diff options
| author | Cody P Schafer <cody@linux.vnet.ibm.com> | 2013-07-03 15:04:44 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-07-03 16:07:40 -0700 |
| commit | 55878e88c59221c3187e1c24ec3b15eb79c374c0 (patch) | |
| tree | f0c9a994d63b3fb64dffe6477317db53453b2b61 | |
| parent | b26a3dfd4c0b888303a5909ef37febeb582e190e (diff) | |
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@linux.vnet.ibm.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jiang Liu <liuj97@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/mmzone.h | 4 | ||||
| -rw-r--r-- | mm/sparse.c | 3 |
2 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 09d381b71fd8..ae19af5ec02c 100644 --- a/include/linux/mmzone.h +++ b/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 --git a/mm/sparse.c b/mm/sparse.c index 1c91f0d3f6ab..3194ec414728 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(); |