diff mbox series

[V5,08/12] block: use per-task poll context to implement bio based io polling

Message ID 20210401021927.343727-9-ming.lei@redhat.com (mailing list archive)
State New
Headers show
Series block: support bio based io polling | expand

Commit Message

Ming Lei April 1, 2021, 2:19 a.m. UTC
Currently bio based IO polling needs to poll all hw queue blindly, this
way is very inefficient, and one big reason is that we can't pass any
bio submission result to blk_poll().

In IO submission context, track associated underlying bios by per-task
submission queue and store returned 'cookie' in
bio->bi_iter.bi_private_data, and return current->pid to caller of
submit_bio() for any bio based driver's IO, which is submitted from FS.

In IO poll context, the passed cookie tells us the PID of submission
context, then we can find bios from the per-task io pull context of
submission context. Moving bios from submission queue to poll queue of
the poll context, and keep polling until these bios are ended. Remove
bio from poll queue if the bio is ended. Add bio flags of BIO_DONE and
BIO_END_BY_POLL for such purpose.

In was found in Jeffle Xu's test that kfifo doesn't scale well for a
submission queue as queue depth is increased, so a new mechanism for
tracking bios is needed. So far bio's size is close to 2 cacheline size,
and it may not be accepted to add new field into bio for solving the
scalability issue by tracking bios via linked list, switch to bio group
list for tracking bio, the idea is to reuse .bi_end_io for linking bios
into a linked list for all sharing same .bi_end_io(call it bio group),
which is recovered before ending bio really, since BIO_END_BY_POLL is
added for enhancing this point. Usually .bi_end_bio is same for all
bios in same layer, so it is enough to provide very limited groups, such
as 16 or less for fixing the scalability issue.

Usually submission shares context with io poll. The per-task poll context
is just like stack variable, and it is cheap to move data between the two
per-task queues.

Also when the submission task is exiting, drain pending IOs in the context
until all are done.

Tested-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/bio.c               |   5 +
 block/blk-core.c          | 155 +++++++++++++++++++++++-
 block/blk-ioc.c           |   3 +
 block/blk-mq.c            | 244 +++++++++++++++++++++++++++++++++++++-
 block/blk.h               |  10 ++
 include/linux/blk_types.h |  26 +++-
 6 files changed, 439 insertions(+), 4 deletions(-)

Comments

Christoph Hellwig April 12, 2021, 9:54 a.m. UTC | #1
On Thu, Apr 01, 2021 at 10:19:23AM +0800, Ming Lei wrote:
> Currently bio based IO polling needs to poll all hw queue blindly, this
> way is very inefficient, and one big reason is that we can't pass any
> bio submission result to blk_poll().
> 
> In IO submission context, track associated underlying bios by per-task
> submission queue and store returned 'cookie' in
> bio->bi_iter.bi_private_data, and return current->pid to caller of
> submit_bio() for any bio based driver's IO, which is submitted from FS.
> 
> In IO poll context, the passed cookie tells us the PID of submission
> context, then we can find bios from the per-task io pull context of
> submission context. Moving bios from submission queue to poll queue of
> the poll context, and keep polling until these bios are ended. Remove
> bio from poll queue if the bio is ended. Add bio flags of BIO_DONE and
> BIO_END_BY_POLL for such purpose.
> 
> In was found in Jeffle Xu's test that kfifo doesn't scale well for a
> submission queue as queue depth is increased, so a new mechanism for
> tracking bios is needed. So far bio's size is close to 2 cacheline size,
> and it may not be accepted to add new field into bio for solving the
> scalability issue by tracking bios via linked list, switch to bio group
> list for tracking bio, the idea is to reuse .bi_end_io for linking bios
> into a linked list for all sharing same .bi_end_io(call it bio group),
> which is recovered before ending bio really, since BIO_END_BY_POLL is
> added for enhancing this point. Usually .bi_end_bio is same for all
> bios in same layer, so it is enough to provide very limited groups, such
> as 16 or less for fixing the scalability issue.
> 
> Usually submission shares context with io poll. The per-task poll context
> is just like stack variable, and it is cheap to move data between the two
> per-task queues.
> 
> Also when the submission task is exiting, drain pending IOs in the context
> until all are done.
> 
> Tested-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> Reviewed-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  block/bio.c               |   5 +
>  block/blk-core.c          | 155 +++++++++++++++++++++++-
>  block/blk-ioc.c           |   3 +
>  block/blk-mq.c            | 244 +++++++++++++++++++++++++++++++++++++-
>  block/blk.h               |  10 ++
>  include/linux/blk_types.h |  26 +++-
>  6 files changed, 439 insertions(+), 4 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 26b7f721cda8..04c043dc60fc 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1402,6 +1402,11 @@ static inline bool bio_remaining_done(struct bio *bio)
>   **/
>  void bio_endio(struct bio *bio)
>  {
> +	/* BIO_END_BY_POLL has to be set before calling submit_bio */
> +	if (bio_flagged(bio, BIO_END_BY_POLL)) {
> +		bio_set_flag(bio, BIO_DONE);
> +		return;
> +	}

