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Re: [Qemu-devel] [PATCH v2 9/9] tests: Add coverage for recent block geo

From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH v2 9/9] tests: Add coverage for recent block geometry fixes
Date: Fri, 18 Nov 2016 00:42:00 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 17.11.2016 21:14, Eric Blake wrote:
> Use blkdebug's new geometry constraints to emulate setups that
> have caused recent regression fixes: write zeroes asserting
> when running through a loopback block device with max-transfer
> smaller than cluster size, and discard rounding away requests
> that were not aligned to power-of-two boundaries.  Also, add
> coverage that the block layer is honoring max transfer limits.
> For now, a single iotest performs all actions, with the idea
> that we can add future blkdebug constraint test cases in the
> same file; but it can be split into multiple iotests if we find
> reason to run one portion of the test in more setups than what
> are possible in the other.
> Signed-off-by: Eric Blake <address@hidden>
> ---
>  tests/qemu-iotests/173     | 115 
> +++++++++++++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/173.out |  49 +++++++++++++++++++
>  tests/qemu-iotests/group   |   1 +
>  3 files changed, 165 insertions(+)
>  create mode 100755 tests/qemu-iotests/173
>  create mode 100644 tests/qemu-iotests/173.out
> diff --git a/tests/qemu-iotests/173 b/tests/qemu-iotests/173
> new file mode 100755
> index 0000000..1215759
> --- /dev/null
> +++ b/tests/qemu-iotests/173


> +# Dell Equallogic iSCSI device is unusual with its 15M page size
> +echo
> +echo "== non-power-of-2 write zeroes =="
> +
> +limits=opt-write-zero=15M,max-write-zero=15M,opt-discard=15M,max-discard=15M
> +$QEMU_IO -c "open -o $options,$limits blkdebug::$TEST_IMG" \
> +         -c "write -z 32M 32M" | _filter_qemu_io
> +
> +echo
> +echo "== non-power-of-2 discard =="
> +
> +limits=opt-write-zero=15M,max-write-zero=15M,opt-discard=15M,max-discard=15M
> +$QEMU_IO -c "open -o $options,$limits blkdebug::$TEST_IMG" \
> +         -c "discard 80000000 30M" | _filter_qemu_io

Question: What does this test has to do with iscsi?

The first case just tests that we fall back to writing the head and tail
as full zeroes when the driver returns -ENOTSUP.

The second test, as far as I can see, just gives some discard request to
blkdebug (split up into head, mid and tail), which blkdebug just passes
on (because 80000000 is a multiple of 512). qcow2 then discards part of
that and drops the head and tail of the request it receives (but head
and tail are now calculated based on qcow2's 64k limit).

What does that have to do with said iscsi device, though?


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