linux-kernel - Re: [PATCH] drm/i915/gvt: use DEFINE_DEBUGFS_ATTRIBUTE with debugfs_create_file

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Date:   Fri, 30 Oct 2020 11:52:42 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Deepak R Varma <mh12gx2825@...il.com>,
        outreachy-kernel@...glegroups.com,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     mh12gx2825@...il.com, melissa.srw@...il.com, daniel.vetter@...ll.ch
Subject: Re: [PATCH] drm/i915/gvt: use DEFINE_DEBUGFS_ATTRIBUTE with debugfs_create_file_unsafe()

On Fri, 30 Oct 2020, Deepak R Varma <mh12gx2825@...il.com> wrote:
> Using DEFINE_DEBUGFS_ATTRIBUTE macro with debugfs_create_file_unsafe()
> function in place of the debugfs_create_file() function will make the
> file operation struct "reset" aware of the file's lifetime. Additional
> details here: https://lists.archive.carbon60.com/linux/kernel/2369498

Please describe what the functional impact is in the commit message. I
don't understand what 'make the file operation struct "reset" aware of
the file's lifetime' means here.

For referencing LKML posts, please prefer https://lore.kernel.org/.

For referencing commits already in the kernel, please prefer the format
c64688081490 ("debugfs: add support for self-protecting attribute file
fops").


BR,
Jani.

>
> Issue reported by Coccinelle script:
> scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci
>
> Signed-off-by: Deepak R Varma <mh12gx2825@...il.com>
> ---
> Please Note: This is a Outreachy project task patch.
>
>  drivers/gpu/drm/i915/gvt/debugfs.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gvt/debugfs.c b/drivers/gpu/drm/i915/gvt/debugfs.c
> index 62e6a14ad58e..18adfa2d5f5b 100644
> --- a/drivers/gpu/drm/i915/gvt/debugfs.c
> +++ b/drivers/gpu/drm/i915/gvt/debugfs.c
> @@ -147,9 +147,8 @@ vgpu_scan_nonprivbb_set(void *data, u64 val)
>  	return 0;
>  }
>  
> -DEFINE_SIMPLE_ATTRIBUTE(vgpu_scan_nonprivbb_fops,
> -			vgpu_scan_nonprivbb_get, vgpu_scan_nonprivbb_set,
> -			"0x%llx\n");
> +DEFINE_DEBUGFS_ATTRIBUTE(vgpu_scan_nonprivbb_fops, vgpu_scan_nonprivbb_get,
> +			 vgpu_scan_nonprivbb_set, "0x%llx\n");
>  
>  /**
>   * intel_gvt_debugfs_add_vgpu - register debugfs entries for a vGPU
> @@ -165,8 +164,8 @@ void intel_gvt_debugfs_add_vgpu(struct intel_vgpu *vgpu)
>  	debugfs_create_bool("active", 0444, vgpu->debugfs, &vgpu->active);
>  	debugfs_create_file("mmio_diff", 0444, vgpu->debugfs, vgpu,
>  			    &vgpu_mmio_diff_fops);
> -	debugfs_create_file("scan_nonprivbb", 0644, vgpu->debugfs, vgpu,
> -			    &vgpu_scan_nonprivbb_fops);
> +	debugfs_create_file_unsafe("scan_nonprivbb", 0644, vgpu->debugfs, vgpu,
> +				   &vgpu_scan_nonprivbb_fops);
>  }
>  
>  /**

-- 
Jani Nikula, Intel Open Source Graphics Center