[dm-devel] [PATCH v4 1/2] block: add ->poll_bio to block_device_operations

[Mike Snitzer]

From: Ming Lei <ming.lei at 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 at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
 block/blk-core.c       | 12 +++++++++---
 block/genhd.c          |  2 ++
 include/linux/blkdev.h |  2 ++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 94bf37f8e61d..e739c6264331 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -985,10 +985,16 @@ int bio_poll(struct bio *bio, struct io_comp_batch *iob, 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)) {
 		ret = blk_mq_poll(q, cookie, iob, flags);
+	} else {
+		struct gendisk *disk = q->disk;
+
+		if (disk && disk->fops->poll_bio)
+			ret = disk->fops->poll_bio(bio, iob, flags);
+		else
+			ret = !WARN_ON_ONCE(1);
+	}
 	blk_queue_exit(q);
 	return ret;
 }
diff --git a/block/genhd.c b/block/genhd.c
index e351fac41bf2..eb43fa63ba47 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -410,6 +410,8 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
 	struct device *ddev = disk_to_dev(disk);
 	int ret;
 
+	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 f757f9c2871f..51f1b1ddbed2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1455,6 +1455,8 @@ enum blk_unique_id {
 
 struct block_device_operations {
 	void (*submit_bio)(struct bio *bio);
+	int (*poll_bio)(struct bio *bio, struct io_comp_batch *iob,
+			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);
-- 
2.15.0