linux-kernel - Re: [PATCH v5 01/10] mmap locking API: initial implementation as rwsem wrappers

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Date:   Mon, 18 May 2020 15:18:29 +0200
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     Michel Lespinasse <walken@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        Liam Howlett <Liam.Howlett@...cle.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        David Rientjes <rientjes@...gle.com>,
        Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH v5 01/10] mmap locking API: initial implementation as
 rwsem wrappers

Le 22/04/2020 à 02:14, Michel Lespinasse a écrit :
> 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@...gle.com>
> Reviewed-by: Daniel Jordan <daniel.m.jordan@...cle.com>
> Reviewed-by: Davidlohr Bueso <dbueso@...e.de>

Reviewed-by: Laurent Dufour <ldufour@...ux.ibm.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 5a323422d783..051ec782bdbb 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..97ac53b66052
> --- /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_write_downgrade(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 */
>