bpf: Add bpf_selem_free()

This patch refactors the selem freeing logic into bpf_selem_free().
It is a preparation work for a later patch using
bpf_mem_cache_alloc/free. The other kfree(selem) cases
are also changed to bpf_selem_free(..., reuse_now = true).
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20230308065936.1550103-10-martin.lau@linux.devSigned-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf_local_storage.h

@@ -152,6 +152,10 @@ struct bpf_local_storage_elem *
 bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, void *value,
 		bool charge_mem, gfp_t gfp_flags);
 
+void bpf_selem_free(struct bpf_local_storage_elem *selem,
+		    struct bpf_local_storage_map *smap,
+		    bool reuse_now);
+
 int
 bpf_local_storage_alloc(void *owner,
 			struct bpf_local_storage_map *smap,

kernel/bpf/bpf_local_storage.c

@@ -125,6 +125,17 @@ static void bpf_selem_free_trace_rcu(struct rcu_head *rcu)
 		call_rcu(rcu, bpf_selem_free_rcu);
 }
 
+void bpf_selem_free(struct bpf_local_storage_elem *selem,
+		    struct bpf_local_storage_map *smap,
+		    bool reuse_now)
+{
+	bpf_obj_free_fields(smap->map.record, SDATA(selem)->data);
+	if (!reuse_now)
+		call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu);
+	else
+		call_rcu(&selem->rcu, bpf_selem_free_rcu);
+}
+
 /* local_storage->lock must be held and selem->local_storage == local_storage.
  * The caller must ensure selem->smap is still valid to be
  * dereferenced for its smap->elem_size and smap->cache_idx.
@@ -175,11 +186,7 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
 	    SDATA(selem))
 		RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
 
-	bpf_obj_free_fields(smap->map.record, SDATA(selem)->data);
-	if (!reuse_now)
-		call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu);
-	else
-		call_rcu(&selem->rcu, bpf_selem_free_rcu);
+	bpf_selem_free(selem, smap, reuse_now);
 
 	if (rcu_access_pointer(local_storage->smap) == smap)
 		RCU_INIT_POINTER(local_storage->smap, NULL);
@@ -423,7 +430,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 
 		err = bpf_local_storage_alloc(owner, smap, selem, gfp_flags);
 		if (err) {
-			kfree(selem);
+			bpf_selem_free(selem, smap, true);
 			mem_uncharge(smap, owner, smap->elem_size);
 			return ERR_PTR(err);
 		}
@@ -517,7 +524,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 	if (selem) {
 		mem_uncharge(smap, owner, smap->elem_size);
-		kfree(selem);
+		bpf_selem_free(selem, smap, true);
 	}
 	return ERR_PTR(err);
 }

net/core/bpf_sk_storage.c

@@ -197,7 +197,7 @@ int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk)
 		} else {
 			ret = bpf_local_storage_alloc(newsk, smap, copy_selem, GFP_ATOMIC);
 			if (ret) {
-				kfree(copy_selem);
+				bpf_selem_free(copy_selem, smap, true);
 				atomic_sub(smap->elem_size,
 					   &newsk->sk_omem_alloc);
 				bpf_map_put(map);