Merge branch 'virtio_net-fix-lock-warning-and-unrecoverable-state'

Heng Qi says:

====================
virtio_net: fix lock warning and unrecoverable state

Patch 1 describes and fixes an issue where dim cannot return to
normal state in certain scenarios.

Patch 2 attempts to resolve lockdep's complaints that holding many
nested locks.
====================

Link: https://lore.kernel.org/r/20240528134116.117426-1-hengqi@linux.alibaba.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/virtio_net.c

@@ -4259,7 +4259,6 @@ static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi,
 	struct virtio_net_ctrl_coal_rx *coal_rx __free(kfree) = NULL;
 	bool rx_ctrl_dim_on = !!ec->use_adaptive_rx_coalesce;
 	struct scatterlist sgs_rx;
-	int ret = 0;
 	int i;
 
 	if (rx_ctrl_dim_on && !virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL))
@@ -4269,27 +4268,27 @@ static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi,
 			       ec->rx_max_coalesced_frames != vi->intr_coal_rx.max_packets))
 		return -EINVAL;
 
-	/* Acquire all queues dim_locks */
-	for (i = 0; i < vi->max_queue_pairs; i++)
-		mutex_lock(&vi->rq[i].dim_lock);
-
 	if (rx_ctrl_dim_on && !vi->rx_dim_enabled) {
 		vi->rx_dim_enabled = true;
-		for (i = 0; i < vi->max_queue_pairs; i++)
+		for (i = 0; i < vi->max_queue_pairs; i++) {
+			mutex_lock(&vi->rq[i].dim_lock);
 			vi->rq[i].dim_enabled = true;
-		goto unlock;
+			mutex_unlock(&vi->rq[i].dim_lock);
+		}
+		return 0;
 	}
 
 	coal_rx = kzalloc(sizeof(*coal_rx), GFP_KERNEL);
-	if (!coal_rx) {
-		ret = -ENOMEM;
-		goto unlock;
-	}
+	if (!coal_rx)
+		return -ENOMEM;
 
 	if (!rx_ctrl_dim_on && vi->rx_dim_enabled) {
 		vi->rx_dim_enabled = false;
-		for (i = 0; i < vi->max_queue_pairs; i++)
+		for (i = 0; i < vi->max_queue_pairs; i++) {
+			mutex_lock(&vi->rq[i].dim_lock);
 			vi->rq[i].dim_enabled = false;
+			mutex_unlock(&vi->rq[i].dim_lock);
+		}
 	}
 
 	/* Since the per-queue coalescing params can be set,
@@ -4302,22 +4301,19 @@ static int virtnet_send_rx_notf_coal_cmds(struct virtnet_info *vi,
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
 				  VIRTIO_NET_CTRL_NOTF_COAL_RX_SET,
-				  &sgs_rx)) {
-		ret = -EINVAL;
-		goto unlock;
-	}
+				  &sgs_rx))
+		return -EINVAL;
 
 	vi->intr_coal_rx.max_usecs = ec->rx_coalesce_usecs;
 	vi->intr_coal_rx.max_packets = ec->rx_max_coalesced_frames;
 	for (i = 0; i < vi->max_queue_pairs; i++) {
+		mutex_lock(&vi->rq[i].dim_lock);
 		vi->rq[i].intr_coal.max_usecs = ec->rx_coalesce_usecs;
 		vi->rq[i].intr_coal.max_packets = ec->rx_max_coalesced_frames;
-	}
-unlock:
-	for (i = vi->max_queue_pairs - 1; i >= 0; i--)
 		mutex_unlock(&vi->rq[i].dim_lock);
+	}
 
-	return ret;
+	return 0;
 }
 
 static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
@@ -4419,9 +4415,9 @@ static void virtnet_rx_dim_work(struct work_struct *work)
 		if (err)
 			pr_debug("%s: Failed to send dim parameters on rxq%d\n",
 				 dev->name, qnum);
-		dim->state = DIM_START_MEASURE;
 	}
 out:
+	dim->state = DIM_START_MEASURE;
 	mutex_unlock(&rq->dim_lock);
 }