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Fix Qemu probes for disk format and zero-byte skipping support - #14272
sureshanaparti wants to merge 3 commits into
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…pport probe
Due to changes in the format of `qemu-img --help` in Qemu 10.x, the previous logic always returns false, as --target-is-zero is no longer a top-level suggested flag.
The flag continues showing in qemu-img convert --help however. The whole skipZero feature appears unused by native CloudStack, but this preserves the support while remaining backwards compatible with Qemu 8.x
ie:
```
$ qemu-img --version && qemu-img convert --help | grep target-is-zero
qemu-img version 10.1.0 (qemu-kvm-10.1.0-17.el9_8.5)
Copyright (c) 2003-2025 Fabrice Bellard and the QEMU Project developers
[-n] [--target-is-zero] [-c]
--target-is-zero
```
```
$ qemu-img --version && qemu-img convert --help | grep target-is-zero
qemu-img version 8.2.0 (qemu-kvm-8.2.0-11.el9_4)
Copyright (c) 2003-2023 Fabrice Bellard and the QEMU Project developers
convert [--object objectdef] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O output_fmt] [-B backing_file [-F backing_fmt]] [-o options] [-l snapshot_param] [-S sparse_size] [-r rate_limit] [-m num_coroutines] [-W] [--salvage] filename [filename2 [...]] output_filename
```
Due to changes in the format of `qemu-img --help` in Qemu 10.x, the previous logic always returns false: ``` $ qemu-img --help ... Supported image formats: blkdebug blklogwrites blkverify compress copy-before-write copy-on-read file ftp ftps host_cdrom host_device http https io_uring luks nbd null-aio null-co nvme nvme-io_uring preallocate qcow2 quorum raw rbd snapshot-access throttle vdi vhdx virtio-blk-vfio-pci virtio-blk-vhost-user virtio-blk-vhost-vdpa vmdk vpc ``` The approach of doing a create -f $format -o help and relying on the exit code is more robust as a first level probe
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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@blueorangutan package |
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@sureshanaparti a [SL] Jenkins job has been kicked to build packages. It will be bundled with KVM, XenServer and VMware SystemVM templates. I'll keep you posted as I make progress. |
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## 4.22 #14272 +/- ##
============================================
- Coverage 18.00% 17.99% -0.02%
+ Complexity 16219 16214 -5
============================================
Files 5936 5936
Lines 535716 535721 +5
Branches 65596 65597 +1
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- Misses 428268 428346 +78
+ Partials 10989 10983 -6
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Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ el10 ✔️ debian ✔️ suse15. SL-JID 19354 |
| // - prints supported format options with rc=0 on known format, and | ||
| // - error message with rc=1 on unsupported format | ||
| final Script createProbe = new Script(_qemuImgPath, timeout); | ||
| createProbe.add("create", "-f", format.toString(), "-o", "help"); |
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is this still needed? #13587 already handles the new help header on 4.22, and the current check finds qcow2 in the 10.x output from the description
| if (skipZeroIfSupported) { | ||
| final Script s = new Script(_qemuImgPath, timeout); | ||
| s.add("--help"); | ||
| s.add("convert", "--help"); |
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main already checks this flag a different way since #14256. should this match it so the forward merge doesnt conflict?
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+1 to both of @Damans227 points.
Note that zero-skipping is used on 4.22: backup restore, ScaleIO/PowerFlex, Linstor (zeroed devices) and StorPool encryption all ask for it. With qemu 10.x they currently write zeros into thin targets, so the second fix is worth having on 4.22. One small request: could you fill in "How Has This Been Tested?" with the hosts it was checked on? For example, the qemu versions (8.2 / 10.1), whether Happy to add a unit test for the probe when backporting, since main lacks one too. |
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@sureshanaparti @nvazquez As offered, a unit test for the It needs neither qemu-img nor libvirt, so it runs in CI. That matters here: the smoke tests run on OL8, whose qemu still lists the flag in I'll open it as a separate PR against main. For 4.22 it can go in together with the backport here; I'm happy to share the patch for this branch if that's easier. |
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Description
This PR fixes two Qemu feature detection probes that broke between Qemu 8.x and Qemu 10.x:
Disk format support
Due to changes in the format of
qemu-img --helpin Qemu 10.x, the previous logic always returns false:The approach of doing a create -f $format -o help and relying on the exit code is more robust as a first level probe
--target-is-zero support
Due to changes in the format of
qemu-img --helpin Qemu 10.x, the previous logic always returns false, as --target-is-zero is no longer a top-level suggested flag.The flag continues showing in qemu-img convert --help however. The whole skipZero feature appears unused by native CloudStack, but this preserves the support while remaining backwards compatible with Qemu 8.x
ie:
Types of changes
Feature/Enhancement Scale or Bug Severity
Feature/Enhancement Scale
Bug Severity
Screenshots (if appropriate):
How Has This Been Tested?
How did you try to break this feature and the system with this change?