From 01c7437cc4f5246e85aacdad3a027db79e00100b Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.com>
Date: Wed, 7 Jun 2017 10:05:03 +0200
Subject: [PATCH 3/4] mm: unify new_node_page and alloc_migrate_target
Git-commit: 8b9132388964df2cfe151a88fd1dd8219dabf23c
Patch-mainline: v4.13-rc1
References: bnc#1042553

394e31d2ceb4 ("mem-hotplug: alloc new page from a nearest neighbor node
when mem-offline") has duplicated a large part of alloc_migrate_target
with some hotplug specific special casing. To be more precise it tried
to enfore the allocation from a different node than the original page.
As a result the two function diverged in their shared logic, e.g. the
hugetlb allocation strategy. Let's unify the two and express different
NUMA requirements by the given nodemask. new_node_page will simply
exclude the node it doesn't care about and alloc_migrate_target will
use all the available nodes. alloc_migrate_target will then learn to
migrate hugetlb pages more sanely and use preallocated pool when
possible.

Please note that alloc_migrate_target used to call alloc_page resp.
alloc_pages_current so the memory policy of the current context which
is quite strange when we consider that it is used in the context of
alloc_contig_range which just tries to migrate pages which stand in the
way.

Signed-off-by: Michal Hocko <mhocko@suse.com>

---
 include/linux/migrate.h |   18 ++++++++++++++++++
 mm/memory_hotplug.c     |   12 +-----------
 mm/page_isolation.c     |   18 ++----------------
 3 files changed, 21 insertions(+), 27 deletions(-)

--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -4,6 +4,7 @@
 #include <linux/mm.h>
 #include <linux/mempolicy.h>
 #include <linux/migrate_mode.h>
+#include <linux/hugetlb.h>
 
 typedef struct page *new_page_t(struct page *page, unsigned long private,
 				int **reason);
@@ -30,6 +31,23 @@ enum migrate_reason {
 /* In mm/debug.c; also keep sync with include/trace/events/migrate.h */
 extern char *migrate_reason_names[MR_TYPES];
 
+static inline struct page *new_page_nodemask(struct page *page, int preferred_nid,
+		nodemask_t *nodemask)
+{
+	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
+
+	if (PageHuge(page))
+		return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
+				nodemask);
+
+	if (PageHighMem(page)
+	    || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
+		gfp_mask |= __GFP_HIGHMEM;
+
+	return __alloc_pages_nodemask(gfp_mask, 0,
+			node_zonelist(preferred_nid, gfp_mask), nodemask);
+}
+
 #ifdef CONFIG_MIGRATION
 
 extern void putback_movable_pages(struct list_head *l);
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1451,7 +1451,6 @@ static unsigned long scan_movable_pages(
 static struct page *new_node_page(struct page *page, unsigned long private,
 		int **result)
 {
-	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
 	int nid = page_to_nid(page);
 	nodemask_t nmask = node_states[N_MEMORY];
 
@@ -1464,16 +1463,7 @@ static struct page *new_node_page(struct
 	if (nodes_empty(nmask))
 		node_set(nid, nmask);
 
-	if (PageHuge(page))
-		return alloc_huge_page_nodemask(
-				page_hstate(compound_head(page)), &nmask);
-
-	if (PageHighMem(page)
-	    || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
-		gfp_mask |= __GFP_HIGHMEM;
-
-	return __alloc_pages_nodemask(gfp_mask, 0,
-			node_zonelist(nid, gfp_mask), &nmask);
+	return new_page_nodemask(page, nid, &nmask);
 }
 
 #define NR_OFFLINE_AT_ONCE_PAGES	(256)
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -8,6 +8,7 @@
 #include <linux/memory.h>
 #include <linux/hugetlb.h>
 #include <linux/page_owner.h>
+#include <linux/migrate.h>
 #include "internal.h"
 
 #define CREATE_TRACE_POINTS
@@ -294,20 +295,5 @@ int test_pages_isolated(unsigned long st
 struct page *alloc_migrate_target(struct page *page, unsigned long private,
 				  int **resultp)
 {
-	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
-
-	/*
-	 * TODO: allocate a destination hugepage from a nearest neighbor node,
-	 * accordance with memory policy of the user process if possible. For
-	 * now as a simple work-around, we use the next node for destination.
-	 */
-	if (PageHuge(page))
-		return alloc_huge_page_node(page_hstate(compound_head(page)),
-					    next_node_in(page_to_nid(page),
-							 node_online_map));
-
-	if (PageHighMem(page))
-		gfp_mask |= __GFP_HIGHMEM;
-
-	return alloc_page(gfp_mask);
+	return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);
 }