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=-15.3 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=unavailable 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 78A16C433E0 for ; Fri, 15 Jan 2021 08:00:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 33572221FB for ; Fri, 15 Jan 2021 08:00:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732100AbhAOH7w (ORCPT ); Fri, 15 Jan 2021 02:59:52 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:10725 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731999AbhAOH7w (ORCPT ); Fri, 15 Jan 2021 02:59:52 -0500 Received: from DGGEMS409-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4DHD7H0y3Nzl4xP; Fri, 15 Jan 2021 15:57:47 +0800 (CST) Received: from [10.136.110.154] (10.136.110.154) by smtp.huawei.com (10.3.19.209) with Microsoft SMTP Server (TLS) id 14.3.498.0; Fri, 15 Jan 2021 15:59:03 +0800 Subject: Re: [PATCH v2] f2fs: fix to keep isolation of atomic write To: Jaegeuk Kim CC: , , References: <20201230075557.108818-1-yuchao0@huawei.com> From: Chao Yu Message-ID: <3923906d-f208-f6c2-f121-5e77e8fb6b28@huawei.com> Date: Fri, 15 Jan 2021 15:59:03 +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 2021/1/15 5:53, Jaegeuk Kim wrote: > On 12/30, Chao Yu wrote: >> ThreadA ThreadB >> - f2fs_ioc_start_atomic_write >> - write >> - f2fs_ioc_commit_atomic_write >> - f2fs_commit_inmem_pages >> - f2fs_drop_inmem_pages >> - f2fs_drop_inmem_pages >> - __revoke_inmem_pages >> - f2fs_vm_page_mkwrite >> - set_page_dirty >> - tag ATOMIC_WRITTEN_PAGE and add page >> to inmem_pages list >> - clear_inode_flag(FI_ATOMIC_FILE) >> - f2fs_vm_page_mkwrite >> - set_page_dirty >> - f2fs_update_dirty_page >> - f2fs_trace_pid >> - tag inmem page private to pid > > Hmm, how about removing fs/f2fs/trace.c to make private more complicated > like this? I think we can get IO traces from tracepoints. Hmm, actually, there is are issues, one is the trace IO, the other is the race issue (atomic_start,commit,drop vs mkwrite) which can make isolation semantics of transaction be broken. Or can we avoid atomic file racing with file mmap? - atomic_start - file_mmap - inode_lock - if (FI_ATOMIC_FILE) return - inode_lock - if (FI_MMAP_FILE) return Thanks, > >> - truncate >> - f2fs_invalidate_page >> - set page->mapping to NULL >> then it will cause panic once we >> access page->mapping >> >> The root cause is we missed to keep isolation of atomic write in the case >> of commit_atomic_write vs mkwrite, let commit_atomic_write helds i_mmap_sem >> lock to avoid this issue. >> >> Signed-off-by: Chao Yu >> --- >> v2: >> - use i_mmap_sem to avoid mkwrite racing with below flows: >> * f2fs_ioc_start_atomic_write >> * f2fs_drop_inmem_pages >> * f2fs_commit_inmem_pages >> >> fs/f2fs/file.c | 3 +++ >> fs/f2fs/segment.c | 7 +++++++ >> 2 files changed, 10 insertions(+) >> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >> index 4e6d4b9120a8..a48ec650d691 100644 >> --- a/fs/f2fs/file.c >> +++ b/fs/f2fs/file.c >> @@ -2050,6 +2050,7 @@ 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 >> @@ -2060,6 +2061,7 @@ 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; >> } >> @@ -2073,6 +2075,7 @@ 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 d8570b0359f5..dab870d9faf6 100644 >> --- a/fs/f2fs/segment.c >> +++ b/fs/f2fs/segment.c >> @@ -327,6 +327,8 @@ void f2fs_drop_inmem_pages(struct inode *inode) >> struct f2fs_sb_info *sbi = F2FS_I_SB(inode); >> struct f2fs_inode_info *fi = F2FS_I(inode); >> >> + down_write(&F2FS_I(inode)->i_mmap_sem); >> + >> while (!list_empty(&fi->inmem_pages)) { >> mutex_lock(&fi->inmem_lock); >> __revoke_inmem_pages(inode, &fi->inmem_pages, >> @@ -344,6 +346,8 @@ void f2fs_drop_inmem_pages(struct inode *inode) >> sbi->atomic_files--; >> } >> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]); >> + >> + up_write(&F2FS_I(inode)->i_mmap_sem); >> } >> >> void f2fs_drop_inmem_page(struct inode *inode, struct page *page) >> @@ -467,6 +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); >> @@ -478,6 +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 > . >