linux-kernel - Re: [PATCH 06/24] fs: add a kern

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Message-ID: <20200720181706.GR2786714@ZenIV.linux.org.uk>
Date:   Mon, 20 Jul 2020 19:17:06 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH 06/24] fs: add a kern_chdir helper

On Mon, Jul 20, 2020 at 05:58:44PM +0200, Christoph Hellwig wrote:
> Add a simple helper for a chdir with a kernelspace name and use it in the
> early init code instead of relying on the implicit set_fs(KERNEL_DS)
> there.  Remove the now unused ksys_chdir.

FWIW, my problem with that is that you are making it first-class primitive.
And I don't see any valid use for it - existing one is really "we have
a userland process that would be making syscalls if we only could have it
done right; the only reason we can't is that the infrastructure to build
the binary would be hell to maintain in the tree".  It's *NOT* "kernel
code that has a valid reason to get the syscall functionality".