Why can't driver that implements bio based polling call a separate
bio_endio_polled instead?

> +static inline void *bio_grp_data(struct bio *bio)
> +{
> +	return bio->bi_poll;
> +}

What is the purpose of this helper?  And why does it have to lose the
type information?

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Christoph Hellwig April 12, 2021, 10:16 a.m. UTC | #2
> +static int blk_bio_poll_io(struct io_context *submit_ioc,
> +		struct io_context *poll_ioc)

Givem that poll_ioc is always current->io_context there is no
need to pass it.

> +	struct blk_bio_poll_ctx *poll_ctx = poll_ioc ?
> +		poll_ioc->data : NULL;

and it really should not be NULL here, should it?

> +static int __blk_bio_poll(blk_qc_t cookie)
> +{
> +	struct io_context *poll_ioc = current->io_context;
> +	pid_t pid;
> +	struct task_struct *submit_task;
> +	int ret;
> +
> +	pid = (pid_t)cookie;
> +
> +	/* io poll often share io submission context */
> +	if (likely(current->pid == pid && blk_bio_ioc_valid(current)))
> +		return blk_bio_poll_io(poll_ioc, poll_ioc);
> +
> +	submit_task = find_get_task_by_vpid(pid);
> +	if (likely(blk_bio_ioc_valid(submit_task)))
> +		ret = blk_bio_poll_io(submit_task->io_context, poll_ioc);
> +	else
> +		ret = 0;
> +	if (likely(submit_task))
> +		put_task_struct(submit_task);

Wouldn't it make more sense to just store the submitting context
in the bio, even if that uses more space?  Having to call
find_get_task_by_vpid in the poll context seems rather problematic.

Note that this requires doing the refacoring to get rid of the separate
blk_qc_t passed up the stack I asked for earlier, but hiding all these
details seems like a really useful change anyway.

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Ming Lei April 12, 2021, 10:20 a.m. UTC | #3
On Mon, Apr 12, 2021 at 10:54:27AM +0100, Christoph Hellwig wrote:
> On Thu, Apr 01, 2021 at 10:19:23AM +0800, Ming Lei wrote:
> > Currently bio based IO polling needs to poll all hw queue blindly, this
> > way is very inefficient, and one big reason is that we can't pass any
> > bio submission result to blk_poll().
> > 
> > In IO submission context, track associated underlying bios by per-task
> > submission queue and store returned 'cookie' in
> > bio->bi_iter.bi_private_data, and return current->pid to caller of
> > submit_bio() for any bio based driver's IO, which is submitted from FS.
> > 
> > In IO poll context, the passed cookie tells us the PID of submission
> > context, then we can find bios from the per-task io pull context of
> > submission context. Moving bios from submission queue to poll queue of
> > the poll context, and keep polling until these bios are ended. Remove
> > bio from poll queue if the bio is ended. Add bio flags of BIO_DONE and
> > BIO_END_BY_POLL for such purpose.
> > 
> > In was found in Jeffle Xu's test that kfifo doesn't scale well for a
> > submission queue as queue depth is increased, so a new mechanism for
> > tracking bios is needed. So far bio's size is close to 2 cacheline size,
> > and it may not be accepted to add new field into bio for solving the
> > scalability issue by tracking bios via linked list, switch to bio group
> > list for tracking bio, the idea is to reuse .bi_end_io for linking bios
> > into a linked list for all sharing same .bi_end_io(call it bio group),
> > which is recovered before ending bio really, since BIO_END_BY_POLL is
> > added for enhancing this point. Usually .bi_end_bio is same for all
> > bios in same layer, so it is enough to provide very limited groups, such
> > as 16 or less for fixing the scalability issue.
> > 
> > Usually submission shares context with io poll. The per-task poll context
> > is just like stack variable, and it is cheap to move data between the two
> > per-task queues.
> > 
> > Also when the submission task is exiting, drain pending IOs in the context
> > until all are done.
> > 
> > Tested-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> > Reviewed-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> >  block/bio.c               |   5 +
> >  block/blk-core.c          | 155 +++++++++++++++++++++++-
> >  block/blk-ioc.c           |   3 +
> >  block/blk-mq.c            | 244 +++++++++++++++++++++++++++++++++++++-
> >  block/blk.h               |  10 ++
> >  include/linux/blk_types.h |  26 +++-
> >  6 files changed, 439 insertions(+), 4 deletions(-)
> > 
> > diff --git a/block/bio.c b/block/bio.c
> > index 26b7f721cda8..04c043dc60fc 100644
> > --- a/block/bio.c
> > +++ b/block/bio.c
> > @@ -1402,6 +1402,11 @@ static inline bool bio_remaining_done(struct bio *bio)
> >   **/
> >  void bio_endio(struct bio *bio)
> >  {
> > +	/* BIO_END_BY_POLL has to be set before calling submit_bio */
> > +	if (bio_flagged(bio, BIO_END_BY_POLL)) {
> > +		bio_set_flag(bio, BIO_DONE);
> > +		return;
> > +	}
> 
> Why can't driver that implements bio based polling call a separate
> bio_endio_polled instead?

