[linux-lvm] LVM2 modifies the buffer_head struct?

[Andrew Morton]

Jens Axboe wrote:
> 
> ...
> > We just want ext3/jbd to make sure that it only calls bh2jh on
> > an unlocked buffer... is that easy?
> 
> That's the question indeed, someone with a good grasp of jbd should make
> that call. If that is the only 'violator' (depending on your point of
> view), then yes lets just fix that up and say that the above is pb
> private is valid.

We really don't want to do this, please.  Changing things so
that we can only run bh2jh() and, particularly, journal_add_journal_head()
on a locked buffer would involve fairly unpleasant surgery against
parts of ext3 which are already prone to exploding.  Like
do_get_write_access().

If it was needed for 2.5 then hmm, maybe.  But as this is only a
2.4 problem then I really don't think we should risk breaking
or slowing down the filesystem for this.

Look, it's easy: delete buffer_head.b_inode (which is only used as 
a boolean), move its function to a b_state bit.  Add a new
buffer_head.ext3_hack and we can use that for pointing at the journal_head.

<insert "stable kernel" mantra here ;)>

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