linux-kernel - Re: fs/dlm/midcomms.c:913:22: sparse: sparse: restricted _

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Message-ID: <Ygnk6niBpaxF8rwr@zeniv-ca.linux.org.uk>
Date:   Mon, 14 Feb 2022 05:13:14 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Alexander Aring <aahringo@...hat.com>
Cc:     kernel test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, David Teigland <teigland@...hat.com>,
        cluster-devel <cluster-devel@...hat.com>
Subject: Re: fs/dlm/midcomms.c:913:22: sparse: sparse: restricted __le32
 degrades to integer

On Sat, Jan 22, 2022 at 01:28:20PM -0500, Alexander Aring wrote:
> Hi,
> 
> On Fri, Jan 21, 2022 at 9:45 PM kernel test robot <lkp@...el.com> wrote:
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   9b57f458985742bd1c585f4c7f36d04634ce1143
> > commit: 658bd576f95ed597e519cdadf1c86ac87c17aea5 fs: dlm: move version conversion to compile time
> > date:   3 months ago
> > config: x86_64-rhel-8.3-kselftests (https://download.01.org/0day-ci/archive/20220122/202201221028.YKA8kSdm-lkp@intel.com/config)
> > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> > reproduce:
> >         # apt-get install sparse
> >         # sparse version: v0.6.4-dirty
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=658bd576f95ed597e519cdadf1c86ac87c17aea5
> >         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> >         git fetch --no-tags linus master
> >         git checkout 658bd576f95ed597e519cdadf1c86ac87c17aea5
> >         # save the config file to linux build tree
> >         mkdir build_dir
> >         make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash
> >
> > If you fix the issue, kindly add following tag as appropriate
> 
> I have it on my list but it isn't easy to make sparse happy here...
> this is the second time the robot reported this issue. Is there a way
> to turn the robot off in that case?
> 
> Maybe some human who reads that knows the answer?

Frankly, these "convert in place" functions (dlm_message_in(), etc.) are
asking for trouble.  IOW, it's a genuinely fishy code.

Saner approach is to keep them in little-endian through the entire thing,
but it's quite a bit of massage.