_offset + spi->bitmap_nr_bits;
+	     cur_bit++) {
 		unsigned long flags;
 		u64 cur;
-		u16 tmp = (1 << cur_bit);
 
 		spin_lock_irqsave(&subpage->lock, flags);
-		if (!(tmp & subpage->dirty_bitmap)) {
+		if (!test_bit(cur_bit, subpage->bitmaps)) {
 			spin_unlock_irqrestore(&subpage->lock, flags);
-			cur_bit++;
 			continue;
 		}
 		spin_unlock_irqrestore(&subpage->lock, flags);
@@ -896,7 +898,7 @@ static bool btree_dirty_folio(struct address_space *mapping,
 		btrfs_assert_tree_write_locked(eb);
 		free_extent_buffer(eb);
 
-		cur_bit += (fs_info->nodesize >> fs_info->sectorsize_bits);
+		cur_bit += (fs_info->nodesize >> fs_info->sectorsize_bits) - 1;
 	}
 	return filemap_dirty_folio(mapping, folio);
 }