[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH v2 2/2] iotests: New test 223 for exporting dirty bitmap over NBD
Date: Tue, 3 Jul 2018 11:17:40 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0

On 07/03/2018 05:09 AM, Vladimir Sementsov-Ogievskiy wrote:
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.

+echo "=== End NBD server ==="
+_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?

I guess it's symmetric in that since we hotplugged the disk, we would also make sure hotunplug works after everything else has quit using it. But even the nbd-server-stop is not strictly necessary, since quitting qemu should have the same effect. At this point, I'm not too worried about changing the test.

with or without:

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

Thanks for the review; the pull request went through without your notation being appended, but it never hurts to have additional review (and we still have time even after 3.0 soft freeze to fix any important bugs in what went in).

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

reply via email to

[Prev in Thread] Current Thread [Next in Thread]