18905879458
80%
master: 80%

Ran 29 Oct 2025 11:11AM UTC

Jobs 1

Files 34

Run time 1min

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Committed 29 Oct 2025 08:28AM UTC coverage: 80.368%. Remained the same

Build # 18905879458

Build Type

push

github

Committed by

web-flow

Commit Message

`ocaml/libs`: Check if blocks are filled with zeros in `vhd_format` (#6720)

`find_data_blocks` is used to determine which blocks need to be copied
to the destination VHD file during export. It uses `lseek(SEEK_DATA)` to
skip "holes" in files. Raw files presented by the storage layer,
however, do not have holes, instead returning blocks filled with zeros.
This means that `vhd-tool` ends up allocating every single block (even
if all of them contain zeroes and no actual data).

In addition to using `lseek_data`, read the whole block and check if it
only contains zeros. This avoids allocating zero blocks and greatly
speeds up export from raw to vhd (which happens when exporting qcow2 to
vhd as well).

Before this fix, when exporting a QCOW2-backed VDI (which vhd-tool falls
back to treating as "raw"):

    $ xe vdi-export uuid=VDI_UUID filename=test.vhd format=vhd
    $ ll -h test.vhd
    2.1G test.vhd

Compared to the qcow2 backing file:

    $ ll -h /var/run/sr-mount/SR_UUID/VDI_UUID.qcow2
    165M /var/run/sr-mount/SR_UUID/VDI_UUID.qcow2

After this fix:

    $ ll -h test.vhd
    219M test.vhd

Run Details

3496 of 4350 relevant lines covered (80.37%)

0.8 hits per line

Jobs

ID	Job ID	Ran	Files	Coverage
1	python3.11 - 18905879458.1	29 Oct 2025 11:11AM UTC	34	80.37	GitHub Action Run

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