From 125b860b251ad226b1384b6db06be37485127f69 Mon Sep 17 00:00:00 2001 From: Pingfan Liu Date: Fri, 28 Dec 2018 00:38:43 -0800 Subject: [PATCH] mm/pageblock: throw compile error if pageblock_bits cannot hold MIGRATE_TYPES Currently, NR_PAGEBLOCK_BITS and MIGRATE_TYPES are not associated by code. If someone adds extra migrate type, then he may forget to enlarge the NR_PAGEBLOCK_BITS. Hence it requires some way to fix. NR_PAGEBLOCK_BITS depends on MIGRATE_TYPES, while these macro spread on two different .h file with reverse dependency, it is a little hard to refer to MIGRATE_TYPES in pageblock-flag.h. This patch tries to remind such relation in compiling-time. Link: http://lkml.kernel.org/r/1544508709-11358-1-git-send-email-kernelfans@gmail.com Signed-off-by: Pingfan Liu Reviewed-by: Andrew Morton Acked-by: Vlastimil Babka Cc: Michal Hocko Cc: Pavel Tatashin Cc: Oscar Salvador Cc: Mike Rapoport Cc: Joonsoo Kim Cc: Alexander Duyck Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/pageblock-flags.h | 3 ++- mm/page_alloc.c | 1 + 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h index 9132c5cb41f1..06a66327333d 100644 --- a/include/linux/pageblock-flags.h +++ b/include/linux/pageblock-flags.h @@ -25,10 +25,11 @@ #include +#define PB_migratetype_bits 3 /* Bit indices that affect a whole block of pages */ enum pageblock_bits { PB_migrate, - PB_migrate_end = PB_migrate + 3 - 1, + PB_migrate_end = PB_migrate + PB_migratetype_bits - 1, /* 3 bits required for migrate types */ PB_migrate_skip,/* If set the block is skipped by compaction */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b4fcf211ca69..cd1c9d32ef9a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -431,6 +431,7 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags, unsigned long old_word, word; BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4); + BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits)); bitmap = get_pageblock_bitmap(page, pfn); bitidx = pfn_to_bitidx(page, pfn);