This bio is blk-mq IO which is underlying bio of DM or bio based driver, so
they doesn't belong to DM or bio based driver. Actually the bio_endio()
is called by blk_update_request().

The patch just tracks underlying bio-mq bios in current context, then
poll them until all are done.

> 
> > +static inline void *bio_grp_data(struct bio *bio)
> > +{
> > +	return bio->bi_poll;
> > +}
> 
> What is the purpose of this helper?  And why does it have to lose the
> type information?

This patch stores bio->bi_end_io(shared with ->bi_poll) into one per-task
data structure, and links all bios sharing same .bi_end_io into one list
via ->bi_end_io. And their ->bi_end_io is recovered before calling
bio_endio().

The helper is used for checking if one bio can be added to bio group,
and storing the data. The helper just serves for document purpose.

And the type info doesn't matter.


Thanks,
Ming

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Christoph Hellwig April 12, 2021, 10:29 a.m. UTC | #4
On Mon, Apr 12, 2021 at 06:20:55PM +0800, Ming Lei wrote:
> > > +static inline void *bio_grp_data(struct bio *bio)
> > > +{
> > > +	return bio->bi_poll;
> > > +}
> > 
> > What is the purpose of this helper?  And why does it have to lose the
> > type information?
> 
> This patch stores bio->bi_end_io(shared with ->bi_poll) into one per-task
> data structure, and links all bios sharing same .bi_end_io into one list
> via ->bi_end_io. And their ->bi_end_io is recovered before calling
> bio_endio().
> 
> The helper is used for checking if one bio can be added to bio group,
> and storing the data. The helper just serves for document purpose.
> 
> And the type info doesn't matter.

So why is bi_poll typed to start with then just to need a accessor
to remove the typer information?

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Ming Lei April 12, 2021, 10:37 a.m. UTC | #5
On Mon, Apr 12, 2021 at 11:16:59AM +0100, Christoph Hellwig wrote:
> > +static int blk_bio_poll_io(struct io_context *submit_ioc,
> > +		struct io_context *poll_ioc)
> 
> Givem that poll_ioc is always current->io_context there is no
> need to pass it.

Yeah, it is true.

> 
> > +	struct blk_bio_poll_ctx *poll_ctx = poll_ioc ?
> > +		poll_ioc->data : NULL;
> 
> and it really should not be NULL here, should it?

Yeah, it is NULL just in case of memory allocation failure.

> 
> > +static int __blk_bio_poll(blk_qc_t cookie)
> > +{
> > +	struct io_context *poll_ioc = current->io_context;
> > +	pid_t pid;
> > +	struct task_struct *submit_task;
> > +	int ret;
> > +
> > +	pid = (pid_t)cookie;
> > +
> > +	/* io poll often share io submission context */
> > +	if (likely(current->pid == pid && blk_bio_ioc_valid(current)))
> > +		return blk_bio_poll_io(poll_ioc, poll_ioc);
> > +
> > +	submit_task = find_get_task_by_vpid(pid);
> > +	if (likely(blk_bio_ioc_valid(submit_task)))
> > +		ret = blk_bio_poll_io(submit_task->io_context, poll_ioc);
> > +	else
> > +		ret = 0;
> > +	if (likely(submit_task))
> > +		put_task_struct(submit_task);
> 
> Wouldn't it make more sense to just store the submitting context
> in the bio, even if that uses more space?  Having to call

But where to store the submitting context in bio? pid is 32bit and we can
pass it from submit_bio() perfectly, then avoid to add anything to bio.

