Re: [PATCH v3 09/12] mm, swap: use the swap table to track the swap count

[Chris Li <chrisl@kernel.org>]

On Wed, Feb 18, 2026 at 4:23 AM Kairui Song <ryncsn@gmail.com> wrote:
>
> On Wed, Feb 18, 2026 at 06:40:16PM +0800, kernel test robot wrote:
> > Hi Kairui,
> >
> > kernel test robot noticed the following build warnings:
> >
> > [auto build test WARNING on d9982f38eb6e9a0cb6bdd1116cc87f75a1084aad]
> >
> > url:    https://github.com/intel-lab-lkp/linux/commits/Kairui-Song-via-B4-Relay/mm-swap-protect-si-swap_file-properly-and-use-as-a-mount-indicator/20260218-040852
> > base:   d9982f38eb6e9a0cb6bdd1116cc87f75a1084aad
> > patch link:    https://lore.kernel.org/r/20260218-swap-table-p3-v3-9-f4e34be021a7%40tencent.com
> > patch subject: [PATCH v3 09/12] mm, swap: use the swap table to track the swap count
> > config: i386-buildonly-randconfig-001-20260218 (https://download.01.org/0day-ci/archive/20260218/202602181835.58TEynxc-lkp@intel.com/config)
> > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260218/202602181835.58TEynxc-lkp@intel.com/reproduce)
> >
> > 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/202602181835.58TEynxc-lkp@intel.com/
> >
> > All warnings (new ones prefixed by >>):
> >
> > >> mm/swapfile.c:1627:6: warning: shift count >= width of type [-Wshift-count-overflow]
> >     1626 |                 VM_WARN_ON_ONCE(ci->extend_table[ci_off] >=
> >          |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >     1627 |                                 (BIT(BITS_PER_TYPE(ci->extend_table[0]))) - 1);
> >          |                                 ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    include/vdso/bits.h:7:26: note: expanded from macro 'BIT'
> >        7 | #define BIT(nr)                 (UL(1) << (nr))
> >          |                                        ^
> >    include/linux/mmdebug.h:123:50: note: expanded from macro 'VM_WARN_ON_ONCE'
> >      123 | #define VM_WARN_ON_ONCE(cond) (void)WARN_ON_ONCE(cond)
> >          |                                     ~~~~~~~~~~~~~^~~~~
> >    include/asm-generic/bug.h:120:25: note: expanded from macro 'WARN_ON_ONCE'
> >      120 |         int __ret_warn_on = !!(condition);                              \
> >          |                                ^~~~~~~~~
> >    1 warning generated.
>
> Nice catch from the bot. It's a new added sanity check in V3 just
> in case the swap count maybe grow larger than UINT_MAX, which should
> never happen, but just in case.
>
> I really should just use the existing helper macro for that:

With this fix up.

Acked-by: Chris Li <chrisl@kernel.org>

Chris

>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 801d8092be51..34b38255f72a 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1624,7 +1624,7 @@ static int __swap_cluster_dup_entry(struct swap_cluster_info *ci,
>                 }
>         } else if (count == SWP_TB_COUNT_MAX) {
>                 VM_WARN_ON_ONCE(ci->extend_table[ci_off] >=
> -                               (BIT(BITS_PER_TYPE(ci->extend_table[0]))) - 1);
> +                               type_max(typeof(ci->extend_table[0])));
>                 ++ci->extend_table[ci_off];
>         } else {
>                 /* Never happens unless counting went wrong */
>