From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752887AbeEGUqc (ORCPT ); Mon, 7 May 2018 16:46:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:53070 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752693AbeEGUqb (ORCPT ); Mon, 7 May 2018 16:46:31 -0400 Date: Mon, 7 May 2018 13:46:30 -0700 From: Jaegeuk Kim To: Chao Yu Cc: Chao Yu , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] f2fs: fix to wait IO writeback in __revoke_inmem_pages() Message-ID: <20180507204630.GB83867@jaegeuk-macbookpro.roam.corp.google.com> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3cae6be6-365d-8e48-b1db-8b04f96634e4@huawei.com> User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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]); > 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 > > > > . > >