Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753699AbYJ1VD3 (ORCPT ); Tue, 28 Oct 2008 17:03:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752687AbYJ1VDU (ORCPT ); Tue, 28 Oct 2008 17:03:20 -0400 Received: from mx2.redhat.com ([66.187.237.31]:49617 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752558AbYJ1VDT (ORCPT ); Tue, 28 Oct 2008 17:03:19 -0400 Message-ID: <49077E1A.5080105@redhat.com> Date: Tue, 28 Oct 2008 23:03:22 +0200 From: Avi Kivity User-Agent: Thunderbird 2.0.0.16 (X11/20080723) MIME-Version: 1.0 To: Glauber Costa CC: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, aliguori@codemonkey.ws, npiggin@suse.de, Jeremy Fitzhardinge , Krzysztof Helt Subject: Re: [PATCH] regression: vmalloc easily fail. References: <1225234513-3996-1-git-send-email-glommer@redhat.com> In-Reply-To: <1225234513-3996-1-git-send-email-glommer@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1429 Lines: 39 Glauber Costa wrote: > Commit db64fe02258f1507e13fe5212a989922323685ce broke > KVM (the symptom) for me. The cause is that vmalloc > allocations fail, despite of the fact that /proc/meminfo > shows plenty of vmalloc space available. > > After some investigation, it seems to me that the current > way to compute the next addr in the rb-tree transversal > leaves a spare page between each allocation. After a few > allocations, regardless of their size, we run out of vmalloc > space. > > > while (addr + size >= first->va_start && addr + size <= vend) { > - addr = ALIGN(first->va_end + PAGE_SIZE, align); > + addr = ALIGN(first->va_end, align); > > n = rb_next(&first->rb_node); > if (n) > I'm guessing that the missing comment explains that this is intentional, to trap buffer overflows? (okay that was a cheap shot. I don't comment nearly enough either) Even if you leave a page between allocations, I don't see how you can fail a one page allocation, unless you've allocated at least N/2 pages (where N is the size of the vmalloc space in pages). -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/