Merge branch 'for-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu

Pull percpu updates from Dennis Zhou:
 "This includes changes to let percpu_ref release the backing percpu
  memory earlier after it has been switched to atomic in cases where the
  percpu ref is not revived.

  This will help recycle percpu memory earlier in cases where the
  refcounts are pinned for prolonged periods of time"

* 'for-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu:
  percpu_ref: release percpu memory early without PERCPU_REF_ALLOW_REINIT
  md: initialize percpu refcounters using PERCU_REF_ALLOW_REINIT
  io_uring: initialize percpu refcounters using PERCU_REF_ALLOW_REINIT
  percpu_ref: introduce PERCPU_REF_ALLOW_REINIT flag

1 files changed, 11 insertions, 2 deletions

diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 071a76c7bac0..4f6c6ebbbbde 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -70,11 +70,14 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release,
                 return -ENOMEM;
 
         ref->force_atomic = flags & PERCPU_REF_INIT_ATOMIC;
+        ref->allow_reinit = flags & PERCPU_REF_ALLOW_REINIT;
 
-        if (flags & (PERCPU_REF_INIT_ATOMIC | PERCPU_REF_INIT_DEAD))
+        if (flags & (PERCPU_REF_INIT_ATOMIC | PERCPU_REF_INIT_DEAD)) {
                 ref->percpu_count_ptr |= __PERCPU_REF_ATOMIC;
-        else
+                ref->allow_reinit = true;
+        } else {
                 start_count += PERCPU_COUNT_BIAS;
+        }
 
         if (flags & PERCPU_REF_INIT_DEAD)
                 ref->percpu_count_ptr |= __PERCPU_REF_DEAD;
@@ -120,6 +123,9 @@ static void percpu_ref_call_confirm_rcu(struct rcu_head *rcu)
         ref->confirm_switch = NULL;
         wake_up_all(&percpu_ref_switch_waitq);
 
+        if (!ref->allow_reinit)
+                percpu_ref_exit(ref);
+
         /* drop ref from percpu_ref_switch_to_atomic() */
         percpu_ref_put(ref);
 }
@@ -195,6 +201,9 @@ static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref)
         if (!(ref->percpu_count_ptr & __PERCPU_REF_ATOMIC))
                 return;
 
+        if (WARN_ON_ONCE(!ref->allow_reinit))
+                return;
+
         atomic_long_add(PERCPU_COUNT_BIAS, &ref->count);
 
         /*