Description of problem:

When importing a gzipped raw image, nbdkid is started with the following args:

I0523 14:20:31.215028 1 nbdkit.go:238] Start nbdkit with: ['--foreground' '--readonly' '--exit-with-parent' '-U' '/var/run/nbdkit.sock' '--pidfile' '/var/run/nbdkit.pid' '--filter=gzip' '-r' 'curl' 'url=http://cdi-file-host.cdi/tinyCore.iso.gz']

The gzip plugin is specified. Internally, the gzip plugin downloads/uncompresses the target file to a temporary dir when it is initially accessed. See [1]. Unfortunately, that temp dir is on the container filesystem, not a PVC. This is obviously problematic for large images.

[1] https://github.com/libguestfs/nbdkit/blob/v1.31.7/filters/gzip/gzip.c#L126-L250

Version-Release number of selected component (if applicable):

How reproducible: 100%

Steps to Reproduce:
1. make cluster-up cluster-sync

2. Create this DataVolume

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
metadata:
name: dv1
annotations:
"cdi.kubevirt.io/storage.pod.retainAfterCompletion": "true"
spec:
source:
http:
url: "http://cdi-file-host.cdi/tinyCore.iso.gz"
pvc:
volumeMode: Filesystem
accessModes:

• ReadWriteOnce
  resources:
  requests:
  storage: 1Gi

3. Check pod log to confirm that gzip plugin is used

Actual results:

Image is downloaded/uncompressed to container filesystem

Expected results:

It should be possible for the image to be downloaded/uncompressed directly to the target PVC with no temporary space

Additional info: