From nobody Sat Apr 11 06:45:19 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 C24DAC00140 for ; Mon, 15 Aug 2022 07:57:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241546AbiHOH5x (ORCPT ); Mon, 15 Aug 2022 03:57:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55332 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230137AbiHOH5s (ORCPT ); Mon, 15 Aug 2022 03:57:48 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CAD3F1DA6D for ; Mon, 15 Aug 2022 00:57:46 -0700 (PDT) Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.54]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4M5mnB2Hz4zGpXl; Mon, 15 Aug 2022 15:56:14 +0800 (CST) Received: from kwepemm600016.china.huawei.com (7.193.23.20) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 15 Aug 2022 15:57:44 +0800 Received: from huawei.com (10.175.124.27) by kwepemm600016.china.huawei.com (7.193.23.20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 15 Aug 2022 15:57:43 +0800 From: Shuqi Zhang To: , CC: , , Subject: [PATCH -next] f2fs: fix wrong dirty page count when race between mmap and fallocate. Date: Mon, 15 Aug 2022 16:15:55 +0800 Message-ID: <20220815081555.2961943-1-zhangshuqi3@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemm600016.china.huawei.com (7.193.23.20) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This is a BUG_ON issue as follows when running xfstest-generic-503: WARNING: CPU: 21 PID: 1385 at fs/f2fs/inode.c:762 f2fs_evict_inode+0x847/0x= aa0 Modules linked in: CPU: 21 PID: 1385 Comm: umount Not tainted 5.19.0-rc5+ #73 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 0= 4/01/2014 Call Trace: evict+0x129/0x2d0 dispose_list+0x4f/0xb0 evict_inodes+0x204/0x230 generic_shutdown_super+0x5b/0x1e0 kill_block_super+0x29/0x80 kill_f2fs_super+0xe6/0x140 deactivate_locked_super+0x44/0xc0 deactivate_super+0x79/0x90 cleanup_mnt+0x114/0x1a0 __cleanup_mnt+0x16/0x20 task_work_run+0x98/0x100 exit_to_user_mode_prepare+0x3d0/0x3e0 syscall_exit_to_user_mode+0x12/0x30 do_syscall_64+0x42/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 Function flow analysis when BUG occurs: f2fs_fallocate mmap do_page_fault pte_spinlock // ---lock_pte do_wp_page wp_page_shared pte_unmap_unlock // unlock_pte do_page_mkwrite f2fs_vm_page_mkwrite down_read(i_mmap_sem) lock_page if (PageMappedToDisk(page)) goto out; // set_page_dirty --NOT RUN out: up_read(i_mmap_sem) lock_page finish_mkwrite_fault // unlock_pte f2fs_collapse_range down_write(i_mmap_sem) truncate_pagecache unmap_mapping_pages i_mmap_lock_write // down_write(i_mmap_rwsem) ...... zap_pte_range pte_offset_map_lock // ---lock_pte f2fs_set_data_page_dirty if (!PageDirty(page)) { fault_dirty_shared_page f2fs_set_data_page_dirty if (!PageDirty(page)) { __set_page_dirty_nobuffer f2fs_update_dirty_page // ++ } unlock_page __set_page_dirty_nobuffers f2fs_update_dirty_page // page count++ } pte_unmap_unlock // --unlock_pte i_mmap_unlock_write // up_write(i_mmap_rwsem) truncate_inode_pages up_write(i_mmap_sem) When race happens between mmap-do_page_fault-wp_page_shared and fallocate-truncate_pagecache-zap_pte_range, the zap_pte_range calls function set_page_dirty without page lock. Besides, though truncate_pagecache has immap and pte lock, wp_page_shared calls fault_dirty_shared_page without any. In this case, two threads race in f2fs_set_data_page_dirty function. Page is set to dirty only ONCE, but the count is added TWICE by calling f2fs_update_dirty_page. Thus the count of dirty page cannot accord with the real dirty pages. Following is the solution to in case of race happens without any lock. If making sure f2fs_vm_page_mkwrite calls set_page_dirty within immap lock area, page will already be dirtied when running into fault_dirty_shared_page-f2fs_set_data_page_dirty. The count of dirty page will not be increased wrong times. Signed-off-by: Shuqi Zhang --- fs/f2fs/file.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index ce4905a073b3..d837359a9c00 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -140,7 +140,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault = *vmf) * check to see if the page is mapped already (no holes) */ if (PageMappedToDisk(page)) - goto out_sem; + goto set_dirty; =20 /* page is wholly or partially inside EOF */ if (((loff_t)(page->index + 1) << PAGE_SHIFT) > @@ -150,14 +150,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_faul= t *vmf) offset =3D i_size_read(inode) & ~PAGE_MASK; zero_user_segment(page, offset, PAGE_SIZE); } - set_page_dirty(page); - if (!PageUptodate(page)) - SetPageUptodate(page); =20 f2fs_update_iostat(sbi, APP_MAPPED_IO, F2FS_BLKSIZE); - f2fs_update_time(sbi, REQ_TIME); =20 +set_dirty: trace_f2fs_vm_page_mkwrite(page, DATA); + set_page_dirty(page); + if (!PageUptodate(page)) + SetPageUptodate(page); + f2fs_update_time(sbi, REQ_TIME); out_sem: filemap_invalidate_unlock_shared(inode->i_mapping); =20 --=20 2.25.1