Am 19.04.2021 um 10:36 hat Peter Lieven geschrieben: > > > > Am 15.04.2021 um 17:22 schrieb Kevin Wolf <kw...@redhat.com>: > > > > Peter, three years ago you changed 'qemu-img convert' to sacrifice some > > sparsification in order to get aligned requests on the target image. At > > the time, I thought the impact would be small, but it turns out that > > this can end up wasting gigabytes of storagee (like converting a fully > > zeroed 10 GB image taking 2.8 GB instead of a few kilobytes). > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1882917 > > > > I'm not entirely sure how to attack this best since this is a tradeoff, > > but maybe the approach in this series is still good enough for the case > > that you wanted to fix back then? > > > > Of course, it would be possible to have a more complete fix like looking > > forward a few blocks more before writing data, but that would probably > > not be entirely trivial because you would have to merge blocks with ZERO > > block status with DATA blocks that contain only zeros. I'm not sure if > > it's worth this complication of the code. > > I will try to look into this asap. > > Is there a hint which FS I need to set the extent hint when creating > the raw image? I was not able to do that.
Grepping the current kernel source, it seems extent size hints still work only on XFS. But I don't think it's necessary for reproducing this bug. In fact, disabling the extent size hint should cause a lot more fragmentation, which should make the problem more visible. Kevin
