Re: [PATCH bpf-next v6 3/4] bpf: Handle show_fdinfo for the parameterized task BPF iterators

[Yonghong Song <yhs@fb.com>]

On 8/19/22 3:09 PM, Kui-Feng Lee wrote:
> Show information of iterators in the respective files under
> /proc/<pid>/fdinfo/.

Please show more information about what are dumped in
the commit message.

> 
> Signed-off-by: Kui-Feng Lee <kuifeng@fb.com>
> ---
>   kernel/bpf/task_iter.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
> index 927b3a1cf354..5303eddb264b 100644
> --- a/kernel/bpf/task_iter.c
> +++ b/kernel/bpf/task_iter.c
> @@ -611,6 +611,11 @@ static int bpf_iter_fill_link_info(const struct bpf_iter_aux_info *aux, struct b
>   	return 0;
>   }
>   
> +static void bpf_iter_task_show_fdinfo(const struct bpf_iter_aux_info *aux, struct seq_file *seq)
> +{
> +	seq_printf(seq, "task_type:\t%d\npid:\t%d\n", aux->task.type, aux->task.pid);

It would be good if we can print either 'tid: <number>' or 'pid: 
<number>' instead of just 'pid: <number>' in all cases.
Also you don't need to print pid if it is 0 (to traverse all tasks).

We should use a string instead of an int for aux->task.type so user 
doesn't need to look at kernel source which they may not have.

> +}
> +
>   static struct bpf_iter_reg task_reg_info = {
>   	.target			= "task",
>   	.attach_target		= bpf_iter_attach_task,
> @@ -622,6 +627,7 @@ static struct bpf_iter_reg task_reg_info = {
>   	},
>   	.seq_info		= &task_seq_info,
>   	.fill_link_info		= bpf_iter_fill_link_info,
> +	.show_fdinfo		= bpf_iter_task_show_fdinfo,
>   };
>   
>   static const struct bpf_iter_seq_info task_file_seq_info = {
> @@ -644,6 +650,7 @@ static struct bpf_iter_reg task_file_reg_info = {
>   	},
>   	.seq_info		= &task_file_seq_info,
>   	.fill_link_info		= bpf_iter_fill_link_info,
> +	.show_fdinfo		= bpf_iter_task_show_fdinfo,
>   };
>   
>   static const struct bpf_iter_seq_info task_vma_seq_info = {
> @@ -666,6 +673,7 @@ static struct bpf_iter_reg task_vma_reg_info = {
>   	},
>   	.seq_info		= &task_vma_seq_info,
>   	.fill_link_info		= bpf_iter_fill_link_info,
> +	.show_fdinfo		= bpf_iter_task_show_fdinfo,
>   };
>   
>   BPF_CALL_5(bpf_find_vma, struct task_struct *, task, u64, start,