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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html