From 7ee5ea99aeb697069572a479b30d7451626d1caa Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Fri, 3 Apr 2026 14:06:31 +0100
Subject: [PATCH] cow: Fix block -> fd calculation

This calculation was plainly wrong, so the other overlay files were
never used.

Fixes: commit eb79a0e0c63ba1884bde02dc884a26aea2fc4324
(cherry picked from commit 7180bbf0f3d7b29e7eccf30207980849f3586583)
---
 filters/cow/blk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/filters/cow/blk.c b/filters/cow/blk.c
index afb48af9..3a416d55 100644
--- a/filters/cow/blk.c
+++ b/filters/cow/blk.c
@@ -324,7 +324,7 @@ blk_set_size (struct blk_overlay *blk, uint64_t new_size)
 static int
 get_fd_for_blknum (struct blk_overlay *blk, uint64_t blknum)
 {
-  size_t i = blknum / MAX_FILE_SIZE / blksize;
+  size_t i = blknum * blksize / MAX_FILE_SIZE;
   assert (i < blk->fds.len);
   return blk->fds.ptr[i];
 }
-- 
2.47.3