Re: [lc-devel] UML swap bug fixed

[David C. <dav...@rc...>]

Is this the bug that I point out in my previous mail to the list? Or it 
is caused by a different issue? Please clarify, since I don't have 
enough time to understand all the code at the moment. Thanks.

David

Rodrigo Souza de Castro wrote:

>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 -----
>