If we save the submitting context in bio, we still have to handle task
exit related race, not see any benefit.

So far bio is ~128byte with typical setting, and people usually hate to
add more stuff into bio.

> find_get_task_by_vpid in the poll context seems rather problematic.

Why? We already handle submit context early exit.

> 
> Note that this requires doing the refacoring to get rid of the separate
> blk_qc_t passed up the stack I asked for earlier, but hiding all these
> details seems like a really useful change anyway.

That is hard to do because of race between submission and completion:

1) HIPRI could be cleared because of bio splitting, so we can't do that
for this kind of bio

2) we have to make sure that the bio won't be completed when storing
cookie into this bio. BIO_END_BY_POLL is added in this patch for bio
based polling. You mean we may cover all normal blk-mq polling via
BIO_END_BY_POLL?



Thanks,
Ming

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Ming Lei April 12, 2021, 11:42 a.m. UTC | #6
On Mon, Apr 12, 2021 at 11:29:47AM +0100, Christoph Hellwig wrote:
> On Mon, Apr 12, 2021 at 06:20:55PM +0800, Ming Lei wrote:
> > > > +static inline void *bio_grp_data(struct bio *bio)
> > > > +{
> > > > +	return bio->bi_poll;
> > > > +}
> > > 
> > > What is the purpose of this helper?  And why does it have to lose the
> > > type information?
> > 
> > This patch stores bio->bi_end_io(shared with ->bi_poll) into one per-task
> > data structure, and links all bios sharing same .bi_end_io into one list
> > via ->bi_end_io. And their ->bi_end_io is recovered before calling
> > bio_endio().
> > 
> > The helper is used for checking if one bio can be added to bio group,
> > and storing the data. The helper just serves for document purpose.
> > 
> > And the type info doesn't matter.
> 
> So why is bi_poll typed to start with then just to need a accessor
> to remove the typer information?

It should be a bug from the beginning, either .bi_poll can be dropped
or it should be 'void *'. Just find it, thanks for pointing it out.


Thanks,
Ming

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diff mbox series

Patch

diff --git a/block/bio.c b/block/bio.c
index 26b7f721cda8..04c043dc60fc 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1402,6 +1402,11 @@  static inline bool bio_remaining_done(struct bio *bio)
  **/
 void bio_endio(struct bio *bio)
 {
+	/* BIO_END_BY_POLL has to be set before calling submit_bio */
+	if (bio_flagged(bio, BIO_END_BY_POLL)) {
+		bio_set_flag(bio, BIO_DONE);
+		return;
+	}
 again:
 	if (!bio_remaining_done(bio))
 		return;
diff --git a/block/blk-core.c b/block/blk-core.c
index a777ba4fe06f..760e7d96f258 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -805,6 +805,81 @@  static inline unsigned int bio_grp_list_size(unsigned int nr_grps)
 		sizeof(struct bio_grp_list_data);
 }
 
