Re: [PATCH v3 01/10] mmap locking API: initial implementation as rwsem wrappers (Michel Lespinasse)

SeongJae Park
2020-03-28T08:58:08Z

On 2020-03-27T15:50:53-07:00 Michel Lespinasse <walken@google.com> wrote:

> 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 | 54 +++++++++++++++++++++++++++++++++++++++
> 2 files changed, 55 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..8b5a3cd56118
> --- /dev/null
> +++ b/include/linux/mmap_lock.h
> @@ -0,0 +1,54 @@
> +#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);
> +}
> +
> +#endif /* _LINUX_MMAP_LOCK_H */

Reviewed-by: SeongJae Park <sjpark@amazon.de>

> --
> 2.26.0.rc2.310.g2932bb562d-goog
>