linux-kernel - Re: [PATCH 3/6] bpf: task_group_seq_get_next: fix the skip_if_dup

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Message-ID: <25be098a-dc41-7907-5590-1835308ebe28@linux.dev>
Date:   Mon, 28 Aug 2023 20:30:29 -0400
From:   Yonghong Song <yonghong.song@...ux.dev>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Yonghong Song <yhs@...com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kui-Feng Lee <kuifeng@...com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...nel.org>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] bpf: task_group_seq_get_next: fix the
 skip_if_dup_files check



On 8/28/23 3:54 AM, Oleg Nesterov wrote:
> On 08/27, Yonghong Song wrote:
>>
>> On 8/27/23 1:19 PM, Oleg Nesterov wrote:
>>>
>>> But. if the group leader M exits then M->files == NULL. And in this case
>>> task_seq_get_next() will need to "inspect" all the sub-threads even if they all
>>> have the same ->files pointer.
>>
>> That is correct. I do not have practical experience on how much
>> possibility this scenario may happen. I assume it should be very low.
> 
> Yes. I just tried to explain why the ->files check looks confusing to me.
> Nevermind.
> 
> Could you review 6/6 as well?

I think we can wait patch 6/6 after
    https://lore.kernel.org/all/20230824143142.GA31222@redhat.com/
is merged.

> 
> Should I fold 1-5 into a single patch? I tried to document every change
> and simplify the review, but I do not want to blow the git history.

Currently, because patch 6, the whole patch set cannot be tested by
bpf CI since it has a build failure:
   https://github.com/kernel-patches/bpf/pull/5580
I suggest you get patch 1-5 and resubmit with tag like
   "bpf-next v2"
   [Patch bpf-next v2 x/5] ...
so CI can build with different architectures and compilers to
ensure everything builds and runs fine.

> 
> Oleg.
>