Re: Visible /.journal

["Stephen C. Tweedie" <sct redhat com>]

Hi,

On Thu, Dec 27, 2001 at 11:57:03PM -0700, Andreas Dilger wrote:
 
> Hmm, maybe RH should just change the installer so that it does "mke2fs -j"
> for the root fs always, mounts it as ext2 during the install, and then if
> the user doesn't want to have it as ext3 they can just remove the (unused)
> journal via "tune2fs -O ^has_journal" at that time?  Stephen, are you
> listening? ;-)

The alternative would be to have tune2fs -j create a hidden journal in
the first place.  That would require some kernel help, though.

> > Given the number of questions we've received about the .journal file,
> > it just might be worth cluttering the kernel with the code to move the
> > journal to the hidden inode....
> 
> Hmm, what would be involved for the kernel code?  If we caught it between
> journal recovery, but before the journal was busy,

No, you want to do it once the journal is initialised and running, so
that on a crash, recovery will work to make the update atomic, keeping
all bitmaps and group descriptors in sync.

> Sadly, the ext3 code opens the journal of a filesystem even when it is a
> read-only mount, rather than opening it only when the fs is mounted
> read-write, so it would not be possible to restrict this to when the fs is
> mounted read-only.  That has caused me some headaches in the past as well.
> 
> Maybe it is time that we change ext3 so that we still do a journal
> recovery for a read-only mount (on rw media), but then close the journal
> again until we do a real read-write mount?

Recovery requires genuine filesystem write activity: we need to be
able to do orphan cleanup.  Closing the journal after that is
possible, definitely: the locking code required to quiesce the journal
is all already there.

Cheers,
 Stephen