Re: [PATCH] i386 CPA fix - do not free reserved pages

[Frederik Deweerdt <deweerdt@free.fr>]

On Tue, Jul 03, 2007 at 01:33:24PM -0400, Mathieu Desnoyers wrote:
> Right, there is a test missing, can you try this fix on top of my
> x86_64 mm cpa cache flush fix ?
No warning with both patches applied, thanks Mathieu.

Frederik
> 
> 
> i386 CPA fix - do not free reserved pages
> 
> We have to use the same conditions found in change_page_attr in
> global_tlb_flush regarding the conditions that leads to free the page.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> ---
>  arch/i386/mm/pageattr.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6-lttng/arch/i386/mm/pageattr.c
> ===================================================================
> --- linux-2.6-lttng.orig/arch/i386/mm/pageattr.c	2007-07-03 13:25:48.000000000 -0400
> +++ linux-2.6-lttng/arch/i386/mm/pageattr.c	2007-07-03 13:28:34.000000000 -0400
> @@ -247,7 +247,7 @@
>  	list_for_each_entry_safe(pg, next, &l, lru) {
>  		clear_bit(PG_arch_1, &pg->flags);
>  		list_del(&pg->lru);
> -		if (page_private(pg) != 0)
> +		if (PageReserved(pg) || !cpu_has_pse || page_private(pg) != 0)
>  			continue;
>  		ClearPagePrivate(pg);
>  		__free_page(pg);
> 
> 
> * Frederik Deweerdt (deweerdt@free.fr) wrote:
> > On Tue, Jul 03, 2007 at 11:37:47AM -0400, Mathieu Desnoyers wrote:
> > > Hi Alan,
> > > 
> > > I already sent a fix to Andrew and Andi for this (hrm, forget to CC
> > > lkml on the original message):
> > > 
> > > 
> > > x86_64 mm cpa cache flush fix
> > > 
> > > X86_64 and i386 cpa cache flush fix:
> > > 
> > > list_del the deferred list entries to poison their pointers.
> > > clear the flag for every page put in the list.
> > > 
> > Hi Mathieu,
> > 
> > I've tried the patch on rc6-mm1, but it doesn't seem to fix the
> > problem. From what I understood, the bad_page() is called on PG_reserved
> > being set (flags:0x00000400), not the lru pointer being not NULL or
> > PG_arch_1 being set.
> > 
> > Regards,
> > Frederik
> > 
> > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> > > CC: Andi Kleen <ak@suse.de>
> > [...]
> > >  	flush_map(&l);
> > >  	list_for_each_entry_safe(pg, next, &l, lru) {
> > > +		clear_bit(PG_arch_1, &pg->flags);
> > > +		list_del(&pg->lru);
> > >  		if (page_private(pg) != 0)
> > >  			continue;
> > >  		ClearPagePrivate(pg);
> > > -		clear_bit(PG_arch_1, &pg->flags);
> > >  		__free_page(pg);
> > >  	}
> > >  }
> > [...]
> > > * Alan Cox (alan@lxorguk.ukuu.org.uk) wrote:
> > > > X86 32bit with lots of debug turned on I get this:
> > [...]
> > > > Bad page state in process 'swapper'
> > > > page:c10000c0 flags:0x00000400 mapping:00000000 mapcount:0 count:0
> > > > Trying to fix it up, but a reboot is needed
> > > > Backtrace:
> > > >  [<c024589c>] bad_page+0x6c/0x100
> > > >  [<c024648d>] free_hot_cold_page+0x5d/0x140
> > > >  [<c02116c2>] global_flush_tlb+0x112/0x130
> > > >  [<c020102d>] init_post+0xd/0xe0
> > > >  [<c047c876>] kernel_init+0x216/0x220
> > > >  [<c0214c50>] schedule_tail+0x0/0xe0
> > > >  [<c047c660>] kernel_init+0x0/0x220
> > > >  [<c047c660>] kernel_init+0x0/0x220
> > > >  [<c0204227>] kernel_thread_helper+0x7/0x10
> > > >  =======================
> > > > Hexdump:
> > > > 000: 00 06 00 00 01 00 00 00 ff ff ff ff 0f 00 00 00
> > > > 010: 00 00 00 00 00 00 00 00 78 00 00 c1 b8 00 00 c1
> > > > 020: 00 06 00 00 01 00 00 00 ff ff ff ff a7 03 00 00
> > > > 030: 00 00 00 00 00 00 00 00 98 00 00 c1 d8 00 00 c1
> > > > 040: 00 04 00 00 00 00 00 00 ff ff ff ff 00 00 00 00
> > > > 050: 00 00 00 00 00 00 00 00 b8 00 00 c1 f8 00 00 c1
> > > > 060: 00 06 00 00 01 00 00 00 ff ff ff ff 00 04 00 00
> > > > 070: 00 00 00 00 00 00 00 00 d8 00 00 c1 18 01 00 c1
> > > > 080: 00 06 00 00 01 00 00 00 ff ff ff ff 9c 03 00 00
> > > > 090: 00 00 00 00 00 00 00 00 f8 00 00 c1 38 01 00 c1
> > > > 0a0: 00 06 00 00 01 00 00 00 ff ff ff ff 00 04 00 00
> > > > 0b0: 00 00 00 00 00 00 00 00 18 01 00 c1 58 01 00 c1
> > > > -
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> > > 
> > > -- 
> > > Mathieu Desnoyers
> > > Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
> > > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
> > > -
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> > > 
> > 
> 
> -- 
> Mathieu Desnoyers
> Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
> -
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