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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 1AF04CA9ECF for ; Thu, 31 Oct 2019 15:11:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DEA20217D9 for ; Thu, 31 Oct 2019 15:11:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bF10RdFc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728138AbfJaPLk (ORCPT ); Thu, 31 Oct 2019 11:11:40 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:23461 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726540AbfJaPLj (ORCPT ); Thu, 31 Oct 2019 11:11:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1572534698; 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=0VSvvKijFyEH1t8VcmSOVjO1qeKSdmMeXOa2d+3aPNU=; b=bF10RdFcKMbwzfOuKbcmZMbmc96bFYHLyzbuVYIQPghzHW2bkGhRf/zkwLVspTrEqxPxOH KsxMB8dOWhd5p0MxPAbI0vhrukYLap0QJDV29vIRNqDShzq80Sgy/OZFnkCXjc4aLWUMr/ p9opYneY/SKjt6ol/inRREzD82gTaj4= 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-25-0p8D1KgMMzyGyZWARpBKrw-1; Thu, 31 Oct 2019 11:11:32 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AE7A51800D6B; Thu, 31 Oct 2019 15:11:30 +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 DED1360852; Thu, 31 Oct 2019 15:11:27 +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: <4892d186-8eb0-a282-e7e6-e79958431a54@rasmusvillemoes.dk> References: <4892d186-8eb0-a282-e7e6-e79958431a54@rasmusvillemoes.dk> <157186182463.3995.13922458878706311997.stgit@warthog.procyon.org.uk> <157186186167.3995.7568100174393739543.stgit@warthog.procyon.org.uk> To: Rasmus Villemoes Cc: dhowells@redhat.com, Ilya Dryomov , Linus Torvalds , 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 , linux-security-module@vger.kernel.org, linux-fsdevel , linux-api@vger.kernel.org, LKML Subject: Re: [RFC PATCH 04/10] pipe: Use head and tail pointers for the ring, not cursor and length [ver #2] MIME-Version: 1.0 Content-ID: <16619.1572534687.1@warthog.procyon.org.uk> Date: Thu, 31 Oct 2019 15:11:27 +0000 Message-ID: <16620.1572534687@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: 0p8D1KgMMzyGyZWARpBKrw-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 How about: * We use head and tail indices that aren't masked off, except at the * point of dereference, but rather they're allowed to wrap naturally. * This means there isn't a dead spot in the buffer, provided the ring * size is a power of two and <=3D 2^31. David