Re: [PATCH v3 2/3] iotests/298: add testcase for async writes with preallocation filter

[Kevin Wolf <kwolf@redhat.com>]

Am 16.07.2024 um 16:41 hat Andrey Drobyshev geschrieben:
> The testcase simply creates a 64G image with 1M clusters, generates a list
> of 1M aligned offsets and feeds aio_write commands with those offsets to
> qemu-io run with '--aio native --nocache'.  Then we check the data
> written at each of the offsets.  Before the previous commit this could
> result into a race within the preallocation filter which would zeroize
> some clusters after actually writing data to them.
> 
> Note: the test doesn't fail in 100% cases as there's a race involved,
> but the failures are pretty consistent so it should be good enough for
> detecting the problem.
> 
> Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>

I left it running in a loop for a while, but couldn't reproduce the bug
with this test.

>  tests/qemu-iotests/298     | 49 ++++++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/298.out |  4 ++--
>  2 files changed, 51 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/qemu-iotests/298 b/tests/qemu-iotests/298
> index 09c9290711..b7126e9e15 100755
> --- a/tests/qemu-iotests/298
> +++ b/tests/qemu-iotests/298
> @@ -20,8 +20,10 @@
>  
>  import os
>  import iotests
> +import random
>  
>  MiB = 1024 * 1024
> +GiB = MiB * 1024
>  disk = os.path.join(iotests.test_dir, 'disk')
>  overlay = os.path.join(iotests.test_dir, 'overlay')
>  refdisk = os.path.join(iotests.test_dir, 'refdisk')
> @@ -176,5 +178,52 @@ class TestTruncate(iotests.QMPTestCase):
>          self.do_test('off', '150M')
>  
>  
> +class TestPreallocAsyncWrites(iotests.QMPTestCase):
> +    def setUp(self):
> +        # Make sure we get reproducible write patterns on each run
> +        random.seed(42)
> +        iotests.qemu_img_create('-f', iotests.imgfmt, disk, '-o',
> +                                f'cluster_size={MiB},lazy_refcounts=on',
> +                                str(64 * GiB))
> +
> +    def tearDown(self):
> +        os.remove(disk)
> +
> +    def test_prealloc_async_writes(self):
> +        def gen_write_pattern():
> +            n = 0
> +            while True:
> +                yield '-P 0xaa' if n else '-z'
> +                n = 1 - n

This looks like a complicated way to write the following?

    # Alternate between write_zeroes and writing data
    def gen_write_pattern():
        while True:
            yield '-z'
            yield '-P 0xaa'

> +        def gen_read_pattern():
> +            n = 0
> +            while True:
> +                yield '-P 0xaa' if n else '-P 0x00'
> +                n = 1 - n

Same here.

Kevin