On 08/28/2015 09:06 AM, Markus Armbruster wrote: > John Snow <js...@redhat.com> 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. >
Oh, taking a look at it, it needs to writethat MBR data to the file before it opens it. We don't have an existing qemu-io dependency here to use. I could add it, but the line between iotest and qtest starts to get pretty fuzzy. Thoughts? --js
