linux-ext4 - Re: Do we really need parallel resizer?

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Message-Id: <606DB4F9-C7D5-4853-B1FB-CF15E96AC037@gmail.com>
Date:	Sat, 25 Jun 2011 10:42:48 -0600
From:	Andreas Dilger <aedilger@...il.com>
To:	Yongqiang Yang <xiaoqiangnk@...il.com>
Cc:	"adilger@...ger.ca" <adilger@...ger.ca>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: Do we really need parallel resizer?

I don't care particularly about parallel resize being a common usage. My only concern is to prevent filesystem corruption in case it happens by accident.

I'm not sure why you think it is better to have a flag to indicate resize in progress instead of just having a lock.

If you could please explain the benefit of this then it is possible to make a decision on why this code should be changed. 

Cheers, Andreas

On 2011-06-24, at 8:17 PM, Yongqiang Yang <xiaoqiangnk@...il.com> wrote:

> On Fri, Jun 24, 2011 at 4:41 PM, Yongqiang Yang <xiaoqiangnk@...il.com> wrote:
>> Hi Andreas,
>> 
>> I noticed that resize is protected by resize_lock.  Then parallel
>> resizer works.  However, I think there is no need to make parallel
>> resizer work.
>> 
>> I think we can use an atomic integer 'resize_flag' instead of
>> resize_lock,  resize_flag is set to 1 before the kernel does resizing
>> work,  while resize_flag is set to 0 after the kernel finishes
>> resizing work.  Resizing is allowed only if resize_flag is 0.  If
>> resize_flag is 1, kernel returns -EBUSY to userspace.
> Sorry, I made an error.  we should use an integer protected by resize_lock.
> 
> Yongqiang.
>> 
>> What about your opinion?
>> 
>> Yongqiang.
>> 
>> --
>> Best Wishes
>> Yongqiang Yang
>> 
> 
> 
> 
> -- 
> Best Wishes
> Yongqiang Yang
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