[PATCH v7 3/5] mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY

[Feng Tang]

From: Ben Widawsky <ben.widawsky@xxxxxxxxx>

Implement the missing huge page allocation functionality while obeying
the preferred node semantics. This is similar to the implementation
for general page allocation, as it uses a fallback mechanism to try
multiple preferred nodes first, and then all other nodes.

[akpm: fix compling issue when merging with other hugetlb patch]
[Thanks to 0day bot for catching the missing #ifdef CONFIG_NUMA issue]
Link: https://lore.kernel.org/r/20200630212517.308045-12-ben.widawsky@xxxxxxxxx
Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
Co-developed-by: Feng Tang <feng.tang@xxxxxxxxx>
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
---
 mm/hugetlb.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 95714fb28150..9279f6d478d9 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1166,7 +1166,20 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 
 	gfp_mask = htlb_alloc_mask(h);
 	nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
+#ifdef CONFIG_NUMA
+	if (mpol->mode == MPOL_PREFERRED_MANY) {
+		page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);
+		if (page)
+			goto check_reserve;
+		/* Fallback to all nodes */
+		nodemask = NULL;
+	}
+#endif
 	page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);
+
+#ifdef CONFIG_NUMA
+check_reserve:
+#endif
 	if (page && !avoid_reserve && vma_has_reserves(vma, chg)) {
 		SetHPageRestoreReserve(page);
 		h->resv_huge_pages--;
@@ -2147,6 +2160,21 @@ struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
 	nodemask_t *nodemask;
 
 	nid = huge_node(vma, addr, gfp_mask, &mpol, &nodemask);
+#ifdef CONFIG_NUMA
+	if (mpol->mode == MPOL_PREFERRED_MANY) {
+		gfp_t gfp = gfp_mask | __GFP_NOWARN;
+
+		gfp &=  ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL);
+		page = alloc_surplus_huge_page(h, gfp, nid, nodemask, false);
+		if (page) {
+			mpol_cond_put(mpol);
+			return page;
+		}
+
+		/* Fallback to all nodes */
+		nodemask = NULL;
+	}
+#endif
 	page = alloc_surplus_huge_page(h, gfp_mask, nid, nodemask, false);
 	mpol_cond_put(mpol);
 
-- 
2.14.1