0da9856851
When querying image extents for raw image, qemu-nbd reports holes as
zero:
$ qemu-nbd -t -r -f raw empty-6g.raw
$ qemu-img map --output json nbd://localhost
[{ "start": 0, "length": 6442450944, "depth": 0, "zero": true, "data": true, "offset": 0}]
$ qemu-img map --output json empty-6g.raw
[{ "start": 0, "length": 6442450944, "depth": 0, "zero": true, "data": false, "offset": 0}]
Turns out that qemu-img map reports a hole based on BDRV_BLOCK_DATA, but
nbd server reports a hole based on BDRV_BLOCK_ALLOCATED.
The NBD protocol says:
NBD_STATE_HOLE (bit 0): if set, the block represents a hole (and
future writes to that area may cause fragmentation or encounter an
NBD_ENOSPC error); if clear, the block is allocated or the server
could not otherwise determine its status.
qemu-img manual says:
whether the sectors contain actual data or not (boolean field data;
if false, the sectors are either unallocated or stored as
optimized all-zero clusters);
To me, data=false looks compatible with NBD_STATE_HOLE. From user point
of view, getting same results from qemu-nbd and qemu-img is more
important than being more correct about allocation status.
Changing nbd server to report holes using BDRV_BLOCK_DATA makes qemu-nbd
results compatible with qemu-img map:
$ qemu-img map --output json nbd://localhost
[{ "start": 0, "length": 6442450944, "depth": 0, "zero": true, "data": false, "offset": 0}]
Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-Id: <20210219160752.1826830-1-nsoffer@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
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| .. | ||
| acceptance | ||
| data | ||
| decode | ||
| docker | ||
| fp | ||
| guest-debug | ||
| image-fuzzer | ||
| include | ||
| keys | ||
| migration | ||
| multiboot | ||
| perf/block/qcow2 | ||
| plugin | ||
| qapi-schema | ||
| qemu-iotests | ||
| qtest | ||
| rocker | ||
| tcg | ||
| tsan | ||
| uefi-test-tools | ||
| vm | ||
| vmstate-static-checker-data | ||
| atomic64-bench.c | ||
| atomic_add-bench.c | ||
| benchmark-crypto-cipher.c | ||
| benchmark-crypto-hash.c | ||
| benchmark-crypto-hmac.c | ||
| check-block-qdict.c | ||
| check-block.sh | ||
| check-qdict.c | ||
| check-qjson.c | ||
| check-qlist.c | ||
| check-qlit.c | ||
| check-qnull.c | ||
| check-qnum.c | ||
| check-qobject.c | ||
| check-qom-interface.c | ||
| check-qom-proplist.c | ||
| check-qstring.c | ||
| crypto-tls-psk-helpers.c | ||
| crypto-tls-psk-helpers.h | ||
| crypto-tls-x509-helpers.c | ||
| crypto-tls-x509-helpers.h | ||
| dbus-vmstate-daemon.sh | ||
| io-channel-helpers.c | ||
| io-channel-helpers.h | ||
| iothread.c | ||
| iothread.h | ||
| Makefile.include | ||
| meson.build | ||
| pkix_asn1_tab.c | ||
| ptimer-test-stubs.c | ||
| ptimer-test.c | ||
| ptimer-test.h | ||
| qht-bench.c | ||
| rcutorture.c | ||
| requirements.txt | ||
| socket-helpers.c | ||
| socket-helpers.h | ||
| test-aio-multithread.c | ||
| test-aio.c | ||
| test-authz-list.c | ||
| test-authz-listfile.c | ||
| test-authz-pam.c | ||
| test-authz-simple.c | ||
| test-base64.c | ||
| test-bdrv-drain.c | ||
| test-bdrv-graph-mod.c | ||
| test-bitcnt.c | ||
| test-bitmap.c | ||
| test-bitops.c | ||
| test-block-backend.c | ||
| test-block-iothread.c | ||
| test-blockjob-txn.c | ||
| test-blockjob.c | ||
| test-bufferiszero.c | ||
| test-char.c | ||
| test-clone-visitor.c | ||
| test-coroutine.c | ||
| test-crypto-afsplit.c | ||
| test-crypto-block.c | ||
| test-crypto-cipher.c | ||
| test-crypto-hash.c | ||
| test-crypto-hmac.c | ||
| test-crypto-ivgen.c | ||
| test-crypto-pbkdf.c | ||
| test-crypto-secret.c | ||
| test-crypto-tlscredsx509.c | ||
| test-crypto-tlssession.c | ||
| test-crypto-xts.c | ||
| test-cutils.c | ||
| test-fdmon-epoll.c | ||
| test-hbitmap.c | ||
| test-image-locking.c | ||
| test-int128.c | ||
| test-io-channel-buffer.c | ||
| test-io-channel-command.c | ||
| test-io-channel-file.c | ||
| test-io-channel-socket.c | ||
| test-io-channel-tls.c | ||
| test-io-task.c | ||
| test-iov.c | ||
| test-keyval.c | ||
| test-logging.c | ||
| test-mul64.c | ||
| test-opts-visitor.c | ||
| test-qapi-util.c | ||
| test-qdev-global-props.c | ||
| test-qdist.c | ||
| test-qemu-opts.c | ||
| test-qga.c | ||
| test-qgraph.c | ||
| test-qht-par.c | ||
| test-qht.c | ||
| test-qmp-cmds.c | ||
| test-qmp-event.c | ||
| test-qobject-input-visitor.c | ||
| test-qobject-output-visitor.c | ||
| test-rcu-list.c | ||
| test-rcu-simpleq.c | ||
| test-rcu-slist.c | ||
| test-rcu-tailq.c | ||
| test-replication.c | ||
| test-shift128.c | ||
| test-string-input-visitor.c | ||
| test-string-output-visitor.c | ||
| test-thread-pool.c | ||
| test-throttle.c | ||
| test-timed-average.c | ||
| test-util-filemonitor.c | ||
| test-util-sockets.c | ||
| test-uuid.c | ||
| test-visitor-serialization.c | ||
| test-vmstate.c | ||
| test-write-threshold.c | ||
| test-x86-cpuid.c | ||
| test-xbzrle.c | ||
| vhost-user-bridge.c | ||