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-rw-r--r--include/linux/pageblock-flags.h3
-rw-r--r--mm/page_alloc.c1
2 files changed, 3 insertions, 1 deletions
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 <linux/types.h>
+#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);