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Date:   Sat, 16 Jan 2021 10:07:21 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Andy Lutomirski <luto@kernel.org>
Cc:     Arnd Bergmann <arnd@kernel.org>, Christoph Hellwig <hch@lst.de>,
        Ryan Houdek <sonicadvance1@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Minchan Kim <minchan@kernel.org>,
        Aleksa Sarai <cyphar@cyphar.com>,
        Sargun Dhillon <sargun@sargun.me>,
        Miklos Szeredi <mszeredi@redhat.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Amanieu d'Antras <amanieu@gmail.com>,
        Willem de Bruijn <willemb@google.com>,
        YueHaibing <yuehaibing@huawei.com>,
        Xiaoming Ni <nixiaoming@huawei.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
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        Arnaldo Carvalho de Melo <acme@redhat.com>,
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Subject: Re: [PATCH] Adds a new ioctl32 syscall for backwards compatibility
 layers
Message-ID: <20210116090721.GA30277@lst.de>
References: <20210106064807.253112-1-Sonicadvance1@gmail.com> <CAK8P3a2tV3HzPpbCR7mAeutx38_D2d-vfpEgpXv+GW_98w3VSQ@mail.gmail.com> <CABnRqDfQ5Qfa2ybut0qXcKuYnsMcG7+9gqjL-e7nZF1bkvhPRw@mail.gmail.com> <CAK8P3a2vfVfEWTk1ig349LGqt8bkK8YQWjE6PRyx+xvgYx7-gA@mail.gmail.com> <CALCETrUtyVaGSE9fcFAkhrGCpkyYcYnZb6tj8227o2EH5hgOfg@mail.gmail.com>
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On Fri, Jan 15, 2021 at 04:07:46PM -0800, Andy Lutomirski wrote:
> Finally, I'm not convinced that this patch works correctly.  We have
> in_compat_syscall(), and code that uses it may well be reachable from
> ioctl.

ioctls are the prime user of in_compat_syscall().

> I personally would like to see in_compat_syscall() go away,
> but some other people (Hi, Christoph!) disagree, and usage seems to be
> increasing, not decreasing.

I'm absolutely against it going away.  in_compat_syscall helped to
remove so much crap compared to the explicit compat syscalls.