bpf: Refactor codes into bpf_local_storage_destroy

This patch first renames bpf_local_storage_unlink_nolock to
bpf_local_storage_destroy(). It better reflects that it is only
used when the storage's owner (sk/task/cgrp/inode) is being kfree().

All bpf_local_storage_destroy's caller is taking the spin lock and
then free the storage. This patch also moves these two steps into
the bpf_local_storage_destroy.

This is a preparation work for a later patch that uses
bpf_mem_cache_alloc/free in the bpf_local_storage.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20230308065936.1550103-3-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf_local_storage.h

@@ -128,7 +128,7 @@ bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
 			 struct bpf_local_storage_map *smap,
 			 bool cacheit_lockit);
 
-bool bpf_local_storage_unlink_nolock(struct bpf_local_storage *local_storage);
+void bpf_local_storage_destroy(struct bpf_local_storage *local_storage);
 
 void bpf_local_storage_map_free(struct bpf_map *map,
 				struct bpf_local_storage_cache *cache,

kernel/bpf/bpf_cgrp_storage.c

@@ -46,8 +46,6 @@ static struct bpf_local_storage __rcu **cgroup_storage_ptr(void *owner)
 void bpf_cgrp_storage_free(struct cgroup *cgroup)
 {
 	struct bpf_local_storage *local_storage;
-	bool free_cgroup_storage = false;
-	unsigned long flags;
 
 	rcu_read_lock();
 	local_storage = rcu_dereference(cgroup->bpf_cgrp_storage);
@@ -57,14 +55,9 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup)
 	}
 
 	bpf_cgrp_storage_lock();
-	raw_spin_lock_irqsave(&local_storage->lock, flags);
-	free_cgroup_storage = bpf_local_storage_unlink_nolock(local_storage);
-	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
+	bpf_local_storage_destroy(local_storage);
 	bpf_cgrp_storage_unlock();
 	rcu_read_unlock();
-
-	if (free_cgroup_storage)
-		kfree_rcu(local_storage, rcu);
 }
 
 static struct bpf_local_storage_data *

kernel/bpf/bpf_inode_storage.c

@@ -57,7 +57,6 @@ static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode,
 void bpf_inode_storage_free(struct inode *inode)
 {
 	struct bpf_local_storage *local_storage;
-	bool free_inode_storage = false;
 	struct bpf_storage_blob *bsb;
 
 	bsb = bpf_inode(inode);
@@ -72,13 +71,8 @@ void bpf_inode_storage_free(struct inode *inode)
 		return;
 	}
 
-	raw_spin_lock_bh(&local_storage->lock);
-	free_inode_storage = bpf_local_storage_unlink_nolock(local_storage);
-	raw_spin_unlock_bh(&local_storage->lock);
+	bpf_local_storage_destroy(local_storage);
 	rcu_read_unlock();
-
-	if (free_inode_storage)
-		kfree_rcu(local_storage, rcu);
 }
 
 static void *bpf_fd_inode_storage_lookup_elem(struct bpf_map *map, void *key)

kernel/bpf/bpf_local_storage.c

@@ -652,11 +652,12 @@ int bpf_local_storage_map_check_btf(const struct bpf_map *map,
 	return 0;
 }
 
-bool bpf_local_storage_unlink_nolock(struct bpf_local_storage *local_storage)
+void bpf_local_storage_destroy(struct bpf_local_storage *local_storage)
 {
 	struct bpf_local_storage_elem *selem;
 	bool free_storage = false;
 	struct hlist_node *n;
+	unsigned long flags;
 
 	/* Neither the bpf_prog nor the bpf_map's syscall
 	 * could be modifying the local_storage->list now.
@@ -667,6 +668,7 @@ bool bpf_local_storage_unlink_nolock(struct bpf_local_storage *local_storage)
 	 * when unlinking elem from the local_storage->list and
 	 * the map's bucket->list.
 	 */
+	raw_spin_lock_irqsave(&local_storage->lock, flags);
 	hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
 		/* Always unlink from map before unlinking from
 		 * local_storage.
@@ -681,8 +683,10 @@ bool bpf_local_storage_unlink_nolock(struct bpf_local_storage *local_storage)
 		free_storage = bpf_selem_unlink_storage_nolock(
 			local_storage, selem, false, false);
 	}
+	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 
-	return free_storage;
+	if (free_storage)
+		kfree_rcu(local_storage, rcu);
 }
 
 u64 bpf_local_storage_map_mem_usage(const struct bpf_map *map)

kernel/bpf/bpf_task_storage.c

@@ -72,8 +72,6 @@ task_storage_lookup(struct task_struct *task, struct bpf_map *map,
 void bpf_task_storage_free(struct task_struct *task)
 {
 	struct bpf_local_storage *local_storage;
-	bool free_task_storage = false;
-	unsigned long flags;
 
 	rcu_read_lock();
 
@@ -84,14 +82,9 @@ void bpf_task_storage_free(struct task_struct *task)
 	}
 
 	bpf_task_storage_lock();
-	raw_spin_lock_irqsave(&local_storage->lock, flags);
-	free_task_storage = bpf_local_storage_unlink_nolock(local_storage);
-	raw_spin_unlock_irqrestore(&local_storage->lock, flags);
+	bpf_local_storage_destroy(local_storage);
 	bpf_task_storage_unlock();
 	rcu_read_unlock();
-
-	if (free_task_storage)
-		kfree_rcu(local_storage, rcu);
 }
 
 static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)

net/core/bpf_sk_storage.c

@@ -49,7 +49,6 @@ static int bpf_sk_storage_del(struct sock *sk, struct bpf_map *map)
 void bpf_sk_storage_free(struct sock *sk)
 {
 	struct bpf_local_storage *sk_storage;
-	bool free_sk_storage = false;
 
 	rcu_read_lock();
 	sk_storage = rcu_dereference(sk->sk_bpf_storage);
@@ -58,13 +57,8 @@ void bpf_sk_storage_free(struct sock *sk)
 		return;
 	}
 
-	raw_spin_lock_bh(&sk_storage->lock);
-	free_sk_storage = bpf_local_storage_unlink_nolock(sk_storage);
-	raw_spin_unlock_bh(&sk_storage->lock);
+	bpf_local_storage_destroy(sk_storage);
 	rcu_read_unlock();
-
-	if (free_sk_storage)
-		kfree_rcu(sk_storage, rcu);
 }
 
 static void bpf_sk_storage_map_free(struct bpf_map *map)