[PATCH V6 07/12] block: create io poll context for submission and poll task

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

Create per-task io poll context for both IO submission and poll task
if the queue is bio based and supports polling.

This io polling context includes two queues:

1) submission queue(sq) for storing HIPRI bio, written by submission task
   and read by poll task.
2) polling queue(pq) for holding data moved from sq, only used in poll
   context for running bio polling.

Following patches will support bio based io polling.

Reviewed-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-core.c          | 24 +++++++++-------
 block/blk-ioc.c           |  1 +
 block/blk-poll.c          | 51 +++++++++++++++++++++++++++++++++
 block/blk.h               | 60 +++++++++++++++++++++++++++++++++++++++
 include/linux/iocontext.h |  2 ++
 5 files changed, 127 insertions(+), 11 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index d44a8b934608..5830ef4d733e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -868,8 +868,19 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
 		}
 	}
 
-	if (!blk_queue_poll(q))
-		bio->bi_opf &= ~REQ_HIPRI;
+	/*
+	 * Various block parts want %current->io_context, so allocate it up
+	 * front rather than dealing with lots of pain to allocate it only
+	 * where needed. This may fail and the block layer knows how to live
+	 * with it.
+	 */
+	if (unlikely(!current->io_context))
+		create_task_io_context(current, GFP_ATOMIC, q->node);
+
+	if ((bio->bi_opf & REQ_HIPRI) && blk_queue_support_bio_poll(q))
+		blk_create_io_poll_context(q);
+
+	blk_poll_prepare(q, bio);
 
 	switch (bio_op(bio)) {
 	case REQ_OP_DISCARD:
@@ -908,15 +919,6 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
 		break;
 	}
 
-	/*
-	 * Various block parts want %current->io_context, so allocate it up
-	 * front rather than dealing with lots of pain to allocate it only
-	 * where needed. This may fail and the block layer knows how to live
-	 * with it.
-	 */
-	if (unlikely(!current->io_context))
-		create_task_io_context(current, GFP_ATOMIC, q->node);
-
 	if (blk_throtl_bio(bio)) {
 		blkcg_bio_issue_init(bio);
 		return false;
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index b0cde18c4b8c..5574c398eff6 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -19,6 +19,7 @@ static struct kmem_cache *iocontext_cachep;
 
 static inline void free_io_context(struct io_context *ioc)
 {
+	kfree(ioc->data);
 	kmem_cache_free(iocontext_cachep, ioc);
 }
 
diff --git a/block/blk-poll.c b/block/blk-poll.c
index 0a38c25bcee5..8e4bec55293e 100644
--- a/block/blk-poll.c
+++ b/block/blk-poll.c
@@ -4,11 +4,14 @@
 #include <linux/blkdev.h>
 #include <linux/sched.h>
 #include <linux/hrtimer.h>
+#include <linux/bio.h>
 
 #include <linux/blk-mq.h>
 #include "blk.h"
 #include "blk-mq.h"
 
+static int blk_bio_poll(struct request_queue *q, blk_qc_t cookie, bool spin);
+
 /* Enable polling stats and return whether they were already enabled. */
 static bool blk_poll_stats_enable(struct request_queue *q)
 {
@@ -165,6 +168,9 @@ int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
 	if (current->plug)
 		blk_flush_plug_list(current->plug, false);
 
+	if (!queue_is_mq(q))
+		return blk_bio_poll(q, cookie, spin);
+
 	hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
 
