Re: [Qemu-devel] hd-geo-test creates 4GB files on FSes that don't support sparse images, doesn't delete them on error

[Markus Armbruster]

John Snow <address@hidden> writes:

> On 08/27/2015 11:29 AM, Eric Blake wrote:
>> On 08/27/2015 09:17 AM, Peter Maydell wrote:
>>> I've noticed recently that tests/hd-geo-test.c creates test disk
>>> images which are 4GB in size, which is a problem if the filesystem
>>> on the host doesn't support sparse files. In particular, OSX's HFS+
>>> doesn't have sparse file support, and Windows probably doesn't either.
>> 
>> Windows NTFS supports sparse files (minimum hole size of 64k), but it
>> can be a pain to set up, and while it saves disk space, it may actually
>> slow your program down.
>> 
>> [At one point cygwin created sparse files on windows by default, but
>> because it was demonstrated to hurt performance in dealing with sparse
>> files, because Windows doesn't handle sparse files efficiently, the
>> cygwin defaults were switched so that it now requires an explicit opt-in
>> mount option before even attempting sparse files]
>> 
>>> Worse, if the test fails an assertion somewhere the test doesn't
>>> clean up after itself and leaves a 4GB file lying around in /tmp/.
>>>
>>> It would be nice if we could skip these tests on filesystems that
>>> don't have sparse file support...
>> 
>> Or even where sparse files are supported but not default.
>> 
>
> Does this test *require* the raw format?

If memory serves, the test doesn't require a specific format, only the
size and the contents of the MBR matters.

> Use tests/libqos/libqos.c mkqcow2 instead. I'll send a patch.

Go right ahead.