Re: [PATCH v2 5/7] fuse: {io-uring} Allow reduced number of ring queues

[Bernd Schubert <bschubert@ddn.com>]

On 10/3/25 12:06, Bernd Schubert wrote:
> Queues selection (fuse_uring_get_queue) can handle reduced number
> queues - using io-uring is possible now even with a single
> queue and entry.
> 
> Signed-off-by: Bernd Schubert <bschubert@ddn.com>
> ---
>  fs/fuse/dev_uring.c | 35 +++--------------------------------
>  1 file changed, 3 insertions(+), 32 deletions(-)
> 
> diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
> index bb5d7a98536963ec2e4c10982d33633db2573f4d..f5946bb1bbea930522921d49c04e047c70d21ee2 100644
> --- a/fs/fuse/dev_uring.c
> +++ b/fs/fuse/dev_uring.c
> @@ -998,31 +998,6 @@ static int fuse_uring_commit_fetch(struct io_uring_cmd *cmd, int issue_flags,
>  	return 0;
>  }
>  
> -static bool is_ring_ready(struct fuse_ring *ring, int current_qid)
> -{
> -	int qid;
> -	struct fuse_ring_queue *queue;
> -	bool ready = true;
> -
> -	for (qid = 0; qid < ring->max_nr_queues && ready; qid++) {
> -		if (current_qid == qid)
> -			continue;
> -
> -		queue = ring->queues[qid];
> -		if (!queue) {
> -			ready = false;
> -			break;
> -		}
> -
> -		spin_lock(&queue->lock);
> -		if (list_empty(&queue->ent_avail_queue))
> -			ready = false;
> -		spin_unlock(&queue->lock);
> -	}
> -
> -	return ready;
> -}
> -
>  /*
>   * fuse_uring_req_fetch command handling
>   */
> @@ -1047,13 +1022,9 @@ static void fuse_uring_do_register(struct fuse_ring_ent *ent,
>  	cpumask_set_cpu(queue->qid, ring->numa_registered_q_mask[node]);
>  
>  	if (!ring->ready) {
> -		bool ready = is_ring_ready(ring, queue->qid);
> -
> -		if (ready) {
> -			WRITE_ONCE(fiq->ops, &fuse_io_uring_ops);
> -			WRITE_ONCE(ring->ready, true);
> -			wake_up_all(&fc->blocked_waitq);
> -		}
> +		WRITE_ONCE(fiq->ops, &fuse_io_uring_ops);
> +		WRITE_ONCE(ring->ready, true);
> +		wake_up_all(&fc->blocked_waitq);
>  	}
>  }
>  
> 

We actually need to add a FUSE_INIT flag, fuse-server needs
to know when it can reduce the number of queues. If fuse-server
would do a lower number of queues unconditionally, the mount
point will hang after FUSE_INIT.


Thanks,
Bernd