From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755209AbXFVM2z (ORCPT ); Fri, 22 Jun 2007 08:28:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751987AbXFVM2r (ORCPT ); Fri, 22 Jun 2007 08:28:47 -0400 Received: from extu-mxob-1.symantec.com ([216.10.194.28]:33902 "EHLO extu-mxob-1.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751681AbXFVM2r (ORCPT ); Fri, 22 Jun 2007 08:28:47 -0400 Date: Fri, 22 Jun 2007 13:00:23 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.wat.veritas.com To: Marc Pignat cc: Nicolas Ferre , ARM Linux Mailing List , Linux Kernel list , Andrew Victor , Pierre Ossman Subject: Re: [PATCH] mmc-atmel : fix kunmap wrong usage In-Reply-To: <200706220828.18750.marc.pignat@hevs.ch> Message-ID: References: <467A4532.40301@rfo.atmel.com> <200706211657.49427.marc.pignat@hevs.ch> <467A9F43.1050007@rfo.atmel.com> <200706220828.18750.marc.pignat@hevs.ch> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Brightmail-Verdict: VlJEQwAAAAIAAAABAAAAAAAAAAEAAAAAAAAABmluYm94AGxpbnV4LWtlcm5lbEB2Z2VyLmtlcm5lbC5vcmcAYW5kcmV3QHNhbnBlb3BsZS5jb20Abmljb2xhcy5mZXJyZUByZm8uYXRtZWwuY29tAGxpbnV4LWFybS1rZXJuZWxAbGlzdHMuYXJtLmxpbnV4Lm9yZy51awBtYXJjLnBpZ25hdEBoZXZzLmNoAGRyemV1c0BkcnpldXMuY3gA X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 22 Jun 2007, Marc Pignat wrote: > from: Marc Pignat > > kunmap must be called on the pointer returned by kmap. Not necessarily: an offset within the same page is acceptable. > > Signed-off-by: Marc Pignat > > --- > > N.B: This is the same patch as yesterday, with proper Signed-off-by and more > comments. > > The buffer variable is used this way: > buffer = kmap_atomic(sg->page, KM_BIO_SRC_IRQ) + sg->offset; > So we can't do > kunmap_atomic(buffer, KM_BIO_SRC_IRQ); > we must do > kunmap_atomic(buffer - sg->offset, KM_BIO_SRC_IRQ); > > Strangely this misuse showed no problem using CONFIG_SLAB, but oops using > CONFIG_SLUB, (lkml ''Oops in a driver while using SLUB as a SLAB allocator"). 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. 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. 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. Hugh > > Regards > > Marc > > --- drivers/mmc/host/at91_mci.c-2.6.22-rc5.orig 2007-06-21 16:27:31.000000000 +0200 > +++ drivers/mmc/host/at91_mci.c-2.6.22-rc5 2007-06-21 16:42:48.000000000 +0200 > @@ -164,7 +164,7 @@ static inline void at91mci_sg_to_dma(str > else > memcpy(dmabuf, sgbuffer, amount); > > - kunmap_atomic(sgbuffer, KM_BIO_SRC_IRQ); > + kunmap_atomic(sgbuffer - sg->offset, KM_BIO_SRC_IRQ); > > if (size == 0) > break; > @@ -293,7 +293,7 @@ static void at91mci_post_dma_read(struct > buffer[index] = swab32(buffer[index]); > } > > - kunmap_atomic(buffer, KM_BIO_SRC_IRQ); > + kunmap_atomic(buffer - sg->offset, KM_BIO_SRC_IRQ); > flush_dcache_page(sg->page);