1 files changed, 20 insertions, 14 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
index 28c37a2e2de2..2473ff06dc76 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -116,9 +116,9 @@ static int pcpu_atom_size __read_mostly;
 static int pcpu_nr_slots __read_mostly;
 static size_t pcpu_chunk_struct_size __read_mostly;
 
-/* cpus with the lowest and highest unit numbers */
-static unsigned int pcpu_first_unit_cpu __read_mostly;
-static unsigned int pcpu_last_unit_cpu __read_mostly;
+/* cpus with the lowest and highest unit addresses */
+static unsigned int pcpu_low_unit_cpu __read_mostly;
+static unsigned int pcpu_high_unit_cpu __read_mostly;
 
 /* the address of the first chunk which starts with the kernel static area */
 void *pcpu_base_addr __read_mostly;
@@ -985,19 +985,19 @@ phys_addr_t per_cpu_ptr_to_phys(void *addr)
 {
         void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
         bool in_first_chunk = false;
-        unsigned long first_start, first_end;
+        unsigned long first_low, first_high;
         unsigned int cpu;
 
         /*
-         * The following test on first_start/end isn't strictly
+         * The following test on unit_low/high isn't strictly
          * necessary but will speed up lookups of addresses which
          * aren't in the first chunk.
          */
-        first_start = pcpu_chunk_addr(pcpu_first_chunk, pcpu_first_unit_cpu, 0);
-        first_end = pcpu_chunk_addr(pcpu_first_chunk, pcpu_last_unit_cpu,
-                                    pcpu_unit_pages);
-        if ((unsigned long)addr >= first_start &&
-            (unsigned long)addr < first_end) {
+        first_low = pcpu_chunk_addr(pcpu_first_chunk, pcpu_low_unit_cpu, 0);
+        first_high = pcpu_chunk_addr(pcpu_first_chunk, pcpu_high_unit_cpu,
+                                     pcpu_unit_pages);
+        if ((unsigned long)addr >= first_low &&
+            (unsigned long)addr < first_high) {
                 for_each_possible_cpu(cpu) {
                         void *start = per_cpu_ptr(base, cpu);
 
@@ -1234,7 +1234,9 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
 
         for (cpu = 0; cpu < nr_cpu_ids; cpu++)
                 unit_map[cpu] = UINT_MAX;
-        pcpu_first_unit_cpu = NR_CPUS;
+
+        pcpu_low_unit_cpu = NR_CPUS;
+        pcpu_high_unit_cpu = NR_CPUS;
 
         for (group = 0, unit = 0; group < ai->nr_groups; group++, unit += i) {
                 const struct pcpu_group_info *gi = &ai->groups[group];
@@ -1254,9 +1256,13 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
                         unit_map[cpu] = unit + i;
                         unit_off[cpu] = gi->base_offset + i * ai->unit_size;
 
-                        if (pcpu_first_unit_cpu == NR_CPUS)
-                                pcpu_first_unit_cpu = cpu;
-                        pcpu_last_unit_cpu = cpu;
+                        /* determine low/high unit_cpu */
+                        if (pcpu_low_unit_cpu == NR_CPUS ||
+                            unit_off[cpu] < unit_off[pcpu_low_unit_cpu])
+                                pcpu_low_unit_cpu = cpu;
+                        if (pcpu_high_unit_cpu == NR_CPUS ||
+                            unit_off[cpu] > unit_off[pcpu_high_unit_cpu])
+                                pcpu_high_unit_cpu = cpu;
                 }
         }
         pcpu_nr_units = unit;