From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DAABC32771 for ; Wed, 22 Jan 2020 03:23:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 61EBE217F4 for ; Wed, 22 Jan 2020 03:23:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="WqqDeek7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729095AbgAVDXC (ORCPT ); Tue, 21 Jan 2020 22:23:02 -0500 Received: from mail-pl1-f195.google.com ([209.85.214.195]:38513 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728900AbgAVDXB (ORCPT ); Tue, 21 Jan 2020 22:23:01 -0500 Received: by mail-pl1-f195.google.com with SMTP id f20so2305924plj.5 for ; Tue, 21 Jan 2020 19:23:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=WzWlqSAwBUYEHp474vY25WNq5cVSn3o2GyR5izuQQ6I=; b=WqqDeek7IOETWuK4uyhivNNdGgPsGTJ+LQ4rSmigeF5wvVloRRnW12aj64MLBWr6jj /ESnNSbAnL/NKNkcNYKOUoj4VKBb/N2QWdU/ZQIHt89BWLB7lLagV1EMWo00XgtcP+Rm 0obLYR61L1gI1UB9v0WOJgixa+wrnRME/jorMM3AtfVfL1xLSVWLr5WUv4sbYuHwzKI0 5WOBxlpUzIWV2u26LJoUn/7WsbyEyY9HMt80MIOfexO/ibceakxxAGnNAoksNRFvmleF ndamVdEYFdkDsEoPm26uKMK8EC+AvcwbvKiuI3PfcsgEeHM7dxRWrk7K05HgZ5y18Nn0 CBWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=WzWlqSAwBUYEHp474vY25WNq5cVSn3o2GyR5izuQQ6I=; b=BCpVb3x384t2rX6KV3GBbn4tAhpmuVR25yNuXEA0IAHZRoGWcD2OqRN/hUGO44dOta mKe6sVxaC+H2Dcm2kAt0OlQnF3+iAMt55N3BAzj5BOPAU0geS+ZolFeoHNHIQaTTmBJG vuT2JgAE4mEEE+mvEN+CvZuolOMecE0ibb5ucFwK88nxsoDmVe1McrwmxaY2WWyKUcTP 7IWdb9RCJXxYK9jjNJPC1gBVpFq41Ehx486llBZ5Lp6m6R6FFk95g1lUE/6evuoo2ilm u7XdGdfIA0TmVUu0mrNF7ZPRiglxRB1ul1h54ErGjO4GlVJnwUWLLDp9s6jHUPGSDqo5 8uag== X-Gm-Message-State: APjAAAWLebshzA185Q7fv/LuYwLcKf2Y7TJ3W/o/EWRVQ3bbhPR3zg/i 74cuSlgHxiqWiCXzEIf0NxHraw== X-Google-Smtp-Source: APXvYqx45UJwpaZsGhTx3w8CdAdqEztpeY705Gedj+Y8kUrFvfcZfV4c4AtGUUhl24em2ZBh1jkXUw== X-Received: by 2002:a17:90b:8b:: with SMTP id bb11mr567939pjb.27.1579663381129; Tue, 21 Jan 2020 19:23:01 -0800 (PST) Received: from [192.168.1.188] ([66.219.217.145]) by smtp.gmail.com with ESMTPSA id w4sm830441pjt.23.2020.01.21.19.23.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Jan 2020 19:23:00 -0800 (PST) Subject: Re: [PATCH 3/3] io_uring: add splice(2) support To: Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Alexander Viro References: <8bfd9a57bf42cfc10ee7195969058d6da277deed.1579649589.git.asml.silence@gmail.com> <6d43b9d7-209a-2bbf-e2c2-e125e84b46ab@kernel.dk> <14499431-0409-5d57-9b08-aff95b9d2160@gmail.com> <578003e9-1af2-4df6-d9e1-cdbbbb701bf7@gmail.com> From: Jens Axboe Message-ID: <60459de4-3497-0226-127a-e748486852c6@kernel.dk> Date: Tue, 21 Jan 2020 20:22:58 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <578003e9-1af2-4df6-d9e1-cdbbbb701bf7@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 1/21/20 8:16 PM, Pavel Begunkov wrote: > On 22/01/2020 05:47, Jens Axboe wrote: >> On 1/21/20 7:40 PM, Pavel Begunkov wrote: >>>>> @@ -719,6 +730,11 @@ static const struct io_op_def io_op_defs[] = { >>>>> .needs_file = 1, >>>>> .fd_non_neg = 1, >>>>> }, >>>>> + [IORING_OP_SPLICE] = { >>>>> + .needs_file = 1, >>>>> + .hash_reg_file = 1, >>>>> + .unbound_nonreg_file = 1, >>>>> + } >>>>> }; >>>>> >>>>> static void io_wq_submit_work(struct io_wq_work **workptr); >>>> >>>> I probably want to queue up a reservation for the EPOLL_CTL that I >>>> haven't included yet, but which has been tested. But that's easily >>>> manageable, so no biggy on my end. >>> >>> I didn't quite get it. Do you mean collision of opcode numbers? >> >> Yeah that's all I meant, sorry wasn't too clear. But you can disregard, >> I'll just pop a reservation in front if/when this is ready to go in if >> it's before EPOLL_CTL op. >> >>>>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h >>>>> index 57d05cc5e271..f234b13e7ed3 100644 >>>>> --- a/include/uapi/linux/io_uring.h >>>>> +++ b/include/uapi/linux/io_uring.h >>>>> @@ -23,8 +23,14 @@ struct io_uring_sqe { >>>>> __u64 off; /* offset into file */ >>>>> __u64 addr2; >>>>> }; >>>>> - __u64 addr; /* pointer to buffer or iovecs */ >>>>> - __u32 len; /* buffer size or number of iovecs */ >>>>> + union { >>>>> + __u64 addr; /* pointer to buffer or iovecs */ >>>>> + __u64 off_out; >>>>> + }; >>>>> + union { >>>>> + __u32 len; /* buffer size or number of iovecs */ >>>>> + __s32 fd_out; >>>>> + }; >>>>> union { >>>>> __kernel_rwf_t rw_flags; >>>>> __u32 fsync_flags; >>>>> @@ -37,10 +43,12 @@ struct io_uring_sqe { >>>>> __u32 open_flags; >>>>> __u32 statx_flags; >>>>> __u32 fadvise_advice; >>>>> + __u32 splice_flags; >>>>> }; >>>>> __u64 user_data; /* data to be passed back at completion time */ >>>>> union { >>>>> __u16 buf_index; /* index into fixed buffers, if used */ >>>>> + __u64 splice_len; >>>>> __u64 __pad2[3]; >>>>> }; >>>>> }; >>>> >>>> Not a huge fan of this, also mean splice can't ever used fixed buffers. >>>> Hmm... >>> >>> But it's not like splice() ever uses user buffers. Isn't it? vmsplice >>> does, but that's another opcode. >> >> I guess that's true, I had vmsplice on my mind for this as well. But >> won't be a problem there, since it doesn't take 6 arguments like splice >> does. >> >> Another option is to do an indirect for splice, stuff the arguments in a >> struct that's passed in as a pointer in ->addr. A bit slower, but >> probably not a huge deal. >> >>>>> @@ -67,6 +75,9 @@ enum { >>>>> /* always go async */ >>>>> #define IOSQE_ASYNC (1U << IOSQE_ASYNC_BIT) >>>>> >>>>> +/* op custom flags */ >>>>> +#define IOSQE_SPLICE_FIXED_OUT (1U << 16) >>>>> + >>>> >>>> I don't think it's unreasonable to say that if you specify >>>> IOSQE_FIXED_FILE, then both are fixed. If not, then none of them are. >>>> What do you think? >>>> >>> >>> It's plausible to register only one end for splicing, e.g. splice from >>> short-lived sockets to pre-registered buffers-pipes. And it's clearer >>> do it now. >> >> You're probably right, though it's a bit nasty to add an unrelated flag >> in the splice flag space... We should probably reserve it in splice >> instead, and just not have it available from the regular system call. >> > Agree, it looks bad. I don't want to add it into sqe->splice_flags to > not clash with splice(2) in the future, but could have a separate > field in @sqe... or can leave in in sqe->flags, as it's done in the > patch, but that's like a portion of bits would be opcode specific and > we would need to set rules for their use. It won't clash with splice(2), just make that flag illegal if done through splice(2) directly. Honestly I think that's (by FAR) the best way to do it, having a private io_uring flag that acts as a splice flag is really confusing and prone to breakage. Not that it's a huge issue with splice as the flags have been stable for years, so don't really see a high risk of collision. But we should still do it right, which means adding SPLICE_F_OUT_FIXED or whatever you want to call it. Do that as a prep patch, make do_splice() into __do_splice(), and have io_uring call __do_splice(). Currently splice(2) is permissive in terms of flags, so maybe just mask it in do_splice() to be on the safe side. Then we know only internal users will set SPLICE_F_OUT_FIXED, and we'll never run into the risk of having a collision as it's part of the flag space anyway. The sqe->flags space is very tight, so adding a splice specific opcode there would be bad. -- Jens Axboe