[PATCH 4/4] nvme-core: Get lowlevel disk for target polling queue task

[Ping Gan]

When enabling multipath, if the block device of nvmet is
a nvme_ns_head disk, then we should get the lowlevel block
device to do bio split.

Signed-off-by: Ping Gan <jacky_gam_2001@xxxxxxx>
---
 drivers/nvme/host/multipath.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 0a88d7bdc5e3..f6063600e06e 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -371,6 +371,25 @@ static bool nvme_available_path(struct nvme_ns_head *head)
 	return false;
 }
 
+//for polling queue task to get lowlevel block device
+struct block_device *nvme_mpath_get_bdev(struct block_device *bdev)
+{
+	struct nvme_ns_head *head = bdev->bd_disk->private_data;
+	int srcu_idx;
+	struct nvme_ns *ns;
+	struct block_device *ret = NULL;
+
+	if (!multipath)
+		return NULL;
+	srcu_idx = srcu_read_lock(&head->srcu);
+	ns = nvme_find_path(head);
+	if (likely(ns))
+		ret = ns->disk->part0;
+	srcu_read_unlock(&head->srcu, srcu_idx);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nvme_mpath_get_bdev);
+
 static void nvme_ns_head_submit_bio(struct bio *bio)
 {
 	struct nvme_ns_head *head = bio->bi_bdev->bd_disk->private_data;
@@ -452,6 +471,7 @@ const struct block_device_operations nvme_ns_head_ops = {
 	.report_zones	= nvme_ns_head_report_zones,
 	.pr_ops		= &nvme_pr_ops,
 };
+EXPORT_SYMBOL_GPL(nvme_ns_head_ops);
 
 static inline struct nvme_ns_head *cdev_to_ns_head(struct cdev *cdev)
 {
-- 
2.26.2