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

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Date:	Fri, 22 Jun 2007 08:28:18 +0200
From:	Marc Pignat <marc.pignat@...s.ch>
To:	Nicolas Ferre <nicolas.ferre@....atmel.com>
Cc:	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: [PATCH] mmc-atmel : fix kunmap wrong usage

from: Marc Pignat <marc.pignat@...s.ch>

kunmap must be called on the pointer returned by kmap.

Signed-off-by: Marc Pignat <marc.pignat@...s.ch>

---

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").

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);
 	}

-
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