[PATCH 3/3] mm/hugetlb: add hugepage isolation support

[Doug Berger <opendmb@gmail.com>]

When a range of pageblocks is isolated there is at most one
hugepage that has only tail pages overlapping that range (i.e.
a hugepage that overlaps the beginning of the range).

However, that hugepage is the first migration target for an
alloc_contig_range() attempt so it already receives special
attention.

Checking whether the pageblock containing the head of a hugepage
is isolated is an inexpensive way to avoid hugepage allocations
from isolated pageblocks which makes alloc_contig_range() more
efficient.

Signed-off-by: Doug Berger <opendmb@gmail.com>
---
 mm/hugetlb.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index eab812760fbe..3a2f0b55059d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -33,6 +33,7 @@
 #include <linux/migrate.h>
 #include <linux/nospec.h>
 #include <linux/delayacct.h>
+#include <linux/page-isolation.h>
 
 #include <asm/page.h>
 #include <asm/pgalloc.h>
@@ -1135,6 +1136,10 @@ static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
 		if (PageHWPoison(page))
 			continue;
 
+		/* Check head pageblock isolation */
+		if (is_migrate_isolate_page(page))
+			continue;
+
 		list_move(&page->lru, &h->hugepage_activelist);
 		set_page_refcounted(page);
 		ClearHPageFreed(page);
-- 
2.25.1