From: Niraj Kulkarni <kulkarniniraj14@gmail.com>
To: Ding Dinghua <dingdinghua85@gmail.com>
Cc: Yongqiang Yang <xiaoqiangnk@gmail.com>, linux-ext4@vger.kernel.org
Subject: Re: Need of revoke mechanism in JBD
Date: Tue, 26 Apr 2011 16:17:12 +0530 [thread overview]
Message-ID: <4DB6A2B0.7050708@gmail.com> (raw)
In-Reply-To: <BANLkTikV4nU4Zc4OxNa6q8wDtM7cLUF_ig@mail.gmail.com>
If I am thinking correctly, journal would be checkpointed on filesystem
unmount calls.
This implies the given scenario would be pretty rare.
ie first filesystem should be mounted in full-journal mode, and crashed
prior to checkpoint.
then it should be remounted in no-journalled-data mode without recovery
and again remounted in full journalled mode with recovery.
Am I thinking on correct lines?
On Tuesday 26 April 2011 02:53 PM, Ding Dinghua wrote:
> I think it's not only a performance issue but more important, a
> correctness issue.
> Revoke table is used for preventing the wrong replay of journal which
> cause data corruption:
> If block A has been journalled its modification, committed to journal
> and hasn't been checkpointed,
> and in later transactions block A is freed and reused for data in
> no-journalled-data mode, then If
> we don't have revoke table which recording the releasing event, replay
> of journal will overwrite the new data,
> which causing data corruption.
>
> 2011/4/26 Yongqiang Yang<xiaoqiangnk@gmail.com>:
>> AFAIK, it can accelerate the recovering process. If a block is in the
>> revoke table of a transaction t1 and t1 is committed, then the there
>> is no need to recover the block in transactions which is earlier than
>> t1.
>>
>> On Tue, Apr 26, 2011 at 4:29 PM, Niraj Kulkarni
>> <kulkarniniraj14@gmail.com> wrote:
>>> Hi all,
>>> I am new to fs development. I am trying to modify the journal structure
>>> of JBD. While analyzing the code, I could understand most of the things, but
>>> I am not able to understand the need of revoke mechanism. Can anybody
>>> enlighten me on this issue?
>>>
>>> Regards
>>> Niraj
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>>> the body of a message to majordomo@vger.kernel.org
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>>>
>>
>>
>> --
>> Best Wishes
>> Yongqiang Yang
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>
>
next prev parent reply other threads:[~2011-04-26 10:42 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-26 8:29 Need of revoke mechanism in JBD Niraj Kulkarni
2011-04-26 8:56 ` Yongqiang Yang
2011-04-26 9:23 ` Ding Dinghua
2011-04-26 10:47 ` Niraj Kulkarni [this message]
2011-04-26 10:57 ` Amir Goldstein
2011-04-26 17:27 ` Andreas Dilger
2011-04-27 0:52 ` Ding Dinghua
2011-04-26 12:25 ` Ted Ts'o
2011-04-29 19:45 ` Amir Goldstein
2011-04-30 2:06 ` Niraj Kulkarni
2011-05-01 22:28 ` Ted Ts'o
2011-05-02 10:42 ` Amir Goldstein
2011-05-02 14:43 ` Ted Ts'o
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