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Re: [Qemu-devel] [PATCH v2 10/11] block/backup: support bitmap sync mode
From: |
Max Reitz |
Subject: |
Re: [Qemu-devel] [PATCH v2 10/11] block/backup: support bitmap sync modes for non-bitmap backups |
Date: |
Tue, 16 Jul 2019 13:45:48 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 |
On 16.07.19 02:01, John Snow wrote:
> Accept bitmaps and sync policies for the other backup modes.
> This allows us to do things like create a bitmap synced to a full backup
> without a transaction, or start a resumable backup process.
>
> Some combinations don't make sense, though:
>
> - NEVER policy combined with any non-BITMAP mode doesn't do anything,
> because the bitmap isn't used for input or output.
> It's harmless, but is almost certainly never what the user wanted.
>
> - sync=NONE is more questionable. It can't use on-success because this
> job never completes with success anyway, and the resulting artifact
> of 'always' is suspect: because we start with a full bitmap and only
> copy out segments that get written to, the final output bitmap will
> always be ... a fully set bitmap.
>
> Maybe there's contexts in which bitmaps make sense for sync=none,
> but not without more severe changes to the current job, and omitting
> it here doesn't prevent us from adding it later.
>
> Signed-off-by: John Snow <address@hidden>
> ---
> block/backup.c | 8 +-------
> blockdev.c | 22 ++++++++++++++++++++++
> qapi/block-core.json | 6 ++++--
> 3 files changed, 27 insertions(+), 9 deletions(-)
Reviewed-by: Max Reitz <address@hidden>
(I’ve seen Markus’s concern, but I think management applications can
just see whether specifying sync={full,top} + bitmap works if they want
to use it.)
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- Re: [Qemu-devel] [PATCH v2 07/11] block/backup: centralize copy_bitmap initialization, (continued)
- [Qemu-devel] [PATCH v2 08/11] block/backup: add backup_is_cluster_allocated, John Snow, 2019/07/15
- [Qemu-devel] [PATCH v2 05/11] iotests/257: test API failures, John Snow, 2019/07/15
- [Qemu-devel] [PATCH v2 06/11] block/backup: improve sync=bitmap work estimates, John Snow, 2019/07/15
- [Qemu-devel] [PATCH v2 10/11] block/backup: support bitmap sync modes for non-bitmap backups, John Snow, 2019/07/15
- [Qemu-devel] [PATCH v2 09/11] block/backup: teach TOP to never copy unallocated regions, John Snow, 2019/07/15
[Qemu-devel] [PATCH v2 03/11] iotests/257: Refactor backup helpers, John Snow, 2019/07/15
[Qemu-devel] [PATCH v2 11/11] iotests/257: test traditional sync modes, John Snow, 2019/07/15