ask for help; hash-directory machanism of ext3 cannot work well

ask for help; hash-directory machanism of ext3 cannot work well

[LIOU Payphone]

firstly, with many thanks! ^-^

my problem :
(1) when i want to format /dev/sda1 to be ext3-filesystem, i  set
"s_def_hash_version" of "struct ext3_super_block" to be "DX_HASH_LEGACY".
when the filesystem was formatted successfully, i mounted it under a
directory named "/mnt". 
(2) subsequently, i created 40000 empty regular-files under "/mnt" named
from "0" to "39999".
(3) then , "ls -li  /mnt" was executed; i saw a puzzling thing : there are
two indentical entries of the directory named "mnt"!  both inode->i_ino and
filename are in the same. 

32203 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24010
32204 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24011
32205 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24012
32206 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24013 
32207 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24014
32208 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24015
32209 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24016
33220 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 25027
3220 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3090
3350 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3220
3350 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3220

(4) when i change "DX_HASH_LEGACY" to be "DX_HASH_TEA", the problem listed
above not happend. 

i scratched my head over it, failed to find any reasonable answers.  :-(
so, i sent my question to u and expecting eagerly some help from you. 

thanks again! :-)
  Payphone LIOU

Re: ask for help; hash-directory machanism of ext3 cannot work well

[Theodore Tso]

On Thu, Jun 21, 2007 at 04:40:55PM +0800, LIOU Payphone wrote:
> 
> my problem :

First of all, what version of e2fsprogs and kernel are you using?n

> (1) when i want to format /dev/sda1 to be ext3-filesystem, i  set
> "s_def_hash_version" of "struct ext3_super_block" to be "DX_HASH_LEGACY".
> when the filesystem was formatted successfully, i mounted it under a
> directory named "/mnt". 

How did you set the s_def_hash_version?   Were you using debugfs?

And did you turn on the dir_index feature?  

With recent versions of e2fsprogs the dir_index feature is enabled
default, with DX_HASH_TEA as the default.

> (2) subsequently, i created 40000 empty regular-files under "/mnt" named
> from "0" to "39999".
> (3) then , "ls -li  /mnt" was executed; i saw a puzzling thing : there are
> two indentical entries of the directory named "mnt"!  both inode->i_ino and
> filename are in the same. 

Huh?  What do you mean by that?  Are you seeing two entries named
"mnt" in the /mnt directory?   I wasn't able to reproduce this.

> 32203 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24010
> 32204 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24011
> 32205 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24012
> 32206 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24013 
> 32207 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24014
> 32208 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24015
> 32209 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24016
> 33220 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 25027
> 3220 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3090
> 3350 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3220
> 3350 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3220

You didn't list any "mnt" entries above.  So I don't know what you saw.

						- Ted

Re: ask for help; hash-directory machanism of ext3 cannot work well

[LIOU Payphone]

Hello, Ted. I think I failed to represent it very well. But many thanks. :-)

What makes me puzzled is there are two entries both  named  "3220" with ino
"3350" were shown under "/mnt" when I "ls  -li  /mnt".
The version of kernel is 2.6.17-1.2142; and e2fsprogs-1.28. 
You know that we can set "s_def_hash_version" to be "DX_HASH_LEAGCY" in
function  "main{}" of mke2fs.c 
But I don't know why the latest version e2fsprogs-1.39 takes "DX_HASH_TEA"
for default. Why "DX_HASH_LEAGCY" cannot be taken for default? Could you
tell me the reason for it? Thanks.  :-)

------
On Thu, Jun 21, 2007 at 04:40:55PM +0800, LIOU Payphone wrote:
> 
> my problem :

First of all, what version of e2fsprogs and kernel are you using?n

> (1) when i want to format /dev/sda1 to be ext3-filesystem, i  set
> "s_def_hash_version" of "struct ext3_super_block" to be "DX_HASH_LEGACY".
> when the filesystem was formatted successfully, i mounted it under a
> directory named "/mnt". 

How did you set the s_def_hash_version?   Were you using debugfs?

And did you turn on the dir_index feature?  

With recent versions of e2fsprogs the dir_index feature is enabled
default, with DX_HASH_TEA as the default.

> (2) subsequently, i created 40000 empty regular-files under "/mnt" named
> from "0" to "39999".
> (3) then , "ls -li  /mnt" was executed; i saw a puzzling thing : there are
> two indentical entries under the directory named "mnt"!  both inode->i_ino
and
> filename are in the same. The filename is 3220 and ino 3350

Huh?  What do you mean by that?  Are you seeing two entries named
"mnt" in the /mnt directory?   I wasn't able to reproduce this.

> 32203 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24010
> 32204 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24011
> 32205 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24012
> 32206 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24013 
> 32207 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24014
> 32208 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24015
> 32209 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 24016
> 33220 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:37 25027
> 3220 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3090
> 3350 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3220
> 3350 -rwxrwxrwx 1 liupf liupf 0 Jun 14 11:31 3220

You didn't list any "mnt" entries above.  So I don't know what you saw.

						- Ted

Re: ask for help; hash-directory machanism of ext3 cannot work well

[Theodore Tso]

On Fri, Jun 22, 2007 at 09:52:55AM +0800, LIOU Payphone wrote:
> 
> What makes me puzzled is there are two entries both  named  "3220" with ino
> "3350" were shown under "/mnt" when I "ls  -li  /mnt".

Hmm.  I still can't verify this.

Can you replicate the result?  If so, can you send me the output of
dumpe2fs?

> The version of kernel is 2.6.17-1.2142; and e2fsprogs-1.28. 

That looks like a vendor version of the kernel; what distribution are
you using?

E2fsprogs 1.28 is a frighteningly old version of e2fsprogs.  Did you
really mean 1.28?  Or 1.38?

> You know that we can set "s_def_hash_version" to be "DX_HASH_LEAGCY" in
> function  "main{}" of mke2fs.c 

Oh, so you were modifying your sources to set this variable?

> But I don't know why the latest version e2fsprogs-1.39 takes "DX_HASH_TEA"
> for default. Why "DX_HASH_LEAGCY" cannot be taken for default? Could you
> tell me the reason for it? Thanks.  :-)

Because DX_HASH_TEA is a better hash, and because it is keyed off of a
per-filesystem secret hash value stored in the superblock.

						- Ted