[Nbd] [CFT][PATCH 3/4] nbd: support ROTATIONAL

[Paolo Bonzini <pbonzini@...696...>]

From: Alex Bligh <alex@...872...>

Cc: Paul Clements <Paul.Clements@...124...>
Cc: <nbd-general@...72...>
Signed-off-by: Alex Bligh <alex@...872...>
Signed-off-by: Paolo Bonzini <pbonzini@...696...>
---
 drivers/block/nbd.c |    8 ++++----
 include/linux/nbd.h |    1 +
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index bece3cc..930b4df 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -699,6 +699,10 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *lo,
 			return -EINVAL;
 
 		mutex_unlock(&lo->tx_lock);
+		if (lo->flags & NBD_FLAG_ROTATIONAL)
+			queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, lo->disk->queue);
+		else
+			queue_flag_set_unlocked(QUEUE_FLAG_NONROT, lo->disk->queue);
 
 		thread = kthread_create(nbd_thread, lo, lo->disk->disk_name);
 		if (IS_ERR(thread)) {
@@ -820,10 +824,6 @@ static int __init nbd_init(void)
 		 * unless the relevant flag bit is set
 		 */
 		blk_queue_flush(disk->queue, REQ_FLUSH | REQ_FUA);
-		/*
-		 * Tell the block layer that we are not a rotational device
-		 */
-		queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue);
 	}
 
 	if (register_blkdev(NBD_MAJOR, "nbd")) {
diff --git a/include/linux/nbd.h b/include/linux/nbd.h
index d8cd251..5037b0b 100644
--- a/include/linux/nbd.h
+++ b/include/linux/nbd.h
@@ -44,6 +44,7 @@ enum {
 #define NBD_FLAG_READ_ONLY	(1 << 1)	/* Device is read only */
 #define NBD_FLAG_SEND_FLUSH	(1 << 2)	/* Send FLUSH */
 #define NBD_FLAG_SEND_FUA	(1 << 3)	/* Send FUA (Force Unit Access) */
+#define NBD_FLAG_ROTATIONAL	(1 << 4)	/* Use elevator algorithm - rotational media */
 
 #define nbd_cmd(req) ((req)->cmd[0])
 
-- 
1.7.6