linux-kernel - [PATCH 2/2] powerpc/hotplug: Ensure nodes initialized for hotplug

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Date:   Mon, 18 Sep 2017 13:28:41 -0500
From:   Michael Bringmann <mwb@...ux.vnet.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Michael Bringmann <mwb@...ux.vnet.ibm.com>,
        John Allen <jallen@...ux.vnet.ibm.com>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>
Subject: [PATCH 2/2] powerpc/hotplug: Ensure nodes initialized for hotplug

powerpc/hotplug: On systems like PowerPC which allow 'hot-add' of CPU,
it may occur that the new resources are to be inserted into nodes
that were not used for memory resources at bootup.  Many different
configurations of PowerPC resources may need to be supported depending
upon the environment.  This patch fixes some problems encountered at
runtime with configurations that support memory-less nodes, but which
allow CPUs to be added at and after boot.

Signed-off-by: Michael Bringmann <mwb@...ux.vnet.ibm.com>
---
 arch/powerpc/mm/numa.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index b385cd0..e811dd1 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -551,7 +551,7 @@ static int numa_setup_cpu(unsigned long lcpu)
 	nid = of_node_to_nid_single(cpu);
 
 out_present:
-	if (nid < 0 || !node_online(nid))
+	if (nid < 0 || !node_possible(nid))
 		nid = first_online_node;
 
 	map_cpu_to_node(lcpu, nid);
@@ -1325,6 +1325,17 @@ static long vphn_get_associativity(unsigned long cpu,
 	return rc;
 }
 
+static int verify_node_preparation(int nid)
+{
+	if ((NODE_DATA(nid) == NULL) ||
+	    (NODE_DATA(nid)->node_spanned_pages == 0)) {
+		if (try_online_node(nid))
+			return first_online_node;
+	}
+
+	return nid;
+}
+
 /*
  * Update the CPU maps and sysfs entries for a single CPU when its NUMA
  * characteristics change. This function doesn't perform any locking and is
@@ -1433,9 +1444,11 @@ int numa_update_cpu_topology(bool cpus_locked)
 		/* Use associativity from first thread for all siblings */
 		vphn_get_associativity(cpu, associativity);
 		new_nid = associativity_to_nid(associativity);
-		if (new_nid < 0 || !node_online(new_nid))
+		if (new_nid < 0 || !node_possible(new_nid))
 			new_nid = first_online_node;
 
+		new_nid = verify_node_preparation(new_nid);
+
 		if (new_nid == numa_cpu_lookup_table[cpu]) {
 			cpumask_andnot(&cpu_associativity_changes_mask,
 					&cpu_associativity_changes_mask,