30.09.2020 15:11, Eric Blake wrote:
Allow the server to expose an additional metacontext to be requested by savvy clients. qemu-nbd adds a new option -A to expose the qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this can also be set via QMP when using block-export-add.qemu as client can be hacked into viewing this new context by using the now-misnamed x-dirty-bitmap option when creating an NBD blockdev (even though our x- naming means we could rename it, I did not think it worth breaking back-compat of tools that have been using it while waiting for a better solution). It is worth noting the decoding of how such context information will appear in 'qemu-img map --output=json': NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false NBD_STATE_DEPTH_BACKING => "zero":true, "data":true libnbd as client is probably a nicer way to get at the information without having to decipher such hacks in qemu as client. ;) Signed-off-by: Eric Blake <ebl...@redhat.com> --- docs/tools/qemu-nbd.rst | 6 ++++ qapi/block-core.json | 7 ++-- qapi/block-export.json | 6 +++- blockdev-nbd.c | 2 ++ nbd/server.c | 2 ++ qemu-nbd.c | 14 ++++++-- tests/qemu-iotests/309 | 73 ++++++++++++++++++++++++++++++++++++++ tests/qemu-iotests/309.out | 22 ++++++++++++ tests/qemu-iotests/group | 1 + 9 files changed, 127 insertions(+), 6 deletions(-) create mode 100755 tests/qemu-iotests/309 create mode 100644 tests/qemu-iotests/309.out diff --git a/docs/tools/qemu-nbd.rst b/docs/tools/qemu-nbd.rst index 667861cb22e9..0e545a97cfa3 100644 --- a/docs/tools/qemu-nbd.rst +++ b/docs/tools/qemu-nbd.rst @@ -72,6 +72,12 @@ driver options if ``--image-opts`` is specified. Export the disk as read-only. +.. option:: -A, --allocation-depth + + Expose allocation depth information via the + ``qemu:allocation-depth`` context accessible through + NBD_OPT_SET_META_CONTEXT. + .. option:: -B, --bitmap=NAME If *filename* has a qcow2 persistent bitmap *NAME*, expose diff --git a/qapi/block-core.json b/qapi/block-core.json index d620bd1302b2..0379eb992db8 100644
[..]
+echo +echo "=== Check allocation over NBD ===" +echo + +# Normal -f raw NBD block status loses access to allocation information
^this comment is not for the next line, but for further lines ...
+$QEMU_IMG map --output=json -f qcow2 "$TEST_IMG" +IMG="driver=nbd,server.type=unix,server.path=$nbd_unix_socket" +nbd_server_start_unix_socket -r -f qcow2 -A "$TEST_IMG"
... should it be here?
+$QEMU_IMG map --output=json --image-opts \ + "$IMG" | _filter_qemu_img_map +# But since we used -A, and use x-dirty-bitmap as a hack for reading bitmaps, +# we can reconstruct it, by abusing block status to report: +# NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true +# NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false +# NBD_STATE_DEPTH_BACKING => "zero":true, "data":true +$QEMU_IMG map --output=json --image-opts \ + "$IMG,x-dirty-bitmap=qemu:allocation-depth" | _filter_qemu_img_map + +# success, all done +echo '*** done'
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> -- Best regards, Vladimir
