Re: [Libguestfs] [nbdkit PATCH 3/3] tests: Add regression test for NBDKIT_EMULATE_CACHE fix

Add testsuite coverage for the bug fixed in the previous patch (done separately, to make it easier to prove the test fails without the patch). --- tests/Makefile.am | 2 + tests/test-eval-cache.sh | 85 ++++++++++++++++++++++++++++++++++++++++

+# This plugin requests nbdkit to emulate caching with pread. When the witness +# file exists, cache reads; when absent, reads fail if not already cached. +export witness="$PWD/eval-cache.witness" +export cache="$PWD/eval-cache.cache" +export script=' +import os +import errno + +witness = os.getenv("witness") + +def touch(path): + open(path, "a").close() + +# Test that uncached read fails +try: + h.pread(1024 * 1024, 0) +except nbd.Error as ex: + assert ex.errnum == errno.EIO + +# Cache the entire image; nbdkit should break it into 64k preads

+touch(witness) +h.cache(h.get_size(), 0) +os.unlink(witness) + +# Now read should succeed +buf = h.pread(64 * 1024 * 1024, 64 * 1024 * 1024) +if hasattr(buf, "is_zero"): + assert buf.is_zero() +' +nbdkit -U - -v eval \ + get_size='echo 128M' can_cache='echo emulate' open='touch "$cache"' \ + pread=' + if test -f "$witness"; then + echo "$3 $4" >> "$cache" + elif ! grep -q "^$3 $4$" "$cache"; then + echo EIO >&2; exit 1 + fi + dd if=/dev/zero count=$3 iflag=count_bytes + ' --run 'nbdsh -u "$uri" -c "$script"'