From nobody Mon Feb 9 20:30:32 2026 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 56BD7C7EE24 for ; Fri, 12 May 2023 07:21:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240322AbjELHVh (ORCPT ); Fri, 12 May 2023 03:21:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240193AbjELHUv (ORCPT ); Fri, 12 May 2023 03:20:51 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E87D51992 for ; Fri, 12 May 2023 00:20:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1683876048; x=1715412048; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=vbfbV3YIRAiL+Me0xGu53szMmW7EztoemLnA/EVynh4=; b=MwrY6Owerp5XKQRhA32Uw9W6LaCWSezgBcSt49y10Rft1+oobM3WVZPg cmKGIu/BSUWCn2qCTls6snwXrfLXPh1GbGwYJRhOzAOAafAEafDyV5aYc sGuz/RAhivz7QEF7K91vgutdutzcjT7pd3iVDbIGXbZZwbtNqtm6Wr39r 33raf8DAD15A8F90fGhh+Tcl1+va5DVNzB8zKt6lH5xp1f5DylyDoUncn FUMzQJJ3Fp1Vuv5mcc9LtrQtN+WPz1DrC9lQ0+sds1/XWl0sq9tRgIK19 /qSv6c9esN3DhrtOV7E3nVEWBOq1CIV9k6/y0OMGybOyr7J1CG4iqhQ9V A==; X-IronPort-AV: E=McAfee;i="6600,9927,10707"; a="349566264" X-IronPort-AV: E=Sophos;i="5.99,269,1677571200"; d="scan'208";a="349566264" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 May 2023 00:20:48 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10707"; a="765073979" X-IronPort-AV: E=Sophos;i="5.99,269,1677571200"; d="scan'208";a="765073979" Received: from junxiaochang.bj.intel.com ([10.238.154.225]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 May 2023 00:20:46 -0700 From: Junxiao Chang To: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, mhocko@suse.com, jmarchan@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mike.kravetz@oracle.com, muchun.song@linux.dev Cc: junxiao.chang@intel.com Subject: [PATCH] mm: fix hugetlb page unmap count balance issue Date: Fri, 12 May 2023 15:20:36 +0800 Message-Id: <20230512072036.1027784-1-junxiao.chang@intel.com> X-Mailer: git-send-email 2.34.1 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" hugetlb page usually is mapped with pmd, but occasionally it might be mapped with pte. QEMU can use udma-buf to create host dmabufs for guest framebuffers. When QEMU is launched with parameter "hugetlb=3Don", udmabuffer driver maps hugetlb page with pte in page fault handler. Call chain looks like: page_add_file_rmap do_set_pte finish_fault __do_fault -> udmabuf_vm_fault, it maps hugetlb page here. do_read_fault In function page_add_file_rmap, compound is false since it is pte mapping. When qemu exits and page is unmapped in function page_remove_rmap, the hugetlb page should not be handled in pmd way. This change is to check compound parameter as well as hugetlb flag. It fixes below kernel bug which is reproduced with 6.3 kernel: [ 114.027754] BUG: Bad page cache in process qemu-system-x86 pfn:37aa00 [ 114.034288] page:000000000dd2153b refcount:514 mapcount:-4 mapping:00000= 0004b01ca30 index:0x13800 pfn:0x37aa00 [ 114.044277] head:000000000dd2153b order:9 entire_mapcount:-4 nr_pages_ma= pped:4 pincount:512 [ 114.052623] aops:hugetlbfs_aops ino:6f93 [ 114.056552] flags: 0x17ffffc0010001(locked|head|node=3D0|zone=3D2|lastcp= upid=3D0x1fffff) [ 114.064115] raw: 0017ffffc0010001 fffff7338deb0008 fffff7338dea0008 ffff= 98dc855ea870 [ 114.071847] raw: 000000000000009c 0000000000000002 00000202ffffffff 0000= 000000000000 [ 114.079572] page dumped because: still mapped when deleted [ 114.085048] CPU: 0 PID: 3122 Comm: qemu-system-x86 Tainted: G BU W = E 6.3.0-v3+ #62 [ 114.093566] Hardware name: Intel Corporation Alder Lake Client Platform = DDR5 SODIMM SBS RVP, BIOS ADLPFWI1.R00.3084.D89.2303211034 03/21/2023 [ 114.106839] Call Trace: [ 114.109291] [ 114.111405] dump_stack_lvl+0x4c/0x70 [ 114.115073] dump_stack+0x14/0x20 [ 114.118395] filemap_unaccount_folio+0x159/0x220 [ 114.123021] filemap_remove_folio+0x54/0x110 [ 114.127295] remove_inode_hugepages+0x111/0x5b0 [ 114.131834] hugetlbfs_evict_inode+0x23/0x50 [ 114.136111] evict+0xcd/0x1e0 [ 114.139083] iput.part.0+0x183/0x1e0 [ 114.142663] iput+0x20/0x30 [ 114.145466] dentry_unlink_inode+0xcc/0x130 [ 114.149655] __dentry_kill+0xec/0x1a0 [ 114.153325] dput+0x1ca/0x3c0 [ 114.156293] __fput+0xf4/0x280 [ 114.159357] ____fput+0x12/0x20 [ 114.162502] task_work_run+0x62/0xa0 [ 114.166088] do_exit+0x352/0xae0 [ 114.169321] do_group_exit+0x39/0x90 [ 114.172892] get_signal+0xa09/0xa30 [ 114.176391] arch_do_signal_or_restart+0x33/0x280 [ 114.181098] exit_to_user_mode_prepare+0x11f/0x190 [ 114.185893] syscall_exit_to_user_mode+0x2a/0x50 [ 114.190509] do_syscall_64+0x4c/0x90 [ 114.194095] entry_SYSCALL_64_after_hwframe+0x72/0xdc Fixes: 53f9263baba6 ("mm: rework mapcount accounting to enable 4k mapping o= f THPs") Signed-off-by: Junxiao Chang --- mm/rmap.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 19392e090bec6..b42fc0389c243 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1377,9 +1377,9 @@ void page_remove_rmap(struct page *page, struct vm_ar= ea_struct *vma, =20 VM_BUG_ON_PAGE(compound && !PageHead(page), page); =20 - /* Hugetlb pages are not counted in NR_*MAPPED */ - if (unlikely(folio_test_hugetlb(folio))) { - /* hugetlb pages are always mapped with pmds */ + /* Hugetlb pages usually are not counted in NR_*MAPPED */ + if (unlikely(folio_test_hugetlb(folio) && compound)) { + /* hugetlb pages are mapped with pmds */ atomic_dec(&folio->_entire_mapcount); return; } --=20 2.34.1