linux-kernel - [RFC PATCH 2/6] refcount: Move refcount

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Date:   Fri, 16 Oct 2020 04:40:15 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Eric Biederman <ebiederm@...ssion.com>,
        Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Will Deacon <will@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: [RFC PATCH 2/6] refcount: Move refcount_t definition into linux/types.h

I want to use refcount_t in mm_struct, but if refcount_t is defined in
linux/refcount.h, that header would have to be included in
linux/mm_types.h; that would be wasteful.

Let's move refcount_t over into linux/types.h so that includes can be
written less wastefully.

Signed-off-by: Jann Horn <jannh@...gle.com>
---
 include/linux/refcount.h | 13 +------------
 include/linux/types.h    | 12 ++++++++++++
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 0e3ee25eb156..fd8cf65e4e2f 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -96,22 +96,11 @@
 #include <linux/bug.h>
 #include <linux/compiler.h>
 #include <linux/limits.h>
+#include <linux/types.h> /* refcount_t is defined here */
 #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)
diff --git a/include/linux/types.h b/include/linux/types.h
index a147977602b5..34e4e779e767 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -175,6 +175,18 @@ typedef struct {
 } atomic64_t;
 #endif
 
+/**
+ * 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;
+
 struct list_head {
 	struct list_head *next, *prev;
 };
-- 
2.29.0.rc1.297.gfa9743e501-goog