[PATCH 02/34] drm: Convert aux_idr to XArray

[Ville Syrjälä]

On Thu, Feb 21, 2019 at 10:41:23AM -0800, Matthew Wilcox wrote:
> Signed-off-by: Matthew Wilcox <willy at infradead.org>
> ---
>  drivers/gpu/drm/drm_dp_aux_dev.c | 41 +++++++++++++-------------------
>  1 file changed, 17 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c b/drivers/gpu/drm/drm_dp_aux_dev.c
> index 0e4f25d63fd2..393a32976900 100644
> --- a/drivers/gpu/drm/drm_dp_aux_dev.c
> +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
> @@ -49,8 +49,7 @@ struct drm_dp_aux_dev {
>  
>  #define DRM_AUX_MINORS	256
>  #define AUX_MAX_OFFSET	(1 << 20)
> -static DEFINE_IDR(aux_idr);
> -static DEFINE_MUTEX(aux_idr_mutex);
> +static DEFINE_XARRAY_ALLOC(aux_xa);
>  static struct class *drm_dp_aux_dev_class;
>  static int drm_dev_major = -1;
>  
> @@ -58,19 +57,21 @@ static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
>  {
>  	struct drm_dp_aux_dev *aux_dev = NULL;
>  
> -	mutex_lock(&aux_idr_mutex);
> -	aux_dev = idr_find(&aux_idr, index);
> +	xa_lock(&aux_xa);
> +	aux_dev = xa_load(&aux_xa, index);
>  	if (!kref_get_unless_zero(&aux_dev->refcount))
>  		aux_dev = NULL;
> -	mutex_unlock(&aux_idr_mutex);
> +	xa_unlock(&aux_xa);
>  
>  	return aux_dev;
>  }
>  
>  static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
>  {
> +	static u32 next;

Is there a particular reason for that being static?

> +
>  	struct drm_dp_aux_dev *aux_dev;
> -	int index;
> +	int err;
>  
>  	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
>  	if (!aux_dev)
> @@ -79,15 +80,12 @@ static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
>  	atomic_set(&aux_dev->usecount, 1);
>  	kref_init(&aux_dev->refcount);
>  
> -	mutex_lock(&aux_idr_mutex);
> -	index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
> -				 GFP_KERNEL);
> -	mutex_unlock(&aux_idr_mutex);
> -	if (index < 0) {
> +	err = xa_alloc_cyclic(&aux_xa, &aux_dev->index, aux_dev,
> +			XA_LIMIT(0, DRM_AUX_MINORS), &next, GFP_KERNEL);
> +	if (err < 0) {
>  		kfree(aux_dev);
> -		return ERR_PTR(index);
> +		return ERR_PTR(err);
>  	}
> -	aux_dev->index = index;
>  
>  	return aux_dev;
>  }
> @@ -246,22 +244,19 @@ static const struct file_operations auxdev_fops = {
>  
>  static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
>  {
> -	struct drm_dp_aux_dev *iter, *aux_dev = NULL;
> -	int id;
> +	struct drm_dp_aux_dev *aux_dev;
> +	unsigned long id;
>  
>  	/* don't increase kref count here because this function should only be
>  	 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
>  	 * least one reference - the one that drm_dp_aux_register_devnode
>  	 * created
>  	 */
> -	mutex_lock(&aux_idr_mutex);
> -	idr_for_each_entry(&aux_idr, iter, id) {
> -		if (iter->aux == aux) {
> -			aux_dev = iter;
> +	xa_for_each(&aux_xa, id, aux_dev) {
> +		if (aux_dev->aux == aux)
>  			break;
> -		}
>  	}
> -	mutex_unlock(&aux_idr_mutex);
> +
>  	return aux_dev;
>  }
>  
> @@ -274,9 +269,7 @@ void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
>  	if (!aux_dev) /* attach must have failed */
>  		return;
>  
> -	mutex_lock(&aux_idr_mutex);
> -	idr_remove(&aux_idr, aux_dev->index);
> -	mutex_unlock(&aux_idr_mutex);
> +	xa_erase(&aux_xa, aux_dev->index);
>  
>  	atomic_dec(&aux_dev->usecount);
>  	wait_var_event(&aux_dev->usecount, !atomic_read(&aux_dev->usecount));
> -- 
> 2.20.1
> 
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-- 
Ville Syrjälä
Intel