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Date:   Fri, 7 Jul 2023 17:00:49 -0400
From:   Peter Xu <peterx@redhat.com>
To:     Axel Rasmussen <axelrasmussen@google.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Brian Geffon <bgeffon@google.com>,
        Christian Brauner <brauner@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Gaosheng Cui <cuigaosheng1@huawei.com>,
        Huang Ying <ying.huang@intel.com>,
        Hugh Dickins <hughd@google.com>,
        James Houghton <jthoughton@google.com>,
        "Jan Alexander Steffens (heftig)" <heftig@archlinux.org>,
        Jiaqi Yan <jiaqiyan@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        "Liam R. Howlett" <Liam.Howlett@oracle.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        "Mike Rapoport (IBM)" <rppt@kernel.org>,
        Muchun Song <muchun.song@linux.dev>,
        Nadav Amit <namit@vmware.com>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        Ryan Roberts <ryan.roberts@arm.com>,
        Shuah Khan <shuah@kernel.org>,
        Suleiman Souhlal <suleiman@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        "T.J. Alumbaugh" <talumbau@google.com>,
        Yu Zhao <yuzhao@google.com>,
        ZhangPeng <zhangpeng362@huawei.com>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v3 7/8] selftests/mm: refactor uffd_poll_thread to allow
 custom fault handlers
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On Fri, Jul 07, 2023 at 01:38:16PM -0700, Axel Rasmussen wrote:
> Ah, so I tried switching back to the {0} initializer, and was reminded
> why I didn't do that in v1. :) Ignoring the missing braces warning I
> talked about before, using {0} here is actually an error
> ("variable-sized object may not be initialized") because this is a
> variable sized array (nr_cpus isn't constant). So, that option is out.
> 
> I'm not a huge fan of adding the free() cleanup and dealing with all
> of the err() calls this function has.

Oh, that's definitely not needed - as long as we know we're going to quit,
we let kernel clean everything is fine.

I just worry in the future there can be a loop of userfaultfd_stress() so
it can OOM a host even if no err() hit but by looping.  I hope I explained
what I meant.. so it's still good we make sure things freed properly when
in success paths and when we're at it.

> 
> Originally I switched to calloc() because I'm not a big fan of VLAs
> anyway. But, as a compromise in v4 I'll leave it a VLA, and switch to
> memset() for initializing it.

That'll be good enough to me.  Thanks a lot,

-- 
Peter Xu