Subject: Re: Log area on-disk for the journal
To: Ignatios Souvatzis <email@example.com>
From: Bill Studenmund <firstname.lastname@example.org>
Date: 10/22/2006 18:07:32
Content-Type: text/plain; charset=us-ascii
On Sat, Oct 21, 2006 at 12:58:05PM +0200, Ignatios Souvatzis wrote:
> On Fri, Oct 20, 2006 at 02:40:52PM -0700, Jason Thorpe wrote:
> > On Oct 20, 2006, at 2:08 PM, M J Fleming wrote:
> > >Wouldn't this rule out the possibility of adding journaling to a pre-=
> > >existing
> > >filesystem?
> > No -- just allocate the inode and mark it as "special" in some way.
> Using an inode, and block lists, surely is an elegant way; I think
> BSD LFS does it too for some of its meta data (the i file). However,
> ISTR that this - using the inode/block allocation used for normal
> files also for meta data - was mentioned as problematic wrt. LFS
> because in some situations, the filesystem has to fight its normal
> operation to make sure it stays consistent, which needs special
> effort to do it right.
I think an inode is the best way for now. I don't think a jffs will have=20
the same problem LFS has as files stay put on ffs once allocated. While=20
the contents of the journal will change with time, its location won't.=20
Thus the only metadata updates would be m & a time. Assuming we desired=20
keeping them current (which I don't think we need to bother with).
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