linux-kernel - Re: [PATCH] mmc-atmel : fix kunmap wrong usage

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Date:	Fri, 22 Jun 2007 15:34:07 +0200
From:	Nicolas Ferre <nicolas.ferre@....atmel.com>
To:	Hugh Dickins <hugh@...itas.com>
CC:	Marc Pignat <marc.pignat@...s.ch>,
	ARM Linux Mailing List 
	<linux-arm-kernel@...ts.arm.linux.org.uk>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Andrew Victor <andrew@...people.com>,
	Pierre Ossman <drzeus@...eus.cx>
Subject: Re: [PATCH] mmc-atmel : fix kunmap wrong usage

Hugh Dickins :
> Aren't you just guessing there?  Those kunmap_atomics in at91_mci.c
> may look wrong to you, but they're not incorrect (so long as sg->offset
> falls within the page, as it must do here to make sense of the page).
> Especially not on ARM, where kunmap_atomic actually has no interest
> in the argument passed.  And the oops was in the flush_dcache_page.
> 
> If you actually reproduced Nicolas' problem on ARM, and verified
> that your patch then fixes it, please let us know: that will be
> remarkably interesting.

Patch tested without success. Indeed, I always see the Oops with 
Marc's patch.

> I believe I posted the correct fix last night (or at least a safe fix
> for now: Christoph Lameter may prefer to undo it and change ARM's
> dma_mapping at leisure later), checking PageSlab in page_mapping;
> and Linus has already put that one into his git tree.

Here:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=b9bae3402572dc50a1e084c5b1ae5117918ef0f0

> But it would be good to hear from Nicolas whether that indeed fixes
> his oops: I couldn't actually try my patch on ARM either.

Ok tested on Atmel ARM AT91 (at91sam9263), this fixes this oops.

Thanks a lot to all of you for your precise help.

Regards,
-- 
Nicolas Ferre


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