Daniel Phillips wrote: > > On Tuesday 22 May 2001 22:10, Andreas Dilger wrote: > > Peter Braam writes: > > > File system journal recovery can corrupt a snapshot, because it > > > copies data that needs to be preserved in a snapshot. During > > > journal replay such data may be copied again, but the source can > > > have new data already. > > > > The way it is implemented in reiserfs is to wait for existing > > transactions to complete, entirely flush the journal and block all > > new transactions from starting. Stephen implemented a journal flush > > API to do this for ext3, but the hooks to call it from LVM are not in > > place yet. This way the journal is totally empty at the time the > > snapshot is done, so the read-only copy does not need to do journal > > recovery, so no problems can arise. > > I suppose I'm just reiterating the obvious, but we should eventually > have a generic filesystem transaction API at the VFS level, once we > have enough data points to know what the One True API should be. > > -- > Daniel > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ Daniel, implementing transactions is not a trivial thing as you probably know. It requires that you resolve such issues as, what happens if the user forgets to close the transaction, issues of lock/transaction duration, of transaction batching, of levels of isolation, of concurrent transactions modifying global fs metadata and some but not all of those concurrent transactions receiving a rollback, and of permissions relating to keeping transactions open. I would encourage you to participate in the reiser4 design discussion we will be having over the next 6 months, and give us your opinions. Josh will be leading that design effort for the ReiserFS team. Hans