+static inline void *bio_grp_data(struct bio *bio)
+{
+	return bio->bi_poll;
+}
+
+/* add bio into bio group list, return true if it is added */
+static bool bio_grp_list_add(struct bio_grp_list *list, struct bio *bio)
+{
+	int i;
+	struct bio_grp_list_data *grp;
+
+	for (i = 0; i < list->nr_grps; i++) {
+		grp = &list->head[i];
+		if (grp->grp_data == bio_grp_data(bio)) {
+			__bio_grp_list_add(&grp->list, bio);
+			return true;
+		}
+	}
+
+	if (i == list->max_nr_grps)
+		return false;
+
+	/* create a new group */
+	grp = &list->head[i];
+	bio_list_init(&grp->list);
+	grp->grp_data = bio_grp_data(bio);
+	__bio_grp_list_add(&grp->list, bio);
+	list->nr_grps++;
+
+	return true;
+}
+
+static int bio_grp_list_find_grp(struct bio_grp_list *list, void *grp_data)
+{
+	int i;
+	struct bio_grp_list_data *grp;
+
+	for (i = 0; i < list->nr_grps; i++) {
+		grp = &list->head[i];
+		if (grp->grp_data == grp_data)
+			return i;
+	}
+
+	if (i < list->max_nr_grps) {
+		grp = &list->head[i];
+		bio_list_init(&grp->list);
+		return i;
+	}
+
+	return -1;
+}
+
+/* Move as many as possible groups from 'src' to 'dst' */
+void bio_grp_list_move(struct bio_grp_list *dst, struct bio_grp_list *src)
+{
+	int i, j, cnt = 0;
+	struct bio_grp_list_data *grp;
+
+	for (i = src->nr_grps - 1; i >= 0; i--) {
+		grp = &src->head[i];
+		j = bio_grp_list_find_grp(dst, grp->grp_data);
+		if (j < 0)
+			break;
+		if (bio_grp_list_grp_empty(&dst->head[j])) {
+			dst->head[j].grp_data = grp->grp_data;
+			dst->nr_grps++;
+		}
+		__bio_grp_list_merge(&dst->head[j].list, &grp->list);
+		bio_list_init(&grp->list);
+		cnt++;
+	}
+
+	src->nr_grps -= cnt;
+}
+
 static void bio_poll_ctx_init(struct blk_bio_poll_ctx *pc)
 {
 	pc->sq = (void *)pc + sizeof(*pc);
@@ -866,6 +941,47 @@  static inline void blk_bio_poll_preprocess(struct request_queue *q,
 		bio->bi_opf |= REQ_POLL_CTX;
 }
 
+static inline void blk_bio_poll_mark_queued(struct bio *bio, bool queued)
+{
+	/*
+	 * The bio has been added to per-task poll queue, mark it as
+	 * END_BY_POLL, so that this bio is always completed from
+	 * blk_poll() which is provided with cookied from this bio's
+	 * submission.
+	 */
+	if (!queued)
+		bio->bi_opf &= ~(REQ_HIPRI | REQ_POLL_CTX);
+	else
+		bio_set_flag(bio, BIO_END_BY_POLL);
+}
+
+static bool blk_bio_poll_prep_submit(struct io_context *ioc, struct bio *bio)
+{
+	struct blk_bio_poll_ctx *pc = ioc->data;
+	unsigned int queued;
+
+	/*
+	 * We rely on immutable .bi_end_io between blk-mq bio submission
+	 * and completion. However, bio crypt may update .bi_end_io during
+	 * submission, so simply don't support bio based polling for this
+	 * setting.
+	 */
+	if (likely(!bio_has_crypt_ctx(bio))) {
+		/* track this bio via bio group list */
+		spin_lock(&pc->sq_lock);
+		queued = bio_grp_list_add(pc->sq, bio);
+		blk_bio_poll_mark_queued(bio, queued);
+		if (queued)
+			bio_set_private_data(bio, BLK_QC_T_NOT_READY);
+		spin_unlock(&pc->sq_lock);
+	} else {
+		queued = false;
+		blk_bio_poll_mark_queued(bio, false);
+	}
+
+	return queued;
+}
+
 static noinline_for_stack bool submit_bio_checks(struct bio *bio)
 {
 	struct block_device *bdev = bio->bi_bdev;
@@ -1024,7 +1140,7 @@  static blk_qc_t __submit_bio(struct bio *bio)
  * bio_list_on_stack[1] contains bios that were submitted before the current
  *	->submit_bio_bio, but that haven't been processed yet.
  */
-static blk_qc_t __submit_bio_noacct(struct bio *bio)
+static blk_qc_t __submit_bio_noacct_ctx(struct bio *bio, struct io_context *ioc)
 {
 	struct bio_list bio_list_on_stack[2];
 	blk_qc_t ret = BLK_QC_T_NONE;
@@ -1047,7 +1163,15 @@  static blk_qc_t __submit_bio_noacct(struct bio *bio)
 		bio_list_on_stack[1] = bio_list_on_stack[0];
 		bio_list_init(&bio_list_on_stack[0]);
 
-		ret = __submit_bio(bio);
+		if (ioc && queue_is_mq(q) && (bio->bi_opf & REQ_HIPRI)) {
+			bool queued = blk_bio_poll_prep_submit(ioc, bio);
+
+			ret = __submit_bio(bio);
+			if (queued)
+				bio_set_private_data(bio, ret);
+		} else {
+			ret = __submit_bio(bio);
+		}
 
 		/*
 		 * Sort new bios into those for a lower level and those for the
@@ -1073,6 +1197,33 @@  static blk_qc_t __submit_bio_noacct(struct bio *bio)
 	return ret;
 }
 
