Re: [linux-next:master 5002/7443] include/linux/compiler_types.h:357:45: error: call to '__compiletime_assert_474' declared with attribute error: BUILD_BUG_ON failed: PERCPU_DYNAMIC_EARLY_SIZE < NR_KMALLOC_TYPES * KMALLOC_SHIFT_HIGH * sizeof(struct kmem_cache_cpu)

[Vlastimil Babka <vbabka@suse.cz>]

On 11/14/22 08:44, Baoquan He wrote:
> Hi,
> 
> I reproduced the build failure according to lkp report and made a patch
> as below to fix it.
> 
> From dae7dd9705015ce36db757e88c78802584f949b1 Mon Sep 17 00:00:00 2001
> From: Baoquan He <bhe@redhat.com>
> Date: Sun, 13 Nov 2022 18:08:27 +0800
> Subject: [PATCH] percpu: adjust the value of PERCPU_DYNAMIC_EARLY_SIZE
> Content-type: text/plain
> 
> LKP reported a build failure as below on the patch "mm/slub, percpu:
> correct the calculation of early percpu allocation size"

Since I have that patch in slab.git exposed to -next, should I take this fix
too, to make things simpler? Dennis?

> ~~~~~~
> In file included from <command-line>:
> In function 'alloc_kmem_cache_cpus',
>    inlined from 'kmem_cache_open' at mm/slub.c:4340:6:
>>> include/linux/compiler_types.h:357:45: error: call to '__compiletime_assert_474' declared with attribute error:
> BUILD_BUG_ON failed: PERCPU_DYNAMIC_EARLY_SIZE < NR_KMALLOC_TYPES * KMALLOC_SHIFT_HIGH * sizeof(struct kmem_cache_cpu)
>      357 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> ~~~~~~
> 
> From the kernel config file provided by LKP, the building was made on
> arm64 with below Kconfig item enabled:
> 
>   CONFIG_ZONE_DMA=y
>   CONFIG_SLUB_CPU_PARTIAL=y
>   CONFIG_DEBUG_LOCK_ALLOC=y
>   CONFIG_SLUB_STATS=y
>   CONFIG_ARM64_PAGE_SHIFT=16
>   CONFIG_ARM64_64K_PAGES=y
> 
> Then we will have:
>   NR_KMALLOC_TYPES:4
>   KMALLOC_SHIFT_HIGH:17
>   sizeof(struct kmem_cache_cpu):184
> 
> The product of them is 12512, which is bigger than PERCPU_DYNAMIC_EARLY_SIZE,
> 12K. Hence, the BUILD_BUG_ON in alloc_kmem_cache_cpus() is triggered.
> 
> Earlier, in commit 099a19d91ca4 ("percpu: allow limited allocation
> before slab is online"), PERCPU_DYNAMIC_EARLY_SIZE was introduced and
> set to 12K which is equal to the then PERPCU_DYNAMIC_RESERVE.
> Later, in commit 1a4d76076cda ("percpu: implement asynchronous chunk
> population"), PERPCU_DYNAMIC_RESERVE was increased by 8K, while
> PERCPU_DYNAMIC_EARLY_SIZE was kept unchanged.
> 
> So, here increase PERCPU_DYNAMIC_EARLY_SIZE by 8K too to accommodate to
> the slub's requirement.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  include/linux/percpu.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/percpu.h b/include/linux/percpu.h
> index 70bc17db00a6..1338ea2aa720 100644
> --- a/include/linux/percpu.h
> +++ b/include/linux/percpu.h
> @@ -41,7 +41,7 @@
>   * for this.  Keep PERCPU_DYNAMIC_RESERVE equal to or larger than
>   * PERCPU_DYNAMIC_EARLY_SIZE.
>   */
> -#define PERCPU_DYNAMIC_EARLY_SIZE	(12 << 10)
> +#define PERCPU_DYNAMIC_EARLY_SIZE	(20 << 10)
>  
>  /*
>   * PERCPU_DYNAMIC_RESERVE indicates the amount of free area to piggy