From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754081AbeEHGGT (ORCPT ); Tue, 8 May 2018 02:06:19 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:7238 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752497AbeEHGGS (ORCPT ); Tue, 8 May 2018 02:06:18 -0400 Subject: Re: [PATCH] f2fs: fix to wait IO writeback in __revoke_inmem_pages() To: Jaegeuk Kim CC: Chao Yu , , 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> <20180507204630.GB83867@jaegeuk-macbookpro.roam.corp.google.com> <20180508033155.GC17507@jaegeuk-macbookpro.roam.corp.google.com> From: Chao Yu Message-ID: <50b77166-754b-fe14-8dd4-b6e96790fe2e@huawei.com> Date: Tue, 8 May 2018 14:06:05 +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: <20180508033155.GC17507@jaegeuk-macbookpro.roam.corp.google.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 On 2018/5/8 11:31, Jaegeuk Kim wrote: > On 05/08, Chao Yu wrote: >> On 2018/5/8 4:46, Jaegeuk Kim wrote: >>> On 04/27, 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 >>> >>> How about, in block_operations(), >>> >>> down_read_trylock(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>> if (fail) >>> wait_on_all_pages_writeback(F2FS_WB_DATA); >>> else >>> up_read(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >> >> I sent one patch for that, could you check it? >> >> Adding wait_on_all_pages_writeback in block_operations() can make checkpoint() >> wait pages writeback one more time, which break IO flow, so what's your concern >> here? > > Performance. And I can see wait_on_all_pages_writeback() waits only for > F2FS_WB_CP_DATA in checkpoint()? Oh, you mean wait all F2FS_WB_DATA pages writeback, what about just treating atomic write page as F2FS_WB_CP_DATA, and we can wait atomic pages in wait_on_all_pages_writeback() in do_checkpoitn(). Thanks, > > >> >> Thanks, >> >>> >>> >>>> 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 >>>>> >>>>> . >>>>> >>> >>> . >>> > > . >