Merge branch 'for-5.1/nfit/ars' into libnvdimm-for-next

Merge several updates to the ARS implementation. Highlights include:

* Support retrieval of short-ARS results if the ARS state is "requires
  continuation", and even if the "no_init_ars" module parameter is
  specified.
* Allow busy-polling of the kernel ARS state by allowing root to reset
  the exponential back-off timer.
* Filter potentially stale ARS results by tracking query-ARS relative to
  the previous start-ARS.

1 files changed, 10 insertions, 2 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index b155cd17c1bd..8577bb7f8be6 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -713,8 +713,13 @@ static int map_lookup_elem(union bpf_attr *attr)
 
         if (bpf_map_is_dev_bound(map)) {
                 err = bpf_map_offload_lookup_elem(map, key, value);
-        } else if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
-                   map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
+                goto done;
+        }
+
+        preempt_disable();
+        this_cpu_inc(bpf_prog_active);
+        if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
+            map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
                 err = bpf_percpu_hash_copy(map, key, value);
         } else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
                 err = bpf_percpu_array_copy(map, key, value);
@@ -744,7 +749,10 @@ static int map_lookup_elem(union bpf_attr *attr)
                 }
                 rcu_read_unlock();
         }
+        this_cpu_dec(bpf_prog_active);
+        preempt_enable();
 
+done:
         if (err)
                 goto free_value;