linux-kernel - Re: [PATCH 2/3] writeback: fix incorrect return value type of bdi_dirty

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Message-ID: <CAKYAXd8pEYcnLf7+YWF8i4ytO2dhUvt2+85VyC2sttmedPkf_Q@mail.gmail.com>
Date:	Mon, 20 Aug 2012 09:09:42 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/3] writeback: fix incorrect return value type of bdi_dirty_limit

2012/8/19, Fengguang Wu <fengguang.wu@...el.com>:
> On Sat, Aug 18, 2012 at 05:49:21AM -0400, Namjae Jeon wrote:
>> unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long
>> dirty)
>>
>> Above function return type is unsigned long, but return value is
>> kept in "u64 bdi_dirty".
>> It can return incorrect value by type casting.
>
> I don't see how the cast can return wrong value.
> The u64 is necessary for the intermediate calculations.
>
> Thanks,
> Fengguang
Hi Wu.
I understand.
Thanks for your reply.
>
>> Signed-off-by: Namjae Jeon <linkinjeon@...il.com>
>> ---
>>  mm/page-writeback.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
>> index 49133b6..73a7a06 100644
>> --- a/mm/page-writeback.c
>> +++ b/mm/page-writeback.c
>> @@ -546,7 +546,7 @@ static unsigned long hard_dirty_limit(unsigned long
>> thresh)
>>   */
>>  unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long
>> dirty)
>>  {
>> -	u64 bdi_dirty;
>> +	unsigned long bdi_dirty;
>>  	long numerator, denominator;
>>
>>  	/*
>> --
>> 1.7.9.5
>
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