On Tue, Feb 25, 2025 at 11:30:20PM +0800, Jingxiang Zeng wrote:
> From: Zeng Jingxiang <linuszeng@xxxxxxxxxxx>
>
> In the following memcg_list_lru_alloc() function, mlru here is almost
> always NULL, so in most cases this should save a function call, mark
> mlru as unlikely to optimize the code.
> do {
> xas_lock_irqsave(&xas, flags);
> if (!xas_load(&xas) && !css_is_dying(&pos->css)) {
> xas_store(&xas, mlru);
> if (!xas_error(&xas))
> mlru = NULL;
> }
> xas_unlock_irqrestore(&xas, flags);
> } while (xas_nomem(&xas, GFP_KERNEL));
> > if (mlru)
> kfree(mlru);
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-kbuild-all/202412290924.UTP7GH2Z-lkp@xxxxxxxxx/
> Signed-off-by: Zeng Jingxiang <linuszeng@xxxxxxxxxxx>
> ---
> mm/list_lru.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index 064d2018e265..e7e13513ff8e 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -552,7 +552,7 @@ static int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru)
> }
> xas_unlock_irqrestore(&xas, flags);
> } while (xas_nomem(&xas, GFP_KERNEL));
> - if (mlru)
> + if (unlikely(mlru))
> kfree(mlru);
The report is saying not to check at all. So, just remove the check and
simply call kfree(mlru) as it handles the NULL check efficiently.
> set_active_memcg(cur);
> } while (pos != memcg && !css_is_dying(&pos->css));
> --
> 2.43.5
>
>
