Add percpu_ref_atomic_count(), which returns number of references of a
percpu_ref switched prior into atomic mode, so the caller is responsible
to make sure it's in the right mode.
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
include/linux/percpu-refcount.h | 1 +
lib/percpu-refcount.c | 26 ++++++++++++++++++++++++++
2 files changed, 27 insertions(+)
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 16c35a728b4c..0ff40e79efa2 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -131,6 +131,7 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
void percpu_ref_resurrect(struct percpu_ref *ref);
void percpu_ref_reinit(struct percpu_ref *ref);
bool percpu_ref_is_zero(struct percpu_ref *ref);
+unsigned long percpu_ref_atomic_count(struct percpu_ref *ref);
/**
* percpu_ref_kill - drop the initial ref
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index a1071cdefb5a..56286995e2b8 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -425,6 +425,32 @@ bool percpu_ref_is_zero(struct percpu_ref *ref)
}
EXPORT_SYMBOL_GPL(percpu_ref_is_zero);
+/**
+ * percpu_ref_atomic_count - returns number of left references
+ * @ref: percpu_ref to test
+ *
+ * This function is safe to call as long as @ref is switch into atomic mode,
+ * and is between init and exit.
+ */
+unsigned long percpu_ref_atomic_count(struct percpu_ref *ref)
+{
+ unsigned long __percpu *percpu_count;
+ unsigned long count, flags;
+
+ if (WARN_ON_ONCE(__ref_is_percpu(ref, &percpu_count)))
+ return -1UL;
+
+ /* protect us from being destroyed */
+ spin_lock_irqsave(&percpu_ref_switch_lock, flags);
+ if (ref->data)
+ count = atomic_long_read(&ref->data->count);
+ else
+ count = ref->percpu_count_ptr >> __PERCPU_REF_FLAG_BITS;
+ spin_unlock_irqrestore(&percpu_ref_switch_lock, flags);
+
+ return count;
+}
+
/**
* percpu_ref_reinit - re-initialize a percpu refcount
* @ref: perpcu_ref to re-initialize
--
2.24.0
