Re: Oops in __free_pages_ok (pre7-1) (Long) (backtrace)

[Rajagopal Ananthanarayanan <ananth@sgi.com>]

Linus Torvalds wrote:
> 
> Ok,
>  there's a pre7-4 out there that does the swapout with the page locked.
> I've given it some rudimentary testing, but certainly nothing really
> exotic. Please comment..

One quick comment: Looking at this part of the diff to mm/vmscan.c:

----------
@@ -138,6 +139,7 @@
                flush_tlb_page(vma, address);
                vmlist_access_unlock(vma->vm_mm);
                error = swapout(page, file);
+               UnlockPage(page);
                if (file) fput(file);
                if (!error)
                        goto out_free_success;
-----------------

Didn't you mean the UnlockPage() to go before swapout(...)?
For example, one of the swapout routines, filemap_write_page()
expects the page to be unlocked. If called with page locked,
I'd expect a "double-trip" dead-lock. Right?

Like you said in an  earlier mail, most of the code in
try_to_swap_out expects the page to be unlocked. Now,
of course, the reverse is true ... need to watch out!

-- 
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Rajagopal Ananthanarayanan ("ananth")
Member Technical Staff, SGI.
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