Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757264AbcLUNNh (ORCPT ); Wed, 21 Dec 2016 08:13:37 -0500 Received: from mail-pg0-f67.google.com ([74.125.83.67]:33898 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751175AbcLUNNg (ORCPT ); Wed, 21 Dec 2016 08:13:36 -0500 Date: Wed, 21 Dec 2016 13:13:32 +0000 From: Wei Yang To: Michal Hocko Cc: Wei Yang , trivial@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2 2/2] mm/memblock.c: check return value of memblock_reserve() in memblock_virt_alloc_internal() Message-ID: <20161221131332.GB23096@vultr.guest> Reply-To: Wei Yang 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161221075115.GE16502@dhcp22.suse.cz> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1947 Lines: 63 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. Not sure whether I get it clarified. >> >> >> >> if (nid != NUMA_NO_NODE) { >> >> alloc = memblock_find_in_range_node(size, align, min_addr, >> >> max_addr, NUMA_NO_NODE, >> >> flags); >> >> - if (alloc) >> >> + if (alloc && !memblock_reserve(alloc, size)) >> >> goto done; >> >> } >> > >> >This doesn't look right. You can end up leaking the first allocated >> >range. >> > >> >> Hmm... why? >> >> If first memblock_reserve() succeed, it will jump to done, so that no 2nd >> allocation. >> If the second executes, it means the first allocation failed. >> memblock_find_in_range_node() doesn't modify the memblock, it just tell you >> there is a proper memory region available. > >yes, my bad. I have missed this. Sorry about the confusion So do you agree with my patch now? >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me