Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v5 01/10] mmap locking API: initial implementation as
 rwsem wrappers
To:     Michel Lespinasse <walken@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        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>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        Davidlohr Bueso <dbueso@suse.de>
References: <20200422001422.232330-1-walken@google.com>
 <20200422001422.232330-2-walken@google.com>
From:   Laurent Dufour <ldufour@linux.ibm.com>
Message-ID: <f39081c8-cbcc-4478-5f9b-4f73651bc6a7@linux.ibm.com>
Date:   Mon, 18 May 2020 15:18:29 +0200
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0)
 Gecko/20100101 Thunderbird/68.8.0
MIME-Version: 1.0
In-Reply-To: <20200422001422.232330-2-walken@google.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@google.com>
> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> Reviewed-by: Davidlohr Bueso <dbueso@suse.de>

Reviewed-by: Laurent Dufour <ldufour@linux.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 */
>