Re: [PATCH v4 3/8] fuse: {io-uring} Use bitmaps to track registered queues

[Luis Henriques <luis@igalia.com>]

On Mon, Apr 13 2026, Bernd Schubert via B4 Relay wrote:

> From: Bernd Schubert <bschubert@ddn.com>
>
> Add per-CPU and per-NUMA node bitmasks to track which
> io-uring queues are registered.
>
> Signed-off-by: Bernd Schubert <bschubert@ddn.com>
> ---
>  fs/fuse/dev_uring.c   | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/fuse/dev_uring_i.h | 20 ++++++++++++++
>  2 files changed, 93 insertions(+)
>
> diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
> index 08c49e5b65ee950a9749a034b1e9d0a8883e1d31..1d1305d38efa07641128a865aec1745d2e040b93 100644
> --- a/fs/fuse/dev_uring.c
> +++ b/fs/fuse/dev_uring.c
> @@ -186,6 +186,25 @@ bool fuse_uring_request_expired(struct fuse_conn *fc)
>  	return false;
>  }
>  
> +static void fuse_ring_destruct_q_map(struct fuse_queue_map *q_map)
> +{
> +	free_cpumask_var(q_map->registered_q_mask);
> +	kfree(q_map->cpu_to_qid);
> +}
> +
> +static void fuse_uring_destruct_q_masks(struct fuse_ring *ring)
> +{
> +	int node;
> +
> +	fuse_ring_destruct_q_map(&ring->q_map);
> +
> +	if (ring->numa_q_map) {
> +		for (node = 0; node < ring->nr_numa_nodes; node++)
> +			fuse_ring_destruct_q_map(&ring->numa_q_map[node]);
> +		kfree(ring->numa_q_map);
> +	}
> +}
> +
>  void fuse_uring_destruct(struct fuse_conn *fc)
>  {
>  	struct fuse_ring *ring = fc->ring;
> @@ -217,11 +236,44 @@ void fuse_uring_destruct(struct fuse_conn *fc)
>  		ring->queues[qid] = NULL;
>  	}
>  
> +	fuse_uring_destruct_q_masks(ring);
>  	kfree(ring->queues);
>  	kfree(ring);
>  	fc->ring = NULL;
>  }
>  
> +static int fuse_uring_init_q_map(struct fuse_queue_map *q_map, size_t nr_cpu)
> +{
> +	if (!zalloc_cpumask_var(&q_map->registered_q_mask, GFP_KERNEL_ACCOUNT))
> +		return -ENOMEM;
> +
> +	q_map->cpu_to_qid = kzalloc_objs(*q_map->cpu_to_qid, nr_cpu,
> +					 GFP_KERNEL_ACCOUNT);
> +

Missing NULL check here (and corresponding call to free_cpumask_var()).

> 
> +	return 0;
> +}
> +
> +static int fuse_uring_create_q_masks(struct fuse_ring *ring)
> +{
> +	int err, node;
> +
> +	err = fuse_uring_init_q_map(&ring->q_map, ring->max_nr_queues);
> +	if (err)
> +		return err;
> +
> +	ring->numa_q_map = kzalloc_objs(*ring->numa_q_map, ring->nr_numa_nodes,
> +					GFP_KERNEL_ACCOUNT);
> +	if (!ring->numa_q_map)
> +		return -ENOMEM;

Missing call to fuse_ring_destruct_q_map().

> +	for (node = 0; node < ring->nr_numa_nodes; node++) {
> +		err = fuse_uring_init_q_map(&ring->numa_q_map[node],
> +					   ring->max_nr_queues);
> +		if (err)
> +			return err;

Cleanup also missing here.

