On 12/29/25 17:07, Denis V. Lunev wrote:
> This series is a followup to my previous patch sent under
> "qcow2: add very final sync on QCOW2 image closing". Could be considered
> as v2.
>
> This series addresses two problems:
> 1. bdrv_co_flush() at the end of bdrv_driver_pwritev() and
> bdrv_co_do_pwrite_zeroes() could be effectively no op. The problem is
> that bdrv_co_flush() is optimized internally this way to track real
> requests which were making changes in the image and without such
> requests from previous flush() do nothing. Requests are tracked using
> write_gen on BDS. This field should be incremented after write is
> completed but before flush is called.
>
> This could be considered as potential data loss if caller relies on
> BDRV_REQ_FUA flag which means that such requests are really lands on
> the underlying device, which could not due to missed flush().
>
> 2. qcow2_update_header() must actually write header with BDRV_REQ_FUA
> flag as image processing on open relies on the fact that header is
> actual and it is not possible to reorder header modifications and
> image content modifications.
>
> Changes:
> * added patches 1 & 2
>
> Signed-off-by: Denis V. Lunev <[email protected]>
> CC: Andrey Drobyshev <[email protected]>
> CC: Kevin Wolf <[email protected]>
> CC: Hanna Reitz <[email protected]>
>
ping
