From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f178.google.com (mail-ig0-f178.google.com [209.85.213.178]) by kanga.kvack.org (Postfix) with ESMTP id 9192C6B0032 for ; Thu, 15 Jan 2015 22:30:15 -0500 (EST) Received: by mail-ig0-f178.google.com with SMTP id b16so1427464igk.5 for ; Thu, 15 Jan 2015 19:30:15 -0800 (PST) Received: from resqmta-po-04v.sys.comcast.net (resqmta-po-04v.sys.comcast.net. [2001:558:fe16:19:96:114:154:163]) by mx.google.com with ESMTPS id ba10si6005907icc.24.2015.01.15.19.30.14 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Thu, 15 Jan 2015 19:30:14 -0800 (PST) Date: Thu, 15 Jan 2015 21:30:12 -0600 (CST) From: Christoph Lameter Subject: Re: [PATCH v2 2/2] mm: don't use compound_head() in virt_to_head_page() In-Reply-To: <20150115171646.8fec31e2.akpm@linux-foundation.org> Message-ID: References: <1421307633-24045-1-git-send-email-iamjoonsoo.kim@lge.com> <1421307633-24045-2-git-send-email-iamjoonsoo.kim@lge.com> <20150115171646.8fec31e2.akpm@linux-foundation.org> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Joonsoo Kim , Pekka Enberg , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jesper Dangaard Brouer , rostedt@goodmis.org, Thomas Gleixner On Thu, 15 Jan 2015, Andrew Morton wrote: > And perhaps some explanation here as to why virt_to_head_page() can > safely use compound_head_fast(). There's an assumption here that > nobody will be dismantling the compound page while virt_to_head_page() > is in progress, yes? And this assumption also holds for the calling > code, because otherwise the virt_to_head_page() return value is kinda > meaningless. I think this assumption is pretty natural to make. A coupound_head that works well while dismantling a compound page should be marked specially and Joonsoo's definition should be the standard. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org