From: Hou Tao <houtao1@xxxxxxxxxx>
There is no rcu-read-lock requirement for ops->map_fd_get_ptr() or
ops->map_fd_put_ptr(), so doesn't use rcu-read-lock for these two
callbacks.
For bpf_fd_array_map_update_elem(), accessing array->ptrs doesn't need
rcu-read-lock because array->ptrs must still be allocated. For
bpf_fd_htab_map_update_elem(), htab_map_update_elem() only requires
rcu-read-lock to be held to avoid the WARN_ON_ONCE(), so only use
rcu_read_lock() during the invocation of htab_map_update_elem().
Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
kernel/bpf/hashtab.c | 6 ++++++
kernel/bpf/syscall.c | 4 ----
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 5b9146fa825f..ec3bdcc6a3cf 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -2523,7 +2523,13 @@ int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
if (IS_ERR(ptr))
return PTR_ERR(ptr);
+ /* The htab bucket lock is always held during update operations in fd
+ * htab map, and the following rcu_read_lock() is only used to avoid
+ * the WARN_ON_ONCE in htab_map_update_elem().
+ */
+ rcu_read_lock();
ret = htab_map_update_elem(map, key, &ptr, map_flags);
+ rcu_read_unlock();
if (ret)
map->ops->map_fd_put_ptr(map, ptr, false);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index d63c1ed42412..3fcf7741146a 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -184,15 +184,11 @@ static int bpf_map_update_value(struct bpf_map *map, struct file *map_file,
err = bpf_percpu_cgroup_storage_update(map, key, value,
flags);
} else if (IS_FD_ARRAY(map)) {
- rcu_read_lock();
err = bpf_fd_array_map_update_elem(map, map_file, key, value,
flags);
- rcu_read_unlock();
} else if (map->map_type == BPF_MAP_TYPE_HASH_OF_MAPS) {
- rcu_read_lock();
err = bpf_fd_htab_map_update_elem(map, map_file, key, value,
flags);
- rcu_read_unlock();
} else if (map->map_type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY) {
/* rcu_read_lock() is not needed */
err = bpf_fd_reuseport_array_update_elem(map, key, value,
--
2.29.2
