From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751085AbeEEFgt (ORCPT ); Sat, 5 May 2018 01:36:49 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:49894 "EHLO huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750744AbeEEFgs (ORCPT ); Sat, 5 May 2018 01:36:48 -0400 Subject: Re: [PATCH] f2fs: fix to wait IO writeback in __revoke_inmem_pages() From: Chao Yu To: Jaegeuk Kim , Chao Yu CC: , References: <20180426083247.86337-1-yuchao0@huawei.com> <20180426154817.GF68594@jaegeuk-macbookpro.roam.corp.google.com> <7810a3a3-70f3-9b37-e64a-f26dba72b0f9@kernel.org> <20180426163651.GL68594@jaegeuk-macbookpro.roam.corp.google.com> <3cae6be6-365d-8e48-b1db-8b04f96634e4@huawei.com> Message-ID: <8dcbf002-b585-23fa-8c0d-0e3330eb54e5@huawei.com> Date: Sat, 5 May 2018 13:36:39 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <3cae6be6-365d-8e48-b1db-8b04f96634e4@huawei.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ping, On 2018/4/27 10:37, Chao Yu wrote: > On 2018/4/27 0:36, Jaegeuk Kim wrote: >> On 04/26, Chao Yu wrote: >>> On 2018/4/26 23:48, Jaegeuk Kim wrote: >>>> On 04/26, Chao Yu wrote: >>>>> Thread A Thread B >>>>> - f2fs_ioc_commit_atomic_write >>>>> - commit_inmem_pages >>>>> - f2fs_submit_merged_write_cond >>>>> : write data >>>>> - write_checkpoint >>>>> - do_checkpoint >>>>> : commit all node within CP >>>>> -> SPO >>>>> - f2fs_do_sync_file >>>>> - file_write_and_wait_range >>>>> : wait data writeback >>>>> >>>>> In above race condition, data/node can be flushed in reversed order when >>>>> coming a checkpoint before f2fs_do_sync_file, after SPOR, it results in >>>>> atomic written data being corrupted. >>>> >>>> Wait, what is the problem here? Thread B could succeed checkpoint, there is >>>> no problem. If it fails, there is no fsync mark where we can recover it, so >>> >>> Node is flushed by checkpoint before data, with reversed order, that's the problem. >> >> What do you mean? Data should be in disk, in order to proceed checkpoint. > > 1. thread A: commit_inmem_pages submit data into block layer, but haven't waited > it writeback. > 2. thread A: commit_inmem_pages update related node. > 3. thread B: do checkpoint, flush all nodes to disk > 4. SPOR > > Then, atomic file becomes corrupted since nodes is flushed before data. > > Thanks, > >> >>> >>> Thanks, >>> >>>> we can just ignore the last written data as nothing. >>>> >>>>> >>>>> This patch adds f2fs_wait_on_page_writeback in __revoke_inmem_pages() to >>>>> keep data and node of atomic file being flushed orderly. >>>>> >>>>> Signed-off-by: Chao Yu >>>>> --- >>>>> fs/f2fs/file.c | 4 ++++ >>>>> fs/f2fs/segment.c | 3 +++ >>>>> 2 files changed, 7 insertions(+) >>>>> >>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>>> index be7578774a47..a352804af244 100644 >>>>> --- a/fs/f2fs/file.c >>>>> +++ b/fs/f2fs/file.c >>>>> @@ -217,6 +217,9 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end, >>>>> >>>>> trace_f2fs_sync_file_enter(inode); >>>>> >>>>> + if (atomic) >>>>> + goto write_done; >>>>> + >>>>> /* if fdatasync is triggered, let's do in-place-update */ >>>>> if (datasync || get_dirty_pages(inode) <= SM_I(sbi)->min_fsync_blocks) >>>>> set_inode_flag(inode, FI_NEED_IPU); >>>>> @@ -228,6 +231,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end, >>>>> return ret; >>>>> } >>>>> >>>>> +write_done: >>>>> /* if the inode is dirty, let's recover all the time */ >>>>> if (!f2fs_skip_inode_update(inode, datasync)) { >>>>> f2fs_write_inode(inode, NULL); >>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c >>>>> index 584483426584..9ca3d0a43d93 100644 >>>>> --- a/fs/f2fs/segment.c >>>>> +++ b/fs/f2fs/segment.c >>>>> @@ -230,6 +230,8 @@ static int __revoke_inmem_pages(struct inode *inode, >>>>> >>>>> lock_page(page); >>>>> >>>>> + f2fs_wait_on_page_writeback(page, DATA, true); >>>>> + >>>>> if (recover) { >>>>> struct dnode_of_data dn; >>>>> struct node_info ni; >>>>> @@ -415,6 +417,7 @@ static int __commit_inmem_pages(struct inode *inode) >>>>> /* drop all uncommitted pages */ >>>>> __revoke_inmem_pages(inode, &fi->inmem_pages, true, false); >>>>> } else { >>>>> + /* wait all committed IOs writeback and release them from list */ >>>>> __revoke_inmem_pages(inode, &revoke_list, false, false); >>>>> } >>>>> >>>>> -- >>>>> 2.15.0.55.gc2ece9dc4de6 >> >> . >> > > > . >