Am 26.06.2024 um 18:27 hat Nir Soffer geschrieben:
> On Wed, Jun 26, 2024 at 12:17 PM Daniel P. Berrangé <berrange@redhat.com>
> wrote:
>
> > On Mon, Jun 24, 2024 at 06:08:26PM +0200, Kevin Wolf wrote:
> > > Am 24.06.2024 um 17:23 hat Stefan Hajnoczi geschrieben:
> > > > On Wed, Jun 19, 2024 at 08:43:25PM +0300, Nir Soffer wrote:
> > > > > Tested using:
> > > >
> > > > Hi Nir,
> > > > This looks like a good candidate for the qemu-iotests test suite.
> > Adding
> > > > it to the automated tests will protect against future regressions.
> > > >
> > > > Please add the script and the expected output to
> > > > tests/qemu-iotests/test/write-zeroes-unmap and run it using
> > > > `(cd build && tests/qemu-iotests/check write-zeroes-unmap)`.
> > > >
> > > > See the existing test cases in tests/qemu-iotests/ and
> > > > tests/qemu-iotests/tests/ for examples. Some are shell scripts and
> > > > others are Python. I think shell makes sense for this test case. You
> > > > can copy the test framework boilerplate from an existing test case.
> > >
> > > 'du' can't be used like this in qemu-iotests because it makes
> > > assumptions that depend on the filesystem. A test case replicating what
> > > Nir did manually would likely fail on XFS with its preallocation.
> > >
> > > Maybe we could operate on a file exposed by the FUSE export that is
> > > backed by qcow2, and then you can use 'qemu-img map' on that qcow2 image
> > > to verify the allocation status. Somewhat complicated, but I think it
> > > could work.
> >
> > A simpler option would be to use 'du' but with a fuzzy range test,
> > rather than an exact equality test.
> >
> > For the tests which write 1 MB, check the 'du' usage is "at least 1MB",
> > for the tests which expect to unmap blocks, check that the 'du' usage
> > is "less than 256kb". This should be within bounds of xfs speculative
> > allocation.
>
> This should work, I'll start with this approach.
If we're okay with accepting tests that depend on filesystem behaviour,
then 'qemu-img map -f raw --output=json' should be the less risky
approach than checking 'du'.
Unfortunately it does not work since qemu-img map and qemu-nbd reports the allocated
area as zero area with no data.
I tried this:
$ cat test-print-allocation.sh
#!/bin/sh
qemu=${1:?Usage: $0 qemu-executable}
img=/tmp/qemu-test-unmap.img
echo
echo "discard=unmap - write zeroes"
fallocate -l 1m $img
echo -e 'qemu-io none0 "write -z 0 1m"\nquit' | $qemu -monitor stdio \
-drive if=none,file=$img,format=raw,discard=unmap >/dev/null
echo "du:"
du -sh $img
echo "qemu-img map:"
qemu-img map -f raw --output json $img
echo "nbdinfo --map:"
nbdinfo --map -- [ qemu-nbd -r -f raw $img ]
echo
echo "discard=unmap - write zeroes unmap"
fallocate -l 1m $img
echo -e 'qemu-io none0 "write -zu 0 1m"\nquit' | $qemu -monitor stdio \
-drive if=none,file=$img,format=raw,discard=unmap >/dev/null
echo "du:"
du -sh $img
echo "qemu-img map:"
qemu-img map -f raw --output json $img
echo "nbdinfo --map:"
nbdinfo --map -- [ qemu-nbd -r -f raw $img ]
rm $img
$ ./test-print-allocation.sh ./qemu-system-x86_64
discard=unmap - write zeroes
du:
1.0M /tmp/qemu-test-unmap.img
qemu-img map:
[{ "start": 0, "length": 1048576, "depth": 0, "present": true, "zero": true, "data": false, "offset": 0}]
nbdinfo --map:
0 1048576 3 hole,zero
discard=unmap - write zeroes unmap
du:
0 /tmp/qemu-test-unmap.img
qemu-img map:
[{ "start": 0, "length": 1048576, "depth": 0, "present": true, "zero": true, "data": false, "offset": 0}]
nbdinfo --map:
0 1048576 3 hole,zero