Re: [RFC] [patch 0/3] i_version update for ext4

[Mingming Cao <cmm@us.ibm.com>]

Cordenner jean noel wrote:
> Andreas Dilger a écrit :
> 
>> On Jan 23, 2007  18:23 +0100, Cordenner jean noel wrote:
>>
>>> I've updated what was previously the change attribute patch for ext4
>>> initially posted by Alexandre Ratchov. The previous patch was
>>> introducing a change_attribute field, now it uses the i_version field of
>>> the inode.
>>>
>>> The i_version field is a counter that is set on every inode creation and
>>> that is incremented every time the inode data is modified (similarly to
>>> the "ctime" time-stamp).
>>> The aim is to fulfill NFSv4 requirements for rfc3530.
>>> For the moent, the counter is only a 32bit value but it is planned to be
>>> 64bit as required.
>>>
>>> The patch is divided into 3 parts, the vfs layer, the ext4 specific code
>>> and an user part to check i_version changes via stat.
>>
>>
>> Have you had a chance to look at the performance impact of this change
>> (possible with oprofile)?  Always marking the inodes dirty for ext3
>> may have some noticable overhead.
>>
> 
> I did some tests using fileop with the previous version of the patch
> which was very similar. I was surprised that there was no noticable
> overhead:
>  http://www.bullopensource.org/ext4/change_attribute/index.html
> 
> I will use oprofile to check it again.

Could we just increment the counter each time the mtime is modifies(not 
the ctime)? Is that enough to serve NFSv4 need?
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