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 68C83C433EF for ; Fri, 4 Mar 2022 04:04:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237865AbiCDEEt (ORCPT ); Thu, 3 Mar 2022 23:04:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237869AbiCDEEr (ORCPT ); Thu, 3 Mar 2022 23:04:47 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3973D8567B for ; Thu, 3 Mar 2022 20:04:01 -0800 (PST) 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 B34B3B82750 for ; Fri, 4 Mar 2022 04:03:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F30DC340F0; Fri, 4 Mar 2022 04:03:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1646366638; bh=ZzDAu+tbIB7/0OcBmE829NbpfQn4ZDB1VXTaIkXrFQQ=; h=Date:To:From:Subject:From; b=HcCEMtXQSktr1o/0hsHYV1GuozEFiCf4Yyei5ObxrkpZSUL3sfm30ElXBgYbeAWV4 c04y55D5S5471RKWFOCjQM/ok1+JAsRfagj/fZuz90XtA064yE+7QgqiAR7kq4fcQC J4CKYF25/K9dOOetSUWq9COC6+yEUGo79Y8sK6Rc= Date: Thu, 03 Mar 2022 20:03:57 -0800 To: mm-commits@vger.kernel.org, ziy@nvidia.com, shy828301@gmail.com, rcampbell@nvidia.com, kirill.shutemov@linux.intel.com, hughd@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch added to -mm tree Message-Id: <20220304040358.2F30DC340F0@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: refix __split_huge_pmd_locked() for migration PMD has been added to the -mm tree. Its filename is mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Hugh Dickins Subject: mm/thp: refix __split_huge_pmd_locked() for migration PMD Migration entries do not contribute to a page's reference count: move __split_huge_pmd_locked()'s page_ref_add() into pmd_migration's else block (along with the page_count() check - a page is quite likely to to have reference count frozen to 0 when a migration entry is found). This will fix a very rare anonymous memory leak, after a split_huge_pmd() raced with an anon split_huge_page() or an anon THP migrate_pages(): since the wrongly raised refcount stopped the page (perhaps small, perhaps huge, depending on when the race hit) from ever being freed. At first I thought there were worse risks, from prematurely unfreezing a frozen page: but now think that would only affect page cache pages, which do not come this way (except for anonymous pages in swap cache, perhaps). Link: https://lkml.kernel.org/r/84792468-f512-e48f-378c-e34c3641e97@google.com Fixes: ec0abae6dcdf ("mm/thp: fix __split_huge_pmd_locked() for migration PMD") Signed-off-by: Hugh Dickins Reviewed-by: Yang Shi Cc: Ralph Campbell Cc: Zi Yan Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton --- mm/huge_memory.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/huge_memory.c~mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd +++ a/mm/huge_memory.c @@ -2055,9 +2055,9 @@ static void __split_huge_pmd_locked(stru young = pmd_young(old_pmd); soft_dirty = pmd_soft_dirty(old_pmd); uffd_wp = pmd_uffd_wp(old_pmd); + VM_BUG_ON_PAGE(!page_count(page), page); + page_ref_add(page, HPAGE_PMD_NR - 1); } - VM_BUG_ON_PAGE(!page_count(page), page); - page_ref_add(page, HPAGE_PMD_NR - 1); /* * Withdraw the table only after we mark the pmd entry invalid. _ Patches currently in -mm which might be from hughd@google.com are memfd-fix-f_seal_write-after-shmem-huge-page-allocated.patch tmpfs-support-for-file-creation-time-fix.patch mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap.patch mm-thp-clearpagedoublemap-in-first-page_add_file_rmap.patch