[Libguestfs] [nbdkit PATCH v2] tests: Check that cache-min-block-size works properly

[Richard W.M. Jones]

On Mon, Aug 09, 2021 at 10:23:10AM +0200, Martin Kletzander wrote:
> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> ---
>  tests/test-cache-block-size.sh | 41 +++++++++++++++++++++-------------
>  1 file changed, 26 insertions(+), 15 deletions(-)
> 
> diff --git a/tests/test-cache-block-size.sh b/tests/test-cache-block-size.sh
> index d20cc94002b6..403c295e57c9 100755
> --- a/tests/test-cache-block-size.sh
> +++ b/tests/test-cache-block-size.sh
> @@ -43,28 +43,39 @@ rm -f $files
>  cleanup_fn rm -f $files
>  
>  # Create an empty base image.
> -truncate -s 128K cache-block-size.img
> +truncate -s 256K cache-block-size.img
>  
>  # Run nbdkit with the caching filter.
>  start_nbdkit -P cache-block-size.pid -U $sock --filter=cache \
> -             file cache-block-size.img cache-min-block-size=4K
> +             file cache-block-size.img cache-min-block-size=128K \
> +             cache-on-read=true
>  
>  nbdsh --connect "nbd+unix://?socket=$sock" \
>        -c '
> -# Write some pattern data to the overlay and check it reads back OK.
> -buf = b"abcd" * 16384
> -h.pwrite(buf, 32768)
> -zero = h.pread(32768, 0)
> -assert zero == bytearray(32768)
> -buf2 = h.pread(65536, 32768)
> -assert buf == buf2
> +# Read half of cache-min-block-size
> +
> +zero = h.pread(64 * 1024, 0)
> +assert zero == bytearray(64 * 1024)
> +
> +buf = b"abcd" * 16 * 1024
>  
> -# Flushing should write through to the underlying file.
> -h.flush()
> +# Write past the first read
> +with open("cache-block-size.img", "wb") as file:
> +    file.seek(64 * 1024)
> +    file.write(buf * 2)
> +    file.truncate(256 * 1024)
>  
> +# Check that it got written
>  with open("cache-block-size.img", "rb") as file:
> -    zero = file.read(32768)
> -    assert zero == bytearray(32768)
> -    buf2 = file.read(65536)
> -    assert buf == buf2
> +    file.seek(64 * 1024)
> +    buf2 = file.read(128 * 1024)
> +    assert (buf * 2) == buf2
> +
> +# Now read the rest of the cache-min-block-size, it should stay empty
> +zero = h.pread(64 * 1024, 64 * 1024)
> +assert zero == bytearray(64 * 1024)
> +
> +# Read past that, the pattern should be visible there
> +buf2 = h.pread(64 * 1024, 128 * 1024)
> +assert buf == buf2
>  '

Seems reasonable, ACK.

Rich.

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