From patchwork Tue Nov 30 15:18:53 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Begunkov X-Patchwork-Id: 12647595 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8FEB1C433FE for ; Tue, 30 Nov 2021 15:21:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239105AbhK3PYU (ORCPT ); Tue, 30 Nov 2021 10:24:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38532 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245058AbhK3PX1 (ORCPT ); Tue, 30 Nov 2021 10:23:27 -0500 Received: from mail-wr1-x435.google.com (mail-wr1-x435.google.com [IPv6:2a00:1450:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2904C061D62; Tue, 30 Nov 2021 07:19:25 -0800 (PST) Received: by mail-wr1-x435.google.com with SMTP id q3so22359826wru.5; Tue, 30 Nov 2021 07:19:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=OWPM4MjNj1xp6zI+XrQjzvvSmIGxLADJ0APTs0vw/kI=; b=CaPxPEyCe1kuXXrewNdN8vBO3EvThtstOp5TGI+D1wPozl5U5v1lLNrgxWIO4HDVJk ZbfWXNGMnU7w5/FdPooS7tvzLyQvemqC6/29nMG0Oqf00LBct2FMWOvubXLes8Z80s4p IMvcVylXTbYRpnLGR7sf37igl+PgUO8LjdhfL+b6H1hRWGRdum2lnhWXskwnnRE5hksH qIm01YV9LhuU79e2rW6Lnk5GCDZmHo7xCosxr0E3tiyP/td5vqBorwD8YEX4jt7Qg7Pd SzCUp7WgRTSQBw6ekQ6yUxTasPi7MQ8OB0Q6BKtojvOT/JhRJd2bvi0iZ85zi8BlJvyU 9cPA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=OWPM4MjNj1xp6zI+XrQjzvvSmIGxLADJ0APTs0vw/kI=; b=x6SdiOkK6AJQKNkcniNtkOB/yomqXRpY/oLhb3bpqf9Euu/ZhG3JRAsEvauPrQoZUk 0keocMorbPBDbjhJRmUtfDe3WRmV3nuw5fRNy0DM35JxAqTGDS3QNuRokGEuIOMaozix Ygvf9lwERVqktASvBzZFzFGg+6aBc7O9mzPwlLUJaEvf2tWpVnTWp2uYi1bIr7zDg2Y3 MBqOya9CmpLwsyGGlj71tBfZ7FdLs80N8wEFUvR6e1iL0Ye+Gq1nLrlbLU7tkA9scHc/ 9Hm+OMxYbCm4VWfDKTrR3oBFoZiYUJa9cunWQT7f0Y/KQ9H2D7BI5Ju+akZbZEsQDZyc vu3Q== X-Gm-Message-State: AOAM533KpXYcnEbYuzfTow6nD5GynNVD/zIbcYx1x8j9DMYX18srOAdQ P1mQzXigOBTCbrIgfSQoXWtPxd/CWU4= X-Google-Smtp-Source: ABdhPJy+Tx1Ecnf83DrM4/PPgQ5HjYrcJGhemiadOImgqh0svuzJuhLdmncnX+MNa77ew358K1GU3w== X-Received: by 2002:a05:6000:373:: with SMTP id f19mr40529601wrf.311.1638285564137; Tue, 30 Nov 2021 07:19:24 -0800 (PST) Received: from 127.0.0.1localhost ([85.255.232.109]) by smtp.gmail.com with ESMTPSA id d1sm16168483wrz.92.2021.11.30.07.19.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Nov 2021 07:19:23 -0800 (PST) From: Pavel Begunkov To: io-uring@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Jakub Kicinski , Jonathan Lemon , "David S . Miller" , Willem de Bruijn , Eric Dumazet , Hideaki YOSHIFUJI , David Ahern , Jens Axboe , Pavel Begunkov Subject: [RFC 05/12] net: optimise page get/free for bvec zc Date: Tue, 30 Nov 2021 15:18:53 +0000 Message-Id: <72608c13553a1372e7f6f7a32eb53d5d4b23a1fc.1638282789.git.asml.silence@gmail.com> X-Mailer: git-send-email 2.34.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC get_page() in __zerocopy_sg_from_bvec() and matching put_page()s are expensive. However, we can avoid it if the caller can guarantee that pages stay alive until the corresponding ubuf_info is not released. In particular, it targets io_uring with fixed buffers following the described contract. Assuming that nobody yet uses bvec together with zerocopy, make all calls with bvec iterators follow this model. Signed-off-by: Pavel Begunkov --- include/linux/skbuff.h | 10 +++++++++- net/core/datagram.c | 9 +++++++-- net/core/skbuff.c | 16 +++++++++++++--- net/ipv4/ip_output.c | 4 ++++ 4 files changed, 33 insertions(+), 6 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 750b7518d6e2..ebb12a7d386d 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -461,6 +461,11 @@ enum { SKBFL_PURE_ZEROCOPY = BIT(2), SKBFL_DONT_ORPHAN = BIT(3), + + /* page references are managed by the ubuf_info, so it's safe to + * use frags only up until ubuf_info is released + */ + SKBFL_MANAGED_FRAGS = BIT(4), }; #define SKBFL_ZEROCOPY_FRAG (SKBFL_ZEROCOPY_ENABLE | SKBFL_SHARED_FRAG) @@ -3154,7 +3159,10 @@ static inline void __skb_frag_unref(skb_frag_t *frag, bool recycle) */ static inline void skb_frag_unref(struct sk_buff *skb, int f) { - __skb_frag_unref(&skb_shinfo(skb)->frags[f], skb->pp_recycle); + struct skb_shared_info *shinfo = skb_shinfo(skb); + + if (!