Re: [PATCH 10/18] io_uring: batch io_kiocb allocation

[Christoph Hellwig <hch@lst.de>]

> -static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx)
> +static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
> +				   struct io_submit_state *state)
>  {
> +	gfp_t gfp = GFP_ATOMIC | __GFP_NOWARN;

No actually in this patch, but why do we do GFP_ATOMIC allocations
here?  We aren't in irq context or under a spinlock.

> +	if (!state)
> +		req = kmem_cache_alloc(req_cachep, gfp);

Add a
		if (!req)
			goto out;

plus the missing braces here..

> +	else if (!state->free_reqs) {
> +		size_t sz;
> +		int ret;
> +
> +		sz = min_t(size_t, state->ios_left, ARRAY_SIZE(state->reqs));
> +		ret = kmem_cache_alloc_bulk(req_cachep, gfp, sz,
> +						state->reqs);
> +		if (ret <= 0)
> +			goto out;
> +		state->free_reqs = ret - 1;
> +		state->cur_req = 1;
> +		req = state->reqs[0];
> +	} else {
> +		req = state->reqs[state->cur_req];
> +		state->free_reqs--;
> +		state->cur_req++;
> +	}
> +
>  	if (req) {
>  		req->ctx = ctx;
>  		req->flags = 0;
>  		return req;
>  	}

... and we don't need this conditional, which would otherwise also
be in the fast path.