Re: bad page state in 3.13-rc4

[Benjamin LaHaise]

On Fri, Dec 20, 2013 at 04:45:38AM +0900, Linus Torvalds wrote:
> On Fri, Dec 20, 2013 at 4:26 AM, Benjamin LaHaise <bcrl@xxxxxxxxx> wrote:
> >
> > Okay, I'll rewriting it to use truncate to free the pages.
> 
> It already does that in put_aio_ring_file() afaik. No?

Yes, that's what I found when I started looking into this in detail again.  
I think the page reference counting is actually correct.  There are 2 
references on each page: the first is from the find_or_create_page() call, 
and the second is from the get_user_pages() (which also makes sure the page 
is populated into the page tables).  The only place I can see things going 
off the rails is if the get_user_pages() call fails.  It's possible trinity 
could be arranging things so that the get_user_pages() call is failing 
somehow.  Also, if it were a double free of a page, we should at least get 
a VM_BUG() occuring when the page's count is 0.

Dave -- do you have CONFIG_DEBUG_VM on in your test rig?

>                 Linus

-- 
"Thought is the essence of where you are now."
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