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From:   Brian Norris <briannorris@chromium.org>
Date:   Tue, 6 Nov 2018 20:00:36 -0800
Message-ID: <CA+ASDXPMMXCBN6PU8qzRm579sC9VBdwnxZdZwRdPY1cBUP8oGQ@mail.gmail.com>
Subject: Re: [PATCH] Revert "scripts/setlocalversion: git: Make -dirty check
 more robust"
To:     lists@nerdbynature.de
Cc:     sky@genki.is, Guenter Roeck <linux@roeck-us.net>,
        yamada.masahiro@socionext.com,
        Linux Kernel <linux-kernel@vger.kernel.org>
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On Tue, Nov 6, 2018 at 6:58 PM Christian Kujau <lists@nerdbynature.de> wrote:
> FWIW, the issue I reported back in 2013[0] was not an ill-configured NFS
> export, but a read-only NFS export (and then a read-write exported NFS
> export, but the user compiling the kernel did not have write permission)
> and so "test -w .git" did not help in determining if the source tree can
> actually written to. And depending on the user's shell[1], this may or may
> not still be the case.

What do you mean, "depending on the user's shell"? AFAICT, it's not
really a shell-specific question, since POSIX defines '-w':

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/test.html

(I highly doubt we care about a non-POSIX /bin/sh.)

But the dash man-page you point at is correctly noting that 'test -w'
isn't sufficient for noticing a read-only mount (i.e., you have
permissions, but the mount isn't writeable). Contrary to what Guenter
said in his reply, our build isn't actually off a read-only mount --
it's just running without these write permissions, so 'test -w' will
do the right thing.

> So I'm all for the $(touch .git/some-file-here) test to decide if the
> kernel has to be modified during build.

I suppose that could work, if you do that only after checking 'test
-w'. It's important to not even try to write to the source tree when
not permitted.

On a different tangent: how about the --no-optional-locks (see
git(1))? Will this get you your "up-to-date" result without writing to
the .git directory? I've only read the documentation, but not tested
it.

Brian

> Christian.
>
> [0] https://lkml.org/lkml/2013/6/14/574
> [1] https://manpages.debian.org/unstable/dash/dash.1.en.html