Subject: Re: [PATCH v13 vfio 1/7] vfio: Commonize combine_ranges for use in other VFIO drivers

From: Jason Gunthorpe <[email-masked]>
Date: Fri, 4 Aug 2023 13:51:29 -0300

On Tue, Jul 25, 2023 at 02:40:19PM -0700, Brett Creeley wrote:
> Currently only Mellanox uses the combine_ranges function. The
> new pds_vfio driver also needs this function. So, move it to
> a common location for other vendor drivers to use.
> 
> Also, fix RCT ordering while moving/renaming the function.
> 
> Cc: Yishai Hadas <[email-masked]>
> Signed-off-by: Brett Creeley <[email-masked]>
> Signed-off-by: Shannon Nelson <[email-masked]>
> Reviewed-by: Simon Horman <[email-masked]>
> ---
>  drivers/vfio/pci/mlx5/cmd.c | 48 +------------------------------------
>  drivers/vfio/vfio_main.c    | 47 ++++++++++++++++++++++++++++++++++++
>  include/linux/vfio.h        |  3 +++
>  3 files changed, 51 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/vfio/pci/mlx5/cmd.c b/drivers/vfio/pci/mlx5/cmd.c
> index deed156e6165..7f6c51992a15 100644
> --- a/drivers/vfio/pci/mlx5/cmd.c
> +++ b/drivers/vfio/pci/mlx5/cmd.c
> @@ -732,52 +732,6 @@ void mlx5fv_cmd_clean_migf_resources(struct mlx5_vf_migration_file *migf)
>  	mlx5vf_cmd_dealloc_pd(migf);
>  }
>  
> -static void combine_ranges(struct rb_root_cached *root, u32 cur_nodes,
> -			   u32 req_nodes)
> -{
> -	struct interval_tree_node *prev, *curr, *comb_start, *comb_end;
> -	unsigned long min_gap;
> -	unsigned long curr_gap;
> -
> -	/* Special shortcut when a single range is required */
> -	if (req_nodes == 1) {
> -		unsigned long last;
> -
> -		curr = comb_start = interval_tree_iter_first(root, 0, ULONG_MAX);
> -		while (curr) {
> -			last = curr->last;
> -			prev = curr;
> -			curr = interval_tree_iter_next(curr, 0, ULONG_MAX);
> -			if (prev != comb_start)
> -				interval_tree_remove(prev, root);
> -		}
> -		comb_start->last = last;
> -		return;
> -	}
> -
> -	/* Combine ranges which have the smallest gap */
> -	while (cur_nodes > req_nodes) {
> -		prev = NULL;
> -		min_gap = ULONG_MAX;
> -		curr = interval_tree_iter_first(root, 0, ULONG_MAX);
> -		while (curr) {
> -			if (prev) {
> -				curr_gap = curr->start - prev->last;
> -				if (curr_gap < min_gap) {
> -					min_gap = curr_gap;
> -					comb_start = prev;
> -					comb_end = curr;
> -				}
> -			}
> -			prev = curr;
> -			curr = interval_tree_iter_next(curr, 0, ULONG_MAX);
> -		}
> -		comb_start->last = comb_end->last;
> -		interval_tree_remove(comb_end, root);
> -		cur_nodes--;
> -	}
> -}
> -
>  static int mlx5vf_create_tracker(struct mlx5_core_dev *mdev,
>  				 struct mlx5vf_pci_core_device *mvdev,
>  				 struct rb_root_cached *ranges, u32 nnodes)
> @@ -800,7 +754,7 @@ static int mlx5vf_create_tracker(struct mlx5_core_dev *mdev,
>  	int i;
>  
>  	if (num_ranges > max_num_range) {
> -		combine_ranges(ranges, nnodes, max_num_range);
> +		vfio_combine_iova_ranges(ranges, nnodes, max_num_range);
>  		num_ranges = max_num_range;
>  	}
>  
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index f0ca33b2e1df..3bde62f7e08b 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -865,6 +865,53 @@ static int vfio_ioctl_device_feature_migration(struct vfio_device *device,
>  	return 0;
>  }
>  
> +void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes,
> +			      u32 req_nodes)
> +{

It should really gain a kdoc now.

But the code is fine

Reviewed-by: Jason Gunthorpe <[email-masked]>

Jason