Re: [PATCH 2/3] ublk: add feature UBLK_F_QUIESCE

[Ming Lei <ming.lei@redhat.com>]

On Thu, Jun 12, 2025 at 08:17:49AM +0000, Yoav Cohen wrote:
> Hi Ming,
> 
> Thank you very much, I managed to integrate the feature to our application and it seems to work perfectly fine during our update tests.
> Just a double check: when UBLK_F_USER_RECOVERY & UBLK_F_USER_RECOVERY_REISSUE
> and QUIECE_DEV was called - does any IO that will be completed using COMMIT_AND_FETCH with a failure (i.e result=-EIO) will be retry after the recovery stage?
> 

UBLK_F_USER_RECOVERY_REISSUE supposes all inflight IOs are failed, so
these IOs will be re-delivered to ublk server after recovering to LIVE.

So you needn't to complete the IOs with -EIO for retrying them during
recovery, in short:

- if ublk server handles inflight IOs, complete them by sending COMMIT_AND_FETCH
with result before closing '/dev/ublkcN', and these IOs will not be re-issued
by driver after recovery

- otherwise, just ignore & discard inflight IOs, they all will be
re-issued by driver after recovery via UBLK_F_USER_RECOVERY_REISSUE.


Thanks,
Ming