Re: kjournald() with DIO

[Andrea Arcangeli <andrea@suse.de>]

On Thu, Sep 15, 2005 at 01:35:00PM -0700, Andrew Morton wrote:
> I'll need reminding - why was the buffer unfreeable?  Because kjournald had
> a ref on it?  Whereabouts is that happening?

Yes, kjournald had a ref (b_count) on it. It's happening when running
iozone in some way (Badari knows how to reproduce).

I was now wondering why it's a problem to destroy dirty buffers in
invalidate_inode_pages2? (ok, ignoring the detail that PageDirty may
return true inside invalidate_complete_page)

Clearly we can't do that inside releasepage, but invalidate_inode_pages2
is all about destroying the dirty and uptodate information, since we
just finished writing with direct-io (or at least the dirty info isn't
that important anymore, we're still in our write context for those pages
that we're invalidating [even better with the range]).

If we could just have a blocking version of try_to_release_page I guess
that would be better, but even the ->invalidatepage behaviour may not be
that bad for invalidate_inode_pages2. Or am I missing something?