linux-kernel - Re: [PATCH 4/5] mm: rename the global section array to mem

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Date:   Tue, 25 May 2021 09:55:09 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Dong Aisheng <aisheng.dong@....com>, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, dongas86@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>, kexec@...ts.infradead.org
Subject: Re: [PATCH 4/5] mm: rename the global section array to mem_sections

On 17.05.21 13:20, Dong Aisheng wrote:
> In order to distinguish the struct mem_section for a better code
> readability and align with kernel doc [1] name below, change the
> global mem section name to 'mem_sections' from 'mem_section'.
> 
> [1] Documentation/vm/memory-model.rst
> "The `mem_section` objects are arranged in a two-dimensional array
> called `mem_sections`."
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Dave Young <dyoung@...hat.com>
> Cc: Baoquan He <bhe@...hat.com>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: kexec@...ts.infradead.org
> Signed-off-by: Dong Aisheng <aisheng.dong@....com>
> ---
>   include/linux/mmzone.h | 10 +++++-----
>   kernel/crash_core.c    |  4 ++--
>   mm/sparse.c            | 16 ++++++++--------
>   3 files changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index fc23e36cb165..b348a06915c5 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1297,9 +1297,9 @@ struct mem_section {
>   #define SECTION_ROOT_MASK	(SECTIONS_PER_ROOT - 1)
>   
>   #ifdef CONFIG_SPARSEMEM_EXTREME
> -extern struct mem_section **mem_section;
> +extern struct mem_section **mem_sections;
>   #else
> -extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
> +extern struct mem_section mem_sections[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
>   #endif
>   
>   static inline unsigned long *section_to_usemap(struct mem_section *ms)
> @@ -1310,12 +1310,12 @@ static inline unsigned long *section_to_usemap(struct mem_section *ms)
>   static inline struct mem_section *__nr_to_section(unsigned long nr)
>   {
>   #ifdef CONFIG_SPARSEMEM_EXTREME
> -	if (!mem_section)
> +	if (!mem_sections)
>   		return NULL;
>   #endif
> -	if (!mem_section[SECTION_NR_TO_ROOT(nr)])
> +	if (!mem_sections[SECTION_NR_TO_ROOT(nr)])
>   		return NULL;
> -	return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
> +	return &mem_sections[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
>   }
>   extern unsigned long __section_nr(struct mem_section *ms);
>   extern size_t mem_section_usage_size(void);
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 29cc15398ee4..fb1180d81b5a 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -414,8 +414,8 @@ static int __init crash_save_vmcoreinfo_init(void)
>   	VMCOREINFO_SYMBOL(contig_page_data);
>   #endif
>   #ifdef CONFIG_SPARSEMEM
> -	VMCOREINFO_SYMBOL_ARRAY(mem_section);
> -	VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);
> +	VMCOREINFO_SYMBOL_ARRAY(mem_sections);
> +	VMCOREINFO_LENGTH(mem_sections, NR_SECTION_ROOTS);
>   	VMCOREINFO_STRUCT_SIZE(mem_section);
>   	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>   	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
> diff --git a/mm/sparse.c b/mm/sparse.c
> index df4418c12f04..a96e7e65475f 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -24,12 +24,12 @@
>    * 1) mem_section	- memory sections, mem_map's for valid memory
>    */
>   #ifdef CONFIG_SPARSEMEM_EXTREME
> -struct mem_section **mem_section;
> +struct mem_section **mem_sections;
>   #else
> -struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
> +struct mem_section mem_sections[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
>   	____cacheline_internodealigned_in_smp;
>   #endif
> -EXPORT_SYMBOL(mem_section);
> +EXPORT_SYMBOL(mem_sections);
>   
>   #ifdef NODE_NOT_IN_PAGE_FLAGS
>   /*
> @@ -91,14 +91,14 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
>   	 *
>   	 * The mem_hotplug_lock resolves the apparent race below.
>   	 */
> -	if (mem_section[root])
> +	if (mem_sections[root])
>   		return 0;
>   
>   	section = sparse_index_alloc(nid);
>   	if (!section)
>   		return -ENOMEM;
>   
> -	mem_section[root] = section;
> +	mem_sections[root] = section;
>   
>   	return 0;
>   }
> @@ -131,7 +131,7 @@ unsigned long __section_nr(struct mem_section *ms)
>   #else
>   unsigned long __section_nr(struct mem_section *ms)
>   {
> -	return (unsigned long)(ms - mem_section[0]);
> +	return (unsigned long)(ms - mem_sections[0]);
>   }
>   #endif
>   
> @@ -286,8 +286,8 @@ static void __init memblocks_present(void)
>   #ifdef CONFIG_SPARSEMEM_EXTREME
>   	size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
>   	align = 1 << (INTERNODE_CACHE_SHIFT);
> -	mem_section = memblock_alloc(size, align);
> -	if (!mem_section)
> +	mem_sections = memblock_alloc(size, align);
> +	if (!mem_sections)
>   		panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
>   		      __func__, size, align);
>   #endif
> 

Smells like unnecessary code churn. I'd rather just fix the doc because 
it doesn't really improve readability IMHO.

Anyhow, just my 2 cents.

-- 
Thanks,

David / dhildenb