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Subject: Re: [RFC 0/4] Replace mmap_sem by a range lock
To: Matthew Wilcox <willy@infradead.org>
References: <cover.1492595897.git.ldufour@linux.vnet.ibm.com>
 <20170420133338.GC27790@bombadil.infradead.org>
Cc: linux-mm@kvack.org, Davidlohr Bueso <dave@stgolabs.net>,
        akpm@linux-foundation.org, Jan Kara <jack@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Michal Hocko <mhocko@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Mel Gorman <mgorman@techsingularity.net>, haren@linux.vnet.ibm.com,
        aneesh.kumar@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com,
        Paul.McKenney@us.ibm.com, linux-kernel@vger.kernel.org
From: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Date: Thu, 20 Apr 2017 16:39:32 +0200
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On 20/04/2017 15:33, Matthew Wilcox wrote:
> On Wed, Apr 19, 2017 at 02:18:23PM +0200, Laurent Dufour wrote:
>> Following the series pushed by Davidlohr Bueso based on the Jan Kara's
>> work [1] which introduces range locks, this series implements the
>> first step of the attempt to replace the mmap_sem by a range lock.
> 
> Have you previously documented attempts to replace the mmap_sem by an
> existing lock type before introducing a new (and frankly weird) lock?

No :/

> My initial question is "Why not use RCU for this?" -- the rxrpc code
> uses an rbtree protected by RCU.

I'm also working on forward-porting work done by Peter Zijlstra :

https://marc.info/?l=linux-mm&m=141384492326748

I'll send a series on top 4.10 soon.