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From:   SeongJae Park <sj38.park@gmail.com>
To:     Michel Lespinasse <walken@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Matthew Wilcox <willy@infradead.org>,
        Liam Howlett <Liam.Howlett@oracle.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        David Rientjes <rientjes@google.com>,
        Hugh Dickins <hughd@google.com>, Ying Han <yinghan@google.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Markus Elfring <Markus.Elfring@web.de>
Subject: Re: [PATCH v3 01/10] mmap locking API: initial implementation as rwsem wrappers (Michel Lespinasse)
Date:   Sat, 28 Mar 2020 09:57:46 +0100
Message-Id: <20200328085746.4773-1-sj38.park@gmail.com>
In-Reply-To: <20200327225102.25061-2-walken@google.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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
>