From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-f181.google.com (mail-yk0-f181.google.com [209.85.160.181]) by kanga.kvack.org (Postfix) with ESMTP id 3D638828DF for ; Tue, 12 Jan 2016 12:38:37 -0500 (EST) Received: by mail-yk0-f181.google.com with SMTP id k129so436920130yke.0 for ; Tue, 12 Jan 2016 09:38:37 -0800 (PST) Received: from SMTP.CITRIX.COM (smtp.citrix.com. [66.165.176.89]) by mx.google.com with ESMTPS id d81si4389030ywc.22.2016.01.12.09.38.36 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 12 Jan 2016 09:38:36 -0800 (PST) Message-ID: <56953A18.2070407@citrix.com> Date: Tue, 12 Jan 2016 17:38:32 +0000 From: David Vrabel MIME-Version: 1.0 Subject: Re: [Xen-devel] [PATCH v4 2/2] xen_balloon: support memory auto onlining policy References: <1452617777-10598-1-git-send-email-vkuznets@redhat.com> <1452617777-10598-3-git-send-email-vkuznets@redhat.com> In-Reply-To: <1452617777-10598-3-git-send-email-vkuznets@redhat.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Vitaly Kuznetsov , linux-mm@kvack.org Cc: Naoya Horiguchi , linux-doc@vger.kernel.org, Jonathan Corbet , Boris Ostrovsky , Greg Kroah-Hartman , Daniel Kiper , Kay Sievers , linux-kernel@vger.kernel.org, Tang Chen , xen-devel@lists.xenproject.org, Igor Mammedov , David Vrabel , David Rientjes , Xishi Qiu , Dan Williams , "K. Y. Srinivasan" , Mel Gorman , Andrew Morton On 12/01/16 16:56, Vitaly Kuznetsov wrote: > Add support for the newly added kernel memory auto onlining policy to Xen > ballon driver. [...] > --- a/drivers/xen/Kconfig > +++ b/drivers/xen/Kconfig > @@ -37,23 +37,29 @@ config XEN_BALLOON_MEMORY_HOTPLUG > > Memory could be hotplugged in following steps: > > - 1) dom0: xl mem-max > + 1) domU: ensure that memory auto online policy is in effect by > + checking /sys/devices/system/memory/auto_online_blocks file > + (should be 'online'). Step 1 applies to dom0 and domUs. > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -284,7 +284,7 @@ static void release_memory_resource(struct resource *resource) > kfree(resource); > } > > -static enum bp_state reserve_additional_memory(void) > +static enum bp_state reserve_additional_memory(bool online) > { > long credit; > struct resource *resource; > @@ -338,7 +338,18 @@ static enum bp_state reserve_additional_memory(void) > } > #endif > > - rc = add_memory_resource(nid, resource, false); > + /* > + * add_memory_resource() will call online_pages() which in its turn > + * will call xen_online_page() callback causing deadlock if we don't > + * release balloon_mutex here. It is safe because there can only be > + * one balloon_process() running at a time and balloon_mutex is > + * internal to Xen driver, generic memory hotplug code doesn't mess > + * with it. There are multiple callers of reserve_additional_memory() and these are not all serialized via the balloon process. Replace the "It is safe..." sentence with: "Unlocking here is safe because the callers drop the mutex before trying again." > + */ > + mutex_unlock(&balloon_mutex); > + rc = add_memory_resource(nid, resource, online); This should always be memhp_auto_online, because... > @@ -562,14 +573,11 @@ static void balloon_process(struct work_struct *work) > > credit = current_credit(); > > - if (credit > 0) { > - if (balloon_is_inflated()) > - state = increase_reservation(credit); > - else > - state = reserve_additional_memory(); > - } > - > - if (credit < 0) > + if (credit > 0 && balloon_is_inflated()) > + state = increase_reservation(credit); > + else if (credit > 0) > + state = reserve_additional_memory(memhp_auto_online); > + else if (credit < 0) > state = decrease_reservation(-credit, GFP_BALLOON); I'd have preferred this refactored as: if (credit > 0) { if (balloon_is_inflated()) ... else ... } else if (credit < 0) { ... } > > state = update_schedule(state); > @@ -599,7 +607,7 @@ static int add_ballooned_pages(int nr_pages) > enum bp_state st; > > if (xen_hotplug_unpopulated) { > - st = reserve_additional_memory(); > + st = reserve_additional_memory(false); ... we want to auto-online this memory as well. > if (st != BP_ECANCELED) { > mutex_unlock(&balloon_mutex); > wait_event(balloon_wq, > -- 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