linux-kernel - [PATCH] mm: sparse: use __aligned() instead of manual padding in mem

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Date:	Wed, 29 May 2013 16:14:39 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: [PATCH] mm: sparse: use __aligned() instead of manual padding in mem_section

Instead of leaving a trap for the next person who comes along and wants
to add something to mem_section, add an __aligned() and remove the
manual padding added for MEMCG.

Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
---
 include/linux/mmzone.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

---

Also, does anyone know what causes this alignment to be required here? I found
this was breaking things in a patchset I'm working on (WARNs in sysfs code
about duplicate filenames when initing mem_sections). Adding some documentation
for the reason would be appreciated.

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 131989a..a8e8056 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1125,9 +1125,8 @@ struct mem_section {
 	 * section. (see memcontrol.h/page_cgroup.h about this.)
 	 */
 	struct page_cgroup *page_cgroup;
-	unsigned long pad;
 #endif
-};
+} __aligned(2 * sizeof(unsigned long));
 
 #ifdef CONFIG_SPARSEMEM_EXTREME
 #define SECTIONS_PER_ROOT       (PAGE_SIZE / sizeof (struct mem_section))
-- 
1.8.3

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