[RFC PATCH 01/24] MM locking API: initial implementation as rwsem wrappers

[Michel Lespinasse <walken@google.com>]

This change wraps the existing mmap_sem related rwsem calls into a new
MM locking API. This is in preparation to extending that API to support
locking fine grained memory ranges.

Signed-off-by: Michel Lespinasse <walken@google.com>
---
 include/linux/mm.h      |  1 +
 include/linux/mm_lock.h | 59 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 include/linux/mm_lock.h

diff --git include/linux/mm.h include/linux/mm.h
index cfaa8feecfe8..052f423d7f67 100644
--- include/linux/mm.h
+++ include/linux/mm.h
@@ -15,6 +15,7 @@
 #include <linux/atomic.h>
 #include <linux/debug_locks.h>
 #include <linux/mm_types.h>
+#include <linux/mm_lock.h>
 #include <linux/range.h>
 #include <linux/pfn.h>
 #include <linux/percpu-refcount.h>
diff --git include/linux/mm_lock.h include/linux/mm_lock.h
new file mode 100644
index 000000000000..b5f134285e53
--- /dev/null
+++ include/linux/mm_lock.h
@@ -0,0 +1,59 @@
+#ifndef _LINUX_MM_LOCK_H
+#define _LINUX_MM_LOCK_H
+
+static inline void mm_init_lock(struct mm_struct *mm)
+{
+	init_rwsem(&mm->mmap_sem);
+}
+
+static inline void mm_write_lock(struct mm_struct *mm)
+{
+	down_write(&mm->mmap_sem);
+}
+
+static inline int mm_write_lock_killable(struct mm_struct *mm)
+{
+	return down_write_killable(&mm->mmap_sem);
+}
+
+static inline bool mm_write_trylock(struct mm_struct *mm)
+{
+	return down_write_trylock(&mm->mmap_sem) != 0;
+}
+
+static inline void mm_write_unlock(struct mm_struct *mm)
+{
+	up_write(&mm->mmap_sem);
+}
+
+static inline void mm_downgrade_write_lock(struct mm_struct *mm)
+{
+	downgrade_write(&mm->mmap_sem);
+}
+
+static inline void mm_read_lock(struct mm_struct *mm)
+{
+	down_read(&mm->mmap_sem);
+}
+
+static inline int mm_read_lock_killable(struct mm_struct *mm)
+{
+	return down_read_killable(&mm->mmap_sem);
+}
+
+static inline bool mm_read_trylock(struct mm_struct *mm)
+{
+	return down_read_trylock(&mm->mmap_sem) != 0;
+}
+
+static inline void mm_read_unlock(struct mm_struct *mm)
+{
+	up_read(&mm->mmap_sem);
+}
+
+static inline bool mm_is_locked(struct mm_struct *mm)
+{
+	return rwsem_is_locked(&mm->mmap_sem) != 0;
+}
+
+#endif /* _LINUX_MM_LOCK_H */
-- 
2.25.0.341.g760bfbb309-goog