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Re: [Qemu-block] [Qemu-devel] [PATCH for-2.10 2/5] block: Allow reopen r
From: |
Eric Blake |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH for-2.10 2/5] block: Allow reopen rw without BDRV_O_ALLOW_RDWR |
Date: |
Thu, 3 Aug 2017 10:21:24 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
On 08/03/2017 10:02 AM, Kevin Wolf wrote:
> BDRV_O_ALLOW_RDWR is a flag that tells whether qemu can internally
> reopen a node read-write temporarily because the user requested
> read-write for the top-level image, but qemu decided that read-only is
> enough for this node (a backing file).
>
> bdrv_reopen() is different, it is also used for cases where the user
> changed their mind and wants to update the options. There is no reason
> to forbid making a node read-write in that case.
Hmm, I wonder. https://bugzilla.redhat.com/show_bug.cgi?id=1465320
details a failure when starting qemu with a read-write NBD disk, then
taking several snapshots (nbd <- snap1 <- snap2 <- snap3), then where
intermediate commit (snap2 into nbd) works but live commit (snap3 into
nbd) fails with a message that nbd does not support reopening. I'm
presuming that your series may help to address that; I'll give it a spin
and see what happens. But first, the code review:
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
> include/block/block.h | 3 ++-
> block.c | 11 +++++++----
> 2 files changed, 9 insertions(+), 5 deletions(-)
>
Reviewed-by: Eric Blake <address@hidden>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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[Qemu-block] [PATCH for-2.10 1/5] block: Fix order in bdrv_replace_child(), Kevin Wolf, 2017/08/03
[Qemu-block] [PATCH for-2.10 4/5] qemu-io: Allow reopen read-write, Kevin Wolf, 2017/08/03