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Subject: Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9]
From: Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <23894.1531438559@warthog.procyon.org.uk>
Date: Thu, 12 Jul 2018 16:50:13 -0700
Cc: "Theodore Y. Ts'o" <tytso@mit.edu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Lutomirski <luto@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linux API <linux-api@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Jann Horn <jannh@google.com>
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References: <611054C7-D6E8-4C89-958E-3128C9305E1E@amacapital.net> <20180712223223.GA28610@thunk.org> <CA+55aFw1WyKY+-2dg62M-QT_F0-waCTCrba1DW4dStYz-f_fjA@mail.gmail.com> <153126248868.14533.9751473662727327569.stgit@warthog.procyon.org.uk> <153126264966.14533.3388004240803696769.stgit@warthog.procyon.org.uk> <686E805C-81F3-43D0-A096-50C644C57EE3@amacapital.net> <22370.1531293761@warthog.procyon.org.uk> <CALCETrU3kbh-ZRHDj7-Asq+OH-35dQ2p_erpHpYUvN5+BdAoVQ@mail.gmail.com> <7002.1531407244@warthog.procyon.org.uk> <CA+55aFx+xm333ZZ7d2Z39QuhDu=0XM6nTMChbHvWQOXNk32yxw@mail.gmail.com> <16699.1531426991@warthog.procyon.org.uk> <18233.1531430797@warthog.procyon.org.uk> <22105.1531436081@warthog.procyon.org.uk> <23894.1531438559@warthog.procyon.org.uk>
To: David Howells <dhowells@redhat.com>
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> On Jul 12, 2018, at 4:35 PM, David Howells <dhowells@redhat.com> wrote:
>=20
> Andy Lutomirski <luto@amacapital.net> wrote:
>=20
>> I tend to think that this *should* fail using the new API.  The semantics=
 of
>> the second mount request are bizarre at best.
>=20
> You still have to support existing behaviour lest you break userspace.
>=20

I assume the existing behavior is that a bind mount is created?  If so, the n=
ew mount(8) tool could do it in user code.=