linux-kernel - Re: CONFIG_NUMA breaks hibernation on x86-32 with PAE

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Date:	Tue, 11 Nov 2008 11:30:43 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	kernel list <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: CONFIG_NUMA breaks hibernation on x86-32 with PAE

On Mon 2008-11-10 19:28:03, Rafael J. Wysocki wrote:
> On Monday, 10 of November 2008, Andi Kleen wrote:
> > Ingo Molnar <mingo@...e.hu> writes:
> > >
> > > No good ideas - the bug description gives me the impression of memory 
> > > maps save/restore hickup in the hibernation code - and memory maps are 
> > > pretty much the only thing that are significantly different on NUMA. 
> > 
> > I assume the problem happened on a single node system.
> > On single node the memory map should be actually quite similar
> > to the UMA case.
> 
> It is.  However, the problem is 100% reproducible on any 32-bit single-node
> system with CONFIG_NUMA set, from what I can tell.
> 
> It doesn't happen if the kernel is booted with highmem=0, so it looks like
> the code that saves highmem causes the problem to happen.  However, this
> same code works well for all of the !CONFIG_NUMA cases and practically only
> the only non-open-coded it uses is kmap_atomic().

kmap_atomic() and kernel_map_pages(), AFAICT.

Can kmap_atomic() modify pages in highmem, too?

Wait... are we putting kernel pagetables in the high memory?

What about this cleanup (warning: untested)

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 5d2ab83..f1d8336 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -966,7 +966,7 @@ static void copy_data_page(unsigned long
 			 * data modified by kmap_atomic()
 			 */
 			safe_copy_page(buffer, s_page);
-			dst = kmap_atomic(pfn_to_page(dst_pfn), KM_USER0);
+			dst = kmap_atomic(d_page, KM_USER0);
 			memcpy(dst, buffer, PAGE_SIZE);
 			kunmap_atomic(dst, KM_USER0);
 		} else {

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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