[PATCH v6 4/6] 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.

[Thanks to 0day bot for caching 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   | 25 +++++++++++++++++++++++++
 mm/mempolicy.c |  3 ++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 924553aa8f78..3e84508c1b8c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1164,7 +1164,18 @@ 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);
+
+check_reserve:
 	if (page && !avoid_reserve && vma_has_reserves(vma, chg)) {
 		SetHPageRestoreReserve(page);
 		h->resv_huge_pages--;
@@ -2095,6 +2106,20 @@ 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_DIRECT_RECLAIM;
+
+		page = alloc_surplus_huge_page(h, gfp, nid, nodemask);
+		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);
 	mpol_cond_put(mpol);
 
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 9dce67fc9bb6..93f8789758a7 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2054,7 +2054,8 @@ int huge_node(struct vm_area_struct *vma, unsigned long addr, gfp_t gfp_flags,
 					huge_page_shift(hstate_vma(vma)));
 	} else {
 		nid = policy_node(gfp_flags, *mpol, numa_node_id());
-		if ((*mpol)->mode == MPOL_BIND)
+		if ((*mpol)->mode == MPOL_BIND ||
+		    (*mpol)->mode == MPOL_PREFERRED_MANY)
 			*nodemask = &(*mpol)->nodes;
 	}
 	return nid;
-- 
2.7.4