diff --git a/source/fs/mufs/tree.c b/source/fs/mufs/tree.c
index 155089a..0c1a0bb 100644
--- a/source/fs/mufs/tree.c
+++ b/source/fs/mufs/tree.c
@@ -195,3 +195,38 @@ size_t mufs_read(struct mufs *fs, struct mufs_tree *tree, void *data,
 
 	return nbytes;
 }
+
+static size_t mufs_do_write(struct mufs *fs, struct mufs_tree *tree,
+	void *data, uint32_t va, size_t len)
+{
+	uint32_t page, offset;
+
+	offset = va & ((UINT32_C(1) << fs->dev->log2_block_size) - 1);
+	va = align(va, fs->dev->log2_block_size);
+
+	memset(data, 0, len);
+	len = min(len, (UINT32_C(1) << fs->dev->log2_block_size) - offset);
+
+	if (mufs_alloc_page(fs, tree, &page, va) < 0)
+		return 0;
+
+	return flash_write(fs->dev, page, data, len);
+}
+
+size_t mufs_write(struct mufs *fs, struct mufs_tree *tree, void *data,
+	uint32_t va, size_t len)
+{
+	uint8_t *buf = data;
+	size_t ret, nbytes = 0;
+
+	while (len) {
+		if ((ret = mufs_do_write(fs, tree, buf, va, len)) == 0)
+			return nbytes;
+
+		buf += ret;
+		va += ret;
+		len -= ret;
+	}
+
+	return nbytes;
+}
diff --git a/source/fs/mufs/tree.h b/source/fs/mufs/tree.h
index 0604370..0f381da 100644
--- a/source/fs/mufs/tree.h
+++ b/source/fs/mufs/tree.h
@@ -9,3 +9,5 @@ int mufs_extend_tree(struct mufs *fs, struct mufs_tree *tree, uint8_t depth);
 int mufs_shrink_tree(struct mufs *fs, struct mufs_tree *tree, uint32_t max_size);
 size_t mufs_read(struct mufs *fs, struct mufs_tree *tree, void *data,
 	uint32_t va, size_t len);
+size_t mufs_write(struct mufs *fs, struct mufs_tree *tree, void *data,
+	uint32_t va, size_t len);