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

@ -3831,7 +3831,12 @@ static int img_resize(int argc, char **argv)
}
}
ret = blk_truncate(blk, total_size, false, prealloc, &err);
/*
* The user expects the image to have the desired size after
* resizing, so pass @exact=true. It is of no use to report
* success when the image has not actually been resized.
*/
ret = blk_truncate(blk, total_size, true, prealloc, &err);
if (ret < 0) {
error_report_err(err);
goto out;