(shinfo->flags & SKBFL_MANAGED_FRAGS)) + __skb_frag_unref(&shinfo->frags[f], skb->pp_recycle); } /** diff --git a/net/core/datagram.c b/net/core/datagram.c index e00f7e0a7a0a..5cf0672039d6 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -642,7 +642,6 @@ static int __zerocopy_sg_from_bvec(struct sock *sk, struct sk_buff *skb, v = mp_bvec_iter_bvec(from->bvec, bi); copied += v.bv_len; truesize += PAGE_ALIGN(v.bv_len + v.bv_offset); - get_page(v.bv_page); skb_fill_page_desc(skb, frag++, v.bv_page, v.bv_offset, v.bv_len); bvec_iter_advance_single(from->bvec, &bi, v.bv_len); } @@ -671,9 +670,15 @@ int __zerocopy_sg_from_iter(struct sock *sk, struct sk_buff *skb, struct iov_iter *from, size_t length) { int frag = skb_shinfo(skb)->nr_frags; + bool managed = skb_shinfo(skb)->flags & SKBFL_MANAGED_FRAGS; - if (iov_iter_is_bvec(from)) + if (iov_iter_is_bvec(from) && (managed || frag == 0)) { + skb_shinfo(skb)->flags |= SKBFL_MANAGED_FRAGS; return __zerocopy_sg_from_bvec(sk, skb, from, length); + } + + if (managed) + return -EFAULT; while (length && iov_iter_count(from)) { struct page *pages[MAX_SKB_FRAGS]; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index b23db60ea6f9..b7b087815539 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -666,10 +666,14 @@ static void skb_release_data(struct sk_buff *skb) &shinfo->dataref)) goto exit; - skb_zcopy_clear(skb, true); + if (!(shinfo->flags & SKBFL_MANAGED_FRAGS)) { + for (i = 0; i < shinfo->nr_frags; i++) + __skb_frag_unref(&shinfo->frags[i], skb->pp_recycle); + } else { + shinfo->flags &= ~SKBFL_MANAGED_FRAGS; + } - for (i = 0; i < shinfo->nr_frags; i++) - __skb_frag_unref(&shinfo->frags[i], skb->pp_recycle); + skb_zcopy_clear(skb, true); if (shinfo->frag_list) kfree_skb_list(shinfo->frag_list); @@ -1471,6 +1475,7 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask) /* skb frags release userspace buffers */ for (i = 0; i < num_frags; i++) skb_frag_unref(skb, i); + skb_shinfo(skb)->flags &= ~SKBFL_MANAGED_FRAGS; /* skb frags point to kernel buffers */ for (i = 0; i < new_frags - 1; i++) { @@ -1597,6 +1602,7 @@ struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t gfp_mask) BUG_ON(skb_copy_bits(skb, -headerlen, n->head, headerlen + skb->len)); skb_copy_header(n, skb); + skb_shinfo(n)->flags &= ~SKBFL_MANAGED_FRAGS; return n; } EXPORT_SYMBOL(skb_copy); @@ -1653,6 +1659,7 @@ struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom, skb_frag_ref(skb, i); } skb_shinfo(n)->nr_frags = i; + skb_shinfo(n)->flags &= ~SKBFL_MANAGED_FRAGS; } if (skb_has_frag_list(skb)) { @@ -1725,6 +1732,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, refcount_inc(&skb_uarg(skb)->refcnt); for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) skb_frag_ref(skb, i); + skb_shinfo(skb)->flags &= ~SKBFL_MANAGED_FRAGS; if (skb_has_frag_list(skb)) skb_clone_fraglist(skb); @@ -3788,6 +3796,8 @@ int skb_append_pagefrags(struct sk_buff *skb, struct page *page, if (skb_can_coalesce(skb, i, page, offset)) { skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], size); } else if (i < MAX_SKB_FRAGS) { + if (skb_shinfo(skb)->flags & SKBFL_MANAGED_FRAGS) + return -EMSGSIZE; get_page(page); skb_fill_page_desc(skb, i, page, offset, size); } else { diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index f9aab355d283..e6adf96e5530 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -1194,6 +1194,10 @@ static int __ip_append_data(struct sock *sk, err = -ENOMEM; if (!sk_page_frag_refill(sk, pfrag)) goto error; + if (skb_shinfo(skb)->flags & SKBFL_MANAGED_FRAGS) { + err = -EMSGSIZE; + goto error; + } if (!skb_can_coalesce(skb, i, pfrag->page, pfrag->offset)) {