On Fri, Apr 29, 2005 at 02:14:19AM -0700, HC wrote:
> I am trying to port a ext3 COW utility from 2.4 to 2.6.
> One of the major changes I see in the 2.6 ext3 is the use of dx_
> functions. Looking the source code, I understand that some kind of
> hashing is being done in these functions. It would be great if anyone
> can tell me whats is the basic idea behind these dx_ functions.
Directory hashing, aka "htree support". From the mke2fs manual page:
-O feature[,...]
Create filesystem with given features (filesystem options),
[...]
The following filesystem options are supported:
dir_index
Use hashed b-trees to speed up lookups in large
directories.
For more information, see Daniel Phillips' talk at OLS 2002:
http://www.linuxsymposium.org/2002/view_txt.php?text=abstract&talk=3
His paper is in the proceedings.
> General pointers on changes to ext3 in 2.6 will be greatly
> appreciated.
AFAIK the only major change in disk layout is htree support, but ext3
also got quite some speed ups due to more efficient locking. Right now
there are people working on support for extents, but that code isn't in
yet.
Erik
--
Erik Mouw
J.A.K.Mouw@xxxxxxxxxxxxxx mouw@xxxxxxxxxxxx
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