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Subject[PATCH 1/8] mmap locking API: initial implementation as rwsem wrappers
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This change wraps the existing mmap_sem related rwsem calls into a new
mmap locking API. There are two justifications for the new API:

- At first, it provides an easy hooking point to instrument mmap_sem
locking latencies independently of any other rwsems.

- In the future, it may be a starting point for replacing the rwsem
implementation with a different one, such as range locks.

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

diff --git a/include/linux/mm.h b/include/linux/mm.h
index c54fb96cb1e6..2f13c9198999 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -15,6 +15,7 @@
#include <linux/atomic.h>
#include <linux/debug_locks.h>
#include <linux/mm_types.h>
+#include <linux/mmap_lock.h>
#include <linux/range.h>
#include <linux/pfn.h>
#include <linux/percpu-refcount.h>
diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
new file mode 100644
index 000000000000..cffd25afe92b
--- /dev/null
+++ b/include/linux/mmap_lock.h
@@ -0,0 +1,59 @@
+#ifndef _LINUX_MMAP_LOCK_H
+#define _LINUX_MMAP_LOCK_H
+
+static inline void mmap_init_lock(struct mm_struct *mm)
+{
+ init_rwsem(&mm->mmap_sem);
+}
+
+static inline void mmap_write_lock(struct mm_struct *mm)
+{
+ down_write(&mm->mmap_sem);
+}
+
+static inline int mmap_write_lock_killable(struct mm_struct *mm)
+{
+ return down_write_killable(&mm->mmap_sem);
+}
+
+static inline bool mmap_write_trylock(struct mm_struct *mm)
+{
+ return down_write_trylock(&mm->mmap_sem) != 0;
+}
+
+static inline void mmap_write_unlock(struct mm_struct *mm)
+{
+ up_write(&mm->mmap_sem);
+}
+
+static inline void mmap_downgrade_write_lock(struct mm_struct *mm)
+{
+ downgrade_write(&mm->mmap_sem);
+}
+
+static inline void mmap_read_lock(struct mm_struct *mm)
+{
+ down_read(&mm->mmap_sem);
+}
+
+static inline int mmap_read_lock_killable(struct mm_struct *mm)
+{
+ return down_read_killable(&mm->mmap_sem);
+}
+
+static inline bool mmap_read_trylock(struct mm_struct *mm)
+{
+ return down_read_trylock(&mm->mmap_sem) != 0;
+}
+
+static inline void mmap_read_unlock(struct mm_struct *mm)
+{
+ up_read(&mm->mmap_sem);
+}
+
+static inline bool mmap_is_locked(struct mm_struct *mm)
+{
+ return rwsem_is_locked(&mm->mmap_sem) != 0;
+}
+
+#endif /* _LINUX_MMAP_LOCK_H */
--
2.25.1.696.g5e7596f4ac-goog
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