linux-kernel - Re: [PATCH drm-misc-next v2 5/7] drm/gpuvm: add an abstraction for a VM / BO combination

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Message-ID: <b3a322f0-9b0b-0ad8-be5d-e081f4061f13@redhat.com>
Date:   Thu, 7 Sep 2023 11:41:11 +0200
From:   Danilo Krummrich <dakr@...hat.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     airlied@...il.com, daniel@...ll.ch, matthew.brost@...el.com,
        thomas.hellstrom@...ux.intel.com, sarah.walker@...tec.com,
        donald.robson@...tec.com, christian.koenig@....com,
        faith.ekstrand@...labora.com, dri-devel@...ts.freedesktop.org,
        nouveau@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH drm-misc-next v2 5/7] drm/gpuvm: add an abstraction for a
 VM / BO combination

On 9/7/23 10:42, Boris Brezillon wrote:
> On Wed,  6 Sep 2023 23:47:13 +0200
> Danilo Krummrich <dakr@...hat.com> wrote:
> 
>> +void drm_gpuvm_bo_destroy(struct kref *kref);
> 
> I usually keep kref's release functions private so people are not
> tempted to use them.

I think I did that because drm_gpuvm_bo_put() needs it.

> 
>> +
>> +/**
>> + * drm_gpuvm_bo_get() - acquire a struct drm_gpuvm_bo reference
>> + * @vm_bo: the &drm_gpuvm_bo to acquire the reference of
>> + *
>> + * This function acquires an additional reference to @vm_bo. It is illegal to
>> + * call this without already holding a reference. No locks required.
>> + */
>> +static inline struct drm_gpuvm_bo *
>> +drm_gpuvm_bo_get(struct drm_gpuvm_bo *vm_bo)
>> +{
>> +	kref_get(&vm_bo->kref);
>> +	return vm_bo;
>> +}
>> +
>> +/**
>> + * drm_gpuvm_bo_put() - drop a struct drm_gpuvm_bo reference
>> + * @vm_bo: the &drm_gpuvm_bo to release the reference of
>> + *
>> + * This releases a reference to @vm_bo.
>> + */
>> +static inline void
>> +drm_gpuvm_bo_put(struct drm_gpuvm_bo *vm_bo)
>> +{
>> +	kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
> 
> nit: can we have
> 
> 	if (vm_bo)
> 		kref_put(&vm_bo->kref, drm_gpuvm_bo_destroy);
> 
> so we don't have to bother testing the vm_bo value in the error/cleanup
> paths?
> 
>> +}
>> +
>