1 files changed, 51 insertions, 0 deletions
diff --git a/include/linux/cookie.h b/include/linux/cookie.h
new file mode 100644
index 000000000000..0c159f585109
--- /dev/null
+++ b/include/linux/cookie.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_COOKIE_H
+#define __LINUX_COOKIE_H
+
+#include <linux/atomic.h>
+#include <linux/percpu.h>
+#include <asm/local.h>
+
+struct pcpu_gen_cookie {
+	local_t nesting;
+	u64 last;
+} __aligned(16);
+
+struct gen_cookie {
+	struct pcpu_gen_cookie __percpu *local;
+	atomic64_t forward_last ____cacheline_aligned_in_smp;
+	atomic64_t reverse_last;
+};
+
+#define COOKIE_LOCAL_BATCH	4096
+
+#define DEFINE_COOKIE(name)						\
+	static DEFINE_PER_CPU(struct pcpu_gen_cookie, __##name);	\
+	static struct gen_cookie name = {				\
+		.local		= &__##name,				\
+		.forward_last	= ATOMIC64_INIT(0),			\
+		.reverse_last	= ATOMIC64_INIT(0),			\
+	}
+
+static __always_inline u64 gen_cookie_next(struct gen_cookie *gc)
+{
+	struct pcpu_gen_cookie *local = this_cpu_ptr(gc->local);
+	u64 val;
+
+	if (likely(local_inc_return(&local->nesting) == 1)) {
+		val = local->last;
+		if (__is_defined(CONFIG_SMP) &&
+		    unlikely((val & (COOKIE_LOCAL_BATCH - 1)) == 0)) {
+			s64 next = atomic64_add_return(COOKIE_LOCAL_BATCH,
+						       &gc->forward_last);
+			val = next - COOKIE_LOCAL_BATCH;
+		}
+		local->last = ++val;
+	} else {
+		val = atomic64_dec_return(&gc->reverse_last);
+	}
+	local_dec(&local->nesting);
+	return val;
+}
+
+#endif /* __LINUX_COOKIE_H */