On Tue, Jun 06, 2000 at 12:11:08AM -0700, Hans Reiser wrote:
> I want to add reiserfs to linux, not merge it into ext3. This is the crux of
> the argument. Alan says I should wait until ext3 is added so that I can let
> them write part of our FS for us.
I actually didn't read it as that. He wrote that it needs checking
what parts of the journaling code can use common hooks.
Examples where common hooks are needed:
- A path to signal memory pressure to the journal to make it flush its
transaction data (currently there are deadlock situations which are neither
solved in ext3 nor reiser)
- A common solution for the deadlock of nesting journal traffic on
page cleaning (Chris' dirty_inode hook, I'm not sure how Stephen
solves the problem)
- Use a common layer for the write barriers [but Linus seems to prefer
handling them in the fs/journal code anyways]
- There are probably other ``common problems''
There are lots of stuff that can be done to give a common interface
to journal subsystems, without merging them completely. Of course having
a common internal journal API would make sense anyways. It is e.g.
badly needed for writeable snapshots in LVM or reliable Software Raid --
for performance reasons Block Devices and File systems should write to
the same journal. There are other services that could benefit too,
like log failover from nfs servers that share a single disk in case
of a crash. Maybe a kind of ``VFS for journal services'' makes sense
for this?
I don't think it will end up with your fears of ext3 ``eating reiserfs''
-Andi
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