[lc-devel] UML swap bug fixed

[Rodrigo S. de C. <rc...@im...>]

Hi there,

Finally Jeff seems to have fixed that bug which screwed up our vswap
addresses. I think I can continue developing under UML :-)

----- Forwarded message from Jeff Dike <jd...@ka...> -----

Date: Thu, 10 Jan 2002 22:16:18 -0500
From: Jeff Dike <jd...@ka...>
Subject: Re: [uml-devel] swap entry and newpage bit 
To: Rodrigo Souza de Castro <rc...@im...>
Cc: use...@li...

rc...@im... said:
> The problem I noticed is that, when setting a pte to a swap entry, the
> NEWPAGE bit is turned on to tell fix_range() that this address should
> be unmapped. It turns out that, for swap adresses that are shared by
> many ptes, the address is not unmapped and the NEWPAGE bit is not
> turned off soon enough before any pte faults. Then, in fault handlers
> (handle_pte_fault() and do_swap_page()), the pte has a wrong value, so
> I can't find the page in swap cache. For example, if the swap cache
> page is set to 0x3307c and the wrong pte is set to 0x3307e (due to
> newpage bit), I won't be able to find it.

This is an excellent description of the bug that I just spend 5 days chasing.

Unfortunately, I didn't until recently (yesterday) understand enough of the
swap code to tell whether you were describing something real or whether
you were on crack.

It is now fixed.

pte_to_swp_entry now masks off the arch bits.

				Jeff

----- End forwarded message -----

-- 
Rodrigo S. de Castro <rc...@im...>