Re: [PATCH 3/3] f2fs: wait IO writeback in commit_inmem_pages()

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 04/23, 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.
> 
> This patch adds filemap_fdatawait() in commit_inmem_pages() to keep data
> and node of atomic file being flushed orderly.
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  fs/f2fs/file.c    | 21 ++++++++++++---------
>  fs/f2fs/segment.c |  2 ++
>  2 files changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 5d710f7f2684..4ea418cbd189 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -217,15 +217,18 @@ 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);
> -	ret = file_write_and_wait_range(file, start, end);
> -	clear_inode_flag(inode, FI_NEED_IPU);
> -
> -	if (ret) {
> -		trace_f2fs_sync_file_exit(inode, cp_reason, datasync, ret);
> -		return ret;
> +	if (!atomic) {
> +		/* 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);
> +		ret = file_write_and_wait_range(file, start, end);
> +		clear_inode_flag(inode, FI_NEED_IPU);
> +
> +		if (ret) {
> +			trace_f2fs_sync_file_exit(inode, cp_reason, datasync, ret);
> +			return ret;
> +		}
>  	}

write_done:

>  
>  	/* if the inode is dirty, let's recover all the time */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index dcb4fcb8b1b0..3b66c4aa04a6 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -420,6 +420,8 @@ static int __commit_inmem_pages(struct inode *inode)
>  		__revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
>  	} else {
>  		__revoke_inmem_pages(inode, &revoke_list, false, false);
> +
> +		err = filemap_fdatawait(inode->i_mapping);
>  	}
>  
>  	return err;
> -- 
> 2.15.0.55.gc2ece9dc4de6