Re: mm/workingset.c:621 workingset_update_node() warn: unsigned '_x' is never less than zero.

[Andrew Morton <akpm@linux-foundation.org>]

On Sun, 16 Feb 2025 03:56:06 +0800 kernel test robot <lkp@intel.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   7ff71e6d923969d933e1ba7e0db857782d36cd19
> commit: 4715c6a753dccd15fd3a8928168f57e349205bd4 mm: cleanup WORKINGSET_NODES in workingset
> date:   9 months ago
> config: riscv-randconfig-r073-20250213 (https://download.01.org/0day-ci/archive/20250216/202502160323.ZLUfooA0-lkp@intel.com/config)
> compiler: riscv32-linux-gcc (GCC) 14.2.0
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202502160323.ZLUfooA0-lkp@intel.com/
> 
> New smatch warnings:
> mm/workingset.c:621 workingset_update_node() warn: unsigned '_x' is never less than zero.
> mm/workingset.c:746 shadow_lru_isolate() warn: unsigned '_x' is never less than zero.
> 
> Old smatch warnings:
> include/linux/mm.h:1306 virt_to_head_page() warn: unsigned '_x' is never less than zero.
> 
> vim +/_x +621 mm/workingset.c
> 
>    617	
>    618	void workingset_update_node(struct xa_node *node)
>    619	{
>    620		struct address_space *mapping;
>  > 621		struct page *page = virt_to_page(node);

We're seeing several reports like this.  It looks like the RISC-V
virt_to_page() (actualy __pa) implementation needs some attention.