[PATCH 3/4] scsi: sd: register request queue after sd_revalidate_disk is done

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

Prepare for improving SSD performance in the following patch, which
needs to read queue flag of QUEUE_FLAG_NONROT in IO path. So we have
to freeze queue before changing this flag in sd_revalidate_disk().

However, queue freezing becomes quite slow after the queue is registered
because RCU period is involved.

So delay registering queue after sd_revalidate_disk() is done for
avoiding slow queue freezing which will be added to sd_revalidate_disk()
in the following patch.

Cc: Sathya Prakash <sathya.prakash@broadcom.com>
Cc: Chaitra P B <chaitra.basappa@broadcom.com>
Cc: Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumit Saxena <sumit.saxena@broadcom.com>
Cc: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
Cc: Hannes Reinecke <hare@suse.de>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/sd.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 03163ac5fe95..0744c34468e1 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3368,12 +3368,14 @@ static int sd_probe(struct device *dev)
 	}
 
 	blk_pm_runtime_init(sdp->request_queue, dev);
-	device_add_disk(dev, gd, NULL);
+	device_add_disk_no_queue_reg(dev, gd);
 	if (sdkp->capacity)
 		sd_dif_config_host(sdkp);
 
 	sd_revalidate_disk(gd);
 
+	blk_register_queue(gd);
+
 	if (sdkp->security) {
 		sdkp->opal_dev = init_opal_dev(sdp, &sd_sec_submit);
 		if (sdkp->opal_dev)
-- 
2.20.1