[PATCH v3 04/30] block: Introduce blk_zone_update_request_bio()

[Christoph Hellwig]

On Thu, Mar 28, 2024 at 02:20:17PM +0900, Damien Le Moal wrote:
> I do not think that is corect. Because is_flush indicates that RQF_FLUSH_SEQ is
> set, that is, we are in the middle of a flush sequence. And flush sequence
> progression is handled at the request level, not BIOs. Once the sequence
> finishes, then and only then the BIO original endio should be done, meaning that
> we will then take this path and actually do blk_zone_update_request_bio() and
> bio_endio(). So I still think this is correct.

Well.

lk_flush_restore_request with the previous patch now restores rq->__sector,
and the blk_mq_end_request call following it will propagate it to the
original bio.  But blk_flush_restore_request grabs the sector from
rq->bio->bi_iter.bi_sector, and we need to actually get it there first,
which is done by the data I/O completion that has RQF_FLUSH_SEQ set.

I think we really need a good test case for zone append and FUA,
i.e. we need the append op for zonefs, which should exercise the
fua code if O_SYNC/O_DSYNC is set.