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 <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
> >
> > .
> >
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