From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758690Ab2AMSOX (ORCPT ); Fri, 13 Jan 2012 13:14:23 -0500 Received: from mail-gx0-f174.google.com ([209.85.161.174]:58173 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758623Ab2AMSOS (ORCPT ); Fri, 13 Jan 2012 13:14:18 -0500 Date: Fri, 13 Jan 2012 10:14:12 -0800 From: Tejun Heo To: Ingo Molnar , "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org, rjw@sisk.pl, xen-devel@lists.xensource.com, Konrad Rzeszutek Wilk , Benjamin Herrenschmidt Subject: [PATCH 3.3-rc] memblock: Fix alloc failure due to dumb underflow protection in memblock_find_in_range_node() Message-ID: <20120113181412.GA11112@google.com> References: <20120110202838.GA10402@phenom.dumpdata.com> <20120110222625.GA26832@google.com> <20120110224537.GA6572@phenom.dumpdata.com> <20120110231552.GB26832@google.com> <20120111200435.GA8680@phenom.dumpdata.com> <20120113142703.GA7707@phenom.dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120113142703.GA7707@phenom.dumpdata.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 7bd0b0f0da "memblock: Reimplement memblock allocation using reverse free area iterator" implemented simple top-down allocator using reverse memblock iterator. To avoid underflow in the allocator loop, it simply raised the lower boundary to the requested size under the assumption that requested size would be far smaller than available memblocks. This causes early page table allocation failure under certain configurations. Fix it by checking for underflow directly instead of bumping up lower bound. Signed-off-by: Tejun Heo Reported-by: Konrad Rzeszutek Wilk LKML-Reference: <20120110202838.GA10402@phenom.dumpdata.com> --- Sorry, I wrote the patch description and everything but forgot to actually send it out. :) Ingo, the new memblock allocator went too far with simplification and caused unnecessary allocation failure. The fix is fairly obvious and simple. Can you please route this patch? Thanks. mm/memblock.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/memblock.c b/mm/memblock.c index 2f55f19..77b5f22 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -106,14 +106,17 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start, if (end == MEMBLOCK_ALLOC_ACCESSIBLE) end = memblock.current_limit; - /* adjust @start to avoid underflow and allocating the first page */ - start = max3(start, size, (phys_addr_t)PAGE_SIZE); + /* avoid allocating the first page */ + start = max_t(phys_addr_t, start, PAGE_SIZE); end = max(start, end); for_each_free_mem_range_reverse(i, nid, &this_start, &this_end, NULL) { this_start = clamp(this_start, start, end); this_end = clamp(this_end, start, end); + if (this_end < size) + continue; + cand = round_down(this_end - size, align); if (cand >= this_start) return cand;