locking/refcount: Consolidate implementations of refcount_t

The generic implementation of refcount_t should be good enough for
everybody, so remove ARCH_HAS_REFCOUNT and REFCOUNT_FULL entirely,
leaving the generic implementation enabled unconditionally.

Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191121115902.2551-9-will@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 58 insertions, 100 deletions

diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 757d4630115c..0ac50cf62d06 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -1,64 +1,4 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _LINUX_REFCOUNT_H
-#define _LINUX_REFCOUNT_H
-
-#include <linux/atomic.h>
-#include <linux/compiler.h>
-#include <linux/limits.h>
-#include <linux/spinlock_types.h>
-
-struct mutex;
-
-/**
- * struct refcount_t - variant of atomic_t specialized for reference counts
- * @refs: atomic_t counter field
- *
- * The counter saturates at REFCOUNT_SATURATED and will not move once
- * there. This avoids wrapping the counter and causing 'spurious'
- * use-after-free bugs.
- */
-typedef struct refcount_struct {
-	atomic_t refs;
-} refcount_t;
-
-#define REFCOUNT_INIT(n)	{ .refs = ATOMIC_INIT(n), }
-#define REFCOUNT_MAX		INT_MAX
-#define REFCOUNT_SATURATED	(INT_MIN / 2)
-
-enum refcount_saturation_type {
-	REFCOUNT_ADD_NOT_ZERO_OVF,
-	REFCOUNT_ADD_OVF,
-	REFCOUNT_ADD_UAF,
-	REFCOUNT_SUB_UAF,
-	REFCOUNT_DEC_LEAK,
-};
-
-void refcount_warn_saturate(refcount_t *r, enum refcount_saturation_type t);
-
-/**
- * refcount_set - set a refcount's value
- * @r: the refcount
- * @n: value to which the refcount will be set
- */
-static inline void refcount_set(refcount_t *r, int n)
-{
-	atomic_set(&r->refs, n);
-}
-
-/**
- * refcount_read - get a refcount's value
- * @r: the refcount
- *
- * Return: the refcount's value
- */
-static inline unsigned int refcount_read(const refcount_t *r)
-{
-	return atomic_read(&r->refs);
-}
-
-#ifdef CONFIG_REFCOUNT_FULL
-#include <linux/bug.h>
-
 /*
  * Variant of atomic_t specialized for reference counts.
  *
@@ -136,6 +76,64 @@ static inline unsigned int refcount_read(const refcount_t *r)
  *
  */
 
+#ifndef _LINUX_REFCOUNT_H
+#define _LINUX_REFCOUNT_H
+
+#include <linux/atomic.h>
+#include <linux/bug.h>
+#include <linux/compiler.h>
+#include <linux/limits.h>
+#include <linux/spinlock_types.h>
+
+struct mutex;
+
+/**
+ * struct refcount_t - variant of atomic_t specialized for reference counts
+ * @refs: atomic_t counter field
+ *
+ * The counter saturates at REFCOUNT_SATURATED and will not move once
+ * there. This avoids wrapping the counter and causing 'spurious'
+ * use-after-free bugs.
+ */
+typedef struct refcount_struct {
+	atomic_t refs;
+} refcount_t;
+
+#define REFCOUNT_INIT(n)	{ .refs = ATOMIC_INIT(n), }
+#define REFCOUNT_MAX		INT_MAX
+#define REFCOUNT_SATURATED	(INT_MIN / 2)
+
+enum refcount_saturation_type {
+	REFCOUNT_ADD_NOT_ZERO_OVF,
+	REFCOUNT_ADD_OVF,
+	REFCOUNT_ADD_UAF,
+	REFCOUNT_SUB_UAF,
+	REFCOUNT_DEC_LEAK,
+};
+
+void refcount_warn_saturate(refcount_t *r, enum refcount_saturation_type t);
+
+/**
+ * refcount_set - set a refcount's value
+ * @r: the refcount
+ * @n: value to which the refcount will be set
+ */
+static inline void refcount_set(refcount_t *r, int n)
+{
+	atomic_set(&r->refs, n);
+}
+
+/**
+ * refcount_read - get a refcount's value
+ * @r: the refcount
+ *
+ * Return: the refcount's value
+ */
+static inline unsigned int refcount_read(const refcount_t *r)
+{
+	return atomic_read(&r->refs);
+}
+
 /**
  * refcount_add_not_zero - add a value to a refcount unless it is 0
  * @i: the value to add to the refcount
@@ -298,46 +296,6 @@ static inline void refcount_dec(refcount_t *r)
 	if (unlikely(atomic_fetch_sub_release(1, &r->refs) <= 1))
 		refcount_warn_saturate(r, REFCOUNT_DEC_LEAK);
 }
-#else /* CONFIG_REFCOUNT_FULL */
-# ifdef CONFIG_ARCH_HAS_REFCOUNT
-#  include <asm/refcount.h>
-# else
-static inline __must_check bool refcount_add_not_zero(int i, refcount_t *r)
-{
-	return atomic_add_unless(&r->refs, i, 0);
-}
-
-static inline void refcount_add(int i, refcount_t *r)
-{
-	atomic_add(i, &r->refs);
-}
-
-static inline __must_check bool refcount_inc_not_zero(refcount_t *r)
-{
-	return atomic_add_unless(&r->refs, 1, 0);
-}
-
-static inline void refcount_inc(refcount_t *r)
-{
-	atomic_inc(&r->refs);
-}
-
-static inline __must_check bool refcount_sub_and_test(int i, refcount_t *r)
-{
-	return atomic_sub_and_test(i, &r->refs);
-}
-
-static inline __must_check bool refcount_dec_and_test(refcount_t *r)
-{
-	return atomic_dec_and_test(&r->refs);
-}
-
-static inline void refcount_dec(refcount_t *r)
-{
-	atomic_dec(&r->refs);
-}
-# endif /* !CONFIG_ARCH_HAS_REFCOUNT */
-#endif /* !CONFIG_REFCOUNT_FULL */
 
 extern __must_check bool refcount_dec_if_one(refcount_t *r);
 extern __must_check bool refcount_dec_not_one(refcount_t *r);