From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id BB9606B03A5 for ; Wed, 21 Dec 2016 08:22:04 -0500 (EST) Received: by mail-wm0-f71.google.com with SMTP id l2so4477736wml.5 for ; Wed, 21 Dec 2016 05:22:04 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id r129si23859694wmr.28.2016.12.21.05.22.03 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 21 Dec 2016 05:22:03 -0800 (PST) Date: Wed, 21 Dec 2016 14:22:01 +0100 From: Michal Hocko Subject: Re: [PATCH V2 2/2] mm/memblock.c: check return value of memblock_reserve() in memblock_virt_alloc_internal() Message-ID: <20161221132200.GK31118@dhcp22.suse.cz> References: <1482072470-26151-1-git-send-email-richard.weiyang@gmail.com> <1482072470-26151-3-git-send-email-richard.weiyang@gmail.com> <20161219152156.GC5175@dhcp22.suse.cz> <20161220164823.GB13224@vultr.guest> <20161221075115.GE16502@dhcp22.suse.cz> <20161221131332.GB23096@vultr.guest> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161221131332.GB23096@vultr.guest> Sender: owner-linux-mm@kvack.org List-ID: To: Wei Yang Cc: trivial@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed 21-12-16 13:13:32, Wei Yang wrote: > On Wed, Dec 21, 2016 at 08:51:16AM +0100, Michal Hocko wrote: > >On Tue 20-12-16 16:48:23, Wei Yang wrote: > >> On Mon, Dec 19, 2016 at 04:21:57PM +0100, Michal Hocko wrote: > >> >On Sun 18-12-16 14:47:50, Wei Yang wrote: > >> >> memblock_reserve() may fail in case there is not enough regions. > >> > > >> >Have you seen this happenning in the real setups or this is a by-review > >> >driven change? > >> > >> This is a by-review driven change. > >> > >> >[...] > >> >> again: > >> >> alloc = memblock_find_in_range_node(size, align, min_addr, max_addr, > >> >> nid, flags); > >> >> - if (alloc) > >> >> + if (alloc && !memblock_reserve(alloc, size)) > >> >> goto done; > > > >So how exactly does the reserve fail when memblock_find_in_range_node > >found a suitable range for the given size? > > > > Even memblock_find_in_range_node() gets a suitable range, memblock_reserve() > still could fail. And the case just happens when memblock can't resize. > memblock_reserve() reserve a range by adding a range to memblock.reserved. In > case the memblock.reserved is full and can't resize, this fails. Sorry for being dense but what does it mean that the reserved will get full? Also how probable is such a situation? Is it even real? In other words does this fix a real or only a theoretical problem? Anyway this all should be part of the changelog. -- Michal Hocko SUSE Labs -- 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