Add a test for qcow2 copy-on-read behavior, including exposure
for the just-fixed bugs.
The copy-on-read behavior is always to a qcow2 image, but the
test is careful to allow running with most image protocol/format
combos as the backing file being copied from (luks being the
exception, as it is harder to pass the right secret to all the
right places). In fact, for './check nbd', this appears to be
the first time we've had a qcow2 image wrapping NBD, requiring
an additional line in _filter_img_create to match the similar
line in _filter_img_info.
Invoking blkdebug to prove we don't write too much took some
effort to get working; and it requires that $TEST_WRAP (based
on $TEST_DIR) not be subject to word splitting. We may decide
later to have the entire iotests suite use relative rather than
absolute names, to avoid problems inherited by the absolute
name of $PWD or $TEST_DIR, at which point the sanity check in
this commit could be simplified.
This test requires at least 2G of consecutive memory to succeed;
as such, it is prone to spurious failures, particularly on
32-bit machines under load. This situation is detected and
triggers an early exit to skip the test, rather than a failure.
To manually provoke this setup on a beefier machine, I used:
$ (ulimit -S -v 1000000; ./check -qcow2 197)
Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
=== This is the QEMU I/O test suite ===
* Intro
This package contains a simple test suite for the I/O layer of qemu.
It does not require a guest, but only the qemu, qemu-img and qemu-io
binaries. This does limit it to exercise the low-level I/O path only
but no actual block drivers like ide, scsi or virtio.
* Usage
Just run ./check to run all tests for the raw image format, or ./check
-qcow2 to test the qcow2 image format. The output of ./check -h explains
additional options to test further image formats or I/O methods.
* Feedback and patches
Please send improvements to the test suite, general feedback or just
reports of failing tests cases to qemu-devel@nongnu.org with a CC:
to qemu-block@nongnu.org.
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