[PATCH RFC bpf-next v2 02/18] bpf: Add resizable hashtab skeleton

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

From: Mykyta Yatsenko <yatsenko@meta.com>

Added a skeleton for resizable hashtab. Actual implementation follows
in the next patches of the series.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
---
 include/linux/bpf_types.h |   1 +
 kernel/bpf/hashtab.c      | 166 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 167 insertions(+)

diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index b13de31e163f..56e4c3f983d3 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -134,6 +134,7 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_BLOOM_FILTER, bloom_filter_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_USER_RINGBUF, user_ringbuf_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_ARENA, arena_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_INSN_ARRAY, insn_array_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_RHASH, rhtab_map_ops)
 
 BPF_LINK_TYPE(BPF_LINK_TYPE_RAW_TRACEPOINT, raw_tracepoint)
 BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING, tracing)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index bc6bc8bb871d..9e7806814fec 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -9,6 +9,7 @@
 #include <linux/rculist_nulls.h>
 #include <linux/rcupdate_wait.h>
 #include <linux/random.h>
+#include <linux/rhashtable.h>
 #include <uapi/linux/btf.h>
 #include <linux/rcupdate_trace.h>
 #include <linux/btf_ids.h>
@@ -418,6 +419,7 @@ static int htab_map_alloc_check(union bpf_attr *attr)
 	bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
 	bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
 	bool zero_seed = (attr->map_flags & BPF_F_ZERO_SEED);
+	bool resizable = attr->map_type == BPF_MAP_TYPE_RHASH;
 	int numa_node = bpf_map_attr_numa_node(attr);
 
 	BUILD_BUG_ON(offsetof(struct htab_elem, fnode.next) !=
@@ -459,6 +461,9 @@ static int htab_map_alloc_check(union bpf_attr *attr)
 	if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
 		return -E2BIG;
 
+	if (resizable && percpu_lru)
+		return -EINVAL;
+
 	return 0;
 }
 
@@ -2735,3 +2740,164 @@ const struct bpf_map_ops htab_of_maps_map_ops = {
 	BATCH_OPS(htab),
 	.map_btf_id = &htab_map_btf_ids[0],
 };
+
+struct rhtab_elem {
+	struct rhash_head node;
+	/* key bytes, then value bytes follow */
+	u8 data[] __aligned(8);
+};
+
+struct bpf_rhtab {
+	struct bpf_map map;
+	struct rhashtable ht;
+	struct rhashtable_params params;
+	struct bpf_mem_alloc ma;
+	u32 elem_size;
+};
+
+static struct bpf_map *rhtab_map_alloc(union bpf_attr *attr)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+static int rhtab_map_alloc_check(union bpf_attr *attr)
+{
+	return -EOPNOTSUPP;
+}
+
+static void rhtab_map_free(struct bpf_map *map)
+{
+}
+
+static void *rhtab_map_lookup_elem(struct bpf_map *map, void *key) __must_hold(RCU)
+{
+	return NULL;
+}
+
+static long rhtab_map_delete_elem(struct bpf_map *map, void *key)
+{
+	return -EOPNOTSUPP;
+}
+
+static int rhtab_map_lookup_and_delete_elem(struct bpf_map *map, void *key, void *value, u64 flags)
+{
+	return -EOPNOTSUPP;
+}
+
+static long rhtab_map_update_elem(struct bpf_map *map, void *key, void *value, u64 map_flags)
+{
+	return -EOPNOTSUPP;
+}
+
+static void rhtab_map_free_internal_structs(struct bpf_map *map)
+{
+}
+
+static int rhtab_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
+{
+	return -EOPNOTSUPP;
+}
+
+static int rhtab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
+{
+	return -EOPNOTSUPP;
+}
+
+static void rhtab_map_seq_show_elem(struct bpf_map *map, void *key, struct seq_file *m)
+{
+}
+
+static long bpf_each_rhash_elem(struct bpf_map *map, bpf_callback_t callback_fn,
+				void *callback_ctx, u64 flags)
+{
+	return -EOPNOTSUPP;
+}
+
+static u64 rhtab_map_mem_usage(const struct bpf_map *map)
+{
+	return 0;
+}
+
+static int rhtab_map_lookup_batch(struct bpf_map *map, const union bpf_attr *attr,
+				  union bpf_attr __user *uattr)
+{
+	return 0;
+}
+
+static int rhtab_map_lookup_and_delete_batch(struct bpf_map *map, const union bpf_attr *attr,
+					     union bpf_attr __user *uattr)
+{
+	return 0;
+}
+
+struct bpf_iter_seq_rhash_map_info {
+	struct bpf_map *map;
+	struct bpf_rhtab *rhtab;
+	struct rhashtable_iter iter;
+	u32 skip_elems;
+	bool iter_active;
+};
+
+static void *bpf_rhash_map_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	return NULL;
+}
+
+static void *bpf_rhash_map_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	return NULL;
+}
+
+static int bpf_rhash_map_seq_show(struct seq_file *seq, void *v)
+{
+	return 0;
+}
+
+static void bpf_rhash_map_seq_stop(struct seq_file *seq, void *v)
+{
+}
+
+static int bpf_iter_init_rhash_map(void *priv_data, struct bpf_iter_aux_info *aux)
+{
+	return 0;
+}
+
+static void bpf_iter_fini_rhash_map(void *priv_data)
+{
+}
+
+static const struct seq_operations bpf_rhash_map_seq_ops = {
+	.start = bpf_rhash_map_seq_start,
+	.next = bpf_rhash_map_seq_next,
+	.stop = bpf_rhash_map_seq_stop,
+	.show = bpf_rhash_map_seq_show,
+};
+
+static const struct bpf_iter_seq_info rhash_iter_seq_info = {
+	.seq_ops = &bpf_rhash_map_seq_ops,
+	.init_seq_private = bpf_iter_init_rhash_map,
+	.fini_seq_private = bpf_iter_fini_rhash_map,
+	.seq_priv_size = sizeof(struct bpf_iter_seq_rhash_map_info),
+};
+
+BTF_ID_LIST_SINGLE(rhtab_map_btf_ids, struct, bpf_rhtab)
+const struct bpf_map_ops rhtab_map_ops = {
+	.map_meta_equal = bpf_map_meta_equal,
+	.map_alloc_check = rhtab_map_alloc_check,
+	.map_alloc = rhtab_map_alloc,
+	.map_free = rhtab_map_free,
+	.map_get_next_key = rhtab_map_get_next_key,
+	.map_release_uref = rhtab_map_free_internal_structs,
+	.map_lookup_elem = rhtab_map_lookup_elem,
+	.map_lookup_and_delete_elem = rhtab_map_lookup_and_delete_elem,
+	.map_update_elem = rhtab_map_update_elem,
+	.map_delete_elem = rhtab_map_delete_elem,
+	.map_gen_lookup = rhtab_map_gen_lookup,
+	.map_seq_show_elem = rhtab_map_seq_show_elem,
+	.map_set_for_each_callback_args = map_set_for_each_callback_args,
+	.map_for_each_callback = bpf_each_rhash_elem,
+	.map_mem_usage = rhtab_map_mem_usage,
+	BATCH_OPS(rhtab),
+	.map_btf_id = &rhtab_map_btf_ids[0],
+	.iter_seq_info = &rhash_iter_seq_info,
+};

-- 
2.52.0