Re: [Intel-gfx] [PATCH 1/2] drm/drm_vma_manager: Add drm_vma_node_allow_once()

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 17/01/2023 17:52, Nirmoy Das wrote:
> Currently there is no easy way for a drm driver to safely check and allow
> drm_vma_offset_node for a drm file just once. Allow drm drivers to call
> non-refcounted version of drm_vma_node_allow() so that a driver doesn't
> need to keep track of each drm_vma_node_allow() to call subsequent
> drm_vma_node_revoke() to prevent memory leak.
> 
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> 
> Suggested-by: Chris Wilson <chris.p.wilson@intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>   drivers/gpu/drm/drm_vma_manager.c | 76 ++++++++++++++++++++++---------
>   include/drm/drm_vma_manager.h     |  1 +
>   2 files changed, 55 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_vma_manager.c b/drivers/gpu/drm/drm_vma_manager.c
> index 7de37f8c68fd..83229a031af0 100644
> --- a/drivers/gpu/drm/drm_vma_manager.c
> +++ b/drivers/gpu/drm/drm_vma_manager.c
> @@ -240,27 +240,8 @@ void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
>   }
>   EXPORT_SYMBOL(drm_vma_offset_remove);
>   
> -/**
> - * drm_vma_node_allow - Add open-file to list of allowed users
> - * @node: Node to modify
> - * @tag: Tag of file to remove
> - *
> - * Add @tag to the list of allowed open-files for this node. If @tag is
> - * already on this list, the ref-count is incremented.
> - *
> - * The list of allowed-users is preserved across drm_vma_offset_add() and
> - * drm_vma_offset_remove() calls. You may even call it if the node is currently
> - * not added to any offset-manager.
> - *
> - * You must remove all open-files the same number of times as you added them
> - * before destroying the node. Otherwise, you will leak memory.
> - *
> - * This is locked against concurrent access internally.
> - *
> - * RETURNS:
> - * 0 on success, negative error code on internal failure (out-of-mem)
> - */
> -int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
> +static int vma_node_allow(struct drm_vma_offset_node *node,
> +			  struct drm_file *tag, bool ref_counted)
>   {
>   	struct rb_node **iter;
>   	struct rb_node *parent = NULL;
> @@ -282,7 +263,8 @@ int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
>   		entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
>   
>   		if (tag == entry->vm_tag) {
> -			entry->vm_count++;
> +			if (ref_counted)
> +				entry->vm_count++;
>   			goto unlock;
>   		} else if (tag > entry->vm_tag) {
>   			iter = &(*iter)->rb_right;
> @@ -307,8 +289,58 @@ int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
>   	kfree(new);
>   	return ret;
>   }
> +
> +/**
> + * drm_vma_node_allow - Add open-file to list of allowed users
> + * @node: Node to modify
> + * @tag: Tag of file to remove
> + *
> + * Add @tag to the list of allowed open-files for this node. If @tag is
> + * already on this list, the ref-count is incremented.
> + *
> + * The list of allowed-users is preserved across drm_vma_offset_add() and
> + * drm_vma_offset_remove() calls. You may even call it if the node is currently
> + * not added to any offset-manager.
> + *
> + * You must remove all open-files the same number of times as you added them
> + * before destroying the node. Otherwise, you will leak memory.
> + *
> + * This is locked against concurrent access internally.
> + *
> + * RETURNS:
> + * 0 on success, negative error code on internal failure (out-of-mem)
> + */
> +int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
> +{
> +	return vma_node_allow(node, tag, true);
> +}
>   EXPORT_SYMBOL(drm_vma_node_allow);
>   
> +/**
> + * drm_vma_node_allow_once - Add open-file to list of allowed users
> + * @node: Node to modify
> + * @tag: Tag of file to remove
> + *
> + * Add @tag to the list of allowed open-files for this node.
> + *
> + * The list of allowed-users is preserved across drm_vma_offset_add() and
> + * drm_vma_offset_remove() calls. You may even call it if the node is currently
> + * not added to any offset-manager.
> + *
> + * This is not ref-counted unlike drm_vma_node_allow() hence drm_vma_node_revoke()
> + * should only be called once after this.
> + *
> + * This is locked against concurrent access internally.
> + *
> + * RETURNS:
> + * 0 on success, negative error code on internal failure (out-of-mem)
> + */
> +int drm_vma_node_allow_once(struct drm_vma_offset_node *node, struct drm_file *tag)
> +{
> +	return vma_node_allow(node, tag, false);
> +}
> +EXPORT_SYMBOL(drm_vma_node_allow_once);
> +
>   /**
>    * drm_vma_node_revoke - Remove open-file from list of allowed users
>    * @node: Node to modify
> diff --git a/include/drm/drm_vma_manager.h b/include/drm/drm_vma_manager.h
> index 4f8c35206f7c..6c2a2f21dbf0 100644
> --- a/include/drm/drm_vma_manager.h
> +++ b/include/drm/drm_vma_manager.h
> @@ -74,6 +74,7 @@ void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
>   			   struct drm_vma_offset_node *node);
>   
>   int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag);
> +int drm_vma_node_allow_once(struct drm_vma_offset_node *node, struct drm_file *tag);
>   void drm_vma_node_revoke(struct drm_vma_offset_node *node,
>   			 struct drm_file *tag);
>   bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,

LGTM,

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko