linux-kernel - [PATCH] nommu: fix kobjsize() for SLOB and SLUB

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Date:	Thu, 22 May 2008 19:09:04 +0300 (EEST)
From:	Pekka J Enberg <penberg@...helsinki.fi>
To:	dhowells@...hat.com
cc:	clameter@....com, mpm@...enic.com, lethal@...ux-sh.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] nommu: fix kobjsize() for SLOB and SLUB

From: Christoph Lameter <clameter@....com>

As reported by Paul Mundt, kobjsize() does not work properly with SLOB and SLUB
that re-use parts of struct page for their own purposes. Fix it up by using
compound_order() for compound pages that don't have PageSlab set.

Reported-by: Paul Mundt <lethal@...ux-sh.org>
Cc: Christoph Lameter <clameter@....com>
Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
---
I kept the original object size calculation for non-compound pages in this 
version. It looks like the nommu code uses kobjsize() for all sorts of 
interesting things.

 mm/nommu.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)

Index: slab-2.6/mm/nommu.c
===================================================================
--- slab-2.6.orig/mm/nommu.c	2008-05-22 18:59:01.000000000 +0300
+++ slab-2.6/mm/nommu.c	2008-05-22 19:00:36.000000000 +0300
@@ -109,12 +109,22 @@
 	 * If the object we have should not have ksize performed on it,
 	 * return size of 0
 	 */
-	if (!objp || (unsigned long)objp >= memory_end || !((page = virt_to_page(objp))))
+	if (!objp)
+		return 0;
+
+	if ((unsigned long) objp >= memory_end)
+		return 0;
+
+	page = virt_to_head_page(objp);
+	if (!page)
 		return 0;
 
 	if (PageSlab(page))
 		return ksize(objp);
 
+	if (PageCompound(page))
+		return PAGE_SIZE << compound_order(page);
+
 	BUG_ON(page->index < 0);
 	BUG_ON(page->index >= MAX_ORDER);
 
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