On 3/24/21 8:19 PM, Ming Lei wrote:
> Add one req flag REQ_POLL_CTX which will be used in the following patch for
> supporting bio based IO polling.
>
> Exactly this flag can help us to do:
>
> 1) request flag is cloned in bio_fast_clone(), so if we mark one FS bio
> as REQ_POLL_CTX, all bios cloned from this FS bio will be marked as
> REQ_POLL_CTX too.
>
> 2) create per-task io polling context if the bio based queue supports
> polling and the submitted bio is HIPRI. Per-task io poll context will be
> created during submit_bio() before marking this HIPRI bio as REQ_POLL_CTX.
> Then we can avoid to create such io polling context if one cloned bio with
> REQ_POLL_CTX is submitted from another kernel context.
>
> 3) for supporting bio based io polling, we need to poll IOs from all
> underlying queues of the bio device, this way help us to recognize which
> IO needs to polled in bio based style, which will be applied in
> following patch.
>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> ---
> block/blk-core.c | 25 ++++++++++++++++++++++++-
> include/linux/blk_types.h | 4 ++++
> 2 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 4671bbf31fd3..eb07d61cfdc2 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -840,11 +840,30 @@ static inline bool blk_queue_support_bio_poll(struct request_queue *q)
> static inline void blk_bio_poll_preprocess(struct request_queue *q,
> struct bio *bio)
> {
> + bool mq;
> +
> if (!(bio->bi_opf & REQ_HIPRI))
> return;
>
> - if (!blk_queue_poll(q) || (!queue_is_mq(q) && !blk_get_bio_poll_ctx()))
> + /*
> + * Can't support bio based IO polling without per-task poll ctx
> + *
> + * We have created per-task io poll context, and mark this
> + * bio as REQ_POLL_CTX, so: 1) if any cloned bio from this bio is
> + * submitted from another kernel context, we won't create bio
> + * poll context for it, and that bio can be completed by IRQ;
> + * 2) If such bio is submitted from current context, we will
> + * complete it via blk_poll(); 3) If driver knows that one
> + * underlying bio allocated from driver is for FS bio, meantime
> + * it is submitted in current context, driver can mark such bio
> + * as REQ_HIPRI & REQ_POLL_CTX manually, so the bio can be completed
> + * via blk_poll too.
> + */
> + mq = queue_is_mq(q);
> + if (!blk_queue_poll(q) || (!mq && !blk_get_bio_poll_ctx()))
> bio->bi_opf &= ~REQ_HIPRI;
> + else if (!mq)
> + bio->bi_opf |= REQ_POLL_CTX;
> }
>
> static noinline_for_stack bool submit_bio_checks(struct bio *bio)
> @@ -894,8 +913,12 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
> /*
> * Create per-task io poll ctx if bio polling supported and HIPRI
> * set.
> + *
> + * If REQ_POLL_CTX isn't set for this HIPRI bio, we think it originated
> + * from FS and allocate io polling context.
> */
> blk_create_io_context(q, blk_queue_support_bio_poll(q) &&
> + !(bio->bi_opf & REQ_POLL_CTX) &&
> (bio->bi_opf & REQ_HIPRI));
>
> blk_bio_poll_preprocess(q, bio);
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index db026b6ec15a..99160d588c2d 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -394,6 +394,9 @@ enum req_flag_bits {
>
> __REQ_HIPRI,
>
> + /* for marking IOs originated from same FS bio in same context */
> + __REQ_POLL_CTX,
> +
> /* for driver use */
> __REQ_DRV,
> __REQ_SWAP, /* swapping request. */
> @@ -418,6 +421,7 @@ enum req_flag_bits {
>
> #define REQ_NOUNMAP (1ULL << __REQ_NOUNMAP)
> #define REQ_HIPRI (1ULL << __REQ_HIPRI)
> +#define REQ_POLL_CTX (1ULL << __REQ_POLL_CTX)
>
> #define REQ_DRV (1ULL << __REQ_DRV)
> #define REQ_SWAP (1ULL << __REQ_SWAP)
>
--
Thanks,
Jeffle
