GJournal (hopefully) final patches.

Pawel Jakub Dawidek pjd at FreeBSD.org
Thu Aug 10 22:37:33 UTC 2006

On Fri, Aug 11, 2006 at 12:29:42AM +0200, Pawel Jakub Dawidek wrote:
> On Thu, Aug 10, 2006 at 04:05:35PM -0500, Craig Boston wrote:
> > On Thu, Aug 10, 2006 at 09:28:41PM +0200, Pawel Jakub Dawidek wrote:
> > > When you mount file system it sends BIO_GETATTR "GJOURNAL::provider"
> > > requests. So as long as classes between the file system and gjournal
> > > provider pass BIO_GETATTR down, it will work.
> > > 
> > > I prefer to put gjournal on the top, because it gives consistency to
> > > layers below it. [...]
> > >
> > > [snip]
> > > 
> > > Fortunatelly with GEOM you can freely mix your puzzles.
> > 
> > Would there be any ill effects to putting multiple filesystems inside a
> > single gjournal, say with a bsdlabel or gpt on it?
> I don't see any problems with such configuration, but there are no
> optimization like "synchronize all file systems and then switch
> journals", so it will go like "synchronize one file system switch
> journals, synchronize another file system, switch journals, etc.".

Ok, on second thought it won't work.
If you have many file systems on one gjournal, you synchronize one file
system and switch journals leaving the rest of file systems in an
inconsistent state.
To make it work reliable I'd need to implement the optimization I
mentioned, ie. sync all file systems and then switch journals.

Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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