Cheers,
-- 
Luís

> +	}
> +	return 0;
> +}
> +
>  /*
>   * Basic ring setup for this connection based on the provided configuration
>   */
> @@ -231,6 +283,7 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc)
>  	size_t nr_queues = num_possible_cpus();
>  	struct fuse_ring *res = NULL;
>  	size_t max_payload_size;
> +	int err;
>  
>  	ring = kzalloc_obj(*fc->ring, GFP_KERNEL_ACCOUNT);
>  	if (!ring)
> @@ -241,9 +294,15 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc)
>  	if (!ring->queues)
>  		goto out_err;
>  
> +	ring->nr_numa_nodes = num_online_nodes();
> +
>  	max_payload_size = max(FUSE_MIN_READ_BUFFER, fc->max_write);
>  	max_payload_size = max(max_payload_size, fc->max_pages * PAGE_SIZE);
>  
> +	err = fuse_uring_create_q_masks(ring);
> +	if (err)
> +		goto out_err;
> +
>  	spin_lock(&fc->lock);
>  	if (fc->ring) {
>  		/* race, another thread created the ring in the meantime */
> @@ -263,6 +322,7 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc)
>  	return ring;
>  
>  out_err:
> +	fuse_uring_destruct_q_masks(ring);
>  	kfree(ring->queues);
>  	kfree(ring);
>  	return res;
> @@ -425,6 +485,7 @@ static void fuse_uring_log_ent_state(struct fuse_ring *ring)
>  			pr_info(" ent-commit-queue ring=%p qid=%d ent=%p state=%d\n",
>  				ring, qid, ent, ent->state);
>  		}
> +
>  		spin_unlock(&queue->lock);
>  	}
>  	ring->stop_debug_log = 1;
> @@ -471,6 +532,7 @@ static void fuse_uring_async_stop_queues(struct work_struct *work)
>  void fuse_uring_stop_queues(struct fuse_ring *ring)
>  {
>  	int qid;
> +	int node;
>  
>  	for (qid = 0; qid < ring->max_nr_queues; qid++) {
>  		struct fuse_ring_queue *queue = READ_ONCE(ring->queues[qid]);
> @@ -481,6 +543,13 @@ void fuse_uring_stop_queues(struct fuse_ring *ring)
>  		fuse_uring_teardown_entries(queue);
>  	}
>  
> +	/* Reset all queue masks, we won't process any more IO */
> +	cpumask_clear(ring->q_map.registered_q_mask);
> +	for (node = 0; node < ring->nr_numa_nodes; node++) {
> +		if (ring->numa_q_map)
> +			cpumask_clear(ring->numa_q_map[node].registered_q_mask);
> +	}
> +
>  	if (atomic_read(&ring->queue_refs) > 0) {
>  		ring->teardown_time = jiffies;
>  		INIT_DELAYED_WORK(&ring->async_teardown_work,
> @@ -988,6 +1057,10 @@ static void fuse_uring_do_register(struct fuse_ring_ent *ent,
>  	struct fuse_ring *ring = queue->ring;
>  	struct fuse_conn *fc = ring->fc;
>  	struct fuse_iqueue *fiq = &fc->iq;
> +	int node = cpu_to_node(queue->qid);
> +
> +	if (WARN_ON_ONCE(node >= ring->nr_numa_nodes))
> +		node = 0;
>  
>  	fuse_uring_prepare_cancel(cmd, issue_flags, ent);
>  
> diff --git a/fs/fuse/dev_uring_i.h b/fs/fuse/dev_uring_i.h
> index 708412294982566919122a1a0d7f741217c763ce..83506f431b97249c8f0c82f89f0fce41021288dd 100644
> --- a/fs/fuse/dev_uring_i.h
> +++ b/fs/fuse/dev_uring_i.h
> @@ -104,6 +104,17 @@ struct fuse_ring_queue {
>  	bool stopped;
>  };
>  
> +struct fuse_queue_map {
> +	/* Tracks which queues are registered */
> +	cpumask_var_t registered_q_mask;
> +
> +	/* number of registered queues */
> +	size_t nr_queues;
> +
> +	/* cpu to qid mapping */
> +	int *cpu_to_qid;
> +};
> +
>  /**
>   * Describes if uring is for communication and holds alls the data needed
>   * for uring communication
> @@ -115,6 +126,9 @@ struct fuse_ring {
>  	/* number of ring queues */
>  	size_t max_nr_queues;
>  
> +	/* number of numa nodes */
> +	int nr_numa_nodes;
> +
>  	/* maximum payload/arg size */
>  	size_t max_payload_sz;
>  
> @@ -125,6 +139,12 @@ struct fuse_ring {
>  	 */
>  	unsigned int stop_debug_log : 1;
>  
> +	/* per numa node queue tracking */
> +	struct fuse_queue_map *numa_q_map;
> +
> +	/* all queue tracking */
> +	struct fuse_queue_map q_map;
> +
>  	wait_queue_head_t stop_waitq;
>  
>  	/* async tear down */
>
> -- 
> 2.43.0
>
>