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Wed, 27 May 2020 07:21:48 -0700 (PDT) Received: from xz-x1 ([2607:9880:19c0:32::2]) by smtp.gmail.com with ESMTPSA id 88sm2618476qth.9.2020.05.27.07.21.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 May 2020 07:21:45 -0700 (PDT) Date: Wed, 27 May 2020 10:21:43 -0400 From: Peter Xu To: Xiaoming Ni Cc: aarcange@redhat.com, akpm@linux-foundation.org, cracauer@cons.org, dplotnikov@virtuozzo.com, gokhale2@llnl.gov, hannes@cmpxchg.org, hughd@google.com, jglisse@redhat.com, kirill@shutemov.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org, maxime.coquelin@redhat.com, mcfadden8@llnl.gov, mcgrof@kernel.org, mgorman@suse.de, mike.kravetz@oracle.com, pbonzini@redhat.com, rppt@linux.vnet.ibm.com, xemul@virtuozzo.com, keescook@chromium.org 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> MIME-Version: 1.0 In-Reply-To: <3b64de85-beb4-5a07-0093-cad6e8f2a8d8@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: 2EED0180BC833 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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