On 8/8/23 00:28, Richard W.M. Jones wrote: > Occasionally this test will choose a random seed which results in an > all-zeroes disk. The test tries to convert this to a compressed qcow2 > file, and fails because no compressed clusters are detected in the > resulting file. This happens because qcow2 stores zero clusters with > a special sparse representation, they are never stored compressed, so > a disk with only zeroes in it will never contain compressed clusters. > > To fix this, detect an all-zeroes disk and skip. > > Reported-by: Eric Blake > --- > copy/copy-file-to-qcow2-compressed.sh | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/copy/copy-file-to-qcow2-compressed.sh b/copy/copy-file-to-qcow2-compressed.sh > index 018c8bba2f..2706eadd66 100755 > --- a/copy/copy-file-to-qcow2-compressed.sh > +++ b/copy/copy-file-to-qcow2-compressed.sh > @@ -25,6 +25,7 @@ requires $QEMU_NBD --version > requires nbdkit --exit-with-parent --version > requires nbdkit sparse-random --dump-plugin > requires qemu-img --version > +requires nbdinfo --version > #requires stat --version > > # Check the compress driver is supported by this qemu-nbd. > @@ -45,6 +46,15 @@ cleanup_fn rm -f $file1 $file2 $out1 $out2 > size=1G > seed=$RANDOM > > +# Occasionally we will choose a seed which results in a completely > +# empty file. Skip this case. > +if nbdinfo --map --totals -- \ > + [ nbdkit --exit-with-parent sparse-random $size seed=$seed ] | > + grep -sq '100.0%.*hole,zero'; then > + echo "$0: bad seed chosen, skipping the test" > + exit 77 > +fi > + > # Create a compressed qcow2 file1. > # > # sparse-random files should compress easily because by default each Nbdkit uses its own PRNG from "common/include/random.h", not the one from libc. That means the seed=... parameter entirely determines the random series -- not only does it become time-independent, but also platform-independent. And based on that, could we just eliminate "seed=$RANDOM" from this test case, and use simply "seed=1" (for example)? What we want is a sparse-random disk image, generated both times with the same not-fully-zero contents. seed=1 satisfies that, and makes sure the test is always "armed" (and, not least, deterministic).