Re: [PATCH v4 00/10] mirror: allow switching from background to active mode

[Kevin Wolf]

Am 31.10.2023 um 14:54 hat Fiona Ebner geschrieben:
> Changes in v4:
>     * add an iotest for the new functionality
>     * set actively_synced to false when setting dirty bitmap in
>       bdrv_mirror_top_do_write
>     * add comments describing requirements for accessing copy_mode and
>       actively_synced field
>     * add global state code annotation and comment about assumptions
>       in mirror_change method
>     * add comment that change callback can be called before the job
>       coroutine is running
>     * fix typo in QAPI description
> 
> Changes in v3:
>     * unlock the job mutex when calling the new block job driver
>       'query' handler
>     * squash patch adapting iotest output into patch that changes the
>       output
>     * turn accesses to copy_mode and actively_synced atomic
>     * slightly rework error handling in mirror_change
> 
> Changes in v2:
>     * move bitmap to filter which allows to avoid draining when
>       changing the copy mode
>     * add patch to determine copy_to_target only once
>     * drop patches returning redundant information upon query
>     * update QEMU version in QAPI
>     * update indentation in QAPI
>     * update indentation in QAPI (like in a937b6aa73 ("qapi: Reformat
>       doc comments to conform to current conventions"))
>     * add patch to adapt iotest output
> 
> Discussion of v3:
> https://lists.nongnu.org/archive/html/qemu-devel/2023-10/msg04026.html
> 
> Discussion of v2:
> https://lists.nongnu.org/archive/html/qemu-devel/2023-10/msg02290.html
> 
> Discussion of v1:
> https://lists.nongnu.org/archive/html/qemu-devel/2023-02/msg07216.html
> 
> With active mode, the guest write speed is limited by the synchronous
> writes to the mirror target. For this reason, management applications
> might want to start out in background mode and only switch to active
> mode later, when certain conditions are met. This series adds a
> block-job-change QMP command to achieve that, as well as
> job-type-specific information when querying block jobs, which
> can be used to decide when the switch should happen.
> 
> For now, only the direction background -> active is supported.
> 
> The information added upon querying is whether the target is actively
> synced, the total data sent, and the remaining dirty bytes.
> 
> Initially, I tried to go for a more general 'job-change' command, but
> to avoid mutual inclusion of block-core.json and job.json, more
> preparation would be required. More details described here:
> https://lists.nongnu.org/archive/html/qemu-devel/2023-10/msg02993.html
> 
> Fiona Ebner (10):
>   blockjob: introduce block-job-change QMP command
>   block/mirror: set actively_synced even after the job is ready
>   block/mirror: move dirty bitmap to filter
>   block/mirror: determine copy_to_target only once
>   mirror: implement mirror_change method
>   qapi/block-core: use JobType for BlockJobInfo's type
>   qapi/block-core: turn BlockJobInfo into a union
>   blockjob: query driver-specific info via a new 'query' driver method
>   mirror: return mirror-specific information upon query
>   iotests: add test for changing mirror's copy_mode

Thanks, applied to the block branch.

Kevin