x86-64, NUMA: Better explain numa_distance handling

Handling of out-of-bounds distances and allocation failure can use
better documentation.  Add it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/mm/numa_emulation.c b/arch/x86/mm/numa_emulation.c
index 0afa25d967ba..aeecea93820f 100644
--- a/arch/x86/mm/numa_emulation.c
+++ b/arch/x86/mm/numa_emulation.c
@@ -379,7 +379,11 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt)
                 if (emu_nid_to_phys[i] == NUMA_NO_NODE)
                         emu_nid_to_phys[i] = 0;
 
-        /* transform distance table */
+        /*
+         * Transform distance table.  numa_set_distance() ignores all
+         * out-of-bound distances.  Just call it for every possible node
+         * combination.
+         */
         numa_reset_distance();
         for (i = 0; i < MAX_NUMNODES; i++) {
                 for (j = 0; j < MAX_NUMNODES; j++) {