[PATCH] arm64: numa: rightsize the distance array

[Jonathan Cameron]

Unfortunately we are currently calling numa_alloc_distance well before we call
setup_node_to_cpu_mask_map means that nr_node_ids is set to MAX_NUMNODES.
This wastes a bit of memory and is confusing to the reader.

Note we could just decide to hardcode it as MAX_NUMNODES but if so we should
do so explicitly.

Looking at what x86 does, they do a walk of nodes_parsed and locally
establish the maximum node count seen.  We can't actually do that where we
were previously calling it in numa_init because nodes_parsed isn't set up
either yet.  So let us take a leaf entirely out of x86's book and make
the true assumption that nodes_parsed will definitely be set up before
we try to put a real value in this array.  Hence just do it on demand.

In order to avoid trying and failing to allocate the array multiple times
we do the same thing as x86 and set numa_distance = 1. This requires a
few small modifications elsewhere.

Worth noting, that with one exception (which it appears can be removed [1])
the x86 and arm numa distance code is now identical.  Worth factoring it
out to some common location?

[1] https://lkml.kernel.org/r/20170406124459.dwn5zhpr2xqg3lqm@node.shutemov.name

Signed-off-by: Jonathan Cameron <Jonathan.Cameron at huawei.com>
---
arch/arm64/mm/numa.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index aafcee3e3f7e..a2f549ef0a36 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c
@@ -255,13 +255,11 @@ void __init numa_free_distance(void)
 {
 	size_t size;
 
-	if (!numa_distance)
-		return;
-
 	size = numa_distance_cnt * numa_distance_cnt *
 		sizeof(numa_distance[0]);
-
-	memblock_free(__pa(numa_distance), size);
+	/* numa_distance could be 1LU marking allocation failure, test cnt */
+	if (numa_distance_cnt)
+		memblock_free(__pa(numa_distance), size);
 	numa_distance_cnt = 0;
 	numa_distance = NULL;
 }
@@ -271,20 +269,29 @@ void __init numa_free_distance(void)
  */
 static int __init numa_alloc_distance(void)
 {
+	nodemask_t nodes_parsed;
 	size_t size;
+	int i, j, cnt = 0;
 	u64 phys;
-	int i, j;
 
-	size = nr_node_ids * nr_node_ids * sizeof(numa_distance[0]);
+	/* size the new table and allocate it */
+	nodes_parsed = numa_nodes_parsed;
+	for_each_node_mask(i, nodes_parsed)
+		cnt = i;
+	cnt++;
+	size = cnt * cnt * sizeof(numa_distance[0]);
 	phys = memblock_find_in_range(0, PFN_PHYS(max_pfn),
 				      size, PAGE_SIZE);
-	if (WARN_ON(!phys))
+	if (!phys) {
+		pr_warn("Warning: can't allocate distance table!\n");
+		/* don't retry until explicitly reset */
+		numa_distance = (void *)1LU;
 		return -ENOMEM;
-
+	}
 	memblock_reserve(phys, size);
 
 	numa_distance = __va(phys);
-	numa_distance_cnt = nr_node_ids;
+	numa_distance_cnt = cnt;
 
 	/* fill with the default distances */
 	for (i = 0; i < numa_distance_cnt; i++)
@@ -311,10 +318,8 @@ static int __init numa_alloc_distance(void)
  */
 void __init numa_set_distance(int from, int to, int distance)
 {
-	if (!numa_distance) {
-		pr_warn_once("Warning: distance table not allocated yet\n");
+	if (!numa_distance && numa_alloc_distance() < 0)
 		return;
-	}
 
 	if (from >= numa_distance_cnt || to >= numa_distance_cnt ||
 			from < 0 || to < 0) {
@@ -384,10 +389,6 @@ static int __init numa_init(int (*init_func)(void))
 	nodes_clear(node_possible_map);
 	nodes_clear(node_online_map);
 
-	ret = numa_alloc_distance();
-	if (ret < 0)
-		return ret;
-
 	ret = init_func();
 	if (ret < 0)
 		goto out_free_distance;
-- 
2.19.1