linux-ext4 - Re: [PATCH v5 2/2] ext4: clear the verified flag of the modified leaf or idx if error

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Message-ID: <20230214125211.o2j3vpkopvas2niq@quack3>
Date:   Tue, 14 Feb 2023 13:52:11 +0100
From:   Jan Kara <jack@...e.cz>
To:     zhanchengbin <zhanchengbin1@...wei.com>
Cc:     tytso@....edu, jack@...e.com, linux-ext4@...r.kernel.org,
        yi.zhang@...wei.com, linfeilong@...wei.com,
        liuzhiqiang26@...wei.com, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v5 2/2] ext4: clear the verified flag of the modified
 leaf or idx if error

On Mon 13-02-23 16:05:14, zhanchengbin wrote:
> Clear the verified flag from the modified bh when failed in ext4_ext_rm_idx
> or ext4_ext_correct_indexes.
> In this way, the start value of the logical block itself and its
> parents' will be checked in ext4_valid_extent_entries.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: zhanchengbin <zhanchengbin1@...wei.com>
> Link: https://lore.kernel.org/oe-kbuild-all/202302131414.5RKeHgAZ-lkp@intel.com/
> Link: https://lore.kernel.org/oe-kbuild-all/202302131407.XrieHNuN-lkp@intel.com/

Thanks for the patch! Two comments below:

> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 0f95e857089e..bbf34679e10c 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1756,6 +1756,8 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
>  		if (err)
>  			break;
>  	}
> +	while (!(k < 0) && k++ < depth)
> +		clear_buffer_verified(path[k].p_bh);

This would be more understandable as:

	if (k >= 0)
		while (k++ < depth)
			...

Also the loop is IMO wrong because it will run with k == depth as well (due
to post-increment) and that is not initialized. Furthermore it will run
also if we exit the previous loop due to:

                /* change all left-side indexes */
                if (path[k+1].p_idx != EXT_FIRST_INDEX(path[k+1].p_hdr))
                        break;

which is unwanted as well. Which suggests that you didn't test your changes
much (if at all...). So please make sure your changes are tested next time.
Thank you!

								Honza

>  
>  	return err;
>  }
> @@ -2304,6 +2306,7 @@ static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
>  {
>  	int err;
>  	ext4_fsblk_t leaf;
> +	int b_depth = depth;
>  
>  	/* free index block */
>  	depth--;
> @@ -2345,6 +2348,9 @@ static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
>  		if (err)
>  			break;
>  	}
> +	while (!(depth < 0) && depth++ < b_depth - 1)
> +		clear_buffer_verified(path[depth].p_bh);
> +
>  	return err;
>  }
>  
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR