Subject: + sparsemem-add-build_bug_on-when-sizeof-mem_section-is-non-power-of-2.patch added to -mm tree
To: cody@xxxxxxxxxxxxxxxxxx,dave.hansen@xxxxxxxxxxxxxxx,liuj97@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 31 May 2013 14:36:35 -0700
The patch titled
Subject: sparsemem: add BUILD_BUG_ON when sizeof mem_section is non-power-of-2
has been added to the -mm tree. Its filename is
sparsemem-add-build_bug_on-when-sizeof-mem_section-is-non-power-of-2.patch
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From: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
Subject: sparsemem: add BUILD_BUG_ON when sizeof mem_section is non-power-of-2
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 <cody@xxxxxxxxxxxxxxxxxx>
Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Jiang Liu <liuj97@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 4 ++++
mm/sparse.c | 3 +++
2 files changed, 7 insertions(+)
diff -puN include/linux/mmzone.h~sparsemem-add-build_bug_on-when-sizeof-mem_section-is-non-power-of-2 include/linux/mmzone.h
--- a/include/linux/mmzone.h~sparsemem-add-build_bug_on-when-sizeof-mem_section-is-non-power-of-2
+++ a/include/linux/mmzone.h
@@ -1137,6 +1137,10 @@ 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 -puN mm/sparse.c~sparsemem-add-build_bug_on-when-sizeof-mem_section-is-non-power-of-2 mm/sparse.c
--- a/mm/sparse.c~sparsemem-add-build_bug_on-when-sizeof-mem_section-is-non-power-of-2
+++ a/mm/sparse.c
@@ -480,6 +480,9 @@ 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();
_
Patches currently in -mm which might be from cody@xxxxxxxxxxxxxxxxxx are
mm-page_alloc-factor-out-setting-of-pcp-high-and-pcp-batch.patch
mm-page_alloc-prevent-concurrent-updaters-of-pcp-batch-and-high.patch
mm-page_alloc-insert-memory-barriers-to-allow-async-update-of-pcp-batch-and-high.patch
mm-page_alloc-protect-pcp-batch-accesses-with-access_once.patch
mm-page_alloc-convert-zone_pcp_update-to-rely-on-memory-barriers-instead-of-stop_machine.patch
mm-page_alloc-when-handling-percpu_pagelist_fraction-dont-unneedly-recalulate-high.patch
mm-page_alloc-factor-setup_pageset-into-pageset_init-and-pageset_set_batch.patch
mm-page_alloc-relocate-comment-to-be-directly-above-code-it-refers-to.patch
mm-page_alloc-factor-zone_pageset_init-out-of-setup_zone_pageset.patch
mm-page_alloc-in-zone_pcp_update-uze-zone_pageset_init.patch
mm-page_alloc-rename-setup_pagelist_highmark-to-match-naming-of-pageset_set_batch.patch
mm-fix-comment-referring-to-non-existent-size_seqlock-change-to-span_seqlock.patch
mmzone-note-that-node_size_lock-should-be-manipulated-via-pgdat_resize_lock.patch
memory_hotplug-use-pgdat_resize_lock-in-online_pages.patch
memory_hotplug-use-pgdat_resize_lock-in-__offline_pages.patch
memory_hotplug-use-pgdat_resize_lock-in-__offline_pages-fix.patch
sparsemem-add-build_bug_on-when-sizeof-mem_section-is-non-power-of-2.patch
--
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