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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 C7F39C43465 for ; Mon, 21 Sep 2020 16:50:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 92537206DC for ; Mon, 21 Sep 2020 16:50:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600707046; bh=HbNoSSYOXLEEhv12kudrQ5HwgWF88cDoCx4+TtWfGTE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=k6+pSleYy5Ds2GkrRtpGakncvC7d2p7qsP+gfQGcb6SKfmFpExNwunVh9irGRQ6qe lD/4eB741q4l79/5EXOfh+mZ5gz3l1ISCNcpx3hUSppBVvkXQlaSk1FKboqKErUOlZ LsNbVDQyi3M5NAlReulT0LzX2JWbYBU6U3YulojE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730042AbgIUQup (ORCPT ); Mon, 21 Sep 2020 12:50:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:58988 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730008AbgIUQua (ORCPT ); Mon, 21 Sep 2020 12:50:30 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D02292388B; Mon, 21 Sep 2020 16:50:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600707029; bh=HbNoSSYOXLEEhv12kudrQ5HwgWF88cDoCx4+TtWfGTE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=x8rvCthVTse9mr3t32/I6q+bk6gMVGGhm6qHWBXab5zBDeWUppvZGUghNeTENeuIa dnbNSN80dMaTzMnRN354U5ofaisL2iAm9V9EnPLEIXHsQMs6RdcFQ3r0jdpgViIxvY WZF076fxrwcEAUC8Eq5HNUOIMBFTxPhe2xdzWGzc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pavel Tatashin , Andrew Morton , David Rientjes , Vlastimil Babka , Michal Hocko , David Hildenbrand , Oscar Salvador , Wei Yang , Linus Torvalds Subject: [PATCH 5.4 70/72] mm/memory_hotplug: drain per-cpu pages again during memory offline Date: Mon, 21 Sep 2020 18:31:49 +0200 Message-Id: <20200921163125.191811835@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200921163121.870386357@linuxfoundation.org> References: <20200921163121.870386357@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Pavel Tatashin commit 9683182612214aa5f5e709fad49444b847cd866a upstream. There is a race during page offline that can lead to infinite loop: a page never ends up on a buddy list and __offline_pages() keeps retrying infinitely or until a termination signal is received. Thread#1 - a new process: load_elf_binary begin_new_exec exec_mmap mmput exit_mmap tlb_finish_mmu tlb_flush_mmu release_pages free_unref_page_list free_unref_page_prepare set_pcppage_migratetype(page, migratetype); // Set page->index migration type below MIGRATE_PCPTYPES Thread#2 - hot-removes memory __offline_pages start_isolate_page_range set_migratetype_isolate set_pageblock_migratetype(page, MIGRATE_ISOLATE); Set migration type to MIGRATE_ISOLATE-> set drain_all_pages(zone); // drain per-cpu page lists to buddy allocator. Thread#1 - continue free_unref_page_commit migratetype = get_pcppage_migratetype(page); // get old migration type list_add(&page->lru, &pcp->lists[migratetype]); // add new page to already drained pcp list Thread#2 Never drains pcp again, and therefore gets stuck in the loop. The fix is to try to drain per-cpu lists again after check_pages_isolated_cb() fails. Fixes: c52e75935f8d ("mm: remove extra drain pages on pcp list") Signed-off-by: Pavel Tatashin Signed-off-by: Andrew Morton Acked-by: David Rientjes Acked-by: Vlastimil Babka Acked-by: Michal Hocko Acked-by: David Hildenbrand Cc: Oscar Salvador Cc: Wei Yang Cc: Link: https://lkml.kernel.org/r/20200903140032.380431-1-pasha.tatashin@soleen.com Link: https://lkml.kernel.org/r/20200904151448.100489-2-pasha.tatashin@soleen.com Link: http://lkml.kernel.org/r/20200904070235.GA15277@dhcp22.suse.cz Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memory_hotplug.c | 14 ++++++++++++++ mm/page_isolation.c | 8 ++++++++ 2 files changed, 22 insertions(+) --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1566,6 +1566,20 @@ static int __ref __offline_pages(unsigne /* check again */ ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, NULL, check_pages_isolated_cb); + /* + * per-cpu pages are drained in start_isolate_page_range, but if + * there are still pages that are not free, make sure that we + * drain again, because when we isolated range we might + * have raced with another thread that was adding pages to pcp + * list. + * + * Forward progress should be still guaranteed because + * pages on the pcp list can only belong to MOVABLE_ZONE + * because has_unmovable_pages explicitly checks for + * PageBuddy on freed pages on other zones. + */ + if (ret) + drain_all_pages(zone); } while (ret); /* Ok, all of our target is isolated. --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -187,6 +187,14 @@ __first_valid_page(unsigned long pfn, un * pageblocks we may have modified and return -EBUSY to caller. This * prevents two threads from simultaneously working on overlapping ranges. * + * Please note that there is no strong synchronization with the page allocator + * either. Pages might be freed while their page blocks are marked ISOLATED. + * In some cases pages might still end up on pcp lists and that would allow + * for their allocation even when they are in fact isolated already. Depending + * on how strong of a guarantee the caller needs drain_all_pages might be needed + * (e.g. __offline_pages will need to call it after check for isolated range for + * a next retry). + * * Return: the number of isolated pageblocks on success and -EBUSY if any part * of range cannot be isolated. */