netdev - Re: [PATCH v6 10/15] io_uring/zcrx: add io_zcrx

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Message-ID: <433d21ff-6d7f-4123-8b11-c5d3c9a9deb1@gmail.com>
Date: Mon, 21 Oct 2024 17:28:42 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Jens Axboe <axboe@...nel.dk>, David Wei <dw@...idwei.uk>,
 io-uring@...r.kernel.org, netdev@...r.kernel.org
Cc: Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>, David Ahern <dsahern@...nel.org>,
 Mina Almasry <almasrymina@...gle.com>,
 Stanislav Fomichev <stfomichev@...il.com>, Joe Damato <jdamato@...tly.com>,
 Pedro Tammela <pctammela@...atatu.com>
Subject: Re: [PATCH v6 10/15] io_uring/zcrx: add io_zcrx_area

On 10/21/24 16:35, Jens Axboe wrote:
> On 10/16/24 12:52 PM, David Wei wrote:
>> +static int io_zcrx_create_area(struct io_ring_ctx *ctx,
>> +			       struct io_zcrx_ifq *ifq,
>> +			       struct io_zcrx_area **res,
>> +			       struct io_uring_zcrx_area_reg *area_reg)
>> +{
>> +	struct io_zcrx_area *area;
>> +	int i, ret, nr_pages;
>> +	struct iovec iov;
>> +
>> +	if (area_reg->flags || area_reg->rq_area_token)
>> +		return -EINVAL;
>> +	if (area_reg->__resv1 || area_reg->__resv2[0] || area_reg->__resv2[1])
>> +		return -EINVAL;
>> +	if (area_reg->addr & ~PAGE_MASK || area_reg->len & ~PAGE_MASK)
>> +		return -EINVAL;
>> +
>> +	iov.iov_base = u64_to_user_ptr(area_reg->addr);
>> +	iov.iov_len = area_reg->len;
>> +	ret = io_buffer_validate(&iov);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = -ENOMEM;
>> +	area = kzalloc(sizeof(*area), GFP_KERNEL);
>> +	if (!area)
>> +		goto err;
>> +
>> +	area->pages = io_pin_pages((unsigned long)area_reg->addr, area_reg->len,
>> +				   &nr_pages);
>> +	if (IS_ERR(area->pages)) {
>> +		ret = PTR_ERR(area->pages);
>> +		area->pages = NULL;
>> +		goto err;
>> +	}
>> +	area->nia.num_niovs = nr_pages;
>> +
>> +	area->nia.niovs = kvmalloc_array(nr_pages, sizeof(area->nia.niovs[0]),
>> +					 GFP_KERNEL | __GFP_ZERO);
>> +	if (!area->nia.niovs)
>> +		goto err;
>> +
>> +	area->freelist = kvmalloc_array(nr_pages, sizeof(area->freelist[0]),
>> +					GFP_KERNEL | __GFP_ZERO);
>> +	if (!area->freelist)
>> +		goto err;
>> +
>> +	for (i = 0; i < nr_pages; i++) {
>> +		area->freelist[i] = i;
>> +	}
>> +
>> +	area->free_count = nr_pages;
>> +	area->ifq = ifq;
>> +	/* we're only supporting one area per ifq for now */
>> +	area->area_id = 0;
>> +	area_reg->rq_area_token = (u64)area->area_id << IORING_ZCRX_AREA_SHIFT;
>> +	spin_lock_init(&area->freelist_lock);
>> +	*res = area;
>> +	return 0;
>> +err:
>> +	if (area)
>> +		io_zcrx_free_area(area);
>> +	return ret;
>> +}
> 
> Minor nit, but I think this would be nicer returning area and just using
> ERR_PTR() for the errors.

I'd rather avoid it. Too often null vs IS_ERR checking gets
messed up down the road and the compiler doesn't help with it
at all.

Not related to the patch, but would be nice to have a type safer
way for that, e.g. returning some new type not directly
cast'able to the pointer.

> 
> Outside of that:
> 
> Reviewed-by: Jens Axboe <axboe@...nel.dk>
> 

-- 
Pavel Begunkov