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 X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A92F6C433B4 for ; Tue, 13 Apr 2021 03:41:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8899A611C9 for ; Tue, 13 Apr 2021 03:41:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240622AbhDMDmB (ORCPT ); Mon, 12 Apr 2021 23:42:01 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:16905 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237526AbhDMDmA (ORCPT ); Mon, 12 Apr 2021 23:42:00 -0400 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4FKBF05FMCzlXVc; Tue, 13 Apr 2021 11:39:48 +0800 (CST) Received: from [10.136.110.154] (10.136.110.154) by smtp.huawei.com (10.3.19.206) with Microsoft SMTP Server (TLS) id 14.3.498.0; Tue, 13 Apr 2021 11:41:32 +0800 Subject: Re: [PATCH v3] f2fs: fix to keep isolation of atomic write To: Jaegeuk Kim CC: , , , Yi Chen References: <20210412081512.103592-1-yuchao0@huawei.com> From: Chao Yu Message-ID: <1171d722-8810-998c-e4b3-0845dbbdea19@huawei.com> Date: Tue, 13 Apr 2021 11:41:32 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.136.110.154] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/4/13 11:27, Jaegeuk Kim wrote: > On 04/12, Chao Yu wrote: >> As Yi Chen reported, there is a potential race case described as below: >> >> Thread A Thread B >> - f2fs_ioc_start_atomic_write >> - mkwrite >> - set_page_dirty >> - f2fs_set_page_private(page, 0) >> - set_inode_flag(FI_ATOMIC_FILE) >> - mkwrite same page >> - set_page_dirty >> - f2fs_register_inmem_page >> - f2fs_set_page_private(ATOMIC_WRITTEN_PAGE) >> failed due to PagePrivate flag has been set >> - list_add_tail >> - truncate_inode_pages >> - f2fs_invalidate_page >> - clear page private but w/o remove it from >> inmem_list >> - set page->mapping to NULL >> - f2fs_ioc_commit_atomic_write >> - __f2fs_commit_inmem_pages >> - __revoke_inmem_pages >> - f2fs_put_page panic as page->mapping is NULL >> >> The root cause is we missed to keep isolation of atomic write in the case >> of start_atomic_write vs mkwrite, let start_atomic_write helds i_mmap_sem >> lock to avoid this issue. > > My only concern is performance regression. Could you please verify the numbers? Do you have specific test script? IIRC, the scenario you mean is multi-threads write/mmap the same db, right? Thanks, > >> >> Reported-by: Yi Chen >> Signed-off-by: Chao Yu >> --- >> v3: >> - rebase to last dev branch >> - update commit message because this patch fixes a different racing issue >> of atomic write >> fs/f2fs/file.c | 3 +++ >> fs/f2fs/segment.c | 6 ++++++ >> 2 files changed, 9 insertions(+) >> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >> index d697c8900fa7..6284b2f4a60b 100644 >> --- a/fs/f2fs/file.c >> +++ b/fs/f2fs/file.c >> @@ -2054,6 +2054,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) >> goto out; >> >> down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >> + down_write(&F2FS_I(inode)->i_mmap_sem); >> >> /* >> * Should wait end_io to count F2FS_WB_CP_DATA correctly by >> @@ -2064,6 +2065,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) >> inode->i_ino, get_dirty_pages(inode)); >> ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX); >> if (ret) { >> + up_write(&F2FS_I(inode)->i_mmap_sem); >> up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >> goto out; >> } >> @@ -2077,6 +2079,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) >> /* add inode in inmem_list first and set atomic_file */ >> set_inode_flag(inode, FI_ATOMIC_FILE); >> clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST); >> + up_write(&F2FS_I(inode)->i_mmap_sem); >> up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >> >> f2fs_update_time(F2FS_I_SB(inode), REQ_TIME); >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >> index 0cb1ca88d4aa..78c8342f52fd 100644 >> --- a/fs/f2fs/segment.c >> +++ b/fs/f2fs/segment.c >> @@ -325,6 +325,7 @@ void f2fs_drop_inmem_pages(struct inode *inode) >> struct f2fs_inode_info *fi = F2FS_I(inode); >> >> do { >> + down_write(&F2FS_I(inode)->i_mmap_sem); >> mutex_lock(&fi->inmem_lock); >> if (list_empty(&fi->inmem_pages)) { >> fi->i_gc_failures[GC_FAILURE_ATOMIC] = 0; >> @@ -339,11 +340,13 @@ void f2fs_drop_inmem_pages(struct inode *inode) >> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]); >> >> mutex_unlock(&fi->inmem_lock); >> + up_write(&F2FS_I(inode)->i_mmap_sem); >> break; >> } >> __revoke_inmem_pages(inode, &fi->inmem_pages, >> true, false, true); >> mutex_unlock(&fi->inmem_lock); >> + up_write(&F2FS_I(inode)->i_mmap_sem); >> } while (1); >> } >> >> @@ -468,6 +471,7 @@ int f2fs_commit_inmem_pages(struct inode *inode) >> f2fs_balance_fs(sbi, true); >> >> down_write(&fi->i_gc_rwsem[WRITE]); >> + down_write(&F2FS_I(inode)->i_mmap_sem); >> >> f2fs_lock_op(sbi); >> set_inode_flag(inode, FI_ATOMIC_COMMIT); >> @@ -479,6 +483,8 @@ int f2fs_commit_inmem_pages(struct inode *inode) >> clear_inode_flag(inode, FI_ATOMIC_COMMIT); >> >> f2fs_unlock_op(sbi); >> + >> + up_write(&F2FS_I(inode)->i_mmap_sem); >> up_write(&fi->i_gc_rwsem[WRITE]); >> >> return err; >> -- >> 2.29.2 > . >