From nobody Wed Dec 31 03:24:53 2025 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 754D0C4167B for ; Wed, 8 Nov 2023 17:15:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232319AbjKHRPj (ORCPT ); Wed, 8 Nov 2023 12:15:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45170 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229720AbjKHRPh (ORCPT ); Wed, 8 Nov 2023 12:15:37 -0500 Received: from 66-220-144-179.mail-mxout.facebook.com (66-220-144-179.mail-mxout.facebook.com [66.220.144.179]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0969F1BFF for ; Wed, 8 Nov 2023 09:15:34 -0800 (PST) Received: by devbig1114.prn1.facebook.com (Postfix, from userid 425415) id 03FA3EFD51E1; Wed, 8 Nov 2023 09:15:19 -0800 (PST) From: Stefan Roesch To: kernel-team@fb.com Cc: shr@devkernel.io, akpm@linux-foundation.org, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, willy@infradead.org Subject: [PATCH v3] mm: Fix for negative counter: nr_file_hugepages Date: Wed, 8 Nov 2023 09:15:17 -0800 Message-Id: <20231108171517.2436103-1-shr@devkernel.io> X-Mailer: git-send-email 2.39.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" While qualifiying the 6.4 release, the following warning was detected in messages: vmstat_refresh: nr_file_hugepages -15664 The warning is caused by the incorrect updating of the NR_FILE_THPS counter in the function split_huge_page_to_list. The if case is checking for folio_test_swapbacked, but the else case is missing the check for folio_test_pmd_mappable. The other functions that manipulate the counter like __filemap_add_folio and filemap_unaccount_folio have the corresponding check. I have a test case, which reproduces the problem. It can be found here: https://github.com/sroeschus/testcase/blob/main/vmstat_refresh/madv.c The test case reproduces on an XFS filesystem. Running the same test case on a BTRFS filesystem does not reproduce the problem. AFAIK version 6.1 until 6.6 are affected by this problem. Signed-off-by: Stefan Roesch Co-debugged-by: Johannes Weiner Acked-by: Johannes Weiner Cc: stable@vger.kernel.org Reviewed-by: David Hildenbrand Reviewed-by: Matthew Wilcox (Oracle) Reviewed-by: Yang Shi --- mm/huge_memory.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 064fbd90822b4..874000f97bfc1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2737,13 +2737,15 @@ int split_huge_page_to_list(struct page *page, stru= ct list_head *list) int nr =3D folio_nr_pages(folio); =20 xas_split(&xas, folio, folio_order(folio)); - if (folio_test_swapbacked(folio)) { - __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, - -nr); - } else { - __lruvec_stat_mod_folio(folio, NR_FILE_THPS, - -nr); - filemap_nr_thps_dec(mapping); + if (folio_test_pmd_mappable(folio)) { + if (folio_test_swapbacked(folio)) { + __lruvec_stat_mod_folio(folio, + NR_SHMEM_THPS, -nr); + } else { + __lruvec_stat_mod_folio(folio, + NR_FILE_THPS, -nr); + filemap_nr_thps_dec(mapping); + } } } =20 base-commit: ffc253263a1375a65fa6c9f62a893e9767fbebfa --=20 2.39.3