linux-kernel - Re: [PATCH 7/7] ext4: set the type of max_zeroout to unsigned int to avoid overflow

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Date: Tue, 13 Feb 2024 17:38:07 +0100
From: Jan Kara <jack@...e.cz>
To: Baokun Li <libaokun1@...wei.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca,
	jack@...e.cz, ritesh.list@...il.com, linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com, yangerkun@...wei.com, chengzhihao1@...wei.com,
	yukuai3@...wei.com
Subject: Re: [PATCH 7/7] ext4: set the type of max_zeroout to unsigned int to
 avoid overflow

On Fri 26-01-24 16:57:16, Baokun Li wrote:
> The max_zeroout is of type int and the s_extent_max_zeroout_kb is of
> type uint, and the s_extent_max_zeroout_kb can be freely modified via
> the sysfs interface. When the block size is 1024, max_zeroout may
> overflow, so declare it as unsigned int to avoid overflow.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> ---
>  fs/ext4/extents.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 01299b55a567..8653b13e8248 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3425,10 +3425,8 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  	struct ext4_extent zero_ex1, zero_ex2;
>  	struct ext4_extent *ex, *abut_ex;
>  	ext4_lblk_t ee_block, eof_block;
> -	unsigned int ee_len, depth, map_len = map->m_len;
> -	int allocated = 0, max_zeroout = 0;
> -	int err = 0;
> -	int split_flag = EXT4_EXT_DATA_VALID2;
> +	unsigned int ee_len, depth, map_len = map->m_len, max_zeroout = 0;
> +	int err = 0, allocated = 0, split_flag = EXT4_EXT_DATA_VALID2;

Honestly, I prefer if we keep unrelated variables on different lines,
especially when they have initializers. I find the code more readable that
way. So in this case:

	int err = 0;
	int split_flag = EXT4_EXT_DATA_VALID2;
	int allocated = 0;
	unsigned int max_zeroout = 0;

But otherwise the fix looks good!

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR