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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Sat, 10 Nov 2018 01:39:20 +0900
Message-ID: <CAK7LNATPuMXeMkoih0GuF7uq3WbS+t95iZF53=Nj46do0UVYWg@mail.gmail.com>
Subject: Re: [PATCH] Revert "scripts/setlocalversion: git: Make -dirty check
 more robust"
To:     Christian Kujau <lists@nerdbynature.de>
Cc:     Brian Norris <briannorris@chromium.org>, Genki Sky <sky@genki.is>,
        Guenter Roeck <linux@roeck-us.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Nov 7, 2018 at 12:05 PM Christian Kujau <lists@nerdbynature.de> wrote:
>
> On Tue, 6 Nov 2018, Brian Norris wrote:
> > > Perhaps both scenarios could be satisfied by having
> > > scripts/setlocalversion first check if .git has write permissions, and
> > > acting accordingly. Looking into history, this actually used to be
> > > done, but cdf2bc632ebc ("scripts/setlocalversion on write-protected
> > > source tree", 2013-06-14) removed the updating of the index.
> >
> > A "writeable" check (e.g., [ -w . ]) would be sufficient for our case.
> > But I'm not so sure about that older NFS report, and I'm also not sure
> > that we should be writing to the source tree at all in this case. Maybe
> > we can also check whether there's a build output directory specified?
>
> 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.


Hmm, interesting.

The result of "test -w ." depends on the implementation of "test" command.


Bash's build-in 'test' did a good job for me;
"test -w ." returns 1 for read-only mounted NFS.


For Busybox's 'test',
"test -w ." returns 0 for read-only
(or writable, but without no-root-squash) NFS.


> So I'm all for the $(touch .git/some-file-here) test to decide if the
> kernel has to be modified during build.
>
> Christian.
>
> [0] https://lkml.org/lkml/2013/6/14/574
> [1] https://manpages.debian.org/unstable/dash/dash.1.en.html
>
> > > However, I admit I don't understand the justification in that commit
> > > from 2013. I'm no NFS expert, but perhaps the real problem there is an
> > > incorrectly configured NFS setup (uid/gid mismatch between NFS
> > > client/server, or permissions mismatch between mount options and NFS
> > > server?). Christian Kujau: can you speak to that?
> > >
> > > Well, we could also make our check $(touch .git/some-file-here
> > > 2>/dev/null && ...) instead of $(test -w .git) to handle misconfigured
> > > NFS setups. But not sure if that has its own problems.
> >
> > Trying to 'touch' the source tree will also break us. No matter whether
> > you redirect stderr, our sandbox will still notice the build is doing
> > something fishy and complain.
>
> --
> BOFH excuse #192:
>
> runaway cat on system.


-- 
Best Regards
Masahiro Yamada