From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5985BC43382 for ; Wed, 26 Sep 2018 10:09:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07E34214DA for ; Wed, 26 Sep 2018 10:09:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07E34214DA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727055AbeIZQVr (ORCPT ); Wed, 26 Sep 2018 12:21:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42504 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726404AbeIZQVr (ORCPT ); Wed, 26 Sep 2018 12:21:47 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0804FC05D41D; Wed, 26 Sep 2018 10:09:34 +0000 (UTC) Received: from [10.36.117.98] (ovpn-117-98.ams2.redhat.com [10.36.117.98]) by smtp.corp.redhat.com (Postfix) with ESMTP id BDBC526346; Wed, 26 Sep 2018 10:09:11 +0000 (UTC) Subject: Re: [PATCH v2 5/6] powerpc/powernv: hold device_hotplug_lock when calling memtrace_offline_pages() To: Balbir Singh Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, xen-devel@lists.xenproject.org, devel@linuxdriverproject.org, Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Rashmica Gupta , Michael Neuling References: <20180925091457.28651-1-david@redhat.com> <20180925091457.28651-6-david@redhat.com> <20180925121504.GH8537@350D> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20180925121504.GH8537@350D> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 26 Sep 2018 10:09:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/09/2018 14:15, Balbir Singh wrote: > On Tue, Sep 25, 2018 at 11:14:56AM +0200, David Hildenbrand wrote: >> Let's perform all checking + offlining + removing under >> device_hotplug_lock, so nobody can mess with these devices via >> sysfs concurrently. >> >> Cc: Benjamin Herrenschmidt >> Cc: Paul Mackerras >> Cc: Michael Ellerman >> Cc: Rashmica Gupta >> Cc: Balbir Singh >> Cc: Michael Neuling >> Reviewed-by: Pavel Tatashin >> Reviewed-by: Rashmica Gupta >> Signed-off-by: David Hildenbrand >> --- >> arch/powerpc/platforms/powernv/memtrace.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c >> index fdd48f1a39f7..d84d09c56af9 100644 >> --- a/arch/powerpc/platforms/powernv/memtrace.c >> +++ b/arch/powerpc/platforms/powernv/memtrace.c >> @@ -70,6 +70,7 @@ static int change_memblock_state(struct memory_block *mem, void *arg) >> return 0; >> } >> >> +/* called with device_hotplug_lock held */ >> static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages) >> { >> u64 end_pfn = start_pfn + nr_pages - 1; >> @@ -111,6 +112,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size) >> end_pfn = round_down(end_pfn - nr_pages, nr_pages); >> >> for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) { >> + lock_device_hotplug(); > > Why not grab the lock before the for loop? That way we can avoid bad cases like a > large node being scanned for a small number of pages (nr_pages). Ideally we need > a cond_resched() in the loop, but I guess offline_pages() has one. Yes, it does. I can move it out of the loop, thanks! > > Acked-by: Balbir Singh > -- Thanks, David / dhildenb