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Date: Thu, 26 Apr 2018 10:36:51 -0600 From: Jaegeuk Kim <jaegeuk@...nel.org> To: Chao Yu <chao@...nel.org> Cc: Chao Yu <yuchao0@...wei.com>, linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org Subject: Re: [PATCH] f2fs: fix to wait IO writeback in __revoke_inmem_pages() 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. > > 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 <yuchao0@...wei.com> > >> --- > >> 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
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