2007-07-19 13:00:46

by Yan, Zheng

[permalink] [raw]
Subject: Why max_debt isn't used in ext4's find_group_orlov(...) ?

Hi all

max_debt is used in ext2's find_group_orlov . In ext4's
find_group_orlov, max_debt is only computed, but not used. I wonder
whether it's a typo, Can anyone give me a answer? The kernel source I
read is 2.6.22.

Thanks in advance.

----------------
Best Regards

YZ


2007-07-19 14:57:11

by Kalpak Shah

[permalink] [raw]
Subject: Re: Why max_debt isn't used in ext4's find_group_orlov(...) ?

On Thu, 2007-07-19 at 21:00 +0800, Yan Zheng wrote:
> Hi all
>
> max_debt is used in ext2's find_group_orlov . In ext4's
> find_group_orlov, max_debt is only computed, but not used. I wonder
> whether it's a typo, Can anyone give me a answer? The kernel source I
> read is 2.6.22.

I think you are right, max_debt is currently unused in the current
ext3/4 code. In ext2 max_debt is used along with s_debts (in struct
ext2_sb_info) to decide inode allocations. s_debts is no longer present
in ext3/4.

You can find the reason for removing s_debts here:
http://osdir.com/ml/file-systems.ext2.devel/2004-09/msg00027.html

Basically use of s_debts was unsafe since it performed unlocked byte
increment/decrement on words which may be being accessed simultaneously
on other CPUs and since it was a dynamic in-memory table, it required
extension during online resize which needed proper locking.

Until s_debts is added again, I think the code relating to max_debts
should be removed?


Thanks,
Kalpak.

>
> Thanks in advance.
>
> ----------------
> Best Regards
>
> YZ
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