On Fri, Jan 12, 2024 at 12:13 AM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> Hello Yu Zhao,
>
> The patch 081488051d28: "mm/mglru: fix underprotected page cache"
> from Dec 7, 2023 (linux-next), leads to the following Smatch static
> checker warning:
>
> mm/workingset.c:318 lru_gen_refault()
> warn: always true condition '(refs >= ((((1))) << (__builtin_choose_expr((4 == 4), (((2) < (64 - 26 - 3 - 3 - 0 - 10 - 0 - (8 + 14))) ?(2):(64 - 26 - 3 - 3 - 0 - 10 - 0 - (8 + 14))), ))) - 1) => (s32min-s32max >= 0)'
>
> mm/workingset.c
> 308 atomic_long_add(delta, &lrugen->refaulted[hist][type][tier]);
> 309 mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type, delta);
> 310
> 311 /*
> 312 * Count the following two cases as stalls:
> 313 * 1. For pages accessed through page tables, hotter pages pushed out
> 314 * hot pages which refaulted immediately.
> 315 * 2. For pages accessed multiple times through file descriptors,
> 316 * they would have been protected by sort_folio().
> 317 */
> --> 318 if (lru_gen_in_fault() || refs >= BIT(LRU_REFS_WIDTH) - 1) {
> ^^^^^^^^^^^^^^^^^^^^^^^
> In my x86 allmodconfig this is zero and refs is always >= 0. This could
> be intentional, but I thought it was worth checking.
Appreciate the manual work!
This indeed is intentional if LRU_REFS_WIDTH is 0. What would be the
best way to suppress this warning?
