From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id DE23F6B002A for ; Mon, 19 Feb 2018 14:11:08 -0500 (EST) Received: by mail-qk0-f198.google.com with SMTP id v21so10100147qka.6 for ; Mon, 19 Feb 2018 11:11:08 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 51sor1330935qtt.47.2018.02.19.11.11.08 for (Google Transport Security); Mon, 19 Feb 2018 11:11:08 -0800 (PST) Subject: Re: [PATCH] mm: Fix for PG_reserved page flag clearing References: <20180219171916.GR21134@dhcp22.suse.cz> From: Masayoshi Mizuma Message-ID: Date: Mon, 19 Feb 2018 14:11:03 -0500 MIME-Version: 1.0 In-Reply-To: <20180219171916.GR21134@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@suse.com Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, pasha.tatashin@oracle.com, linux-mm@kvack.org Hello Michal, Mon, 19 Feb 2018 18:19:16 +0100 Michal Hocko wrote: > On Mon 19-02-18 12:06:14, Masayoshi Mizuma wrote: >> From: Masayoshi Mizuma >> >> struct page is inizialized as zero in __init_single_page(). >> If the page is offlined page, PG_reserved flag is set in early boot >> time before __init_single_page(), so we should not clear the flag. >> >> The real problem is that we can not online the offlined page >> through following sysfs operation because offlined page is >> expected PG_reserved flag is set. >> It is not needed the initialization, so remove it simply. >> >> Code: >> >> static int online_pages_range(unsigned long start_pfn, >> ... >> if (PageReserved(pfn_to_page(start_pfn))) <= HERE!! >> for (i = 0; i < nr_pages; i++) { >> page = pfn_to_page(start_pfn + i); >> (*online_page_callback)(page); >> onlined_pages++; >> sysfs operation: >> >> # echo online > /sys/devices/system/node/node2/memory12288/online >> # cat /sys/devices/system/node/node2/memory12288/online >> 1 >> # cat /sys/devices/system/node/node2/meminfo >> Node 2 MemTotal: 0 kB > > Nack. The patch is simply wrong. We do need to zero page for the boot > pages. I believe the fix you are looking for is 9bb5a391f9a5 ("mm, > memory_hotplug: fix memmap initialization"). Or do you still see a > problem with this patch applied? I have confirmed the problem is fixed by your patch 9bb5a391f9a5. (I had tested it in 4.15.2, so I did not notice your patch, sorry) Thank you for the fix! - Masayoshi > >> Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap") >> Signed-off-by: Masayoshi Mizuma >> --- >> mm/page_alloc.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 76c9688..3260cd2 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -1179,7 +1179,6 @@ static void free_one_page(struct zone *zone, >> static void __meminit __init_single_page(struct page *page, unsigned long pfn, >> unsigned long zone, int nid) >> { >> - mm_zero_struct_page(page); >> set_page_links(page, zone, nid, pfn); >> init_page_count(page); >> page_mapcount_reset(page); >> -- >> 2.16.1 >> >> - Masayoshi > -- 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