mm: compaction: fix bit ranges in {get,clear,set}_pageblock_skip()

{get,clear,set}_pageblock_skip() use incorrect bit ranges (please compare
to bit ranges used by {get,set}_pageblock_flags() used for migration
types) and can overwrite pageblock migratetype of the next pageblock in
the bitmap.

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Tested-by: Thierry Reding <thierry.reding@avionic-design.de>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pageblock-flags.h

@@ -71,13 +71,13 @@ void set_pageblock_flags_group(struct page *page, unsigned long flags,
 #ifdef CONFIG_COMPACTION
 #define get_pageblock_skip(page) \
 			get_pageblock_flags_group(page, PB_migrate_skip,     \
-							PB_migrate_skip + 1)
+							PB_migrate_skip)
 #define clear_pageblock_skip(page) \
 			set_pageblock_flags_group(page, 0, PB_migrate_skip,  \
-							PB_migrate_skip + 1)
+							PB_migrate_skip)
 #define set_pageblock_skip(page) \
 			set_pageblock_flags_group(page, 1, PB_migrate_skip,  \
-							PB_migrate_skip + 1)
+							PB_migrate_skip)
 #endif /* CONFIG_COMPACTION */
 
 #define get_pageblock_flags(page) \