Re: [PATCH v3 bpf-next 1/2] bpf: Extend batch operations for map-in-map bpf-maps

[Yonghong Song <yhs@fb.com>]

On 4/25/22 11:41 AM, Takshak Chahande wrote:
> This patch extends batch operations support for map-in-map map-types:
> BPF_MAP_TYPE_HASH_OF_MAPS and BPF_MAP_TYPE_ARRAY_OF_MAPS
> 
> A usecase where outer HASH map holds hundred of VIP entries and its
> associated reuse-ports per VIP stored in REUSEPORT_SOCKARRAY type
> inner map, needs to do batch operation for performance gain.
> 
> This patch leverages the exiting generic functions for most of the batch
> operations. As map-in-map's value contains the actual reference of the inner map,
> for BPF_MAP_TYPE_HASH_OF_MAPS type, it needed an extra step to fetch the
> map_id from the reference value.
> 
> selftests are added in next patch that has v1->v3 changes
> 
> Signed-off-by: Takshak Chahande <ctakshak@fb.com>

Ack with a minor issue below.

Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   kernel/bpf/arraymap.c |  2 ++
>   kernel/bpf/hashtab.c  | 12 ++++++++++--
>   2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index 7f145aefbff8..f0852b6617cc 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -1344,6 +1344,8 @@ const struct bpf_map_ops array_of_maps_map_ops = {
>   	.map_fd_put_ptr = bpf_map_fd_put_ptr,
>   	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
>   	.map_gen_lookup = array_of_map_gen_lookup,
> +	.map_lookup_batch = generic_map_lookup_batch,
> +	.map_update_batch = generic_map_update_batch,
>   	.map_check_btf = map_check_no_btf,
>   	.map_btf_name = "bpf_array",
>   	.map_btf_id = &array_of_maps_map_btf_id,
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index c68fbebc8c00..fd537bfba84c 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -139,7 +139,7 @@ static inline bool htab_use_raw_lock(const struct bpf_htab *htab)
>   
>   static void htab_init_buckets(struct bpf_htab *htab)
>   {
> -	unsigned i;
> +	unsigned int i;
>   
>   	for (i = 0; i < htab->n_buckets; i++) {
>   		INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
> @@ -1594,7 +1594,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
>   	void __user *uvalues = u64_to_user_ptr(attr->batch.values);
>   	void __user *ukeys = u64_to_user_ptr(attr->batch.keys);
>   	void __user *ubatch = u64_to_user_ptr(attr->batch.in_batch);
> -	u32 batch, max_count, size, bucket_size;
> +	u32 batch, max_count, size, bucket_size, map_id;
>   	struct htab_elem *node_to_free = NULL;
>   	u64 elem_map_flags, map_flags;
>   	struct hlist_nulls_head *head;
> @@ -1719,6 +1719,13 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
>   			}
>   		} else {
>   			value = l->key + roundup_key_size;
> +			if (map->map_type == BPF_MAP_TYPE_HASH_OF_MAPS) {
> +				struct bpf_map **inner_map = value;

Please leave a blank line here between var declaration and actual codes.

> +				 /* Actual value is the id of the inner map */
> +				map_id = map->ops->map_fd_sys_lookup_elem(*inner_map);
> +				value = &map_id;
> +			}
> +
>   			if (elem_map_flags & BPF_F_LOCK)
>   				copy_map_value_locked(map, dst_val, value,
>   						      true);
> @@ -2425,6 +2432,7 @@ const struct bpf_map_ops htab_of_maps_map_ops = {
>   	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
>   	.map_gen_lookup = htab_of_map_gen_lookup,
>   	.map_check_btf = map_check_no_btf,
> +	BATCH_OPS(htab),
>   	.map_btf_name = "bpf_htab",
>   	.map_btf_id = &htab_of_maps_map_btf_id,
>   };