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 E85B2C433DB for ; Wed, 13 Jan 2021 01:31:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD8DB23135 for ; Wed, 13 Jan 2021 01:31:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727362AbhAMBbP (ORCPT ); Tue, 12 Jan 2021 20:31:15 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:10717 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726473AbhAMBbN (ORCPT ); Tue, 12 Jan 2021 20:31:13 -0500 Received: from DGGEMS409-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4DFqbp5FB0zl4P4; Wed, 13 Jan 2021 09:29:10 +0800 (CST) Received: from [10.136.114.67] (10.136.114.67) by smtp.huawei.com (10.3.19.209) with Microsoft SMTP Server (TLS) id 14.3.498.0; Wed, 13 Jan 2021 09:30:22 +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: <240391d4-c3bb-882d-0e86-1e30e2fd0ef4@huawei.com> Date: Wed, 13 Jan 2021 09:30:21 +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 2021/1/13 6:32, Jaegeuk Kim wrote: > On 01/12, Chao Yu wrote: >> 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? > > Nothing special. Just generating multiple sqlite transactions to the same db. I doubt that start/commit flow race with ->release/->flush interface can cause lower concurrency? f2fs_ioc_start_atomic_write or ->release or ->flush f2fs_ioc_commit_atomic_write - f2fs_drop_inmem_pages down_write(&F2FS_I(inode)->i_mmap_sem); down_write(&F2FS_I(inode)->i_mmap_sem); How about trying this testcase again after removing i_mmap_sem lock in f2fs_drop_inmem_pages()? Thanks, > >> >> 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 >>> . >>> > . >