mainline inclusion
from mainline-v5.11-rc1
commit 7ad69832
category: bugfix
bugzilla: NA
CVE: NA

-----------------------------------------------

When we free a page whose order is very close to MAX_ORDER and greater
than pageblock_order, it wastes some CPU cycles to increase max_order to
MAX_ORDER one by one and check the pageblock migratetype of that page
repeatedly especially when MAX_ORDER is much larger than pageblock_order.

We also should not be checking migratetype of buddy when "order ==
MAX_ORDER - 1" as the buddy pfn may be invalid, so adjust the condition.
With the new check, we don't need the max_order check anymore, so we
replace it.

Also adjust max_order initialization so that it's lower by one than
previously, which makes the code hopefully more clear.

Link: https://lkml.kernel.org/r/20201204155109.55451-1-songmuchun@bytedance.com
Fixes: d9dddbf5 ("mm/page_alloc: prevent merging between isolated and other pageblocks")
Signed-off-by: NMuchun Song <songmuchun@bytedance.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

conflict:
	mm/page_alloc.c
Signed-off-by: NTong Tiangen <tongtiangen@huawei.com>
Reviewed-by: NChen Wandun <chenwandun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>