+static inline blk_qc_t __submit_bio_noacct_poll(struct bio *bio,
+		struct io_context *ioc)
+{
+	struct blk_bio_poll_ctx *pc = ioc->data;
+
+	__submit_bio_noacct_ctx(bio, ioc);
+
+	/* bio submissions queued to per-task poll context */
+	if (READ_ONCE(pc->sq->nr_grps))
+		return current->pid;
+
+	/* swapper's pid is 0, but it can't submit poll IO for us */
+	return BLK_QC_T_BIO_NONE;
+}
+
+static inline blk_qc_t __submit_bio_noacct(struct bio *bio)
+{
+	struct io_context *ioc = current->io_context;
+
+	if (ioc && ioc->data && (bio->bi_opf & REQ_HIPRI))
+		return __submit_bio_noacct_poll(bio, ioc);
+
+	__submit_bio_noacct_ctx(bio, NULL);
+
+	return BLK_QC_T_BIO_NONE;
+}
+
 static blk_qc_t __submit_bio_noacct_mq(struct bio *bio)
 {
 	struct bio_list bio_list[2] = { };
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 5574c398eff6..c1fd7c593a54 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -211,6 +211,9 @@  void exit_io_context(struct task_struct *task)
 	task->io_context = NULL;
 	task_unlock(task);
 
+	/* drain io poll submissions */
+	blk_bio_poll_io_drain(ioc);
+
 	atomic_dec(&ioc->nr_tasks);
 	put_io_context_active(ioc);
 }
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0cb88c719916..20bfc8c2d02e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3865,14 +3865,256 @@  static inline int blk_mq_poll_hctx(struct request_queue *q,
 	return ret;
 }
 
