mm/memory_hotplug: remove a wrapper for alloc_migration_target()

To calculate the correct node to migrate the page for hotplug, we need to
check node id of the page.  Wrapper for alloc_migration_target() exists
for this purpose.

However, Vlastimil informs that all migration source pages come from a
single node.  In this case, we don't need to check the node id for each
page and we don't need to re-set the target nodemask for each page by
using the wrapper.  Set up the migration_target_control once and use it
for all pages.

Signed-off-by: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Roman Gushchin <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

mm/memory_hotplug.c

@@ -1290,27 +1290,6 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
 	return 0;
 }
 
-static struct page *new_node_page(struct page *page, unsigned long private)
-{
-	nodemask_t nmask = node_states[N_MEMORY];
-	struct migration_target_control mtc = {
-		.nid = page_to_nid(page),
-		.nmask = &nmask,
-		.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
-	};
-
-	/*
-	 * try to allocate from a different node but reuse this node if there
-	 * are no other online nodes to be used (e.g. we are offlining a part
-	 * of the only existing node)
-	 */
-	node_clear(mtc.nid, nmask);
-	if (nodes_empty(nmask))
-		node_set(mtc.nid, nmask);
-
-	return alloc_migration_target(page, (unsigned long)&mtc);
-}
-
 static int
 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 {
@@ -1370,9 +1349,28 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 		put_page(page);
 	}
 	if (!list_empty(&source)) {
-		/* Allocate a new page from the nearest neighbor node */
-		ret = migrate_pages(&source, new_node_page, NULL, 0,
-					MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
+		nodemask_t nmask = node_states[N_MEMORY];
+		struct migration_target_control mtc = {
+			.nmask = &nmask,
+			.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
+		};
+
+		/*
+		 * We have checked that migration range is on a single zone so
+		 * we can use the nid of the first page to all the others.
+		 */
+		mtc.nid = page_to_nid(list_first_entry(&source, struct page, lru));
+
+		/*
+		 * try to allocate from a different node but reuse this node
+		 * if there are no other online nodes to be used (e.g. we are
+		 * offlining a part of the only existing node)
+		 */
+		node_clear(mtc.nid, nmask);
+		if (nodes_empty(nmask))
+			node_set(mtc.nid, nmask);
+		ret = migrate_pages(&source, alloc_migration_target, NULL,
+			(unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
 		if (ret) {
 			list_for_each_entry(page, &source, lru) {
 				pr_warn("migrating pfn %lx failed ret:%d ",