linux-kernel - Re: [kbuild] fs/fuse/dax.c:113 fuse_setup_one_mapping() warn: should 'start

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Date:   Tue, 11 May 2021 10:51:57 -0400
From:   Vivek Goyal <vgoyal@...hat.com>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>, kbuild@...ts.01.org,
        lkp@...el.com, kbuild-all@...ts.01.org,
        lkml <linux-kernel@...r.kernel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Liu Bo <bo.liu@...ux.alibaba.com>,
        Peng Tao <tao.peng@...ux.alibaba.com>
Subject: Re: [kbuild] fs/fuse/dax.c:113 fuse_setup_one_mapping() warn: should
 'start_idx << 21' be a 64 bit type?

On Tue, May 11, 2021 at 04:21:32PM +0200, Miklos Szeredi wrote:
> On Mon, May 3, 2021 at 3:27 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master
> > head:   9ccce092fc64d19504fa54de4fd659e279cc92e7
> > commit: c2d0ad00d948de73c78f05d2b3e5bdfa605035cc virtiofs: implement dax read/write operations
> > config: i386-randconfig-m031-20210503 (attached as .config)
> > compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@...el.com>
> > Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> >
> > New smatch warnings:
> > fs/fuse/dax.c:113 fuse_setup_one_mapping() warn: should 'start_idx << 21' be a 64 bit type?
> 
> Yes.
> 
> But does it make any sense to enable virtiofs and/or dax on 32bit
> guest? We sure aren't testing it, as seen from this bug report.
> 
> Vivek, what do you think?

Hi Miklos,

We sure are not testing it but looks like it is possible to compile it
on 32 bit systems. 

I can't think of a good reason that why virtiofs DAX should be disabled on 
32 bit systems. So I sent a patch series to fix this warning here.

https://lore.kernel.org/linux-fsdevel/20210506184304.321645-1-vgoyal@redhat.com/

Thanks
Vivek