+static int blk_mq_poll_io(struct bio *bio)
+{
+	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
+	blk_qc_t cookie = bio_get_private_data(bio);
+	int ret = 0;
+
+	/* wait until the bio is submitted really */
+	if (!blk_qc_t_ready(cookie))
+		return 0;
+
+	if (!bio_flagged(bio, BIO_DONE) && blk_qc_t_valid(cookie)) {
+		struct blk_mq_hw_ctx *hctx =
+			q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
+
+		ret += blk_mq_poll_hctx(q, hctx);
+	}
+	return ret;
+}
+
+static int blk_bio_poll_and_end_io(struct bio_grp_list *grps)
+{
+	int ret = 0;
+	int i;
+
+	/*
+	 * Poll hw queue first.
+	 *
+	 * TODO: limit max poll times and make sure to not poll same
+	 * hw queue one more time.
+	 */
+	for (i = 0; i < grps->nr_grps; i++) {
+		struct bio_grp_list_data *grp = &grps->head[i];
+		struct bio *bio;
+
+		if (bio_grp_list_grp_empty(grp))
+			continue;
+
+		for (bio = grp->list.head; bio; bio = bio->bi_poll)
+			ret += blk_mq_poll_io(bio);
+	}
+
+	/* reap bios */
+	for (i = 0; i < grps->nr_grps; i++) {
+		struct bio_grp_list_data *grp = &grps->head[i];
+		struct bio *bio;
+		struct bio_list bl;
+
+		if (bio_grp_list_grp_empty(grp))
+			continue;
+
+		bio_list_init(&bl);
+
+		while ((bio = __bio_grp_list_pop(&grp->list))) {
+			if (bio_flagged(bio, BIO_DONE)) {
+				/* now recover original data */
+				bio->bi_poll = grp->grp_data;
+
+				/* clear BIO_END_BY_POLL and end me really */
+				bio_clear_flag(bio, BIO_END_BY_POLL);
+				bio_endio(bio);
+			} else {
+				__bio_grp_list_add(&bl, bio);
+			}
+		}
+		__bio_grp_list_merge(&grp->list, &bl);
+	}
+	return ret;
+}
+
+static void blk_bio_poll_pack_groups(struct bio_grp_list *grps)
+{
+	int i, j, k = 0;
+	int cnt = 0;
+
+	for (i = grps->nr_grps - 1; i >= 0; i--) {
+		struct bio_grp_list_data *grp = &grps->head[i];
+		struct bio_grp_list_data *hole = NULL;
+
+		if (bio_grp_list_grp_empty(grp)) {
+			cnt++;
+			continue;
+		}
+
+		for (j = k; j < i; j++) {
+			if (bio_grp_list_grp_empty(&grps->head[j])) {
+				hole = &grps->head[j];
+				break;
+			}
+		}
+		if (hole == NULL)
+			break;
+		*hole = *grp;
+		cnt++;
+		k = j;
+	}
+
+	grps->nr_grps -= cnt;
+}
+
+#define  MAX_BIO_GRPS_ON_STACK  8
+struct bio_grp_list_stack {
+	unsigned int max_nr_grps, nr_grps;
+	struct bio_grp_list_data head[MAX_BIO_GRPS_ON_STACK];
+};
+
+static int blk_bio_poll_io(struct io_context *submit_ioc,
+		struct io_context *poll_ioc)
+
+{
+	struct bio_grp_list_stack _bio_grps = {
+		.max_nr_grps	= ARRAY_SIZE(_bio_grps.head),
+		.nr_grps	= 0
+	};
+	struct bio_grp_list *bio_grps = (struct bio_grp_list *)&_bio_grps;
+	struct blk_bio_poll_ctx *submit_ctx = submit_ioc->data;
+	struct blk_bio_poll_ctx *poll_ctx = poll_ioc ?
+		poll_ioc->data : NULL;
+	int ret = 0;
+
+	/*
+	 * Move IO submission result from submission queue in submission
+	 * context to poll queue of poll context.
+	 */
+	if (READ_ONCE(submit_ctx->sq->nr_grps) > 0) {
+		spin_lock(&submit_ctx->sq_lock);
+		bio_grp_list_move(bio_grps, submit_ctx->sq);
+		spin_unlock(&submit_ctx->sq_lock);
+	}
+
+	/* merge new bios first, then start to poll bios from pq */
+	if (poll_ctx) {
+		spin_lock(&poll_ctx->pq_lock);
+		bio_grp_list_move(poll_ctx->pq, bio_grps);
+		bio_grp_list_move(bio_grps, poll_ctx->pq);
+		spin_unlock(&poll_ctx->pq_lock);
+	}
+
+	do {
+		ret += blk_bio_poll_and_end_io(bio_grps);
+		blk_bio_poll_pack_groups(bio_grps);
+
+		if (bio_grps->nr_grps) {
+			/*
+			 * move back, and keep polling until all can be
+			 * held in either poll queue or submission queue.
+			 */
+			if (poll_ctx) {
+				spin_lock(&poll_ctx->pq_lock);
+				bio_grp_list_move(poll_ctx->pq, bio_grps);
+				spin_unlock(&poll_ctx->pq_lock);
+			} else {
+				spin_lock(&submit_ctx->sq_lock);
+				bio_grp_list_move(submit_ctx->sq, bio_grps);
+				spin_unlock(&submit_ctx->sq_lock);
+			}
+		}
+	} while (bio_grps->nr_grps > 0);
+
+	return ret;
+}
+
+void blk_bio_poll_io_drain(struct io_context *submit_ioc)
+{
+	struct blk_bio_poll_ctx *submit_ctx = submit_ioc->data;
+
+	if (!submit_ctx)
+		return;
+
+	spin_lock(&submit_ctx->sq_lock);
+	while (READ_ONCE(submit_ctx->sq->nr_grps) > 0) {
+		blk_bio_poll_and_end_io(submit_ctx->sq);
+		blk_bio_poll_pack_groups(submit_ctx->sq);
+		cpu_relax();
+	}
+	spin_unlock(&submit_ctx->sq_lock);
+}
+
+static bool blk_bio_ioc_valid(struct task_struct *t)
+{
+	if (!t)
+		return false;
+
+	if (!t->io_context)
+		return false;
+
+	if (!t->io_context->data)
+		return false;
+
+	return true;
+}
+
+static int __blk_bio_poll(blk_qc_t cookie)
+{
+	struct io_context *poll_ioc = current->io_context;
+	pid_t pid;
+	struct task_struct *submit_task;
+	int ret;
+
+	pid = (pid_t)cookie;
+
+	/* io poll often share io submission context */
+	if (likely(current->pid == pid && blk_bio_ioc_valid(current)))
+		return blk_bio_poll_io(poll_ioc, poll_ioc);
+
+	submit_task = find_get_task_by_vpid(pid);
+	if (likely(blk_bio_ioc_valid(submit_task)))
+		ret = blk_bio_poll_io(submit_task->io_context, poll_ioc);
+	else
+		ret = 0;
+	if (likely(submit_task))
+		put_task_struct(submit_task);
+
+	return ret;
+}
+
 static int blk_bio_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
 {
+	long state;
+
+	/* no need to poll */
+	if (cookie == BLK_QC_T_BIO_NONE)
+		return 0;
+
 	/*
 	 * Create poll queue for storing poll bio and its cookie from
 	 * submission queue
 	 */
 	blk_create_io_poll_context(q);
 
