Re: [f2fs-dev] [PATCH v2] f2fs: fix data loss caused by fsync not writing any node folio

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 3/6/26 20:18, Yongpeng Yang wrote:
> From: Yongpeng Yang <yangyongpeng@xiaomi.com>
> 
> During fsync, the flow reaches f2fs_fsync_node_pages(), which scans all
> dirty node folios of the node mapping. If there are no dirty node
> folios, fsync will not write any node folio. The scenario is as follows:
> 
> create & write & fsync 'file A'                 writeback node folio
> - f2fs_do_sync_file // inline inode
>  - f2fs_write_inode // inode folio is dirty
> 
>                                                 - f2fs_write_node_pages
>                                                  - f2fs_sync_node_pages
>  - f2fs_fsync_node_pages // no dirty node folios
>  sudden poweroff and lost 'file A'
> 
> The root cause of the data loss is that although the inode folio is
> written successfully, the corresponding node folio is not written with
> the FSYNC_BIT_SHIFT mark. As a result, the recovery procedure ignores
> this file.
> 
> This patch ensures that fsync writes at least one node folio with the
> FSYNC_BIT_SHIFT mark for the inode, so that the recovery procedure can
> properly detect and process it.

I'm not sure, but I suspect that the problem should has been resolved by
commit 88bd02c9472a ("f2fs: fix conditions to remain recovery information
in f2fs_sync_file") has fixed this problem?

Thanks,

> 
> Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
> ---
> v2:
> - Use f2fs_folio_put instead of folio_put to dec folio ref count.
> ---
>  fs/f2fs/node.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 2fbfecaf3f7b..e14e5db1e8e6 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1982,6 +1982,22 @@ int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>  		folio_batch_release(&fbatch);
>  		cond_resched();
>  	}
> +	/*
> +	 * All dirty node folios may be written by other thread, but CP hasn't
> +	 * been written yet. So, we need to flush one of inode's dnode to
> +	 * recovery this inode when encounter sudden power off.
> +	 */
> +	if (!atomic && nwritten == 0) {
> +		struct folio *ifolio;
> +
> +		ifolio = f2fs_get_inode_folio(sbi, inode->i_ino);
> +		if (IS_ERR(ifolio))
> +			return PTR_ERR(ifolio);
> +		f2fs_folio_wait_writeback(ifolio, NODE, true, true);
> +		folio_mark_dirty(ifolio);
> +		f2fs_folio_put(ifolio, true);
> +		goto retry;
> +	}
>  	if (atomic && !marked) {
>  		f2fs_debug(sbi, "Retry to write fsync mark: ino=%u, idx=%lx",
>  			   ino, last_folio->index);



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