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| 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 /include | |
| parent | b26a3dfd4c0b888303a5909ef37febeb582e190e (diff) | |
| download | linux-55878e88c59221c3187e1c24ec3b15eb79c374c0.tar.gz linux-55878e88c59221c3187e1c24ec3b15eb79c374c0.tar.bz2 linux-55878e88c59221c3187e1c24ec3b15eb79c374c0.zip | |
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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mmzone.h | 4 |
1 files changed, 4 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 |