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From: Andres Freund <[email protected]>
To: Jens Axboe <[email protected]>
Cc: [email protected]
Subject: Re: [PATCH 2/6] io_uring: add IORING_OP_PROVIDE_BUFFERS
Date: Mon, 9 Mar 2020 10:03:13 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

Hi,

I like this feature quite a bit...

Sorry for the late response.


On 2020-02-28 13:30:49 -0700, Jens Axboe wrote:
> +static int io_provide_buffers_prep(struct io_kiocb *req,
> +				   const struct io_uring_sqe *sqe)
> +{
> +	struct io_provide_buf *p = &req->pbuf;
> +	u64 tmp;
> +
> +	if (sqe->ioprio || sqe->rw_flags)
> +		return -EINVAL;
> +
> +	tmp = READ_ONCE(sqe->fd);
> +	if (!tmp || tmp > USHRT_MAX)
> +		return -EINVAL;

Hm, seems like it'd be less confusing if this didn't use
io_uring_sqe->fd, but a separate union member?


> +	p->nbufs = tmp;
> +	p->addr = READ_ONCE(sqe->addr);
> +	p->len = READ_ONCE(sqe->len);
> +
> +	if (!access_ok(u64_to_user_ptr(p->addr), p->len))
> +		return -EFAULT;
> +
> +	p->gid = READ_ONCE(sqe->buf_group);
> +	tmp = READ_ONCE(sqe->off);
> +	if (tmp > USHRT_MAX)
> +		return -EINVAL;

Would it make sense to return a distinct error for the >= USHRT_MAX
cases? E2BIG or something roughly in that direction? Seems good to be
able to recognizably refuse "large" buffer group ids.


> +static int io_add_buffers(struct io_provide_buf *pbuf, struct list_head *list)
> +{
> +	struct io_buffer *buf;
> +	u64 addr = pbuf->addr;
> +	int i, bid = pbuf->bid;
> +
> +	for (i = 0; i < pbuf->nbufs; i++) {
> +		buf = kmalloc(sizeof(*buf), GFP_KERNEL);
> +		if (!buf)
> +			break;
> +
> +		buf->addr = addr;
> +		buf->len = pbuf->len;
> +		buf->bid = bid;
> +		list_add(&buf->list, list);
> +		addr += pbuf->len;
> +		bid++;
> +	}
> +
> +	return i;
> +}

Hm, aren't you loosing an error here if you kmalloc fails for i > 0?
Afaict io_provide_buffes() only checks for ret != 0. I think userland
should know that a PROVIDE_BUFFERS failed, even if just partially (I'd
just make it fail wholesale).


> +static int io_provide_buffers(struct io_kiocb *req, struct io_kiocb **nxt,
> +			      bool force_nonblock)
> +{
> +	struct io_provide_buf *p = &req->pbuf;
> +	struct io_ring_ctx *ctx = req->ctx;
> +	struct list_head *list;
> +	int ret = 0;

> +	list = idr_find(&ctx->io_buffer_idr, p->gid);

I'd rename gid to bgid or such to distinguish from other types of group
ids, but whatever.


Greetings,

Andres Freund

  parent reply	other threads:[~2020-03-09 17:03 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-28 20:30 [PATCHSET v3] io_uring support for automatic buffers Jens Axboe
2020-02-28 20:30 ` [PATCH 1/6] io_uring: buffer registration infrastructure Jens Axboe
2020-02-28 20:30 ` [PATCH 2/6] io_uring: add IORING_OP_PROVIDE_BUFFERS Jens Axboe
2020-02-29  0:43   ` Pavel Begunkov
2020-02-29  4:50     ` Jens Axboe
2020-02-29 11:36       ` Pavel Begunkov
2020-02-29 17:32         ` Jens Axboe
2020-02-29 12:08   ` Pavel Begunkov
2020-02-29 17:34     ` Jens Axboe
2020-02-29 18:11       ` Jens Axboe
2020-03-09 17:03   ` Andres Freund [this message]
2020-03-09 17:17     ` Jens Axboe
2020-03-09 17:28       ` Andres Freund
2020-03-10 13:33         ` Jens Axboe
2020-02-28 20:30 ` [PATCH 3/6] io_uring: support buffer selection Jens Axboe
2020-02-29 12:21   ` Pavel Begunkov
2020-02-29 17:35     ` Jens Axboe
2020-03-09 17:21   ` Andres Freund
2020-03-10 13:37     ` Jens Axboe
2020-02-28 20:30 ` [PATCH 4/6] io_uring: add IOSQE_BUFFER_SELECT support for IORING_OP_READV Jens Axboe
2020-02-28 20:30 ` [PATCH 5/6] net: abstract out normal and compat msghdr import Jens Axboe
2020-02-28 20:30 ` [PATCH 6/6] io_uring: add IOSQE_BUFFER_SELECT support for IORING_OP_RECVMSG Jens Axboe

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