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
(c743849bee came eight months before 55b949c847), 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>
This commit is contained in:
Max Reitz
2019-09-18 11:51:43 +02:00
parent e61a28a9b6
commit e8d04f9237
5 changed files with 31 additions and 7 deletions

View File

@ -1710,7 +1710,12 @@ static int truncate_f(BlockBackend *blk, int argc, char **argv)
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;