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

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Message-ID: <e867978a-f64f-fe32-2671-aeaa34e75b0e@huawei.com>
Date: Sat, 17 Feb 2024 15:45:13 +0800
From: Baokun Li <libaokun1@...wei.com>
To: Jan Kara <jack@...e.cz>
CC: <linux-ext4@...r.kernel.org>, <tytso@....edu>, <adilger.kernel@...ger.ca>,
	<ritesh.list@...il.com>, <linux-kernel@...r.kernel.org>,
	<yi.zhang@...wei.com>, <yangerkun@...wei.com>, <chengzhihao1@...wei.com>,
	<yukuai3@...wei.com>, Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH 7/7] ext4: set the type of max_zeroout to unsigned int to
 avoid overflow

On 2024/2/14 0:38, Jan Kara wrote:
> 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
Totally agree! I will replace it in the next version.

Thanks!
-- 
With Best Regards,
Baokun Li
.