mm, sparse, page_ext: drop ugly N_HIGH_MEMORY branches for allocations

Commit f52407ce ("memory hotplug: alloc page from other node in
memory online") has introduced N_HIGH_MEMORY checks to only use NUMA
aware allocations when there is some memory present because the
respective node might not have any memory yet at the time and so it
could fail or even OOM.

Things have changed since then though.  Zonelists are now always
initialized before we do any allocations even for hotplug (see
959ecc48 ("mm/memory_hotplug.c: fix building of node hotplug
zonelist")).

Therefore these checks are not really needed.  In fact caller of the
allocator should never care about whether the node is populated because
that might change at any time.

Link: http://lkml.kernel.org/r/20170721143915.14161-10-mhocko@kernel.orgSigned-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_ext.c

@@ -222,10 +222,7 @@ static void *__meminit alloc_page_ext(size_t size, int nid)
 		return addr;
 	}
 
-	if (node_state(nid, N_HIGH_MEMORY))
 	addr = vzalloc_node(size, nid);
-	else
-		addr = vzalloc(size);
 
 	return addr;
 }

mm/sparse-vmemmap.c

@@ -54,12 +54,7 @@ void * __meminit vmemmap_alloc_block(unsigned long size, int node)
 	if (slab_is_available()) {
 		struct page *page;
 
-		if (node_state(node, N_HIGH_MEMORY))
-			page = alloc_pages_node(
-				node, GFP_KERNEL | __GFP_ZERO | __GFP_RETRY_MAYFAIL,
-				get_order(size));
-		else
-			page = alloc_pages(
+		page = alloc_pages_node(node,
 			GFP_KERNEL | __GFP_ZERO | __GFP_RETRY_MAYFAIL,
 			get_order(size));
 		if (page)

mm/sparse.c

@@ -65,14 +65,10 @@ static noinline struct mem_section __ref *sparse_index_alloc(int nid)
 	unsigned long array_size = SECTIONS_PER_ROOT *
 				   sizeof(struct mem_section);
 
-	if (slab_is_available()) {
-		if (node_state(nid, N_HIGH_MEMORY))
+	if (slab_is_available())
 		section = kzalloc_node(array_size, GFP_KERNEL, nid);
 	else
-			section = kzalloc(array_size, GFP_KERNEL);
-	} else {
 		section = memblock_virt_alloc_node(array_size, nid);
-	}
 
 	return section;
 }