Re: [PATCH v2 01/12] uprobes: update outdated comment

Andrii Nakryiko
2024-07-03T18:25:02Z

On Wed, Jul 3, 2024 at 4:40 AM Oleg Nesterov <oleg@redhat.com> wrote:
>
> Sorry for the late reply. I'll try to read this version/discussion
> when I have time... yes, I have already promised this before, sorry :/
>
> On 07/01, Andrii Nakryiko wrote:
> >
> > There is no task_struct passed into get_user_pages_remote() anymore,
> > drop the parts of comment mentioning NULL tsk, it's just confusing at
> > this point.
>
> Agreed.
>
> > @@ -2030,10 +2030,8 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
> > goto out;
> >
> > /*
> > - * The NULL 'tsk' here ensures that any faults that occur here
> > - * will not be accounted to the task. 'mm' *is* current->mm,
> > - * but we treat this as a 'remote' access since it is
> > - * essentially a kernel access to the memory.
> > + * 'mm' *is* current->mm, but we treat this as a 'remote' access since
> > + * it is essentially a kernel access to the memory.
> > */
> > result = get_user_pages_remote(mm, vaddr, 1, FOLL_FORCE, &page, NULL);
>
> OK, this makes it less confusing, so
>
> Acked-by: Oleg Nesterov <oleg@redhat.com>
>
>
> ---------------------------------------------------------------------
> but it still looks confusing to me. This code used to pass tsk = NULL
> only to avoid tsk->maj/min_flt++ in faultin_page().
>
> But today mm_account_fault() increments these counters without checking
> FAULT_FLAG_REMOTE, mm == current->mm, so it seems it would be better to
> just use get_user_pages() and remove this comment?

I don't know, it was a drive-by cleanup which I'm starting to regret already :)

>
> Oleg.
>