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 <yuch...@huawei.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
