[PATCH v6 2/6] mm/memplicy: add page allocation function for MPOL_PREFERRED_MANY policy

[Feng Tang]

The semantics of MPOL_PREFERRED_MANY is similar to MPOL_PREFERRED,
that it will first try to allocate memory from the preferred node(s),
and fallback to all nodes in system when first try fails.

Add a dedicated function for it just like 'interleave' policy.

Link: https://lore.kernel.org/r/20200630212517.308045-9-ben.widawsky@xxxxxxxxx
Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
Co-developed-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
---
 mm/mempolicy.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 17b5800b7dcc..d17bf018efcc 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2153,6 +2153,25 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,
 	return page;
 }
 
+static struct page *alloc_page_preferred_many(gfp_t gfp, unsigned int order,
+						struct mempolicy *pol)
+{
+	struct page *page;
+
+	/*
+	 * This is a two pass approach. The first pass will only try the
+	 * preferred nodes but skip the direct reclaim and allow the
+	 * allocation to fail, while the second pass will try all the
+	 * nodes in system.
+	 */
+	page = __alloc_pages(((gfp | __GFP_NOWARN) & ~__GFP_DIRECT_RECLAIM),
+				order, first_node(pol->nodes), &pol->nodes);
+	if (!page)
+		page = __alloc_pages(gfp, order, numa_node_id(), NULL);
+
+	return page;
+}
+
 /**
  * alloc_pages_vma - Allocate a page for a VMA.
  * @gfp: GFP flags.
-- 
2.7.4