mm/page_isolation: do not isolate the max order page

mainline inclusion
from mainline-v5.11-rc1
commit 2484be0f
category: bugfix
bugzilla: 108337 https://gitee.com/openeuler/kernel/issues/I4DDEL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2484be0f88dc6c9670362d51f6a04f2da0626b50

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

A max order page has no buddy page and never merges to another order.  So
isolating and then freeing it is pointless.

Link: https://lkml.kernel.org/r/20201202122114.75316-1-songmuchun@bytedance.com
Fixes: 3c605096 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
Signed-off-by: NMuchun Song <songmuchun@bytedance.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Reviewed-by: NOscar Salvador <osalvador@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NTong Tiangen <tongtiangen@huawei.com>
Reviewed-by: NChen Wandun <chenwandun@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

mm/page_isolation.c

@@ -89,7 +89,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
 	 */
 	if (PageBuddy(page)) {
 		order = buddy_order(page);
-		if (order >= pageblock_order) {
+		if (order >= pageblock_order && order < MAX_ORDER - 1) {
 			pfn = page_to_pfn(page);
 			buddy_pfn = __find_buddy_pfn(pfn, order);
 			buddy = page + (buddy_pfn - pfn);