Online defragmentation

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 ?)

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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.

I haven't tested the defrag code. This came up when i was doing the online migration. With large file having large number of fragmented blocks I was getting the below error during the iput of the temporary inode.

"ext4_free_blocks Freeing blocks not in datazone ...."