[RFC PATCH 3/4] block: add ->poll_bio to block_device_operations

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

Prepare for supporting IO polling for bio based driver.

Add ->poll_bio callback so that bio driver can provide their own logic
for polling bio.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-core.c       | 18 +++++++++++++-----
 block/genhd.c          |  3 +++
 include/linux/blkdev.h |  2 ++
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 1e24c71c6738..a1552ec8d608 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1113,11 +1113,13 @@ EXPORT_SYMBOL(submit_bio);
  */
 int bio_poll(struct bio *bio, unsigned int flags)
 {
-	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
+	struct gendisk *disk = bio->bi_bdev->bd_disk;
+	struct request_queue *q = disk->queue;
 	blk_qc_t cookie = READ_ONCE(bio->bi_cookie);
 	int ret;
 
-	if (cookie == BLK_QC_T_NONE || !blk_queue_poll(q))
+	if ((queue_is_mq(q) && cookie == BLK_QC_T_NONE) ||
+			!blk_queue_poll(q))
 		return 0;
 
 	if (current->plug)
@@ -1125,10 +1127,16 @@ int bio_poll(struct bio *bio, unsigned int flags)
 
 	if (blk_queue_enter(q, BLK_MQ_REQ_NOWAIT))
 		return 0;
-	if (WARN_ON_ONCE(!queue_is_mq(q)))
-		ret = 0;	/* not yet implemented, should not happen */
-	else
+	if (!queue_is_mq(q)) {
+		if (disk->fops->poll_bio) {
+			ret = disk->fops->poll_bio(bio, flags);
+		} else {
+			WARN_ON_ONCE(1);
+			ret = 0;
+		}
+	} else {
 		ret = blk_mq_poll(q, cookie, flags);
+	}
 	blk_queue_exit(q);
 	return ret;
 }
diff --git a/block/genhd.c b/block/genhd.c
index 5f5628216295..042dfa5b3f79 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -471,6 +471,9 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
 {
 	int ret;
 
+	/* ->poll_bio is only for bio based driver */
+	WARN_ON_ONCE(queue_is_mq(disk->queue) && disk->fops->poll_bio);
+
 	/*
 	 * The disk queue should now be all set with enough information about
 	 * the device for the elevator code to pick an adequate default
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index fc0ba0b80776..6da6fb120148 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1858,6 +1858,8 @@ static inline void blk_ksm_unregister(struct request_queue *q) { }
 
 struct block_device_operations {
 	void (*submit_bio)(struct bio *bio);
+	/* ->poll_bio is for bio driver only */
+	int (*poll_bio)(struct bio *bio, unsigned int flags);
 	int (*open) (struct block_device *, fmode_t);
 	void (*release) (struct gendisk *, fmode_t);
 	int (*rw_page)(struct block_device *, sector_t, struct page *, unsigned int);
-- 
2.31.1