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 477AFC433DB for ; Tue, 12 Jan 2021 03:00:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0679A22D37 for ; Tue, 12 Jan 2021 03:00:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733213AbhALC7t (ORCPT ); Mon, 11 Jan 2021 21:59:49 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:10709 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728044AbhALC7t (ORCPT ); Mon, 11 Jan 2021 21:59:49 -0500 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4DFFcZ1vlpzkqyC; Tue, 12 Jan 2021 10:57:50 +0800 (CST) Received: from [10.136.114.67] (10.136.114.67) by smtp.huawei.com (10.3.19.205) with Microsoft SMTP Server (TLS) id 14.3.498.0; Tue, 12 Jan 2021 10:59:03 +0800 Subject: Re: [f2fs-dev] [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: Date: Tue, 12 Jan 2021 10:59:03 +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: [10.136.114.67] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/1/12 0:32, Jaegeuk Kim wrote: > On 01/06, Jaegeuk Kim wrote: >> On 01/06, Jaegeuk Kim wrote: >>> Hi Chao, >>> >>> With a quick test, this patch causes down_write failure resulting in blocking >>> process. I didn't dig in the bug so, please check the code again. :P >> >> nvm. I can see it works now. > > Hmm, this gives a huge perf regression when running sqlite. :( > We may need to check the lock coverage. Thoughts? I added i_mmap_sem lock only, so it can cause atomic_{start,commit,finish} race with mmap and truncation operations in additionally. I'd like to know what's your sqlite testcase? Thanks, > >> >>> >>> 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 >>>> - 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 >>> >>> >>> _______________________________________________ >>> Linux-f2fs-devel mailing list >>> Linux-f2fs-devel@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel >> >> >> _______________________________________________ >> Linux-f2fs-devel mailing list >> Linux-f2fs-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > . >