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Date:   Wed, 27 May 2020 10:21:43 -0400
From:   Peter Xu <peterx@redhat.com>
To:     Xiaoming Ni <nixiaoming@huawei.com>
Cc:     aarcange@redhat.com, akpm@linux-foundation.org, cracauer@cons.org,
        dplotnikov@virtuozzo.com, gokhale2@llnl.gov, hannes@cmpxchg.org,
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Subject: Re: [PATCH v2 1/1] userfaultfd/sysctl: add
 vm.unprivileged_userfaultfd
Message-ID: <20200527142143.GC1194141@xz-x1>
References: <3b64de85-beb4-5a07-0093-cad6e8f2a8d8@huawei.com>
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On Wed, May 27, 2020 at 02:54:13PM +0800, Xiaoming Ni wrote:
> 
> On Tue, Mar 19, 2019 at 11:07:22AM +0800, Peter Xu wrote:
> > Add a global sysctl knob "vm.unprivileged_userfaultfd" to control
> > whether userfaultfd is allowed by unprivileged users.  When this is
> > set to zero, only privileged users (root user, or users with the
> > CAP_SYS_PTRACE capability) will be able to use the userfaultfd
> > syscalls.
> 
> Hello

Hi, Xiaoming,

> I am a bit confused about this patch, can you help to answer it.
> 
> Why the sysctl interface of fs/userfaultfd.c belongs to vm_table instead of
> fs_table ?
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cefdca0a86be517bc390fc4541e3674b8e7803b0

Because I think it makes more sense to put the new key into where it suites
better, irrelevant to which directory the variable is declared.  To me,
unprivileged_userfaultfd is definitely more suitable for vm rather than fs,
because userfaultfd is really about memory management rather than file system.

Thanks,

-- 
Peter Xu