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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 BCFC0CA9ECF for ; Thu, 31 Oct 2019 15:16:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9389D217F9 for ; Thu, 31 Oct 2019 15:16:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="adzTcULU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727705AbfJaPQF (ORCPT ); Thu, 31 Oct 2019 11:16:05 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:40919 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728066AbfJaPQE (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: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: 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