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From: Jonathan Corbet <corbet@lwn.net>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>,
 io-uring@vger.kernel.org
Cc: Caleb Sander Mateos <csander@purestorage.com>, Akilesh Kailash
 <akailash@google.com>, bpf@vger.kernel.org, Alexei Starovoitov
 <ast@kernel.org>, Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH 3/5] io_uring: bpf: extend io_uring with bpf struct_ops
In-Reply-To: <20251104162123.1086035-4-ming.lei@redhat.com>
References: <20251104162123.1086035-1-ming.lei@redhat.com>
 <20251104162123.1086035-4-ming.lei@redhat.com>
Date: Wed, 19 Nov 2025 07:39:12 -0700
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Ming Lei <ming.lei@redhat.com> writes:

> io_uring can be extended with bpf struct_ops in the following ways:

So I have a probably dumb question I ran into as I tried to figure this
stuff out.  You define this maximum here...

> +#define MAX_BPF_OPS_COUNT	(1 << IORING_BPF_OP_BITS)

...which sizes the bpf_ops array:

> +static struct uring_bpf_ops bpf_ops[MAX_BPF_OPS_COUNT];

Later, you do registration here:

> +static int io_bpf_reg_unreg(struct uring_bpf_ops *ops, bool reg)
> +{
> +	struct io_ring_ctx *ctx;
> +	int ret = 0;
> +
> +	guard(mutex)(&uring_bpf_ctx_lock);
> +	list_for_each_entry(ctx, &uring_bpf_ctx_list, bpf_node)
> +		mutex_lock(&ctx->uring_lock);
> +
> +	if (reg) {
> +		if (bpf_ops[ops->id].issue_fn)
> +			ret = -EBUSY;
> +		else
> +			bpf_ops[ops->id] = *ops;
> +	} else {
> +		bpf_ops[ops->id] = (struct uring_bpf_ops) {0};
> +	}
> +
> +	synchronize_srcu(&uring_bpf_srcu);
> +
> +	list_for_each_entry(ctx, &uring_bpf_ctx_list, bpf_node)
> +		mutex_unlock(&ctx->uring_lock);
> +
> +	return ret;
> +}

Nowhere do I find a test ensuring that ops->id is within range;
MAX_BPF_OPS_COUNT never appears in a test.  What am I missing?

Thanks,

jon