vvfat: Fix bug in writing to middle of file

Before this commit, the behavior when calling `commit_one_file` for
example with `offset=0x2000` (second cluster), what will happen is that
we won't fetch the next cluster from the fat, and instead use the first
cluster for the read operation.

This is due to off-by-one error here, where `i=0x2000 !< offset=0x2000`,
thus not fetching the next cluster.

Signed-off-by: Amjad Alsharafi <amjadsharafi10@gmail.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Tested-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <b97c1e1f1bc2f776061ae914f95d799d124fcd73.1721470238.git.amjadsharafi10@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit b881cf00c99e03bc8a3648581f97736ff275b18b)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/block/vvfat.c b/block/vvfat.c
index 723c91216e0c988532663be1d520a7aca76af895..741fdb0341e35f93a426cb2569c089c3be7003b1 100644 (file)
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -2522,8 +2522,9 @@ static int commit_one_file(BDRVVVFATState* s,
         return -1;
     }
 
-    for (i = s->cluster_size; i < offset; i += s->cluster_size)
+    for (i = 0; i < offset; i += s->cluster_size) {
         c = modified_fat_get(s, c);
+    }
 
     fd = qemu_open_old(mapping->path, O_RDWR | O_CREAT | O_BINARY, 0666);
     if (fd < 0) {