Re: [libvirt PATCH 0/6] cleanup and fixes of the mapped-ram feature
On 3/21/25 04:21, Martin Kletzander wrote:
On Fri, Mar 21, 2025 at 08:29:30AM +0000, Daniel P. Berrangé via
Devel wrote:
> On Thu, Mar 20, 2025 at 09:36:15PM -0600, Jim Fehlig via Devel wrote:
>> On 3/20/25 17:07, Pavel Hrdina via Devel wrote:
>> > Pavel Hrdina (6):
>> > tools: remove --parallel from virsh restore command
>> > tools: remote --parallel from virsh save command
>> > qemu: remove VIR_DOMAIN_SAVE_PARALLEL flag
>>
>> Heh, I'm having one of those "why did I not realize that" moments
:-).
>
> IIRC, original we were using --parallel to decide whether to enable
> the new format, so --parallel with channels == 1 /was/ different
> from not setting --parallel at all.
>
Well, restore should figure out the format and save still has
--image-format without which parallel save will fail (unless you have it
set as default in a config). So I think this series is fine, at least
it fixes the unit tests.
Agreed. The new format is enabled with --image-format parameter or by setting it
as default in qemu.conf. And trying to use --parallel-channels without also
specifying sparse fails as expected
# virsh save --parallel-channels 4 test-vm /data/test-vm.sav
error: Failed to save domain 'test-vm' to /data/test-vm.sav
error: invalid argument: Parallel save is only supported with the 'sparse' save
image format
Reviewed-by: Martin Kletzander <mkletzan(a)redhat.com>
But there's more to it than meets the eye.
There is also a check that the number of parallel channels is not lower
than 1, for saving. Restoring happily takes parallel.channels=0 and (at
least for non-sparse images) fails weirdly with:
error: Failed to restore domain from test.img
error: Failed to open file 'test.img': No such file or directory
and the daemon reports:
2025-03-21 10:00:08.490+0000: 4076349: error : virFileIsSharedFSType:3598 :
Invalid relative path 'test.img': Invalid argument
2025-03-21 10:00:08.490+0000: 4076349: error : virQEMUFileOpenAs:10448 : Failed
to open file 'test.img': No such file or directory
even though the file exists. And it works without --parallel-channels,
this only happens with --parallel-channels 0.
Hmm, I don't see this issue
# virsh restore --parallel-channels 0 /data/test-vm.sav.sparse
error: Failed to restore domain from /data/test-vm.sav.sparse
error: invalid argument: number of parallel save channels cannot be less than 1
Could it be that you are using a relative path? Daniel and I just discussed this
in patch1 of the V4 mapped-ram series. I'd provide a link, but
https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/ is currently
down for me. I dropped that patch since we prefer absolute paths.
Last, but not least, our CI is broken with the patches here. And
that
is because now one cannot do save-image-edit, with both the new and the
old format with:
error: failed to write header to domain save file '/home/nert/test.img': Bad
file descriptor
I do see this issue and should have time to investigate it tomorrow.
Regards,
Jim