[PATCH v4 1/2] pcpu_ref: add percpu_ref_tryget_many()

Pavel Begunkov
2019-12-28T11:13:59Z

Add percpu_ref_tryget_many(), which works the same way as
percpu_ref_tryget(), but grabs specified number of refs.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
---
include/linux/percpu-refcount.h | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 390031e816dc..22d9d183950d 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -210,15 +210,17 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
}

/**
- * percpu_ref_tryget - try to increment a percpu refcount
+ * percpu_ref_tryget_many - try to increment a percpu refcount
* @ref: percpu_ref to try-get
+ * @nr: number of references to get
*
- * Increment a percpu refcount unless its count already reached zero.
+ * Increment a percpu refcount by @nr unless its count already reached zero.
* Returns %true on success; %false on failure.
*
* This function is safe to call as long as @ref is between init and exit.
*/
-static inline bool percpu_ref_tryget(struct percpu_ref *ref)
+static inline bool percpu_ref_tryget_many(struct percpu_ref *ref,
+ unsigned long nr)
{
unsigned long __percpu *percpu_count;
bool ret;
@@ -226,10 +228,10 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
rcu_read_lock();

if (__ref_is_percpu(ref, &percpu_count)) {
- this_cpu_inc(*percpu_count);
+ this_cpu_add(*percpu_count, nr);
ret = true;
} else {
- ret = atomic_long_inc_not_zero(&ref->count);
+ ret = atomic_long_add_unless(&ref->count, nr, 0);
}

rcu_read_unlock();
@@ -237,6 +239,20 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
return ret;
}

+/**
+ * percpu_ref_tryget - try to increment a percpu refcount
+ * @ref: percpu_ref to try-get
+ *
+ * Increment a percpu refcount unless its count already reached zero.
+ * Returns %true on success; %false on failure.
+ *
+ * This function is safe to call as long as @ref is between init and exit.
+ */
+static inline bool percpu_ref_tryget(struct percpu_ref *ref)
+{
+ return percpu_ref_tryget_many(ref, 1);
+}
+
/**
* percpu_ref_tryget_live - try to increment a live percpu refcount
* @ref: percpu_ref to try-get
--
2.24.0