linux-kernel - Re: [PATCH] f2fs: fix to avoid atomicity corruption of atomic file

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Message-ID: <Z9SkqFP93rWQrffm@google.com>
Date: Fri, 14 Mar 2025 21:50:32 +0000
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Yeongjin Gil <youngjin.gil@...sung.com>
Cc: chao@...nel.org, daehojeong@...gle.com,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, sj1557.seo@...sung.com,
	s_min.jeong@...sung.com
Subject: Re: [PATCH] f2fs: fix to avoid atomicity corruption of atomic file

On 03/14, Yeongjin Gil wrote:
> In the case of the following call stack for an atomic file,
> FI_DIRTY_INODE is set, but FI_ATOMIC_DIRTIED is not subsequently set.
> 
> f2fs_file_write_iter
>   f2fs_map_blocks
>     f2fs_reserve_new_blocks
>       inc_valid_block_count
>         __mark_inode_dirty(dquot)
>           f2fs_dirty_inode
> 
> If FI_ATOMIC_DIRTIED is not set, atomic file can encounter corruption
> due to a mismatch between old file size and new data.
> 
> To resolve this issue, I changed to set FI_ATOMIC_DIRTIED when
> FI_DIRTY_INODE is set. This ensures that FI_DIRTY_INODE, which was
> previously cleared by the Writeback thread during the commit atomic, is
> set and i_size is updated.
> 
> Fixes: fccaa81de87e ("f2fs: prevent atomic file from being dirtied before commit")
> Reviewed-by: Sungjong Seo <sj1557.seo@...sung.com>
> Reviewed-by: Sunmin Jeong <s_min.jeong@...sung.com>
> Signed-off-by: Yeongjin Gil <youngjin.gil@...sung.com>
> ---
>  fs/f2fs/inode.c | 4 +---
>  fs/f2fs/super.c | 4 ++++
>  2 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> index aa2f41696a88..83f862578fc8 100644
> --- a/fs/f2fs/inode.c
> +++ b/fs/f2fs/inode.c
> @@ -34,10 +34,8 @@ void f2fs_mark_inode_dirty_sync(struct inode *inode, bool sync)
>  	if (f2fs_inode_dirtied(inode, sync))
>  		return;
>  
> -	if (f2fs_is_atomic_file(inode)) {
> -		set_inode_flag(inode, FI_ATOMIC_DIRTIED);
> +	if (f2fs_is_atomic_file(inode))
>  		return;
> -	}
>  
>  	mark_inode_dirty_sync(inode);
>  }
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 397df271885c..c08d52c6467a 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -1534,6 +1534,10 @@ int f2fs_inode_dirtied(struct inode *inode, bool sync)
>  		inc_page_count(sbi, F2FS_DIRTY_IMETA);
>  	}
>  	spin_unlock(&sbi->inode_lock[DIRTY_META]);
> +
> +	if (!ret && f2fs_is_atomic_file(inode))
> +		set_inode_flag(inode, FI_ATOMIC_DIRTIED);
> +

I'm not sure what's different here.

Before and after this patch, set_inode_flag(inode, FI_ATOMIC_DIRTIED) is called
only if f2fs_inode_dirtied() returns zero and f2fs_is_atomic_file(inode).

Note, f2fs_mark_inode_dirty_sync() looks the single caller of f2fs_inode_dirtied.


>  	return ret;
>  }
>  
> -- 
> 2.34.1