From: Ding Dinghua Subject: Re: Need of revoke mechanism in JBD Date: Tue, 26 Apr 2011 17:23:21 +0800 Message-ID: References: <4DB68257.4070407@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Niraj Kulkarni , linux-ext4@vger.kernel.org To: Yongqiang Yang Return-path: Received: from mail-pz0-f46.google.com ([209.85.210.46]:59413 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751940Ab1DZJXV convert rfc822-to-8bit (ORCPT ); Tue, 26 Apr 2011 05:23:21 -0400 Received: by pzk9 with SMTP id 9so157679pzk.19 for ; Tue, 26 Apr 2011 02:23:21 -0700 (PDT) In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 : > AFAIK, it can accelerate the recovering process. =A0If 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 > wrote: >> Hi all, >> =A0 =A0 =A0I am new to fs development. I am trying to modify the jou= rnal structure >> of JBD. While analyzing the code, I could understand most of the thi= ngs, but >> I am not able to understand the need of revoke mechanism. Can anybod= y >> 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 >> More majordomo info at =A0http://vger.kernel.org/majordomo-info.html >> > > > > -- > 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 =A0http://vger.kernel.org/majordomo-info.html > --=20 Ding Dinghua -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html