Re: [PATCH v2 3/7] fuse: {io-uring} Use bitmaps to track registered queues

[Luis Henriques <luis@igalia.com>]

On Fri, Oct 03 2025, Bernd Schubert wrote:

> 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   | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/fuse/dev_uring_i.h |  9 +++++++++
>  2 files changed, 63 insertions(+)
>
> diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
> index 0f5ab27dacb66c9f5f10eac2713d9bd3eb4c26da..dacc07f5b5b1a48acefa278279f851c3ae2b1489 100644
> --- a/fs/fuse/dev_uring.c
> +++ b/fs/fuse/dev_uring.c
> @@ -18,6 +18,8 @@ MODULE_PARM_DESC(enable_uring,
>  
>  #define FUSE_URING_IOV_SEGS 2 /* header and payload */
>  
> +/* Number of queued fuse requests until a queue is considered full */
> +#define FUSE_URING_QUEUE_THRESHOLD 5

Nit: I guess this hunk can be removed from this patch as this constant is
never used and is removed in the next patch.

Cheers,
-- 
Luís

>  bool fuse_uring_enabled(void)
>  {
> @@ -184,6 +186,18 @@ bool fuse_uring_request_expired(struct fuse_conn *fc)
>  	return false;
>  }
>  
> +static void fuse_ring_destruct_q_masks(struct fuse_ring *ring)
> +{
> +	int node;
> +
> +	free_cpumask_var(ring->registered_q_mask);
> +	if (ring->numa_registered_q_mask) {
> +		for (node = 0; node < ring->nr_numa_nodes; node++)
> +			free_cpumask_var(ring->numa_registered_q_mask[node]);
> +		kfree(ring->numa_registered_q_mask);
> +	}
> +}
> +
>  void fuse_uring_destruct(struct fuse_conn *fc)
>  {
>  	struct fuse_ring *ring = fc->ring;
> @@ -215,11 +229,32 @@ void fuse_uring_destruct(struct fuse_conn *fc)
>  		ring->queues[qid] = NULL;
>  	}
>  
> +	fuse_ring_destruct_q_masks(ring);
>  	kfree(ring->queues);
>  	kfree(ring);
>  	fc->ring = NULL;
>  }
>  
> +static int fuse_ring_create_q_masks(struct fuse_ring *ring)
> +{
> +	int node;
> +
> +	if (!zalloc_cpumask_var(&ring->registered_q_mask, GFP_KERNEL_ACCOUNT))
> +		return -ENOMEM;
> +
> +	ring->numa_registered_q_mask = kcalloc(
> +		ring->nr_numa_nodes, sizeof(cpumask_var_t), GFP_KERNEL_ACCOUNT);
> +	if (!ring->numa_registered_q_mask)
> +		return -ENOMEM;
> +	for (node = 0; node < ring->nr_numa_nodes; node++) {
> +		if (!zalloc_cpumask_var(&ring->numa_registered_q_mask[node],
> +					GFP_KERNEL_ACCOUNT))
> +			return -ENOMEM;
> +	}
> +
> +	return 0;
> +}
> +
>  /*
>   * Basic ring setup for this connection based on the provided configuration
>   */
> @@ -229,11 +264,14 @@ 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(sizeof(*fc->ring), GFP_KERNEL_ACCOUNT);
>  	if (!ring)
>  		return NULL;
>  
> +	ring->nr_numa_nodes = num_online_nodes();
> +
>  	ring->queues = kcalloc(nr_queues, sizeof(struct fuse_ring_queue *),
>  			       GFP_KERNEL_ACCOUNT);
>  	if (!ring->queues)
> @@ -242,6 +280,10 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc)
>  	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_ring_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 */
> @@ -261,6 +303,7 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc)
>  	return ring;
>  
>  out_err:
> +	fuse_ring_destruct_q_masks(ring);
>  	kfree(ring->queues);
>  	kfree(ring);
>  	return res;
> @@ -423,6 +466,7 @@ 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;
> @@ -469,6 +513,7 @@ 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]);
> @@ -479,6 +524,11 @@ 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->registered_q_mask);
> +	for (node = 0; node < ring->nr_numa_nodes; node++)
> +		cpumask_clear(ring->numa_registered_q_mask[node]);
> +
>  	if (atomic_read(&ring->queue_refs) > 0) {
>  		ring->teardown_time = jiffies;
>  		INIT_DELAYED_WORK(&ring->async_teardown_work,
> @@ -982,6 +1032,7 @@ 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);
>  
>  	fuse_uring_prepare_cancel(cmd, issue_flags, ent);
>  
> @@ -990,6 +1041,9 @@ static void fuse_uring_do_register(struct fuse_ring_ent *ent,
>  	fuse_uring_ent_avail(ent, queue);
>  	spin_unlock(&queue->lock);
>  
> +	cpumask_set_cpu(queue->qid, ring->registered_q_mask);
> +	cpumask_set_cpu(queue->qid, ring->numa_registered_q_mask[node]);
> +
>  	if (!ring->ready) {
>  		bool ready = is_ring_ready(ring, queue->qid);
>  
> diff --git a/fs/fuse/dev_uring_i.h b/fs/fuse/dev_uring_i.h
> index 708412294982566919122a1a0d7f741217c763ce..35e3b6808b60398848965afd3091b765444283ff 100644
> --- a/fs/fuse/dev_uring_i.h
> +++ b/fs/fuse/dev_uring_i.h
> @@ -115,6 +115,9 @@ 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 +128,12 @@ struct fuse_ring {
>  	 */
>  	unsigned int stop_debug_log : 1;
>  
> +	/* Tracks which queues are registered */
> +	cpumask_var_t registered_q_mask;
> +
> +	/* Tracks which queues are registered per NUMA node */
> +	cpumask_var_t *numa_registered_q_mask;
> +
>  	wait_queue_head_t stop_waitq;
>  
>  	/* async tear down */
>
> -- 
> 2.43.0
>
>