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 majordomo@vger.kernel.org
> 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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu May 31 2001 - 21:00:20 EST