Re: PATCH 2.6.21-rc1 aoe: handle zero _count pages in bios

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 2 Mar 2007 04:30:39 +0000 Christoph Hellwig <hch@infradead.org> wrote:

> But in this case we'd really need to enforce this, and add a
> BUG_ON(PageSlab(page)) in bio_add_page to trip everyone submit
> this kind of pages.

That would be

	BUG_ON(PageSlab(page) && page_count(page) == 0)?


> > So we have a few options to look at:
> > 
> > a) kludge things in AOE.  Unpleasing, and might cause memory leaks
> >    (although it won't, because the caller hasn't run bi_end_io yet).
> > 
> > b) Take a ref on slab pages in slab.  A bit costly, perhaps.
> > 
> > c) teach ext3 and XFS to take a ref on these pages as they are added to
> >    the BIOs, undo that ref in bi_end_io.
> > 
> > I think c)?
> 
> Yes.  I'm perfectly fine with this as long as we document and enforce
> this.

And write the patch ;)