rafs: fix a regression caused by commit 2616fb2

Fix a regression caused by commit 2616fb2.

Signed-off-by: Jiang Liu <gerry@linux.alibaba.com>

rafs/src/metadata/direct_v6.rs

@@ -535,7 +535,7 @@ impl OndiskInodeWrapper {
                 let len = if div_round_up(self.size(), EROFS_BLOCK_SIZE) as usize == block_index + 1
                 {
                     if self.size() % EROFS_BLOCK_SIZE == 0 {
-                        EROFS_BLOCK_SIZE as usize
+                        (EROFS_BLOCK_SIZE - s) as usize
                     } else {
                         (self.size() % EROFS_BLOCK_SIZE - s) as usize
                     }