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Re: [Qemu-devel] [PATCH 5/5] block: Reject writethrough mode except at t
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 5/5] block: Reject writethrough mode except at the root |
Date: |
Mon, 14 Mar 2016 10:50:56 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 |
On 03/14/2016 09:44 AM, Kevin Wolf wrote:
> Writethrough mode is going to become a BlockBackend feature rather than
> a BDS one, so forbid it in places where we won't be able to support it
> when the code finally matches the envisioned design.
>
> We only allowed setting the cache mode of non-root nodes after the 2.5
> release, so we're still free to make this change.
>
> The target of block jobs is now always opened in a writeback mode
> because it doesn't have a BlockBackend attached. This makes more sense
> anyway because block jobs know when to flush. If the graph is modified
> on job completion, the original cache mode moves to the new root, so
> for the guest device writethough always stays enabled if it was
> configured this way.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
> block.c | 7 ++++
> blockdev.c | 19 ++++++++-
> tests/qemu-iotests/142 | 50 +++++++++++------------
> tests/qemu-iotests/142.out | 98
> +++++++++-------------------------------------
> 4 files changed, 68 insertions(+), 106 deletions(-)
>
Reviewed-by: Eric Blake <address@hidden>
> +++ b/tests/qemu-iotests/142
> @@ -96,36 +96,36 @@ function check_cache_all()
> # bs->backing
>
> echo -e "cache.direct=on on none0"
Pre-existing, but 'echo -e' is non-portable (even in bash, you can set
options such that it changes behavior). printf is better, if we're
worried about it.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH 2/5] block: Remove dirty bitmaps from bdrv_move_feature_fields(), (continued)
- [Qemu-devel] [PATCH 2/5] block: Remove dirty bitmaps from bdrv_move_feature_fields(), Kevin Wolf, 2016/03/14
- [Qemu-devel] [PATCH 1/5] block: Remove copy-on-read from bdrv_move_feature_fields(), Kevin Wolf, 2016/03/14
- [Qemu-devel] [PATCH 4/5] block: Make backing files always writeback, Kevin Wolf, 2016/03/14
- [Qemu-devel] [PATCH 3/5] block: Remove cache.writeback from blockdev-add, Kevin Wolf, 2016/03/14
- [Qemu-devel] [PATCH 5/5] block: Reject writethrough mode except at the root, Kevin Wolf, 2016/03/14
- Re: [Qemu-devel] [PATCH 5/5] block: Reject writethrough mode except at the root,
Eric Blake <=
- Re: [Qemu-devel] [PATCH 0/5] block: API changes for 2.6, Kevin Wolf, 2016/03/18