From: Amir Goldstein Subject: Re: Need of revoke mechanism in JBD Date: Fri, 29 Apr 2011 22:45:23 +0300 Message-ID: References: <4DB68257.4070407@gmail.com> <20110426122558.GF9486@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Ding Dinghua , Yongqiang Yang , Niraj Kulkarni , linux-ext4@vger.kernel.org To: "Ted Ts'o" Return-path: Received: from mail-ew0-f46.google.com ([209.85.215.46]:35044 "EHLO mail-ew0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760869Ab1D2TpZ convert rfc822-to-8bit (ORCPT ); Fri, 29 Apr 2011 15:45:25 -0400 Received: by ewy4 with SMTP id 4so1245284ewy.19 for ; Fri, 29 Apr 2011 12:45:24 -0700 (PDT) In-Reply-To: <20110426122558.GF9486@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Apr 26, 2011 at 3:25 PM, Ted Ts'o wrote: > On Tue, Apr 26, 2011 at 05:23:21PM +0800, 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 whic= h >> cause data corruption: >> If block A has been journalled its modification, committed to journa= l >> 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, repl= ay >> of journal will overwrite the new data, >> which causing data corruption. > > Yes, this is correct. =A0It should be covered fairly well in Stephen > Tweedie's, "Journaling the ext2fs file system" paper, which you can > find at: > > https://ext4.wiki.kernel.org/index.php/Publications Actually, the original paper has no mention of revoke records. I went out to look for useful documentation on journal forget/revoke and came back empty handed as well. > > if you'd like more details. > > Hope this helps! > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= =A0 =A0 =A0 =A0 =A0 =A0- Ted > -- > 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 > -- 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