Re: IORING_SEND_NOTIF_REPORT_USAGE (was Re: IORING_CQE_F_COPIED)

[Pavel Begunkov <asml.silence@gmail.com>]

On 10/21/22 15:03, Stefan Metzmacher wrote:
> Am 21.10.22 um 13:09 schrieb Pavel Begunkov:
>> On 10/21/22 10:36, Stefan Metzmacher wrote:
>>> Hi Pavel,
>> [...]
>>>> Right, I'm just tired of back porting patches by hand :)
>>>
>>> ok, I just assumed it would be 6.1 only.
>>
>> I'm fine with 6.1 only, it'd make things easier. I thought from
>> your first postings you wanted it 6.0. Then we don't need to care
>> about the placing of the copied/used flags.
>>
>>>>> Otherwise we could have IORING_CQE_F_COPIED by default without opt-in
>>>>> flag...
>>>
>>> Do you still want an opt-in flag to get IORING_CQE_F_COPIED?
>>> If so what name do you want it to be?
>>
>> Ala a IORING_SEND_* flag? Yes please.
>>
>> *_REPORT_USAGE was fine but I'd make it IORING_SEND_ZC_REPORT_USAGE.
>> And can be extended if there is more info needed in the future.
>>
>> And I don't mind using a bit in cqe->res, makes cflags less polluted.
> 
> So no worries about the delayed/skip sendmsg completion anymore?

I'll just make it incompatible the reporting.

> Should I define it like this, ok?
> 
> #define IORING_NOTIF_USAGE_ZC_COPIED    (1U << 31)
> 
> See the full patch below...

Looks good


> metze
> 
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index d69ae7eba773..32e1f2a55b70 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -296,10 +296,24 @@ enum io_uring_op {
>    *
>    * IORING_RECVSEND_FIXED_BUF    Use registered buffers, the index is stored in
>    *                the buf_index field.
> +
> + * IORING_SEND_NOTIF_REPORT_USAGE
> + *                If SEND[MSG]_ZC should report
> + *                the zerocopy usage in cqe.res
> + *                for the IORING_CQE_F_NOTIF cqe.
> + *                IORING_NOTIF_USAGE_ZC_COPIED if data was copied
> + *                (at least partially).
>    */
>   #define IORING_RECVSEND_POLL_FIRST    (1U << 0)
>   #define IORING_RECV_MULTISHOT        (1U << 1)
>   #define IORING_RECVSEND_FIXED_BUF    (1U << 2)
> +#define IORING_SEND_ZC_REPORT_USAGE    (1U << 3)
> +
> +/*
> + * cqe.res for IORING_CQE_F_NOTIF if
> + * IORING_SEND_ZC_REPORT_USAGE was requested
> + */
> +#define IORING_NOTIF_USAGE_ZC_COPIED    (1U << 31)
> 
>   /*
>    * accept flags stored in sqe->ioprio
> diff --git a/io_uring/net.c b/io_uring/net.c
> index 56078f47efe7..1aa3b50b3e82 100644
> --- a/io_uring/net.c
> +++ b/io_uring/net.c
> @@ -939,7 +939,8 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> 
>       zc->flags = READ_ONCE(sqe->ioprio);
>       if (zc->flags & ~(IORING_RECVSEND_POLL_FIRST |
> -              IORING_RECVSEND_FIXED_BUF))
> +              IORING_RECVSEND_FIXED_BUF |
> +              IORING_SEND_ZC_REPORT_USAGE))
>           return -EINVAL;
>       notif = zc->notif = io_alloc_notif(ctx);
>       if (!notif)
> @@ -957,6 +958,9 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>           req->imu = READ_ONCE(ctx->user_bufs[idx]);
>           io_req_set_rsrc_node(notif, ctx, 0);
>       }
> +    if (zc->flags & IORING_SEND_ZC_REPORT_USAGE) {
> +        io_notif_to_data(notif)->zc_report = true;
> +    }
> 
>       if (req->opcode == IORING_OP_SEND_ZC) {
>           if (READ_ONCE(sqe->__pad3[0]))
> diff --git a/io_uring/notif.c b/io_uring/notif.c
> index e37c6569d82e..4bfef10161fa 100644
> --- a/io_uring/notif.c
> +++ b/io_uring/notif.c
> @@ -18,6 +18,10 @@ static void __io_notif_complete_tw(struct io_kiocb *notif, bool *locked)
>           __io_unaccount_mem(ctx->user, nd->account_pages);
>           nd->account_pages = 0;
>       }
> +
> +    if (nd->zc_report && (nd->zc_copied || !nd->zc_used))
> +        notif->cqe.res |= IORING_NOTIF_USAGE_ZC_COPIED;
> +
>       io_req_task_complete(notif, locked);
>   }
> 
> @@ -28,6 +32,13 @@ static void io_uring_tx_zerocopy_callback(struct sk_buff *skb,
>       struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg);
>       struct io_kiocb *notif = cmd_to_io_kiocb(nd);
> 
> +    if (nd->zc_report) {
> +        if (success && !nd->zc_used && skb)
> +            WRITE_ONCE(nd->zc_used, true);
> +        else if (!success && !nd->zc_copied)
> +            WRITE_ONCE(nd->zc_copied, true);
> +    }
> +
>       if (refcount_dec_and_test(&uarg->refcnt)) {
>           notif->io_task_work.func = __io_notif_complete_tw;
>           io_req_task_work_add(notif);
> @@ -55,6 +66,7 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
>       nd->account_pages = 0;
>       nd->uarg.flags = SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN;
>       nd->uarg.callback = io_uring_tx_zerocopy_callback;
> +    nd->zc_report = nd->zc_used = nd->zc_copied = false;
>       refcount_set(&nd->uarg.refcnt, 1);
>       return notif;
>   }
> diff --git a/io_uring/notif.h b/io_uring/notif.h
> index e4fbcae0f3fd..6be2e5ae8581 100644
> --- a/io_uring/notif.h
> +++ b/io_uring/notif.h
> @@ -15,6 +15,9 @@ struct io_notif_data {
>       struct file        *file;
>       struct ubuf_info    uarg;
>       unsigned long        account_pages;
> +    bool            zc_report;
> +    bool            zc_used;
> +    bool            zc_copied;
>   };
> 
>   void io_notif_flush(struct io_kiocb *notif);
> 

-- 
Pavel Begunkov