From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: Online defragmentation
Date: Wed, 30 May 2007 13:18:07 +0530
Message-ID: <465D2C37.9080905@linux.vnet.ibm.com>
References: <465D2202.60600@linux.vnet.ibm.com>
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Cc: linux-ext4 <linux-ext4@vger.kernel.org>
To: Takashi Sato <sho@tnes.nec.co.jp>
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Aneesh Kumar K.V wrote:
> Hi Takashi,
> 
> I was looking at online defrag code and found that the tmp_inode is 
> created with tmp_inode->i_nlink equal to zero. Now i am not sure whether 
> i understand the code correctly, but AFAIU we allocate contiguous block 
> using this tmp_inode. That means tmp_inode have extent details 
> corresponding to the blocks. Now we are mapping the file data found in 
> the original inode to this new blocks. Towards the end we does a iput. 
> In iput since we have i_nlink as zero it will go ahead and call 
> generic_delete_inode which will cause these data blocks to be marked 
> free (right ?)
> 

Looking at the code again i guess for defragmentation it is okey. I 
guess what actually happens is the blocks that is corresponding to the 
original inode get accounted under tmp_inode. (it actually does a swap 
of blocks ) So doing a iput with i_nlink = 0 is the correct approach.

Correct me if i am wrong.

Sorry for the noise.

-aneesh