[Libguestfs] [nbdkit PATCH] tests: Check that cache-min-block-size works properly

[Richard W.M. Jones]

On Wed, Aug 04, 2021 at 05:08:32PM +0200, Martin Kletzander wrote:
> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> ---
>  tests/test-cache-block-size.sh | 33 ++++++++++++++++++++++-----------
>  1 file changed, 22 insertions(+), 11 deletions(-)
> 
> diff --git a/tests/test-cache-block-size.sh b/tests/test-cache-block-size.sh
> index d20cc94002b6..5e83ebc1cfaa 100755
> --- a/tests/test-cache-block-size.sh
> +++ b/tests/test-cache-block-size.sh
> @@ -47,24 +47,35 @@ truncate -s 128K cache-block-size.img
>  
>  # Run nbdkit with the caching filter.
>  start_nbdkit -P cache-block-size.pid -U $sock --filter=cache \
> -             file cache-block-size.img cache-min-block-size=4K
> +             file cache-block-size.img cache-min-block-size=64K \

Because of commit c1905b0a2 ("cache, cow: Use a 64K block size by
default"), 64K is the default block size.  So this doesn't test that
the parameter works.  Maybe choose a different block size here?

Rest of it is fine, so ACK, but better if the block size above was
changed.

Rich.

> +             cache-on-read=true
>  
>  nbdsh --connect "nbd+unix://?socket=$sock" \
>        -c '
> -# Write some pattern data to the overlay and check it reads back OK.
> -buf = b"abcd" * 16384
> -h.pwrite(buf, 32768)
> +# Read half of cache-min-block-size
> +
>  zero = h.pread(32768, 0)
>  assert zero == bytearray(32768)
> -buf2 = h.pread(65536, 32768)
> -assert buf == buf2
>  
> -# Flushing should write through to the underlying file.
> -h.flush()
> +buf = b"abcd" * 8192
>  
> +# Write past the first read
> +with open("cache-block-size.img", "wb") as file:
> +    file.seek(32768)
> +    file.write(buf * 2)
> +    file.truncate(131072)
> +
> +# Check that it got written
>  with open("cache-block-size.img", "rb") as file:
> -    zero = file.read(32768)
> -    assert zero == bytearray(32768)
> +    file.seek(32768)
>      buf2 = file.read(65536)
> -    assert buf == buf2
> +    assert (buf * 2) == buf2
> +
> +# Now read the rest of the cache-min-block-size, it should stay empty
> +zero = h.pread(32768, 32768)
> +assert zero == bytearray(32768)
> +
> +# Read past that, the pattern should be visible there
> +buf2 = h.pread(32768, 65536)
> +assert buf == buf2
>  '
> -- 
> 2.32.0

-- 
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