Re: [PATCH v3 bpf-next 1/6] bpf: Create BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY

[Eric Dumazet]

On 5/27/19 8:49 PM, brakmo wrote:
> Create new macro BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY() to be used by
> __cgroup_bpf_run_filter_skb for EGRESS BPF progs so BPF programs can
> request cwr for TCP packets.
> 

...

> +#define BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY(array, ctx, func)              
> \
> +     ({                                              \
> +             struct bpf_prog_array_item *_item;      \
> +             struct bpf_prog *_prog;                 \
> +             struct bpf_prog_array *_array;          \
> +             u32 ret;                                \
> +             u32 _ret = 1;                           \
> +             u32 _cn = 0;                            \
> +             preempt_disable();                      \
> +             rcu_read_lock();                        \
> +             _array = rcu_dereference(array);        \

Why _array can not be NULL here ?

> +             _item = &_array->items[0];              \
> +             while ((_prog = READ_ONCE(_item->prog))) {              \
> +                     bpf_cgroup_storage_set(_item->cgroup_storage);  \
> +                     ret = func(_prog, ctx);         \
> +                     _ret &= (ret & 1);              \
> +                     _cn |= (ret & 2);               \
> +                     _item++;                        \
> +             }                                       \
> +             rcu_read_unlock();                      \
> +             preempt_enable_no_resched();    

Why are you using preempt_enable_no_resched() here ?

        \
> +             if (_ret)                               \
> +                     _ret = (_cn ? NET_XMIT_CN : NET_XMIT_SUCCESS);  \
> +             else                                    \
> +                     _ret = (_cn ? NET_XMIT_DROP : -EPERM);          \
> +             _ret;                                   \
> +     })
> +
>  #define BPF_PROG_RUN_ARRAY(array, ctx, func)         \
>       __BPF_PROG_RUN_ARRAY(array, ctx, func, false)
>  
>