 	/*
@@ -204,3 +210,48 @@ int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(blk_poll);
+
+/* bio base io polling  */
+static int blk_bio_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
+{
+	/*
+	 * Create poll queue for storing poll bio and its cookie from
+	 * submission queue
+	 */
+	blk_create_io_poll_context(q);
+
+	return 0;
+}
+
+static inline unsigned int bio_grp_list_size(unsigned int nr_grps)
+{
+	return sizeof(struct bio_grp_list) + nr_grps *
+		sizeof(struct bio_grp_list_data);
+}
+
+static void bio_poll_ctx_init(struct blk_bio_poll_ctx *pc)
+{
+	pc->sq = (void *)pc + sizeof(*pc);
+	pc->sq->max_nr_grps = BLK_BIO_POLL_SQ_SZ;
+
+	pc->pq = (void *)pc->sq + bio_grp_list_size(BLK_BIO_POLL_SQ_SZ);
+	pc->pq->max_nr_grps = BLK_BIO_POLL_PQ_SZ;
+
+	spin_lock_init(&pc->sq_lock);
+	spin_lock_init(&pc->pq_lock);
+}
+
+void bio_poll_ctx_alloc(struct io_context *ioc)
+{
+	struct blk_bio_poll_ctx *pc;
+	unsigned int size = sizeof(*pc) +
+		bio_grp_list_size(BLK_BIO_POLL_SQ_SZ) +
+		bio_grp_list_size(BLK_BIO_POLL_PQ_SZ);
+
+	pc = kzalloc(GFP_ATOMIC, size);
+	if (pc) {
+		bio_poll_ctx_init(pc);
+		if (cmpxchg(&ioc->data, NULL, (void *)pc))
+			kfree(pc);
+	}
+}
diff --git a/block/blk.h b/block/blk.h
index d88b0823738c..bc6d63ae36b7 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -352,4 +352,64 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
 		struct page *page, unsigned int len, unsigned int offset,
 		unsigned int max_sectors, bool *same_page);
 
+/* Grouping bios that share same data into one list */
+struct bio_grp_list_data {
+	void *grp_data;
+
+	/* all bios in this list share same 'grp_data' */
+	struct bio_list list;
+};
+
+struct bio_grp_list {
+	unsigned int max_nr_grps, nr_grps;
+	struct bio_grp_list_data head[0];
+};
+
+struct blk_bio_poll_ctx {
+	spinlock_t sq_lock;
+	struct bio_grp_list *sq;
+
+	spinlock_t pq_lock;
+	struct bio_grp_list *pq;
+};
+
+#define BLK_BIO_POLL_SQ_SZ		16U
+#define BLK_BIO_POLL_PQ_SZ		(BLK_BIO_POLL_SQ_SZ * 2)
+
+void bio_poll_ctx_alloc(struct io_context *ioc);
+
+static inline bool blk_queue_support_bio_poll(struct request_queue *q)
+{
+	return !queue_is_mq(q) && blk_queue_poll(q);
+}
+
+static inline struct blk_bio_poll_ctx *blk_get_bio_poll_ctx(void)
+{
+	struct io_context *ioc = current->io_context;
+
+	return ioc ? ioc->data : NULL;
+}
+
+static inline void blk_poll_prepare(struct request_queue *q,
+		struct bio *bio)
+{
+	if (!(bio->bi_opf & REQ_HIPRI))
+		return;
+
+	if (!blk_queue_poll(q) || (!queue_is_mq(q) && !blk_get_bio_poll_ctx()))
+		bio->bi_opf &= ~REQ_HIPRI;
+}
+
+static inline void blk_create_io_poll_context(struct request_queue *q)
+{
+	struct io_context *ioc;
+
+	if (unlikely(!current->io_context))
+		create_task_io_context(current, GFP_ATOMIC, q->node);
+
+	ioc = current->io_context;
+	if (unlikely(ioc && !ioc->data))
+		bio_poll_ctx_alloc(ioc);
+}
+
 #endif /* BLK_INTERNAL_H */
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 0a9dc40b7be8..f9a467571356 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -110,6 +110,8 @@ struct io_context {
 	struct io_cq __rcu	*icq_hint;
 	struct hlist_head	icq_list;
 
+	void			*data;
+
 	struct work_struct release_work;
 };
 
-- 
2.29.2