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Re: [Qemu-devel] [PATCH v2 2/2] iotests: New test 223 for exporting dirt


From: Vladimir Sementsov-Ogievskiy
Subject: Re: [Qemu-devel] [PATCH v2 2/2] iotests: New test 223 for exporting dirty bitmap over NBD
Date: Tue, 3 Jul 2018 13:09:47 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0

02.07.2018 22:14, Eric Blake wrote:
Although this test is NOT a full test of image fleecing (as it
intentionally uses just a single block device directly exported
over NBD, rather than trying to set up a blockdev-backup job with
multiple BDS involved), it DOES prove that qemu as a server is
able to properly expose a dirty bitmap over NBD.

When coupled with image fleecing, it is then possible for a
third-party client to do an incremental backup by using
qemu-img map with the x-dirty-bitmap option to learn which parts
of the file are dirty (perhaps confusingly, they are the portions
mapped as "data":false - which is part of the reason this is
still in the x- experimental namespace), along with another
normal client (perhaps 'qemu-nbd -c' to expose the server over
/dev/nbd0 and then just use normal I/O on that block device) to
read the dirty sections.

Signed-off-by: Eric Blake <address@hidden>
---
  tests/qemu-iotests/223     | 138 +++++++++++++++++++++++++++++++++++++++++++++
  tests/qemu-iotests/223.out |  49 ++++++++++++++++
  tests/qemu-iotests/group   |   1 +
  3 files changed, 188 insertions(+)
  create mode 100755 tests/qemu-iotests/223
  create mode 100644 tests/qemu-iotests/223.out

diff --git a/tests/qemu-iotests/223 b/tests/qemu-iotests/223
new file mode 100755
index 00000000000..b63b7a4f9e1
--- /dev/null
+++ b/tests/qemu-iotests/223
@@ -0,0 +1,138 @@
+#!/bin/bash

[...]

+
+echo
+echo "=== End NBD server ==="
+echo
+
+_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-remove",
+  "arguments":{"name":"n"}}' "return"
+_send_qemu_cmd $QEMU_HANDLE '{"execute":"nbd-server-stop"}' "return"

blockdev-del is not necessary?

with or without:

Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>


--
Best regards,
Vladimir




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