linux-kernel - Re: [PATCH] nvdimm: constify device

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Message-ID: <CAPcyv4i7-vT+-VqU2n4bxrtcwrYtJ5rcVg3=bf5gCx-YRe3HkA@mail.gmail.com>
Date:   Tue, 24 Jan 2017 18:40:18 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Bhumika Goyal <bhumirks@...il.com>,
        Julia Lawall <julia.lawall@...6.fr>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvdimm: constify device_type structures

On Tue, Jan 24, 2017 at 6:37 PM, Joe Perches <joe@...ches.com> wrote:
> On Wed, 2017-01-25 at 00:54 +0530, Bhumika Goyal wrote:
>> Declare device_type structure as const as it is only stored in the
>> type field of a device structure. This field is of type const, so add
>> const to declaration of device_type structure.
>>
>> File size before:
>>   text           data     bss     dec     hex filename
>>   19278          3199      16   22493    57dd nvdimm/namespace_devs.o
>>
>> File size after:
>>   text           data     bss     dec     hex filename
>>   19929          3160      16   23105    5a41 nvdimm/namespace_devs.o
>
> Fine, but are you sure about the sizes?
>
> It seems odd the text went up 651 bytes
> while the data went down just 39 bytes.
>

Right, the size data wasn't why I applied it. It was the general rule
of "make function pointer data read-only whenever possible to
eliminate a kernel attack vector".  Bhumika, you might want to mention
this as the motivating reason to apply the patch if you do more of
these changes.