how to calculate the journal-blocks when try to start a handle?

["Payphone LIOU" <lioupayphone@xxxxxxxxx>]

Hi, all.

 

in ext3, when we try to make an entry under a directory, ext3_mkdir/ext3_create/...  will start a handle :

 

handle = ext3_journal_start(dir, EXT3_DATA_TRANS_BLOCKS(dir->i_sb) + EXT3_INDEX_EXTRA_TRANS_BLOCKS + 3 +2*EXT3_QUOTA_INIT_BLOCKS(dir->i_sb));

 

"EXT3_DATA_TRANS_BLOCKS(dir->i_sb)"  is for modifying those indirect-blocks and related bitmap/BG blocks

"EXT3_QUOTA_INIT_BLOCKS(dir->i_sb)" is for modify the blocks in quota-files (both user-quota-file and group-quota-file)

 

my question is: why "EXT3_INDEX_EXTRA_TRANS_BLOCKS " was defined to be 8 and what the extra "3"  is for ?

 

thanks everyone. :-)

Payphone LIOU 

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2008-04-25