From d2b4b03a4751ac99848b56c4924f120a4907bb97 Mon Sep 17 00:00:00 2001
From: "E. C. Masloch" <pushbx@ulukai.org>
Date: Tue, 21 Apr 2026 18:15:22 +0200
Subject: [PATCH] fatfs.c: update dir_size during map_cluster extend loop
 [fixes #241]

---
 kernel/fatfs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/fatfs.c b/kernel/fatfs.c
index 411e2d26..ec89418f 100644
--- a/kernel/fatfs.c
+++ b/kernel/fatfs.c
@@ -1028,6 +1028,12 @@ COUNT map_cluster(REG f_node_ptr fnp, COUNT mode)
 
     fnp->f_cluster = cluster;
     fnp->f_cluster_offset++;
+    fnp->f_dir.dir_size =
+      ((ULONG)fnp->f_cluster
+      * (ULONG)fnp->f_dpb->dpb_secsize)
+      <<
+      fnp->f_dpb->dpb_shftcnt;
+    merge_file_changes(fnp, FALSE);
   }
 
 #ifdef DISPLAY_GETBLOCK