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()?
>
> 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 <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
> >>>
> >>> .
> >>>
> >
> > .
> >
