Re: [PATCH V2 4/6] mm: rename the global section array to mem_sections

[Dong Aisheng <dongas86@gmail.com>]

On Tue, Jun 1, 2021 at 4:22 PM David Hildenbrand <david@redhat.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@linux-foundation.org>
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Baoquan He <bhe@redhat.com>
> > Cc: Vivek Goyal <vgoyal@redhat.com>
> > Cc: kexec@lists.infradead.org
> > Signed-off-by: Dong Aisheng <aisheng.dong@nxp.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.

Regards
Aisheng

>
> --
> Thanks,
>
> David / dhildenb
>