mm/page_isolation: unset migratetype directly for non Buddy page

mm/page_isolation: unset migratetype directly for non Buddy page

In unset_migratetype_isolate(), we can bypass the call to
move_freepages_block() for non-buddy pages.

It will save a few cpu cycles for some situations such as cma and
hugetlb when allocating continue pages, in these situation function
alloc_contig_pages will be called.

alloc_contig_pages
	__alloc_contig_migrate_range
	isolate_freepages_range ==> pages has been remove from buddy
	undo_isolate_page_range
		unset_migratetype_isolate ==> can directly set migratetype

[[email protected]: changelog tweak]

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
Signed-off-by: Chen Wandun <[email protected]>
Reviewed-by: Oscar Salvador <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Wang Kefeng <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>