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Message-ID: <f7f77368-72cf-e15d-cc3c-b0ddf86e14fd@redhat.com>
Date: Tue, 1 Jun 2021 10:40:09 +0200
From: David Hildenbrand <david@...hat.com>
To: Dong Aisheng <dongas86@...il.com>
Cc: Dong Aisheng <aisheng.dong@....com>, linux-mm@...ck.org,
open list <linux-kernel@...r.kernel.org>,
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 V2 4/6] mm: rename the global section array to
mem_sections
On 01.06.21 10:37, Dong Aisheng wrote:
> On Tue, Jun 1, 2021 at 4:22 PM David Hildenbrand <david@...hat.com> wrote:
>>
>> On 31.05.21 11:19, 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>
>>> ---
>>> v1->v2:
>>> * no changes
>>> ---
>>> 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 a6bfde85ddb0..0ed61f32d898 100644
>>> --- a/include/linux/mmzone.h
>>> +++ b/include/linux/mmzone.h
>>> @@ -1302,9 +1302,9 @@ 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)
>>> @@ -1315,12 +1315,12 @@ 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 d02ee6bb7cbc..6412010478f7 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
>>> /*
>>> @@ -66,8 +66,8 @@ static void __init sparse_alloc_section_roots(void)
>>>
>>> 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);
>>> }
>>> @@ -103,14 +103,14 @@ 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;
>>> }
>>> @@ -145,7 +145,7 @@ 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
>>>
>>>
>>
>> I repeat: unnecessary code churn IMHO.
>
> Hi David,
>
> Thanks, i explained the reason during my last reply.
> Andrew has already picked this patch to -mm tree.
Just because it's in Andrews tree doesn't mean it will end up upstream. ;)
Anyhow, no really strong opinion, it's simply unnecessary code churn
that makes bisecting harder without real value IMHO.
--
Thanks,
David / dhildenb
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