On Thu, Jun 17, 2021 at 06:35:49PM +0800, Ming Lei wrote:
> Support bio(REQ_POLLED) polling in the following approach:
>
> 1) only support io polling on normal READ/WRITE, and other abnormal IOs
> still fallback on IRQ mode, so the target io is exactly inside the dm
> io.
>
> 2) hold one refcnt on io->io_count after submitting this dm bio with
> REQ_POLLED
>
> 3) support dm native bio splitting, any dm io instance associated with
> current bio will be added into one list which head is bio->bi_end_io
> which will be recovered before ending this bio
>
> 4) implement .poll_bio() callback, call bio_poll() on the single target
> bio inside the dm io which is retrieved via bio->bi_bio_drv_data; call
> dec_pending() after the target io is done in .poll_bio()
>
> 4) enable QUEUE_FLAG_POLL if all underlying queues enable QUEUE_FLAG_POLL,
> which is based on Jeffle's previous patch.
>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
...
> @@ -938,8 +945,12 @@ static void dec_pending(struct dm_io *io, blk_status_t error)
> end_io_acct(io);
> free_io(md, io);
>
> - if (io_error == BLK_STS_DM_REQUEUE)
> + if (io_error == BLK_STS_DM_REQUEUE) {
> + /* not poll any more in case of requeue */
> + if (bio->bi_opf & REQ_POLLED)
> + bio->bi_opf &= ~REQ_POLLED;
It becomes not necessary to clear REQ_POLLED before requeuing since
every dm_io is added into the hlist_head which is reused from
bio->bi_end_io, so all dm-io(include the one to be requeued) will be
polled.
Thanks,
Ming
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