From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id 4269E8D0039 for ; Tue, 8 Mar 2011 19:03:05 -0500 (EST) Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e36.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p28NvDFP030104 for ; Tue, 8 Mar 2011 16:57:13 -0700 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p2902NrQ085956 for ; Tue, 8 Mar 2011 17:02:24 -0700 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p28Nxwnj018803 for ; Tue, 8 Mar 2011 17:00:00 -0700 Subject: Re: [PATCH R4 7/7] xen/balloon: Memory hotplug support for Xen balloon driver From: Dave Hansen In-Reply-To: <20110308215049.GH27331@router-fw-old.local.net-space.pl> References: <20110308215049.GH27331@router-fw-old.local.net-space.pl> Content-Type: text/plain; charset="ISO-8859-1" Date: Tue, 08 Mar 2011 16:02:19 -0800 Message-ID: <1299628939.9014.3499.camel@nimitz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Daniel Kiper Cc: ian.campbell@citrix.com, akpm@linux-foundation.org, andi.kleen@intel.com, haicheng.li@linux.intel.com, fengguang.wu@intel.com, jeremy@goop.org, konrad.wilk@oracle.com, dan.magenheimer@oracle.com, v.tolstov@selfip.ru, pasik@iki.fi, wdauchy@gmail.com, rientjes@google.com, xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Tue, 2011-03-08 at 22:50 +0100, Daniel Kiper wrote: > +static enum bp_state reserve_additional_memory(long credit) > +{ > + int rc; > + unsigned long balloon_hotplug = credit; > + > + balloon_hotplug <<= PAGE_SHIFT; > + > + rc = add_virtual_memory((u64 *)&balloon_hotplug); This would work if all 'unsigned long's were 64-bits. It'll break on 32-bit kernels in a very bad way by overwriting 4 bytes of stack. > + if (rc) { > + pr_info("xen_balloon: %s: add_virtual_memory() failed: %i\n", __func__, rc); > + return BP_EAGAIN; > + } > + > + balloon_hotplug >>= PAGE_SHIFT; > + > + balloon_hotplug -= credit; > + > + balloon_stats.hotplug_pages += credit; > + balloon_stats.balloon_hotplug = balloon_hotplug; > + > + return BP_DONE; > +} > + > +static int xen_online_page_notifier(struct notifier_block *nb, unsigned long val, void *v) > +{ > + struct page *page = v; > + unsigned long pfn = page_to_pfn(page); > + > + if (pfn >= num_physpages) > + num_physpages = pfn + 1; > + > + inc_totalhigh_pages(); > + > +#ifdef CONFIG_FLATMEM > + max_mapnr = max(pfn, max_mapnr); > +#endif I really don't like that this is a direct copy of online_page() up to this point. They're already subtly different. I'm also curious if this breaks on 32-bit kernels because of the unconditional inc_totalhigh_pages(). If it's done this way, I'd almost guarantee that the first time someone fixes a bug or adds a generic feature in online_page() that Xen gets missed. > + mutex_lock(&balloon_mutex); > + > + __balloon_append(page); > + > + if (balloon_stats.hotplug_pages) > + --balloon_stats.hotplug_pages; > + else > + --balloon_stats.balloon_hotplug; > + > + mutex_unlock(&balloon_mutex); > + > + return NOTIFY_STOP; > +} I'm not a _huge_ fan of these notifier chains, but I guess it works. However, if you're going to use these notifier chains, then we probably should use them to full effect. Have a notifier list like this: 1. generic online_page() 2. xen_online_page_notifier() (returns NOTIFY_STOP) 3. free_online_page() Where finish_online_page() does something like this: finish_online_page(...) { ClearPageReserved(page); init_page_count(page); __free_page(page); } These patches are definitely getting there. Just another round or two, and they should be ready to go. -- Dave -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org