block/rnbd: Set write-back cache and fua same to the target device

The rnbd-client always sets the write-back cache and fua attributes
of the rnbd device queue regardless of the target device on the server.
That generates IO hang issue when the target device does not
support both of write-back cacne and fua.

This patch adds more fields for the cache policy and fua into the
device opening message. The rnbd-server sends the information
if the target device supports the write-back cache and fua
and rnbd-client recevives it and set the device queue accordingly.
Signed-off-by: Gioh Kim <gi-oh.kim@cloud.ionos.com>
[jwang: some minor change, rename a few varables, remove unrelated comments.]
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/rnbd/rnbd-clt.c

@@ -88,6 +88,8 @@ static int rnbd_clt_set_dev_attr(struct rnbd_clt_dev *dev,
 	dev->discard_alignment	    = le32_to_cpu(rsp->discard_alignment);
 	dev->secure_discard	    = le16_to_cpu(rsp->secure_discard);
 	dev->rotational		    = rsp->rotational;
+	dev->wc 		    = !!(rsp->cache_policy & RNBD_WRITEBACK);
+	dev->fua		    = !!(rsp->cache_policy & RNBD_FUA);
 
 	dev->max_hw_sectors = sess->max_io_size / SECTOR_SIZE;
 	dev->max_segments = BMAX_SEGMENTS;
@@ -1305,7 +1307,7 @@ static void setup_request_queue(struct rnbd_clt_dev *dev)
 	blk_queue_max_segments(dev->queue, dev->max_segments);
 	blk_queue_io_opt(dev->queue, dev->sess->max_io_size);
 	blk_queue_virt_boundary(dev->queue, SZ_4K - 1);
-	blk_queue_write_cache(dev->queue, true, true);
+	blk_queue_write_cache(dev->queue, dev->wc, dev->fua);
 	dev->queue->queuedata = dev;
 }
 
@@ -1528,13 +1530,13 @@ struct rnbd_clt_dev *rnbd_clt_map_device(const char *sessname,
 	}
 
 	rnbd_clt_info(dev,
-		       "map_device: Device mapped as %s (nsectors: %zu, logical_block_size: %d, physical_block_size: %d, max_write_same_sectors: %d, max_discard_sectors: %d, discard_granularity: %d, discard_alignment: %d, secure_discard: %d, max_segments: %d, max_hw_sectors: %d, rotational: %d)\n",
+		       "map_device: Device mapped as %s (nsectors: %zu, logical_block_size: %d, physical_block_size: %d, max_write_same_sectors: %d, max_discard_sectors: %d, discard_granularity: %d, discard_alignment: %d, secure_discard: %d, max_segments: %d, max_hw_sectors: %d, rotational: %d, wc: %d, fua: %d)\n",
 		       dev->gd->disk_name, dev->nsectors,
 		       dev->logical_block_size, dev->physical_block_size,
 		       dev->max_write_same_sectors, dev->max_discard_sectors,
 		       dev->discard_granularity, dev->discard_alignment,
 		       dev->secure_discard, dev->max_segments,
-		       dev->max_hw_sectors, dev->rotational);
+		       dev->max_hw_sectors, dev->rotational, dev->wc, dev->fua);
 
 	mutex_unlock(&dev->lock);
 

drivers/block/rnbd/rnbd-clt.h

@@ -112,6 +112,8 @@ struct rnbd_clt_dev {
 	enum rnbd_access_mode	access_mode;
 	bool			read_only;
 	bool			rotational;
+	bool			wc;
+	bool			fua;
 	u32			max_hw_sectors;
 	u32			max_write_same_sectors;
 	u32			max_discard_sectors;

drivers/block/rnbd/rnbd-proto.h

@@ -108,6 +108,11 @@ struct rnbd_msg_close {
 	__le32		device_id;
 };
 
+enum rnbd_cache_policy {
+	RNBD_FUA = 1 << 0,
+	RNBD_WRITEBACK = 1 << 1,
+};
+
 /**
  * struct rnbd_msg_open_rsp - response message to RNBD_MSG_OPEN
  * @hdr:		message header
@@ -124,6 +129,7 @@ struct rnbd_msg_close {
  * @max_segments:	max segments hardware support in one transfer
  * @secure_discard:	supports secure discard
  * @rotation:		is a rotational disc?
+ * @cache_policy: 	support write-back caching or FUA?
  */
 struct rnbd_msg_open_rsp {
 	struct rnbd_msg_hdr	hdr;
@@ -139,7 +145,8 @@ struct rnbd_msg_open_rsp {
 	__le16			max_segments;
 	__le16			secure_discard;
 	u8			rotational;
-	u8			reserved[11];
+	u8			cache_policy;
+	u8			reserved[10];
 };
 
 /**

drivers/block/rnbd/rnbd-srv.c

@@ -550,6 +550,7 @@ static void rnbd_srv_fill_msg_open_rsp(struct rnbd_msg_open_rsp *rsp,
 					struct rnbd_srv_sess_dev *sess_dev)
 {
 	struct rnbd_dev *rnbd_dev = sess_dev->rnbd_dev;
+	struct request_queue *q = bdev_get_queue(rnbd_dev->bdev);
 
 	rsp->hdr.type = cpu_to_le16(RNBD_MSG_OPEN_RSP);
 	rsp->device_id =
@@ -574,8 +575,12 @@ static void rnbd_srv_fill_msg_open_rsp(struct rnbd_msg_open_rsp *rsp,
 		cpu_to_le32(rnbd_dev_get_discard_alignment(rnbd_dev));
 	rsp->secure_discard =
 		cpu_to_le16(rnbd_dev_get_secure_discard(rnbd_dev));
-	rsp->rotational =
-		!blk_queue_nonrot(bdev_get_queue(rnbd_dev->bdev));
+	rsp->rotational = !blk_queue_nonrot(q);
+	rsp->cache_policy = 0;
+	if (test_bit(QUEUE_FLAG_WC, &q->queue_flags))
+		rsp->cache_policy |= RNBD_WRITEBACK;
+	if (blk_queue_fua(q))
+		rsp->cache_policy |= RNBD_FUA;
 }
 
 static struct rnbd_srv_sess_dev *