linux-kernel - Re: [PATCH 7/8] mmap locking API: add MMAP_LOCK

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Message-ID: <CANN689GOqEnLQHD-VNjwhTCwvLWNsRPLmo+yBumzE_y2_YsoMQ@mail.gmail.com>
Date:   Mon, 6 Apr 2020 06:04:16 -0700
From:   Michel Lespinasse <walken@...gle.com>
To:     Laurent Dufour <ldufour@...ux.ibm.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        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>
Subject: Re: [PATCH 7/8] mmap locking API: add MMAP_LOCK_INITIALIZER

On Mon, Apr 6, 2020 at 2:46 AM Laurent Dufour <ldufour@...ux.ibm.com> wrote:
>
> Le 26/03/2020 à 08:02, Michel Lespinasse a écrit :
> > Define a new initializer for the mmap locking api.
> > Initially this just evaluates to __RWSEM_INITIALIZER as the API
> > is defined as wrappers around rwsem.
>
> I can't see the benefit of this change.
> The overall idea is to hide the mmap_sem name. Here the macro
> MMAP_LOCK_INITIALIZER() doesn't hide the name.

The idea for the initializer is that it makes it easier to change the
underlying implementation - if we do, we can change the initializer
without having to change every place where it is used. I actually do
that in my other patch series converting the mmap_sem to a range lock.

But you are correct that it does not help with renaming the mmap_sem
field - my next commit in this series still has to do that in every
place this initializer is used.