Re: fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '_x' is never less than zero.

From: Philip Li <philip.li@intel.com>
To: David Laight <david.laight.linux@gmail.com>,
	Dan Carpenter <dan.carpenter@linaro.org>
Cc: Alexandre Ghiti <alex@ghiti.fr>, Christoph Hellwig <hch@lst.de>,
	"kernel test robot" <lkp@intel.com>,
	<oe-kbuild-all@lists.linux.dev>, <linux-kernel@vger.kernel.org>,
	Carlos Maiolino <cem@kernel.org>,
	"Darrick J. Wong" <djwong@kernel.org>,
	<linux-riscv@lists.infradead.org>
Subject: Re: fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '_x' is never less than zero.
Date: Tue, 18 Feb 2025 08:39:21 +0800	[thread overview]
Message-ID: <Z7PWuSA4jtZnxp5J@rli9-mobl> (raw)
In-Reply-To: <20250217131203.2657cc4b@pumpkin>

+ 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@ghiti.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
> 

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