[mm][RFC][PATCH 1/11] mm accessor for replacing mmap_sem

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

This patch implements mm accessor, functions for get/release mm->mmap_sem.
For doing some work related to mmap_sem (relaxing it or count events etc..),
bare access to mm->mmap_sem is the first obstacle.

This patch is for removing direct access to mm->mmap_sem.
(For debugging, renaming mm->mmap_sem is better. But considering bisection,
 this patch leave it as it is. The last patch of this series will rename it.)

Following patches will replace direct access to mmap_sem to use these
accessors.

Based on Christoph Lameter's original work.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
 include/linux/mm_accessor.h |   68 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mm_types.h    |    3 +
 2 files changed, 71 insertions(+)

Index: mmotm-mm-accessor/include/linux/mm_accessor.h
===================================================================
--- /dev/null
+++ mmotm-mm-accessor/include/linux/mm_accessor.h
@@ -0,0 +1,68 @@
+#ifndef __LINUX_MM_ACCESSOR_H
+#define __LINUX_MM_ACCESSOR_H
+
+static inline void mm_read_lock(struct mm_struct *mm)
+{
+	down_read(&mm->mmap_sem);
+}
+
+static inline int mm_read_trylock(struct mm_struct *mm)
+{
+	return down_read_trylock(&mm->mmap_sem);
+}
+
+static inline void mm_read_unlock(struct mm_struct *mm)
+{
+	up_read(&mm->mmap_sem);
+}
+
+static inline void mm_write_lock(struct mm_struct *mm)
+{
+	down_write(&mm->mmap_sem);
+}
+
+static inline void mm_write_unlock(struct mm_struct *mm)
+{
+	up_write(&mm->mmap_sem);
+}
+
+static inline int mm_write_trylock(struct mm_struct *mm)
+{
+	return down_write_trylock(&mm->mmap_sem);
+}
+
+static inline int mm_is_locked(struct mm_struct *mm)
+{
+	return rwsem_is_locked(&mm->mmap_sem);
+}
+
+static inline void mm_write_to_read_lock(struct mm_struct *mm)
+{
+	downgrade_write(&mm->mmap_sem);
+}
+
+static inline void mm_write_lock_nested(struct mm_struct *mm, int x)
+{
+	down_write_nested(&mm->mmap_sem, x);
+}
+
+static inline void mm_lock_init(struct mm_struct *mm)
+{
+	init_rwsem(&mm->mmap_sem);
+}
+
+static inline void mm_lock_prefetch(struct mm_struct *mm)
+{
+	prefetchw(&mm->mmap_sem);
+}
+
+static inline void mm_nest_spin_lock(spinlock_t *s, struct mm_struct *mm)
+{
+	spin_lock_nest_lock(s, &mm->mmap_sem);
+}
+
+static inline void mm_read_might_lock(struct mm_struct *mm)
+{
+	might_lock_read(&mm->mmap_sem);
+}
+#endif
Index: mmotm-mm-accessor/include/linux/mm_types.h
===================================================================
--- mmotm-mm-accessor.orig/include/linux/mm_types.h
+++ mmotm-mm-accessor/include/linux/mm_types.h
@@ -292,4 +292,7 @@ struct mm_struct {
 /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
 #define mm_cpumask(mm) (&(mm)->cpu_vm_mask)
 
+/* Functions for accessing mm_struct */
+#include <linux/mm_accessor.h>
+
 #endif /* _LINUX_MM_TYPES_H */

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