From c9680a33ec34059928a7677691084d57205b17c0 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche@acm.org>
Date: Sun, 10 Mar 2019 05:14:42 +0000
Subject: [PATCH 1/2] scst: Add a percpu_ref backport for kernel versions
 before 3.11, e.g. RHEL 6

git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@8036 d57e44dd-8a1f-0410-8b47-8ef2f437770f
---
 scst/include/backport.h | 68 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/scst/include/backport.h b/scst/include/backport.h
index c13c2c1bb..ad993b748 100644
--- a/scst/include/backport.h
+++ b/scst/include/backport.h
@@ -30,6 +30,9 @@
 #endif
 #include <linux/eventpoll.h>
 #include <linux/iocontext.h>
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 11, 0)
+#include <linux/percpu-refcount.h>
+#endif
 #include <linux/scatterlist.h>	/* struct scatterlist */
 #include <linux/slab.h>		/* kmalloc() */
 #include <linux/stddef.h>	/* sizeof_field() */
@@ -871,6 +874,71 @@ static inline struct ib_pd *ib_alloc_pd_backport(struct ib_device *device)
 #define set_cpus_allowed_ptr(p, new_mask) set_cpus_allowed((p), *(new_mask))
 #endif
 
+/* <linux/percpu-refcount.h> */
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 11, 0)
+struct percpu_ref;
+typedef void (percpu_ref_func_t)(struct percpu_ref *);
+
+struct percpu_ref {
+	atomic_long_t		count;
+	percpu_ref_func_t	*release;
+};
+
+/* @flags for percpu_ref_init() */
+enum {
+	PERCPU_REF_INIT_ATOMIC	= 1 << 0,
+	PERCPU_REF_INIT_DEAD	= 1 << 1,
+};
+
+static inline int __must_check percpu_ref_init(struct percpu_ref *ref,
+				 percpu_ref_func_t *release, unsigned int flags,
+				 gfp_t gfp)
+{
+	WARN_ON_ONCE(flags != PERCPU_REF_INIT_ATOMIC);
+	atomic_long_set(&ref->count, 1);
+	ref->release = release;
+	return 0;
+}
+
+static inline void percpu_ref_exit(struct percpu_ref *ref)
+{
+}
+
+static inline void percpu_ref_switch_to_atomic(struct percpu_ref *ref,
+				 percpu_ref_func_t *confirm_switch)
+{
+}
+
+static inline void percpu_ref_switch_to_atomic_sync(struct percpu_ref *ref)
+{
+}
+
+static inline void percpu_ref_switch_to_percpu(struct percpu_ref *ref)
+{
+}
+
+static inline void percpu_ref_get(struct percpu_ref *ref)
+{
+	atomic_long_inc(&ref->count);
+}
+
+static inline void percpu_ref_put(struct percpu_ref *ref)
+{
+	if (unlikely(atomic_long_dec_and_test(&ref->count)))
+		ref->release(ref);
+}
+
+static inline void percpu_ref_kill(struct percpu_ref *ref)
+{
+	percpu_ref_put(ref);
+}
+
+static inline bool percpu_ref_is_zero(struct percpu_ref *ref)
+{
+	return !atomic_long_read(&ref->count);
+}
+#endif
+
 /* <linux/scatterlist.h> */
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 24)

From c03a6ffd5efc7511a864683498f129b0ba78309a Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche@acm.org>
Date: Sun, 10 Mar 2019 05:18:41 +0000
Subject: [PATCH 2/2] scst, backport.h: Fix RHEL 7 build

git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@8037 d57e44dd-8a1f-0410-8b47-8ef2f437770f
---
 scst/include/backport.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scst/include/backport.h b/scst/include/backport.h
index ad993b748..19e4cd246 100644
--- a/scst/include/backport.h
+++ b/scst/include/backport.h
@@ -875,7 +875,7 @@ static inline struct ib_pd *ib_alloc_pd_backport(struct ib_device *device)
 #endif
 
 /* <linux/percpu-refcount.h> */
-#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 11, 0)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 11, 0) && RHEL_MAJOR -0 <= 6
 struct percpu_ref;
 typedef void (percpu_ref_func_t)(struct percpu_ref *);