block: Pass truncate exact=true where reasonable
This is a change in behavior, so all instances need a good
justification. The comments added here should explain my reasoning.
qed already had a comment that suggests it always expected
bdrv_truncate()/blk_truncate() to behave as if exact=true were passed
(c743849bee7 came eight months before 55b949c8476), so it was simply
broken until now.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190918095144.955-8-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
[mreitz: Changed comment in qed.c to explain why a new QED file must be
empty, as requested and suggested by Maxim]
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 5e9017c..1b7e700 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1710,7 +1710,12 @@
return offset;
}
- ret = blk_truncate(blk, offset, false, PREALLOC_MODE_OFF, &local_err);
+ /*
+ * qemu-io is a debugging tool, so let us be strict here and pass
+ * exact=true. It is better to err on the "emit more errors" side
+ * than to be overly permissive.
+ */
+ ret = blk_truncate(blk, offset, true, PREALLOC_MODE_OFF, &local_err);
if (ret < 0) {
error_report_err(local_err);
return ret;
