percpu: fix unit_map[] verification in pcpu_setup_first_chunk()

pcpu_setup_first_chunk() incorrectly used NR_CPUS as the impossible
unit number while unit number can equal and go over NR_CPUS with
sparse unit map.  This triggers BUG_ON() spuriously on machines which
have non-power-of-two number of cpus.  Use UINT_MAX instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Tony Vroon <tony@linx.net>

diff --git a/mm/percpu.c b/mm/percpu.c
index 43d8cac..e5c4cbd 100644 (file)
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1604,7 +1604,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
        unit_off = alloc_bootmem(nr_cpu_ids * sizeof(unit_off[0]));
 
        for (cpu = 0; cpu < nr_cpu_ids; cpu++)
-               unit_map[cpu] = NR_CPUS;
+               unit_map[cpu] = UINT_MAX;
        pcpu_first_unit_cpu = NR_CPUS;
 
        for (group = 0, unit = 0; group < ai->nr_groups; group++, unit += i) {
@@ -1619,7 +1619,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
                                continue;
 
                        BUG_ON(cpu > nr_cpu_ids || !cpu_possible(cpu));
-                       BUG_ON(unit_map[cpu] != NR_CPUS);
+                       BUG_ON(unit_map[cpu] != UINT_MAX);
 
                        unit_map[cpu] = unit + i;
                        unit_off[cpu] = gi->base_offset + i * ai->unit_size;
@@ -1632,7 +1632,7 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
        pcpu_nr_units = unit;
 
        for_each_possible_cpu(cpu)
-               BUG_ON(unit_map[cpu] == NR_CPUS);
+               BUG_ON(unit_map[cpu] == UINT_MAX);
 
        pcpu_nr_groups = ai->nr_groups;
        pcpu_group_offsets = group_offsets;