linux-kernel - Re: fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '

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Message-ID: <Z7PWuSA4jtZnxp5J@rli9-mobl>
Date: Tue, 18 Feb 2025 08:39:21 +0800
From: Philip Li <philip.li@...el.com>
To: David Laight <david.laight.linux@...il.com>, Dan Carpenter
	<dan.carpenter@...aro.org>
CC: Alexandre Ghiti <alex@...ti.fr>, Christoph Hellwig <hch@....de>, "kernel
 test robot" <lkp@...el.com>, <oe-kbuild-all@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, Carlos Maiolino <cem@...nel.org>, "Darrick J.
 Wong" <djwong@...nel.org>, <linux-riscv@...ts.infradead.org>
Subject: Re: fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '_x'
 is never less than zero.

+ Dan

Hi Dan,

On Mon, Feb 17, 2025 at 01:12:03PM +0000, David Laight wrote:
> On Mon, 17 Feb 2025 13:06:49 +0100
> Alexandre Ghiti <alex@...ti.fr> wrote:
> 
> > Hi Christoph,
> > 
> > On 17/02/2025 10:24, Christoph Hellwig wrote:
> > > On Mon, Feb 17, 2025 at 01:53:08PM +0800, kernel test robot wrote:  
> > >> New smatch warnings:
> > >> fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '_x' is never less than zero.  
> > > Looks like this is an issue in the riscv virt_to_page implementation
> > > which also shows up in various other places.  Any chance this could get
> > > fixed in the riscv code?  
> > 
> > 
> > To me, the only test that could give rise to this warning is the last 
> > part of:
> > 
> > #define is_linear_mapping(x) \
> >          ((x) >= PAGE_OFFSET && (!IS_ENABLED(CONFIG_64BIT) || (x) < 
> > PAGE_OFFSET + KERN_VIRT_SIZE))
> > 
> > But given that the config is a 32-bit config, it should not be evaluated 
> > at all.
> > 
> > Could that be a false-positive and then an issue in smatch?
> 
> Why is smatch even looking.
> The equivalent check in gcc has been moved to -W2 because of all false positives.

Can you help check this one?

Thanks

> 
> 	David
>