linux-kernel - 回复: [PATCH] gpu: drm: use struct

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Date:   Mon, 20 May 2019 23:19:31 +0000
From:   "Pan, Xinhui" <Xinhui.Pan@....com>
To:     Daniel Vetter <daniel@...ll.ch>
CC:     "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "Quan, Evan" <Evan.Quan@....com>,
        xiaolinkui <xiaolinkui@...inos.cn>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: 回复: [PATCH] gpu: drm: use struct_size() in kmalloc()

Daniel, what you are talking about is totally wrong.
1) AFAIK, only one zero-size array can be in the end of a struct.
2) two struct_size will add up struct itself twice. the sum is wrong then.

No offense. I can't help feeling lucky that you are in intel. 


发件人: Daniel Vetter <daniel.vetter@...ll.ch> 代表 Daniel Vetter <daniel@...ll.ch>
发送时间: 2019年5月21日 0:28
收件人: Pan, Xinhui
抄送: Deucher, Alexander; Koenig, Christian; Zhou, David(ChunMing); airlied@...ux.ie; daniel@...ll.ch; Quan, Evan; xiaolinkui; amd-gfx@...ts.freedesktop.org; dri-devel@...ts.freedesktop.org; linux-kernel@...r.kernel.org
主题: Re: [PATCH] gpu: drm: use struct_size() in kmalloc()
 
[CAUTION: External Email]

On Fri, May 17, 2019 at 04:44:30PM +0000, Pan, Xinhui wrote:
> I am going to put more members which are also array after this struct,
> not only obj[].  Looks like this struct_size did not help on multiple
> array case. Thanks anyway.  ________________________________

You can then add them up, e.g. kmalloc(struct_size()+struct_size(),
GFP_KERNEL), so this patch here still looks like a good idea.

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

Cheers, Daniel

> From: xiaolinkui <xiaolinkui@...inos.cn>
> Sent: Friday, May 17, 2019 4:46:00 PM
> To: Deucher, Alexander; Koenig, Christian; Zhou, David(ChunMing); airlied@...ux.ie; daniel@...ll.ch; Pan, Xinhui; Quan, Evan
> Cc: amd-gfx@...ts.freedesktop.org; dri-devel@...ts.freedesktop.org; linux-kernel@...r.kernel.org; xiaolinkui@...inos.cn
> Subject: [PATCH] gpu: drm: use struct_size() in kmalloc()
>
> [CAUTION: External Email]
>
> Use struct_size() helper to keep code simple.
>
> Signed-off-by: xiaolinkui <xiaolinkui@...inos.cn>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> index 22bd21e..4717a64 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> @@ -1375,8 +1375,7 @@ int amdgpu_ras_init(struct amdgpu_device *adev)
>         if (con)
>                 return 0;
>
> -       con = kmalloc(sizeof(struct amdgpu_ras) +
> -                       sizeof(struct ras_manager) * AMDGPU_RAS_BLOCK_COUNT,
> +       con = kmalloc(struct_size(con, objs, AMDGPU_RAS_BLOCK_COUNT),
>                         GFP_KERNEL|__GFP_ZERO);
>         if (!con)
>                 return -ENOMEM;
> --
> 2.7.4
>
>
>

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch