Received: by 2002:a25:31c3:0:0:0:0:0 with SMTP id x186csp1282390ybx; Thu, 31 Oct 2019 08:17:51 -0700 (PDT) X-Google-Smtp-Source: APXvYqwR3eplBp/E3Pvpit39s4eTF/FdkfvegRBJeLFv9IZanADGVuqVc+KUalJbbbPIiGqK6RYZ X-Received: by 2002:a17:906:4bd7:: with SMTP id x23mr4445389ejv.320.1572535071284; Thu, 31 Oct 2019 08:17:51 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1572535071; cv=none; d=google.com; s=arc-20160816; b=kl3qrXgnfch822FkBrfSCxIXVHgN5GlagfnrFiUoSQQQp5gxSVfHoNwaVDczqcudYx pu0XlLw86GsALxnYSxmyTlEgugT6dr/eYXT3ZEAYsCPey0fYe0/cmBCgKp28/L93q2iw uoe42ofIC0QLLUrcbWaqkUjD8wxlIxKHnXvgc97ZWMSMUEc+vzw66bpcSDNXMPWU6ei8 1VessQS1GKjMKfRmQpiE8+dCGwvXuXlsH0FLslKmYKXZxb8ecdTRGp5YlhpY5uocSLfa ettI5RHdyJO8Hinex0kTeSnkVeqWifUOPYOC7BDhoJqMKzZR+sXfZPjSx6VgEiCNfm5/ M3Pg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding:message-id:date :content-id:mime-version:subject:cc:to:references:in-reply-to:from :organization:dkim-signature; bh=zC2mY0mLUqkQzl10meI2dQTcqCAQks3OLoAJrTsT3pg=; b=ttL6lqfS2hYPGFtvu2+eIC0GKFDdi1OIAOkfQMLKuHwBb0nIkMk02K1D7v0Sn9mwjk GrceJSkL2kQDKm1zWsDwJCn8a1sdWMXjCdycwnkUzEOMEx31ss1PaiWtF+NHI/58PrxB GFzAf6Fg8nJXsvpv5hWNjxi448TobI2BoShnTqNNLAuB0sZwdUctTEWfDsYpj3VzJCoA GT9ZOd+9Fa2/Q9m++0l1n6CJfNJfOAC2Fb2ileKPdnAbWas77hGrLtOKTGTsnQVmCtdY UIWQxCTA4VS13wXgtYqKEpCJ7atYeLc7qQDqrHz5knnOhjNJhPyuhNGoCsglVOl2Q7ZT txXw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=adzTcULU; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id f29si3892368ejj.110.2019.10.31.08.17.26; Thu, 31 Oct 2019 08:17:51 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=adzTcULU; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728311AbfJaPQE (ORCPT + 99 others); Thu, 31 Oct 2019 11:16:04 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:43294 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727705AbfJaPQE (ORCPT ); Thu, 31 Oct 2019 11:16:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1572534963; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zC2mY0mLUqkQzl10meI2dQTcqCAQks3OLoAJrTsT3pg=; b=adzTcULULFJy8UcTe4yayYjVO6GidCQ7OQbxa57ibWr9JLlEP+ePDMRYzUW3mi3+VgISKy /xFnGeLG/yFKZ5F9958e/V7wD7sZLOvjx+GP5o/Nsi824j+5D1eciBNAFRU32OAruv9vEr 0XeQU3e10feMJ4Vi8Y61HcBqAZGfR+o= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-253-FXImFqDnP-q7fXpZhf4T8w-1; Thu, 31 Oct 2019 11:16:00 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E87491800D6B; Thu, 31 Oct 2019 15:15:57 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-121-40.rdu2.redhat.com [10.10.121.40]) by smtp.corp.redhat.com (Postfix) with ESMTP id AA8681001920; Thu, 31 Oct 2019 15:15:54 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <157186182463.3995.13922458878706311997.stgit@warthog.procyon.org.uk> <30394.1571936252@warthog.procyon.org.uk> To: Konstantin Khlebnikov Cc: dhowells@redhat.com, torvalds@linux-foundation.org, Rasmus Villemoes , Greg Kroah-Hartman , Peter Zijlstra , nicolas.dichtel@6wind.com, raven@themaw.net, Christian Brauner , keyrings@vger.kernel.org, linux-usb@vger.kernel.org, linux-block@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 11/10] pipe: Add fsync() support [ver #2] MIME-Version: 1.0 Content-ID: <17310.1572534953.1@warthog.procyon.org.uk> Date: Thu, 31 Oct 2019 15:15:53 +0000 Message-ID: <17311.1572534953@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: FXImFqDnP-q7fXpZhf4T8w-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Konstantin Khlebnikov wrote: > Similar synchronization is required for reusing memory after vmsplice()? > I don't see other way how sender could safely change these pages. Sounds like a point - if you have multiple parallel contributors to the pip= e via vmsplice(), then FIONREAD is of no use. To use use FIONREAD, you have = to let the pipe become empty before you can be sure. David