Re: [PATCH 2/8] drm/gem: Introduce drm_gem_get_unmapped_area() fop

["Loïc Molinari" <loic.molinari@collabora.com>]

On 30/09/2025 12:30, Boris Brezillon wrote:
> On Mon, 29 Sep 2025 22:03:10 +0200
>
> Loïc Molinari <loic.molinari@collabora.com> wrote:
>> +unsigned long drm_gem_get_unmapped_area(struct file *filp, unsigned long uaddr,
>> +					unsigned long len, unsigned long pgoff,
>> +					unsigned long flags)
>> +{
>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> +	struct drm_gem_object *obj;
>> +	unsigned long ret;
>> +
>> +	obj = drm_gem_object_lookup_from_offset(filp, pgoff, len >> PAGE_SHIFT);
>> +	if (IS_ERR(obj))
>> +		return mm_get_unmapped_area(current->mm, filp, uaddr, len, 0,
>> +					    flags);
>> +
>> +	ret = shmem_get_unmapped_area(obj->filp, uaddr, len, 0, flags);
>> +
>> +	drm_gem_object_put(obj);
>> +
>> +	return ret;
>> +#else
>> +	return mm_get_unmapped_area(current->mm, filp, uaddr, len, 0, flags);
> 
> Looks like the above code covers the non-THP case too, do we really need
> to specialize for !CONFIG_TRANSPARENT_HUGEPAGE here?

It does cover the !CONFIG_TRANSPARENT_HUGEPAGE case 
(shmem_get_unmapped_area() would just call and return the 
mm_get_unmapped_area() address) but the idea here is to avoid the GEM 
object lookup cost by calling mm_get_unmapped_area() directly.

>> +#endif
>> +}
>> +EXPORT_SYMBOL(drm_gem_get_unmapped_area);

Loïc