nbd: Fix signal handling

Both nbd_send_cmd() and nbd_handle_cmd() return either a negative error
number or a positive blk_status_t value. nbd_queue_rq() converts these
return values into a blk_status_t value. There is a bug in the conversion
code: if nbd_send_cmd() returns BLK_STS_RESOURCE, nbd_queue_rq() should
return BLK_STS_RESOURCE instead of BLK_STS_OK. Fix this, move the
conversion code into nbd_handle_cmd() and fix the remaining sparse warnings.

This patch fixes the following sparse warnings:

drivers/block/nbd.c:673:32: warning: incorrect type in return expression (different base types)
drivers/block/nbd.c:673:32:    expected int
drivers/block/nbd.c:673:32:    got restricted blk_status_t [usertype]
drivers/block/nbd.c:714:48: warning: incorrect type in return expression (different base types)
drivers/block/nbd.c:714:48:    expected int
drivers/block/nbd.c:714:48:    got restricted blk_status_t [usertype]
drivers/block/nbd.c:1120:21: warning: incorrect type in assignment (different base types)
drivers/block/nbd.c:1120:21:    expected int [assigned] ret
drivers/block/nbd.c:1120:21:    got restricted blk_status_t [usertype]
drivers/block/nbd.c:1125:16: warning: incorrect type in return expression (different base types)
drivers/block/nbd.c:1125:16:    expected restricted blk_status_t
drivers/block/nbd.c:1125:16:    got int [assigned] ret

Cc: Christoph Hellwig <hch@lst.de>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Yu Kuai <yukuai3@huawei.com>
Cc: Markus Pargmann <mpa@pengutronix.de>
Fixes: fc17b6534e ("blk-mq: switch ->queue_rq return value to blk_status_t")
Cc: stable@vger.kernel.org
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240510202313.25209-6-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/nbd.c

@@ -588,6 +588,10 @@ static inline int was_interrupted(int result)
 	return result == -ERESTARTSYS || result == -EINTR;
 }
 
+/*
+ * Returns BLK_STS_RESOURCE if the caller should retry after a delay. Returns
+ * -EAGAIN if the caller should requeue @cmd. Returns -EIO if sending failed.
+ */
 static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
 {
 	struct request *req = blk_mq_rq_from_pdu(cmd);
@@ -670,7 +674,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
 				nsock->sent = sent;
 			}
 			set_bit(NBD_CMD_REQUEUED, &cmd->flags);
-			return BLK_STS_RESOURCE;
+			return (__force int)BLK_STS_RESOURCE;
 		}
 		dev_err_ratelimited(disk_to_dev(nbd->disk),
 			"Send control failed (result %d)\n", result);
@@ -711,7 +715,7 @@ send_pages:
 					nsock->pending = req;
 					nsock->sent = sent;
 					set_bit(NBD_CMD_REQUEUED, &cmd->flags);
-					return BLK_STS_RESOURCE;
+					return (__force int)BLK_STS_RESOURCE;
 				}
 				dev_err(disk_to_dev(nbd->disk),
 					"Send data failed (result %d)\n",
@@ -1008,7 +1012,7 @@ static int wait_for_reconnect(struct nbd_device *nbd)
 	return !test_bit(NBD_RT_DISCONNECTED, &config->runtime_flags);
 }
 
-static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
+static blk_status_t nbd_handle_cmd(struct nbd_cmd *cmd, int index)
 {
 	struct request *req = blk_mq_rq_from_pdu(cmd);
 	struct nbd_device *nbd = cmd->nbd;
@@ -1022,14 +1026,14 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
 	if (!config) {
 		dev_err_ratelimited(disk_to_dev(nbd->disk),
 				    "Socks array is empty\n");
-		return -EINVAL;
+		return BLK_STS_IOERR;
 	}
 
 	if (index >= config->num_connections) {
 		dev_err_ratelimited(disk_to_dev(nbd->disk),
 				    "Attempted send on invalid socket\n");
 		nbd_config_put(nbd);
-		return -EINVAL;
+		return BLK_STS_IOERR;
 	}
 	cmd->status = BLK_STS_OK;
 again:
@@ -1052,7 +1056,7 @@ again:
 			 */
 			sock_shutdown(nbd);
 			nbd_config_put(nbd);
-			return -EIO;
+			return BLK_STS_IOERR;
 		}
 		goto again;
 	}
@@ -1065,7 +1069,7 @@ again:
 	blk_mq_start_request(req);
 	if (unlikely(nsock->pending && nsock->pending != req)) {
 		nbd_requeue_cmd(cmd);
-		ret = 0;
+		ret = BLK_STS_OK;
 		goto out;
 	}
 	/*
@@ -1084,19 +1088,19 @@ again:
 				    "Request send failed, requeueing\n");
 		nbd_mark_nsock_dead(nbd, nsock, 1);
 		nbd_requeue_cmd(cmd);
-		ret = 0;
+		ret = BLK_STS_OK;
 	}
 out:
 	mutex_unlock(&nsock->tx_lock);
 	nbd_config_put(nbd);
-	return ret;
+	return ret < 0 ? BLK_STS_IOERR : (__force blk_status_t)ret;
 }
 
 static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
 			const struct blk_mq_queue_data *bd)
 {
 	struct nbd_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
-	int ret;
+	blk_status_t ret;
 
 	/*
 	 * Since we look at the bio's to send the request over the network we
@@ -1116,10 +1120,6 @@ static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
 	 * appropriate.
 	 */
 	ret = nbd_handle_cmd(cmd, hctx->queue_num);
-	if (ret < 0)
-		ret = BLK_STS_IOERR;
-	else if (!ret)
-		ret = BLK_STS_OK;
 	mutex_unlock(&cmd->lock);
 
 	return ret;