linux-kernel - Re: [PATCH 3/4] btrfs: Add zstd support

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Message-ID: <20170626121230.GF2866@twin.jikos.cz>
Date:   Mon, 26 Jun 2017 14:12:30 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Adam Borowski <kilobyte@...band.pl>
Cc:     Nick Terrell <terrelln@...com>, kernel-team@...com,
        Chris Mason <clm@...com>, Yann Collet <cyan@...com>,
        squashfs-devel@...ts.sourceforge.net, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] btrfs: Add zstd support

On Sun, Jun 25, 2017 at 11:30:22PM +0200, Adam Borowski wrote:
> On Mon, Jun 26, 2017 at 03:03:17AM +0800, kbuild test robot wrote:
> > Hi Nick,
> > 
> > url:    https://github.com/0day-ci/linux/commits/Nick-Terrell/lib-Add-xxhash-module/20170625-214344
> > config: i386-allmodconfig (attached as .config)
> > compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
> > reproduce:
> >         # save the attached .config to linux build tree
> >         make ARCH=i386 
> > 
> > All errors (new ones prefixed by >>):
> > 
> > >> ERROR: "__udivdi3" [lib/zstd/zstd_compress.ko] undefined!
> >    ERROR: "__udivdi3" [fs/ufs/ufs.ko] undefined!
> 
> Just to save you time to figure it out:
> for division when one or both arguments are longer than the architecture's
> word, gcc uses helper functions that are included when compiling in a hosted
> environment -- but not in freestanding.
> 
> Thus, you want do_div() instead of /; do check widths and signedness of
> arguments.

No do_div please, div_u64 or div64_u64.