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 22673C43219 for ; Fri, 25 Mar 2022 22:42:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233934AbiCYWn7 (ORCPT ); Fri, 25 Mar 2022 18:43:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233936AbiCYWn4 (ORCPT ); Fri, 25 Mar 2022 18:43:56 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2076B209A7E for ; Fri, 25 Mar 2022 15:41:54 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C5904B82A2F for ; Fri, 25 Mar 2022 22:41:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D75AC3410F; Fri, 25 Mar 2022 22:41:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648248111; bh=bA7b7QbHnBSpkgSd11D2D35Dv89n2ORBhdU9dWIofJo=; h=Date:To:From:Subject:From; b=AcwUc0Qx1zekfcxkAbMEjVV60+24NaD32vHXNzsbIJnoY/BoU/sAaY6YCotpq4721 E/tU+Mf4dkGczuaKG9NkU4RfDgNIJoSymO8asF1Ymo2TQWPdUVZaglfRxZ0LhcCnSY PZcesbm0UYxrNQwMHm/3rz+oDcew2f8SlIcwmUf8= Date: Fri, 25 Mar 2022 15:41:50 -0700 To: mm-commits@vger.kernel.org, shy828301@gmail.com, kirill.shutemov@linux.intel.com, hughd@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged] mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap.patch removed from -mm tree Message-Id: <20220325224151.5D75AC3410F@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/thp: fix NR_FILE_MAPPED accounting in page_*_file_rmap() has been removed from the -mm tree. Its filename was mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Hugh Dickins Subject: mm/thp: fix NR_FILE_MAPPED accounting in page_*_file_rmap() NR_FILE_MAPPED accounting in mm/rmap.c (for /proc/meminfo "Mapped" and /proc/vmstat "nr_mapped" and the memcg's memory.stat "mapped_file") is slightly flawed for file or shmem huge pages. It is well thought out, and looks convincing, but there's a racy case when the careful counting in page_remove_file_rmap() (without page lock) gets discarded. So that in a workload like two "make -j20" kernel builds under memory pressure, with cc1 on hugepage text, "Mapped" can easily grow by a spurious 5MB or more on each iteration, ending up implausibly bigger than most other numbers in /proc/meminfo. And, hypothetically, might grow to the point of seriously interfering in mm/vmscan.c's heuristics, which do take NR_FILE_MAPPED into some consideration. Fixed by moving the __mod_lruvec_page_state() down to where it will not be missed before return (and I've grown a bit tired of that oft-repeated but-not-everywhere comment on the __ness: it gets lost in the move here). Does page_add_file_rmap() need the same change? I suspect not, because page lock is held in all relevant cases, and its skipping case looks safe; but it's much easier to be sure, if we do make the same change. Link: https://lkml.kernel.org/r/e02e52a1-8550-a57c-ed29-f51191ea2375@google.com Fixes: dd78fedde4b9 ("rmap: support file thp") Signed-off-by: Hugh Dickins Reviewed-by: Yang Shi Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton --- mm/rmap.c | 31 ++++++++++++++----------------- 1 file changed, 14 insertions(+), 17 deletions(-) --- a/mm/rmap.c~mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap +++ a/mm/rmap.c @@ -1236,14 +1236,14 @@ void page_add_new_anon_rmap(struct page void page_add_file_rmap(struct page *page, struct vm_area_struct *vma, bool compound) { - int i, nr = 1; + int i, nr = 0; VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page); lock_page_memcg(page); if (compound && PageTransHuge(page)) { int nr_pages = thp_nr_pages(page); - for (i = 0, nr = 0; i < nr_pages; i++) { + for (i = 0; i < nr_pages; i++) { if (atomic_inc_and_test(&page[i]._mapcount)) nr++; } @@ -1271,11 +1271,12 @@ void page_add_file_rmap(struct page *pag VM_WARN_ON_ONCE(!PageLocked(page)); SetPageDoubleMap(compound_head(page)); } - if (!atomic_inc_and_test(&page->_mapcount)) - goto out; + if (atomic_inc_and_test(&page->_mapcount)) + nr++; } - __mod_lruvec_page_state(page, NR_FILE_MAPPED, nr); out: + if (nr) + __mod_lruvec_page_state(page, NR_FILE_MAPPED, nr); unlock_page_memcg(page); mlock_vma_page(page, vma, compound); @@ -1283,7 +1284,7 @@ out: static void page_remove_file_rmap(struct page *page, bool compound) { - int i, nr = 1; + int i, nr = 0; VM_BUG_ON_PAGE(compound && !PageHead(page), page); @@ -1298,12 +1299,12 @@ static void page_remove_file_rmap(struct if (compound && PageTransHuge(page)) { int nr_pages = thp_nr_pages(page); - for (i = 0, nr = 0; i < nr_pages; i++) { + for (i = 0; i < nr_pages; i++) { if (atomic_add_negative(-1, &page[i]._mapcount)) nr++; } if (!atomic_add_negative(-1, compound_mapcount_ptr(page))) - return; + goto out; if (PageSwapBacked(page)) __mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED, -nr_pages); @@ -1311,16 +1312,12 @@ static void page_remove_file_rmap(struct __mod_lruvec_page_state(page, NR_FILE_PMDMAPPED, -nr_pages); } else { - if (!atomic_add_negative(-1, &page->_mapcount)) - return; + if (atomic_add_negative(-1, &page->_mapcount)) + nr++; } - - /* - * We use the irq-unsafe __{inc|mod}_lruvec_page_state because - * these counters are not modified in interrupt context, and - * pte lock(a spinlock) is held, which implies preemption disabled. - */ - __mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr); +out: + if (nr) + __mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr); } static void page_remove_anon_compound_rmap(struct page *page) _ Patches currently in -mm which might be from hughd@google.com are