alloc_percpu: __get_cpu_ptr/get_cpu_ptr/put_cpu_ptr

Now we have a decent implementation it makes sense to have an
interface for "this cpu", analogous to __get_cpu_var.

Alpha is untested.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
---
 arch/alpha/include/asm/percpu.h |    6 ++++++
 include/asm-generic/percpu.h    |   11 +++++++++++
 include/linux/percpu.h          |   16 ++++++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/arch/alpha/include/asm/percpu.h b/arch/alpha/include/asm/percpu.h
--- a/arch/alpha/include/asm/percpu.h
+++ b/arch/alpha/include/asm/percpu.h
@@ -62,6 +62,10 @@ extern unsigned long __per_cpu_offset[NR
 	(*SHIFT_PERCPU_PTR(var, __my_cpu_offset))
 #define per_cpu_ptr(ptr, cpu) \
 	RELOC_HIDE((ptr), (per_cpu_offset(cpu)))
+#define __get_cpu_ptr(ptr) \
+	RELOC_HIDE(ptr, my_cpu_offset)
+#define __raw_get_cpu_ptr(ptr) \
+	RELOC_HIDE(ptr, __my_cpu_offset)
 
 #else /* ! SMP */
 
@@ -71,6 +79,8 @@ extern unsigned long __per_cpu_offset[NR
 #define __get_cpu_var(var)		per_cpu_var(var)
 #define __raw_get_cpu_var(var)		per_cpu_var(var)
 #define per_cpu_ptr(ptr, cpu)		({ (void)(cpu); (ptr); })
+#define __get_cpu_ptr(ptr)		(ptr)
+#define __raw_get_cpu_ptr(ptr)		(ptr)
 
 #define PER_CPU_ATTRIBUTES
 
diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -72,6 +72,15 @@ extern unsigned long __per_cpu_offset[NR
 #define per_cpu_ptr(ptr, cpu) \
 	RELOC_HIDE((ptr), (per_cpu_offset(cpu)))
 
+/**
+ * __get_cpu_ptr - get a pointer to this cpu's allocated memory
+ * @ptr: the pointer returned from alloc_percpu
+ *
+ * Similar to __get_cpu_var(), except for dynamic memory.
+ */
+#define __get_cpu_ptr(ptr) RELOC_HIDE(ptr, my_cpu_offset)
+#define __raw_get_cpu_ptr(ptr) RELOC_HIDE(ptr, __my_cpu_offset)
+
 #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
 extern void setup_per_cpu_areas(void);
 #endif
@@ -82,6 +91,8 @@ extern void setup_per_cpu_areas(void);
 #define __get_cpu_var(var)			per_cpu_var(var)
 #define __raw_get_cpu_var(var)			per_cpu_var(var)
 #define per_cpu_ptr(ptr, cpu)			({ (void)(cpu); (ptr); })
+#define __get_cpu_ptr(ptr)			(ptr)
+#define __raw_get_cpu_ptr(ptr)			(ptr)
 
 #endif	/* SMP */
 
diff --git a/include/linux/percpu.h b/include/linux/percpu.h
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -57,6 +57,22 @@ extern unsigned int percpu_reserve;
 	&__get_cpu_var(var); }))
 #define put_cpu_var(var) preempt_enable()
 
+/**
+ * put_cpu_ptr - return a pointer to this cpu's allocated memory
+ * @ptr: the pointer passed to get_cpu_ptr().
+ *
+ * Counterpart to get_cpu_ptr(): re-enables preemption
+ */
+#define put_cpu_ptr(ptr) preempt_enable()
+
+/**
+ * get_cpu_ptr - hold a pointer to this cpu's allocated memory
+ * @ptr: the pointer returned from alloc_percpu
+ *
+ * Similar to get_cpu_var(), except for dynamic memory.  Disables preemption.
+ */
+#define get_cpu_ptr(ptr) ({ preempt_disable(); __get_cpu_ptr(ptr); })
+
 #ifdef CONFIG_SMP
 void *__alloc_percpu(unsigned long size, unsigned long align);
 void free_percpu(void *pcpuptr);