From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757043AbcLUHsO (ORCPT ); Wed, 21 Dec 2016 02:48:14 -0500 Received: from mail-wj0-f193.google.com ([209.85.210.193]:33972 "EHLO mail-wj0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752094AbcLUHsM (ORCPT ); Wed, 21 Dec 2016 02:48:12 -0500 Date: Wed, 21 Dec 2016 08:48:09 +0100 From: Michal Hocko To: Wei Yang Cc: trivial@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2 1/2] mm/memblock.c: trivial code refine in memblock_is_region_memory() Message-ID: <20161221074809.GD16502@dhcp22.suse.cz> References: <1482072470-26151-1-git-send-email-richard.weiyang@gmail.com> <1482072470-26151-2-git-send-email-richard.weiyang@gmail.com> <20161219151514.GB5175@dhcp22.suse.cz> <20161220163540.GA13224@vultr.guest> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161220163540.GA13224@vultr.guest> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 20-12-16 16:35:40, Wei Yang wrote: > On Mon, Dec 19, 2016 at 04:15:14PM +0100, Michal Hocko wrote: > >On Sun 18-12-16 14:47:49, Wei Yang wrote: > >> The base address is already guaranteed to be in the region by > >> memblock_search(). > > > > Hi, Michal > > Nice to receive your comment. > > >First of all the way how the check is removed is the worst possible... > >Apart from that it is really not clear to me why checking the base > >is not needed. You are mentioning memblock_search but what about other > >callers? adjust_range_page_size_mask e.g... > > > > Hmm... the memblock_search() is called by memblock_is_region_memory(). Maybe I > paste the whole function here would clarify the change. > > int __init_memblock memblock_is_region_memory(phys_addr_t base, phys_addr_t size) > { > int idx = memblock_search(&memblock.memory, base); > phys_addr_t end = base + memblock_cap_size(base, &size); > > if (idx == -1) > return 0; > return memblock.memory.regions[idx].base <= base && > (memblock.memory.regions[idx].base + > memblock.memory.regions[idx].size) >= end; > } Ohh, my bad. I thought that memblock_search is calling memblock_is_region_memory. I didn't notice this is other way around. Then I agree that the check for the base is not needed and can be removed. -- Michal Hocko SUSE Labs