ftl: restructure ftl_write() to use less memory by using flash_write0() and flash_copy()

source/ftl/ftl.c

@@ -44,10 +44,10 @@ size_t ftl_read(struct ftl_map *map, void *data, size_t len, uint32_t va)
 size_t ftl_write(struct ftl_map *map, uint32_t va, const void *udata,
 	size_t len)
 {
-	char data[1 << map->log2_page_size];
 	struct ftl_page_desc page_desc;
+	size_t nbytes;
 	int ret;
-	uint32_t offset, page;
+	uint32_t offset, page, dst, src;
 
 	if (va >= ftl_get_capacity(map))
 		return 0;
@@ -59,20 +59,37 @@ size_t ftl_write(struct ftl_map *map, uint32_t va, const void *udata,
 		ret != -ERR_NOT_FOUND)
 		return 0;
 
-	if (ret == -ERR_NOT_FOUND) {
-		memset(data, 0, 1 << map->log2_page_size);
+	if (ret == -ERR_NOT_FOUND)
 		++map->nused_pages;
-	} else if (flash_read(map->dev, page << map->log2_page_size, data,
-		1 << map->log2_page_size) == 0) {
-		return 0;
-	}
 
 	page_desc.nused_pages = map->nused_pages;
 
+	if (prepare_head(map) < 0)
+		return 0;
+
+	dst = map->head << map->log2_page_size;
+	src = page << map->log2_page_size;
 	len = min(len, (1 << map->log2_page_size) - offset);
-	memcpy(data + offset, udata, len);
 
-	if (write_upage(map, data, &page_desc) < 0)
+	if (ret == -ERR_NOT_FOUND)
+		flash_write0(map->dev, dst, offset);
+	else
+		flash_copy(map->dev, dst, src, offset);
+
+	src += offset;
+	dst += offset;
+	flash_write(map->dev, dst, udata, len);
+
+	src += len;
+	dst += len;
+	nbytes = (1 << map->log2_page_size) - len - offset;
+
+	if (ret == -ERR_NOT_FOUND)
+		flash_write0(map->dev, dst, nbytes);
+	else
+		flash_copy(map->dev, dst, src, nbytes);
+
+	if (write_page_desc(map, &page_desc) < 0)
 		return 0;
 
 	return len;