From patchwork Fri Dec 16 12:45:26 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Benjamin Coddington X-Patchwork-Id: 13074990 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 10EDAC001B2 for ; Fri, 16 Dec 2022 12:46:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229873AbiLPMqe (ORCPT ); Fri, 16 Dec 2022 07:46:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229770AbiLPMq2 (ORCPT ); Fri, 16 Dec 2022 07:46:28 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D22DCF5 for ; Fri, 16 Dec 2022 04:45:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1671194739; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RRe7I7atfJDdvH3YMvA04g6cA61WJxGiVh9qKyM/ZxQ=; b=AhhVSbKr2spjAnMZ7XU7WHNTbokI8CDDNGHo5Qjv3e7HaN//Us+VyCrQZX5weHQETtVLnx arpkQdyAad6QLjRStpMgkgbbva7lA6dLZstraCXw6cRwFyZt2nrJB1YomqgMfweXlH1Hqb My/M+5I8UD3Rg4WMsury595BIYxeAkk= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-593-139zCA0UOC-nCKqE5och2g-1; Fri, 16 Dec 2022 07:45:36 -0500 X-MC-Unique: 139zCA0UOC-nCKqE5och2g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8929B85C06B; Fri, 16 Dec 2022 12:45:34 +0000 (UTC) Received: from bcodding.csb (unknown [10.22.50.3]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3B05914171BE; Fri, 16 Dec 2022 12:45:34 +0000 (UTC) Received: by bcodding.csb (Postfix, from userid 24008) id EB67A10C30E2; Fri, 16 Dec 2022 07:45:33 -0500 (EST) From: Benjamin Coddington To: Jakub Kicinski , Paolo Abeni , "David S. Miller" , Eric Dumazet Cc: Guillaume Nault , Philipp Reisner , Lars Ellenberg , =?utf-8?q?Christoph_B=C3=B6hmwa?= =?utf-8?q?lder?= , Jens Axboe , Josef Bacik , Keith Busch , Christoph Hellwig , Sagi Grimberg , Lee Duncan , Chris Leech , Mike Christie , "James E.J. Bottomley" , "Martin K. Petersen" , Valentina Manea , Shuah Khan , Greg Kroah-Hartman , David Howells , Marc Dionne , Steve French , Christine Caulfield , David Teigland , Mark Fasheh , Joel Becker , Joseph Qi , Eric Van Hensbergen , Latchesar Ionkov , Dominique Martinet , Ilya Dryomov , Xiubo Li , Chuck Lever , Jeff Layton , Trond Myklebust , Anna Schumaker , Steffen Klassert , Herbert Xu , netdev@vger.kernel.org Subject: [PATCH net v4 1/3] net: Introduce sk_use_task_frag in struct sock. Date: Fri, 16 Dec 2022 07:45:26 -0500 Message-Id: <6a2ed9386c45c6b9dd046ab4ffa078b27b5d8800.1671194454.git.bcodding@redhat.com> In-Reply-To: References: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org From: Guillaume Nault Sockets that can be used while recursing into memory reclaim, like those used by network block devices and file systems, mustn't use current->task_frag: if the current process is already using it, then the inner memory reclaim call would corrupt the task_frag structure. To avoid this, sk_page_frag() uses ->sk_allocation to detect sockets that mustn't use current->task_frag, assuming that those used during memory reclaim had their allocation constraints reflected in ->sk_allocation. This unfortunately doesn't cover all cases: in an attempt to remove all usage of GFP_NOFS and GFP_NOIO, sunrpc stopped setting these flags in ->sk_allocation, and used memalloc_nofs critical sections instead. This breaks the sk_page_frag() heuristic since the allocation constraints are now stored in current->flags, which sk_page_frag() can't read without risking triggering a cache miss and slowing down TCP's fast path. This patch creates a new field in struct sock, named sk_use_task_frag, which sockets with memory reclaim constraints can set to false if they can't safely use current->task_frag. In such cases, sk_page_frag() now always returns the socket's page_frag (->sk_frag). The first user is sunrpc, which needs to avoid using current->task_frag but can keep ->sk_allocation set to GFP_KERNEL otherwise. Eventually, it might be possible to simplify sk_page_frag() by only testing ->sk_use_task_frag and avoid relying on the ->sk_allocation heuristic entirely (assuming other sockets will set ->sk_use_task_frag according to their constraints in the future). The new ->sk_use_task_frag field is placed in a hole in struct sock and belongs to a cache line shared with ->sk_shutdown. Therefore it should be hot and shouldn't have negative performance impacts on TCP's fast path (sk_shutdown is tested just before the while() loop in tcp_sendmsg_locked()). Link: https://lore.kernel.org/netdev/b4d8cb09c913d3e34f853736f3f5628abfd7f4b6.1656699567.git.gnault@redhat.com/ Signed-off-by: Guillaume Nault Reviewed-by: Benjamin Coddington --- include/net/sock.h | 11 +++++++++-- net/core/sock.c | 1 + 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index ecea3dcc2217..fefe1f4abf19 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -318,6 +318,9 @@ struct sk_filter; * @sk_stamp: time stamp of last packet received * @sk_stamp_seq: lock for accessing sk_stamp on 32 bit architectures only * @sk_tsflags: SO_TIMESTAMPING flags + * @sk_use_task_frag: allow sk_page_frag() to use current->task_frag. + * Sockets that can be used under memory reclaim should + * set this to false. * @sk_bind_phc: SO_TIMESTAMPING bind PHC index of PTP virtual clock * for timestamping * @sk_tskey: counter to disambiguate concurrent tstamp requests @@ -512,6 +515,7 @@ struct sock { u8 sk_txtime_deadline_mode : 1, sk_txtime_report_errors : 1, sk_txtime_unused : 6; + bool sk_use_task_frag; struct socket *sk_socket; void *sk_user_data; @@ -2561,14 +2565,17 @@ static inline void sk_stream_moderate_sndbuf(struct sock *sk) * socket operations and end up recursing into sk_page_frag() * while it's already in use: explicitly avoid task page_frag * usage if the caller is potentially doing any of them. - * This assumes that page fault handlers use the GFP_NOFS flags. + * This assumes that page fault handlers use the GFP_NOFS flags or + * explicitly disable sk_use_task_frag. * * Return: a per task page_frag if context allows that, * otherwise a per socket one. */ static inline struct page_frag *sk_page_frag(struct sock *sk) { - if ((sk->sk_allocation & (__GFP_DIRECT_RECLAIM | __GFP_MEMALLOC | __GFP_FS)) == + if (sk->sk_use_task_frag && + (sk->sk_allocation & (__GFP_DIRECT_RECLAIM | __GFP_MEMALLOC | + __GFP_FS)) == (__GFP_DIRECT_RECLAIM | __GFP_FS)) return ¤t->task_frag; diff --git a/net/core/sock.c b/net/core/sock.c index d2587d8712db..f954d5893e79 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -3390,6 +3390,7 @@ void sock_init_data(struct socket *sock, struct sock *sk) sk->sk_rcvbuf = READ_ONCE(sysctl_rmem_default); sk->sk_sndbuf = READ_ONCE(sysctl_wmem_default); sk->sk_state = TCP_CLOSE; + sk->sk_use_task_frag = true; sk_set_socket(sk, sock); sock_set_flag(sk, SOCK_ZAPPED);