index directories in ext2 / ext3
 

Hello Everyone,

I am a Belgian student in computer sciences at the Free University of Brussels ( ULB ).





I am currently working on a little article. I would like to explain the differences between ext2, ext3 and ext4.





During my researches, I read that ext2's directories are implemented
with a linked-list structure. I also read Daniel Phillips's article "A Directory index for ext2" (2002) and I'm a bit troubled.




Indeed, I see that the HTree data structure was developed for ext2
but I cannot see anywhere that the current ext2 implementation uses
that data structure.




I opened the dir.c file from ext2 on the last stable kernel sources
and I do not see anything about HTree, but the dir.c file from ext3
uses it, if I do not go wrong.




Could you explain me why people talk about "index directories for
ext2" but there's no ext2 implementation that uses the HTree structure
? Is it only for ext3 ? Since when ? Could you give me some source that
explain when was implemented HTree in ext{2,3} ?








Thanks a lot.

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index directories in ext2 / ext3
 

On 2010-02-08, at 13:59, Gaëtan Podevijn wrote:
I am currently working on a little article. I would like to explain
the differences between ext2, ext3 and ext4.


During my researches, I read that ext2's directories are implemented
with a linked-list structure. I also read Daniel Phillips's article
"A Directory index for ext2" (2002) and I'm a bit troubled.


Indeed, I see that the HTree data structure was developed for ext2
but I cannot see anywhere that the current ext2 implementation uses
that data structure.


That is correct - it was developed for ext2, but since the new
filesystem development was happening in ext3 the feature was landed
only in ext3.


Could you explain me why people talk about "index directories for
ext2" but there's no ext2 implementation that uses the HTree
structure ? Is it only for ext3 ? Since when ? Could you give me
some source that explain when was implemented HTree in ext{2,3} ?



Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.


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