6 files changed, 145 insertions, 7 deletions

diff --git a/lib/Kconfig b/lib/Kconfig
index 71d9f81f6eed..65561716c16c 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -48,6 +48,16 @@ config STMP_DEVICE
 config PERCPU_RWSEM
 	boolean
 
+config ARCH_USE_CMPXCHG_LOCKREF
+	bool
+
+config CMPXCHG_LOCKREF
+	def_bool y if ARCH_USE_CMPXCHG_LOCKREF
+	depends on SMP
+	depends on !GENERIC_LOCKBREAK
+	depends on !DEBUG_SPINLOCK
+	depends on !DEBUG_LOCK_ALLOC
+
 config CRC_CCITT
 	tristate "CRC-CCITT functions"
 	help
diff --git a/lib/Makefile b/lib/Makefile
index 7baccfd8a4e9..f2cb3082697c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -20,6 +20,7 @@ lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
 
 lib-y	+= kobject.o klist.o
+obj-y	+= lockref.o
 
 obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
 	 bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
diff --git a/lib/lockref.c b/lib/lockref.c
new file mode 100644
index 000000000000..7819c2d1d315
--- /dev/null
+++ b/lib/lockref.c
@@ -0,0 +1,127 @@
+#include <linux/export.h>
+#include <linux/lockref.h>
+
+#ifdef CONFIG_CMPXCHG_LOCKREF
+
+/*
+ * Note that the "cmpxchg()" reloads the "old" value for the
+ * failure case.
+ */
+#define CMPXCHG_LOOP(CODE, SUCCESS) do {					\
+	struct lockref old;							\
+	BUILD_BUG_ON(sizeof(old) != 8);						\
+	old.lock_count = ACCESS_ONCE(lockref->lock_count);			\
+	while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) {  	\
+		struct lockref new = old, prev = old;				\
+		CODE								\
+		old.lock_count = cmpxchg(&lockref->lock_count,			\
+					 old.lock_count, new.lock_count);	\
+		if (likely(old.lock_count == prev.lock_count)) {		\
+			SUCCESS;						\
+		}								\
+	}									\
+} while (0)
+
+#else
+
+#define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0)
+
+#endif
+
+/**
+ * lockref_get - Increments reference count unconditionally
+ * @lockcnt: pointer to lockref structure
+ *
+ * This operation is only valid if you already hold a reference
+ * to the object, so you know the count cannot be zero.
+ */
+void lockref_get(struct lockref *lockref)
+{
+	CMPXCHG_LOOP(
+		new.count++;
+	,
+		return;
+	);
+
+	spin_lock(&lockref->lock);
+	lockref->count++;
+	spin_unlock(&lockref->lock);
+}
+EXPORT_SYMBOL(lockref_get);
+
+/**
+ * lockref_get_not_zero - Increments count unless the count is 0
+ * @lockcnt: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count was zero
+ */
+int lockref_get_not_zero(struct lockref *lockref)
+{
+	int retval;
+
+	CMPXCHG_LOOP(
+		new.count++;
+		if (!old.count)
+			return 0;
+	,
+		return 1;
+	);
+
+	spin_lock(&lockref->lock);
+	retval = 0;
+	if (lockref->count) {
+		lockref->count++;
+		retval = 1;
+	}
+	spin_unlock(&lockref->lock);
+	return retval;
+}
+EXPORT_SYMBOL(lockref_get_not_zero);
+
+/**
+ * lockref_get_or_lock - Increments count unless the count is 0
+ * @lockcnt: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count was zero
+ * and we got the lock instead.
+ */
+int lockref_get_or_lock(struct lockref *lockref)
+{
+	CMPXCHG_LOOP(
+		new.count++;
+		if (!old.count)
+			break;
+	,
+		return 1;
+	);
+
+	spin_lock(&lockref->lock);
+	if (!lockref->count)
+		return 0;
+	lockref->count++;
+	spin_unlock(&lockref->lock);
+	return 1;
+}
+EXPORT_SYMBOL(lockref_get_or_lock);
+
+/**
+ * lockref_put_or_lock - decrements count unless count <= 1 before decrement
+ * @lockcnt: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
+ */
+int lockref_put_or_lock(struct lockref *lockref)
+{
+	CMPXCHG_LOOP(
+		new.count--;
+		if (old.count <= 1)
+			break;
+	,
+		return 1;
+	);
+
+	spin_lock(&lockref->lock);
+	if (lockref->count <= 1)
+		return 0;
+	lockref->count--;
+	spin_unlock(&lockref->lock);
+	return 1;
+}
+EXPORT_SYMBOL(lockref_put_or_lock);
diff --git a/lib/lz4/lz4_compress.c b/lib/lz4/lz4_compress.c
index fd94058bd7f9..28321d8f75ef 100644
--- a/lib/lz4/lz4_compress.c
+++ b/lib/lz4/lz4_compress.c
@@ -437,7 +437,7 @@ int lz4_compress(const unsigned char *src, size_t src_len,
 exit:
 	return ret;
 }
-EXPORT_SYMBOL_GPL(lz4_compress);
+EXPORT_SYMBOL(lz4_compress);
 
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("Dual BSD/GPL");
 MODULE_DESCRIPTION("LZ4 compressor");
diff --git a/lib/lz4/lz4_decompress.c b/lib/lz4/lz4_decompress.c
index d3414eae73a1..411be80ddb46 100644
--- a/lib/lz4/lz4_decompress.c
+++ b/lib/lz4/lz4_decompress.c
@@ -299,7 +299,7 @@ exit_0:
 	return ret;
 }
 #ifndef STATIC
-EXPORT_SYMBOL_GPL(lz4_decompress);
+EXPORT_SYMBOL(lz4_decompress);
 #endif
 
 int lz4_decompress_unknownoutputsize(const char *src, size_t src_len,
@@ -319,8 +319,8 @@ exit_0:
 	return ret;
 }
 #ifndef STATIC
-EXPORT_SYMBOL_GPL(lz4_decompress_unknownoutputsize);
+EXPORT_SYMBOL(lz4_decompress_unknownoutputsize);
 
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("Dual BSD/GPL");
 MODULE_DESCRIPTION("LZ4 Decompressor");
 #endif
diff --git a/lib/lz4/lz4hc_compress.c b/lib/lz4/lz4hc_compress.c
index eb1a74f5e368..f344f76b6559 100644
--- a/lib/lz4/lz4hc_compress.c
+++ b/lib/lz4/lz4hc_compress.c
@@ -533,7 +533,7 @@ int lz4hc_compress(const unsigned char *src, size_t src_len,
 exit:
 	return ret;
 }
-EXPORT_SYMBOL_GPL(lz4hc_compress);
+EXPORT_SYMBOL(lz4hc_compress);
 
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("Dual BSD/GPL");
 MODULE_DESCRIPTION("LZ4HC compressor");