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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA380C43334 for ; Mon, 4 Jul 2022 01:33:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232357AbiGDBdh (ORCPT ); Sun, 3 Jul 2022 21:33:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229450AbiGDBdc (ORCPT ); Sun, 3 Jul 2022 21:33:32 -0400 Received: from out0.migadu.com (out0.migadu.com [IPv6:2001:41d0:2:267::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73DB210A6 for ; Sun, 3 Jul 2022 18:33:30 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1656898408; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2DMQHTNxYJaXGXTJwZRtDjz8Ro6QHDIDNISX5LwnZ+s=; b=l1rS6EMHG1eSBfPlLAVtXPJKWp746h4/hewVYtrZpCoo6IKZxse2sDb6ev/jyEWsUZo7fJ v3GnTdI8By0Dq4Ivs0mewBveh6qrJUODaJ7FbyJlI42dDWJsDNdqZx/kmIENvZpBj2kRwd yyTck7qUf8QBlA0Of70QXO1fFeihZyM= From: Naoya Horiguchi To: linux-mm@kvack.org Cc: Andrew Morton , David Hildenbrand , Mike Kravetz , Miaohe Lin , Liu Shixin , Yang Shi , Oscar Salvador , Muchun Song , Naoya Horiguchi , linux-kernel@vger.kernel.org Subject: [mm-unstable PATCH v4 1/9] mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages() Date: Mon, 4 Jul 2022 10:33:04 +0900 Message-Id: <20220704013312.2415700-2-naoya.horiguchi@linux.dev> In-Reply-To: <20220704013312.2415700-1-naoya.horiguchi@linux.dev> References: <20220704013312.2415700-1-naoya.horiguchi@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Naoya Horiguchi I found a weird state of 1GB hugepage pool, caused by the following procedure: - run a process reserving all free 1GB hugepages, - shrink free 1GB hugepage pool to zero (i.e. writing 0 to /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages), then - kill the reserving process. , then all the hugepages are free *and* surplus at the same time. $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages 3 $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/free_hugepages 3 $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/resv_hugepages 0 $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/surplus_hugepages 3 This state is resolved by reserving and allocating the pages then freeing them again, so this seems not to result in serious problem. But it's a little surprising (shrinking pool suddenly fails). This behavior is caused by hstate_is_gigantic() check in return_unused_surplus_pages(). This was introduced so long ago in 2008 by commit aa888a74977a ("hugetlb: support larger than MAX_ORDER"), and at that time the gigantic pages were not supposed to be allocated/freed at run-time. Now kernel can support runtime allocation/free, so let's check gigantic_page_runtime_supported() together. Signed-off-by: Naoya Horiguchi --- v2 -> v3: - Fixed typo in patch description, - add !gigantic_page_runtime_supported() check instead of removing hstate_is_gigantic() check (suggested by Miaohe and Muchun) - add a few more !gigantic_page_runtime_supported() check in set_max_huge_pages() (by Mike). --- mm/hugetlb.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 2a554f006255..bdc4499f324b 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2432,8 +2432,7 @@ static void return_unused_surplus_pages(struct hstate *h, /* Uncommit the reservation */ h->resv_huge_pages -= unused_resv_pages; - /* Cannot return gigantic pages currently */ - if (hstate_is_gigantic(h)) + if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) goto out; /* @@ -3315,7 +3314,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, * the user tries to allocate gigantic pages but let the user free the * boottime allocated gigantic pages. */ - if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) { + if (hstate_is_gigantic(h) && (!IS_ENABLED(CONFIG_CONTIG_ALLOC) || + !gigantic_page_runtime_supported())) { if (count > persistent_huge_pages(h)) { spin_unlock_irq(&hugetlb_lock); mutex_unlock(&h->resize_lock); @@ -3363,6 +3363,19 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, goto out; } + /* + * We can not decrease gigantic pool size if runtime modification + * is not supported. + */ + if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) { + if (count < persistent_huge_pages(h)) { + spin_unlock_irq(&hugetlb_lock); + mutex_unlock(&h->resize_lock); + NODEMASK_FREE(node_alloc_noretry); + return -EINVAL; + } + } + /* * Decrease the pool size * First return free pages to the buddy allocator (being careful -- 2.25.1