From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx111.postini.com [74.125.245.111]) by kanga.kvack.org (Postfix) with SMTP id AEECC6B0034 for ; Thu, 30 May 2013 14:50:12 -0400 (EDT) Received: from /spool/local by e7.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 30 May 2013 14:50:11 -0400 Received: from d01relay06.pok.ibm.com (d01relay06.pok.ibm.com [9.56.227.116]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id B6A176E805F for ; Thu, 30 May 2013 14:50:05 -0400 (EDT) Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by d01relay06.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r4UIo86f44695730 for ; Thu, 30 May 2013 14:50:09 -0400 Received: from d03av03.boulder.ibm.com (loopback [127.0.0.1]) by d03av03.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r4UInu7o008171 for ; Thu, 30 May 2013 12:49:56 -0600 From: Cody P Schafer Subject: [PATCH] sparsemem: BUILD_BUG_ON when sizeof mem_section is non-power-of-2 Date: Thu, 30 May 2013 11:40:48 -0700 Message-Id: <1369939248-10006-1-git-send-email-cody@linux.vnet.ibm.com> In-Reply-To: <51A78EC4.4080703@intel.com> References: <51A78EC4.4080703@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: LKML , Linux MM , David Hansen , Cody P Schafer Instead of leaving a hidden trap for the next person who comes along and wants to add something to mem_section, add a big fat warning about it needing to be a power-of-2, and insert a BUILD_BUG_ON() in sparse_init() to catch mistakes. Right now non-power-of-2 mem_sections cause a number of WARNs at boot (which don't clearly point to the size of mem_section as an issue), but the system limps on (temporarily, at least). This is based upon Dave Hansen's earlier RFC where he ran into the same issue: "sparsemem: fix boot when SECTIONS_PER_ROOT is not power-of-2" http://lkml.indiana.edu/hypermail/linux/kernel/1205.2/03077.html Signed-off-by: Cody P Schafer --- Dave: Consider it resurrected. --- include/linux/mmzone.h | 4 ++++ mm/sparse.c | 3 +++ 2 files changed, 7 insertions(+) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 131989a..88e23f3 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1127,6 +1127,10 @@ struct mem_section { struct page_cgroup *page_cgroup; unsigned long pad; #endif + /* + * WARNING: mem_section must be a power-of-2 in size for the + * calculation and use of SECTION_ROOT_MASK to make sense. + */ }; #ifdef CONFIG_SPARSEMEM_EXTREME diff --git a/mm/sparse.c b/mm/sparse.c index 1c91f0d3..3194ec4 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -481,6 +481,9 @@ void __init sparse_init(void) struct page **map_map; #endif + /* see include/linux/mmzone.h 'struct mem_section' definition */ + BUILD_BUG_ON(!is_power_of_2(sizeof(struct mem_section))); + /* Setup pageblock_order for HUGETLB_PAGE_SIZE_VARIABLE */ set_pageblock_order(); -- 1.8.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org