linux-kernel - Re: [PATCH] percpu: Make pcpu_setup_first

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Date:   Thu, 4 Jul 2019 00:20:53 -0400
From:   Dennis Zhou <dennis@...nel.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] percpu: Make pcpu_setup_first_chunk() void function

On Wed, Jul 03, 2019 at 04:25:52PM +0800, Kefeng Wang wrote:
> pcpu_setup_first_chunk() will panic or BUG_ON if the are some
> error and doesn't return any error, hence it can be defined to
> return void.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>  arch/ia64/mm/contig.c    |  5 +----
>  arch/ia64/mm/discontig.c |  5 +----
>  include/linux/percpu.h   |  2 +-
>  mm/percpu.c              | 17 ++++++-----------
>  4 files changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/ia64/mm/contig.c b/arch/ia64/mm/contig.c
> index d29fb6b9fa33..db09a693f094 100644
> --- a/arch/ia64/mm/contig.c
> +++ b/arch/ia64/mm/contig.c
> @@ -134,10 +134,7 @@ setup_per_cpu_areas(void)
>  	ai->atom_size		= page_size;
>  	ai->alloc_size		= percpu_page_size;
>  
> -	rc = pcpu_setup_first_chunk(ai, __per_cpu_start + __per_cpu_offset[0]);
> -	if (rc)
> -		panic("failed to setup percpu area (err=%d)", rc);
> -
> +	pcpu_setup_first_chunk(ai, __per_cpu_start + __per_cpu_offset[0]);
>  	pcpu_free_alloc_info(ai);
>  }
>  #else
> diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
> index 05490dd073e6..004dee231874 100644
> --- a/arch/ia64/mm/discontig.c
> +++ b/arch/ia64/mm/discontig.c
> @@ -245,10 +245,7 @@ void __init setup_per_cpu_areas(void)
>  		gi->cpu_map		= &cpu_map[unit];
>  	}
>  
> -	rc = pcpu_setup_first_chunk(ai, base);
> -	if (rc)
> -		panic("failed to setup percpu area (err=%d)", rc);
> -
> +	pcpu_setup_first_chunk(ai, base);
>  	pcpu_free_alloc_info(ai);
>  }
>  #endif
> diff --git a/include/linux/percpu.h b/include/linux/percpu.h
> index 9909dc0e273a..5e76af742c80 100644
> --- a/include/linux/percpu.h
> +++ b/include/linux/percpu.h
> @@ -105,7 +105,7 @@ extern struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups,
>  							     int nr_units);
>  extern void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai);
>  
> -extern int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
> +extern void __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
>  					 void *base_addr);
>  
>  #ifdef config_need_per_cpu_embed_first_chunk
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 9821241fdede..ad32c3d11ca7 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -2267,12 +2267,9 @@ static void pcpu_dump_alloc_info(const char *lvl,
>   * share the same vm, but use offset regions in the area allocation map.
>   * the chunk serving the dynamic region is circulated in the chunk slots
>   * and available for dynamic allocation like any other chunk.
> - *
> - * returns:
> - * 0 on success, -errno on failure.
>   */
> -int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
> -				  void *base_addr)
> +void __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
> +				   void *base_addr)
>  {
>  	size_t size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
>  	size_t static_size, dyn_size;
> @@ -2457,7 +2454,6 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
>  
>  	/* we're done */
>  	pcpu_base_addr = base_addr;
> -	return 0;
>  }
>  
>  #ifdef config_smp
> @@ -2710,7 +2706,7 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
>  	struct pcpu_alloc_info *ai;
>  	size_t size_sum, areas_size;
>  	unsigned long max_distance;
> -	int group, i, highest_group, rc;
> +	int group, i, highest_group, rc = 0;
>  
>  	ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
>  				   cpu_distance_fn);
> @@ -2795,7 +2791,7 @@ int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
>  		pfn_down(size_sum), ai->static_size, ai->reserved_size,
>  		ai->dyn_size, ai->unit_size);
>  
> -	rc = pcpu_setup_first_chunk(ai, base);
> +	pcpu_setup_first_chunk(ai, base);
>  	goto out_free;
>  
>  out_free_areas:
> @@ -2920,7 +2916,7 @@ int __init pcpu_page_first_chunk(size_t reserved_size,
>  		unit_pages, psize_str, ai->static_size,
>  		ai->reserved_size, ai->dyn_size);
>  
> -	rc = pcpu_setup_first_chunk(ai, vm.addr);
> +	pcpu_setup_first_chunk(ai, vm.addr);
>  	goto out_free_ar;
>  
>  enomem:
> @@ -3014,8 +3010,7 @@ void __init setup_per_cpu_areas(void)
>  	ai->groups[0].nr_units = 1;
>  	ai->groups[0].cpu_map[0] = 0;
>  
> -	if (pcpu_setup_first_chunk(ai, fc) < 0)
> -		panic("failed to initialize percpu areas.");
> +	pcpu_setup_first_chunk(ai, fc);
>  	pcpu_free_alloc_info(ai);
>  }
>  
> -- 
> 2.20.1
> 

Hi Kefeng,

This makes sense to me. I've applied this to for-5.4.

Thanks,
Dennis