mufs: optimise memory footprint of mufs_do_lookup()

source/fs/mufs/tree.c

@@ -32,8 +32,7 @@ static int mufs_do_lookup(struct mufs *fs, uint32_t *page,
 	unsigned alloc)
 {
 	struct flash_dev *dev = fs->dev;
-	char data[1 << dev->log2_block_size];
+	uint32_t entry;
-	uint32_t *table = (uint32_t *)data;
 	size_t index;
 
 	if (!base)
@@ -44,27 +43,27 @@ static int mufs_do_lookup(struct mufs *fs, uint32_t *page,
 		return 0;
 	}
 
-	if (flash_read(dev, base << dev->log2_block_size, data,
-		sizeof data) == 0)
-		return -1;
-
 	index = va & ((1 << ((depth - 1) * fs->log2_nentries)) - 1);
 
-	if (!table[index]) {
+	if (flash_read(dev, (base << dev->log2_block_size) + index * sizeof entry,
+		&entry, sizeof entry) == 0)
+		return -1;
+
+	if (!entry) {
 		if (alloc) {
 			if (depth == 1 && new_page) {
-				table[index] = new_page;
+				entry = new_page;
-			} else if (mufs_alloc_block(fs, &table[index]) < 0) {
+			} else if (mufs_alloc_block(fs, &entry) < 0) {
 				return -1;
 			}
 		}
 
-		if (flash_write(dev, base << dev->log2_block_size, data,
+		if (flash_write(dev, (base << dev->log2_block_size) +
-			sizeof data) == 0)
+			index * sizeof entry, &entry, sizeof entry) == 0)
 			return -1;
 	}
 
-	return mufs_do_lookup(fs, page, table[index], depth - 1, va, new_page,
+	return mufs_do_lookup(fs, page, entry, depth - 1, va, new_page,
 		alloc);
 }