Re: [PATCH 02/20] ext4: prevent partial update of the extents path

[Jan Kara]

On Wed 10-07-24 12:06:36, libaokun@xxxxxxxxxxxxxxx wrote:
> From: Baokun Li <libaokun1@xxxxxxxxxx>
> 
> In ext4_ext_rm_idx() and ext4_ext_correct_indexes(), there is no proper
> rollback of already executed updates when updating a level of the extents
> path fails, so we may get an inconsistent extents tree, which may trigger
> some bad things in errors=continue mode.
> 
> Hence clear the verified bit of modified extents buffers if the tree fails
> to be updated in ext4_ext_rm_idx() or ext4_ext_correct_indexes(), which
> forces the extents buffers to be checked in ext4_valid_extent_entries(),
> ensuring that the extents tree is consistent.
> 
> Signed-off-by: zhanchengbin <zhanchengbin1@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20230213080514.535568-3-zhanchengbin1@xxxxxxxxxx/
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza

> ---
>  fs/ext4/extents.c | 31 +++++++++++++++++++++++++++----
>  1 file changed, 27 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index bff3666c891a..4d589d34b30e 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1749,12 +1749,23 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
>  			break;
>  		err = ext4_ext_get_access(handle, inode, path + k);
>  		if (err)
> -			break;
> +			goto clean;
>  		path[k].p_idx->ei_block = border;
>  		err = ext4_ext_dirty(handle, inode, path + k);
>  		if (err)
> -			break;
> +			goto clean;
>  	}
> +	return 0;
> +
> +clean:
> +	/*
> +	 * The path[k].p_bh is either unmodified or with no verified bit
> +	 * set (see ext4_ext_get_access()). So just clear the verified bit
> +	 * of the successfully modified extents buffers, which will force
> +	 * these extents to be checked to avoid using inconsistent data.
> +	 */
> +	while (++k < depth)
> +		clear_buffer_verified(path[k].p_bh);
>  
>  	return err;
>  }
> @@ -2312,12 +2323,24 @@ static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
>  			break;
>  		err = ext4_ext_get_access(handle, inode, path + k);
>  		if (err)
> -			break;
> +			goto clean;
>  		path[k].p_idx->ei_block = path[k + 1].p_idx->ei_block;
>  		err = ext4_ext_dirty(handle, inode, path + k);
>  		if (err)
> -			break;
> +			goto clean;
>  	}
> +	return 0;
> +
> +clean:
> +	/*
> +	 * The path[k].p_bh is either unmodified or with no verified bit
> +	 * set (see ext4_ext_get_access()). So just clear the verified bit
> +	 * of the successfully modified extents buffers, which will force
> +	 * these extents to be checked to avoid using inconsistent data.
> +	 */
> +	while (++k < depth)
> +		clear_buffer_verified(path[k].p_bh);
> +
>  	return err;
>  }
>  
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR