[3/3] bpf: bpf_iter_task_next: use next_task(kit->task) rather than next_task(kit->pos)
Commit Message
This looks more clear and simplifies the code. While at it, remove the
unnecessary initialization of pos/task at the start of bpf_iter_task_new().
Note that we can even kill kit->task, we can just use pos->group_leader,
but I don't understand the BUILD_BUG_ON() checks in bpf_iter_task_new().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/bpf/task_iter.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
Comments
On 11/14/23 11:32 AM, Oleg Nesterov wrote:
> This looks more clear and simplifies the code. While at it, remove the
> unnecessary initialization of pos/task at the start of bpf_iter_task_new().
>
> Note that we can even kill kit->task, we can just use pos->group_leader,
> but I don't understand the BUILD_BUG_ON() checks in bpf_iter_task_new().
Let us keep kit->task, which is used in later function
bpf_iter_task_next(). The patch looks good to me.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
On 11/16, Yonghong Song wrote:
>
> On 11/14/23 11:32 AM, Oleg Nesterov wrote:
> >This looks more clear and simplifies the code. While at it, remove the
> >unnecessary initialization of pos/task at the start of bpf_iter_task_new().
> >
> >Note that we can even kill kit->task, we can just use pos->group_leader,
> >but I don't understand the BUILD_BUG_ON() checks in bpf_iter_task_new().
>
> Let us keep kit->task, which is used in later function
> bpf_iter_task_next(). The patch looks good to me.
Yes, but it can use pos->group_leader instead of kit->task.
But I agree, lets keep kit->task.
> Acked-by: Yonghong Song <yonghong.song@linux.dev>
Thanks!
Oleg.
@@ -978,7 +978,6 @@ __bpf_kfunc int bpf_iter_task_new(struct bpf_iter_task *it,
BUILD_BUG_ON(__alignof__(struct bpf_iter_task_kern) !=
__alignof__(struct bpf_iter_task));
- kit->task = kit->pos = NULL;
switch (flags) {
case BPF_TASK_ITER_ALL_THREADS:
case BPF_TASK_ITER_ALL_PROCS:
@@ -1016,18 +1015,15 @@ __bpf_kfunc struct task_struct *bpf_iter_task_next(struct bpf_iter_task *it)
goto get_next_task;
kit->pos = __next_thread(kit->pos);
- if (!kit->pos) {
- if (flags == BPF_TASK_ITER_PROC_THREADS)
- return pos;
- kit->pos = kit->task;
- } else
+ if (kit->pos || flags == BPF_TASK_ITER_PROC_THREADS)
return pos;
get_next_task:
- kit->pos = next_task(kit->pos);
- kit->task = kit->pos;
- if (kit->pos == &init_task)
+ kit->task = next_task(kit->task);
+ if (kit->task == &init_task)
kit->pos = NULL;
+ else
+ kit->pos = kit->task;
return pos;
}