linux-ext4 - Re: [PATCH] ext4: remove unneeded variable.

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Date:	Sun, 20 Nov 2011 02:39:05 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Namjae Jeon <linkinjeon@...il.com>
CC:	tytso@....edu, linux-kernel@...r.kernel.org,
	linux-ext4@...r.kernel.org,
	Amit Sahrawat <amit.sahrawat83@...il.com>
Subject: Re: [PATCH] ext4: remove unneeded variable.

On 11/20/2011 01:41 AM, Srivatsa S. Bhat wrote:
> On 11/11/2011 08:32 PM, Namjae Jeon wrote:
>> ret2 is not needed in ext4_flush_completed_IO().
>>
> 
> Not needed? I went through the code briefly, and I don't agree.
> 
>> Signed-off-by: Namjae Jeon <linkinjeon@...il.com>
>> Signed-off-by: Amit Sahrawat <amit.sahrawat83@...il.com>
>> ---
>>  fs/ext4/fsync.c |    5 +----
>>  1 files changed, 1 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
>> index 00a2cb7..40397ac 100644
>> --- a/fs/ext4/fsync.c
>> +++ b/fs/ext4/fsync.c
>> @@ -81,7 +81,6 @@ int ext4_flush_completed_IO(struct inode *inode)
>>  	struct ext4_inode_info *ei = EXT4_I(inode);
>>  	unsigned long flags;
>>  	int ret = 0;
>> -	int ret2 = 0;
>>
>>  	dump_completed_IO(inode);
>>  	spin_lock_irqsave(&ei->i_completed_io_lock, flags);
>> @@ -105,12 +104,10 @@ int ext4_flush_completed_IO(struct inode *inode)
>>  		 */
>>  		spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
>>  		ret = ext4_end_io_nolock(io);
>> -		if (ret < 0)
>> -			ret2 = ret;
>>  		spin_lock_irqsave(&ei->i_completed_io_lock, flags);
>>  	}
>>  	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
>> -	return (ret2 < 0) ? ret2 : 0;
>> +	return (ret < 0) ? ret : 0;
>>  }
> 
> Please note that there is a while loop involved here. Which means, that ret2
> is used to store the last negative value of ret. And due to the loop, ret can
> be over-written in the next loop iteration, which we can afford, because we
> have already stored what we need to save, in ret2. And this ret2 value is used
> to return appropriate value to the caller. 
> 

Actually, what I really meant was, removing ret2 as merely "unneeded" might not
be the right thing to do because once you apply your patch, you end up altering
the value returned by this function!

If the return value is indeed wrong in the current code, you should rather
be saying that this is a bug fix, with appropriate justification IMO. 

Thanks,
Srivatsa S. Bhat

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