+	state = current->state;
+	do {
+		int ret;
+
+		ret = __blk_bio_poll(cookie);
+		if (ret > 0) {
+			__set_current_state(TASK_RUNNING);
+			return ret;
+		}
+
+		if (signal_pending_state(state, current))
+			__set_current_state(TASK_RUNNING);
+
+		if (current->state == TASK_RUNNING)
+			return 1;
+		if (ret < 0 || !spin)
+			break;
+		cpu_relax();
+	} while (!need_resched());
+
+	__set_current_state(TASK_RUNNING);
 	return 0;
 }
 
@@ -3893,7 +4135,7 @@  int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
 	struct blk_mq_hw_ctx *hctx;
 	long state;
 
-	if (!blk_qc_t_valid(cookie) || !blk_queue_poll(q))
+	if (!blk_queue_poll(q) || (queue_is_mq(q) && !blk_qc_t_valid(cookie)))
 		return 0;
 
 	if (current->plug)
diff --git a/block/blk.h b/block/blk.h
index c1d8456656df..c0216f2e6293 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -381,6 +381,7 @@  struct blk_bio_poll_ctx {
 #define BLK_BIO_POLL_SQ_SZ		16U
 #define BLK_BIO_POLL_PQ_SZ		(BLK_BIO_POLL_SQ_SZ * 2)
 
+void blk_bio_poll_io_drain(struct io_context *submit_ioc);
 void bio_poll_ctx_alloc(struct io_context *ioc);
 
 static inline void blk_create_io_poll_context(struct request_queue *q)
@@ -405,4 +406,13 @@  static inline void bio_set_private_data(struct bio *bio, unsigned int data)
 	bio->bi_iter.bi_private_data = data;
 }
 
+BIO_LIST_HELPERS(__bio_grp_list, poll);
+
+static inline bool bio_grp_list_grp_empty(struct bio_grp_list_data *grp)
+{
+	return bio_list_empty(&grp->list);
+}
+
+void bio_grp_list_move(struct bio_grp_list *dst, struct bio_grp_list *src);
+
 #endif /* BLK_INTERNAL_H */
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 99160d588c2d..178af164ba2a 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -235,7 +235,18 @@  struct bio {
 
 	struct bvec_iter	bi_iter;
 
-	bio_end_io_t		*bi_end_io;
+	union {
+		bio_end_io_t		*bi_end_io;
+		/*
+		 * bio based io polling needs to track bio via bio group
+		 * list which groups bios by their .bi_end_io, and original
+		 * .bi_end_io is saved into the group head. Will recover
+		 * .bi_end_io before really ending bio. BIO_END_BY_POLL
+		 * will make sure that this bio won't be ended before
+		 * recovering .bi_end_io.
+		 */
+		struct bio		*bi_poll;
+	};
 
 	void			*bi_private;
 #ifdef CONFIG_BLK_CGROUP
@@ -304,6 +315,9 @@  enum {
 	BIO_CGROUP_ACCT,	/* has been accounted to a cgroup */
 	BIO_TRACKED,		/* set if bio goes through the rq_qos path */
 	BIO_REMAPPED,
+	BIO_END_BY_POLL,	/* end by blk_bio_poll() explicitly */
+	/* set when bio can be ended, used for bio with BIO_END_BY_POLL */
+	BIO_DONE,
 	BIO_FLAG_LAST
 };
 
@@ -513,6 +527,16 @@  typedef unsigned int blk_qc_t;
 #define BLK_QC_T_NONE		-1U
 #define BLK_QC_T_SHIFT		16
 #define BLK_QC_T_INTERNAL	(1U << 31)
+/* only used for bio based submission, has to be defined as 0 */
+#define BLK_QC_T_BIO_NONE	0
+/* only used for bio based polling, not ready for polling */
+#define BLK_QC_T_NOT_READY	-2U
+
+/* not ready for bio based polling since this bio isn't submitted really */
+static inline bool blk_qc_t_ready(blk_qc_t cookie)
+{
+	return cookie != BLK_QC_T_NOT_READY;
+}
 
 static inline bool blk_qc_t_valid(blk_qc_t cookie)
 {