On 2011-04-26, at 4:47 AM, Niraj Kulkarni wrote: > 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. It shouldn't be possible to mount the filesystem in no-journal mode without doing journal recovery. The filesystem sets an INCOMPAT_RECOVER flag when the journal has any transactions in it, and the journal should be replayed before the filesystem is finished mounting. Looking at ext4_fill_super() the "noload" mount option is used to avoid loading the journal even if there is a journal (COMPAT_HAS_JOURNAL is set), but if INCOMPAT_RECOVER is set the filesystem will refuse to mount. > 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@xxxxxxxxx>: >>> 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@xxxxxxxxx> 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@xxxxxxxxxxxxxxx >>>> More majordomo info at http://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@xxxxxxxxxxxxxxx >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >> >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
