[PATCH] mm: avoid shadowing global mem_map in sparse_init_one_section()

[PATCH] mm: avoid shadowing global mem_map in sparse_init_one_section()

[Anuradha Weeraman]

With W=2, sparse_init_one_section() warns because its mem_map parameter
shadows the global mem_map declaration in linux/mmzone.h.

Rename it to section_mem_map to make that scope explicit and avoid the
shadowing warning.

No functional change.

Signed-off-by: Anuradha Weeraman <anuradha@debian.org>
---
 mm/internal.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 181e79f1d6a2..4943def97167 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -957,7 +957,7 @@ void sparse_init(void);
 int sparse_index_init(unsigned long section_nr, int nid);
 
 static inline void sparse_init_one_section(struct mem_section *ms,
-		unsigned long pnum, struct page *mem_map,
+		unsigned long pnum, struct page *section_mem_map,
 		struct mem_section_usage *usage, unsigned long flags)
 {
 	unsigned long coded_mem_map;
@@ -969,7 +969,7 @@ static inline void sparse_init_one_section(struct mem_section *ms,
 	 * page_to_pfn() on !CONFIG_SPARSEMEM_VMEMMAP can simply subtract it
 	 * from the page pointer to obtain the PFN.
 	 */
-	coded_mem_map = (unsigned long)(mem_map - section_nr_to_pfn(pnum));
+	coded_mem_map = (unsigned long)(section_mem_map - section_nr_to_pfn(pnum));
 	VM_WARN_ON_ONCE(coded_mem_map & ~SECTION_MAP_MASK);
 
 	ms->section_mem_map &= ~SECTION_MAP_MASK;
-- 
2.53.0

Re: [PATCH] mm: avoid shadowing global mem_map in sparse_init_one_section()

[Mike Rapoport]

On Sat, Jul 04, 2026 at 11:54:51PM +0530, Anuradha Weeraman wrote:
> With W=2, sparse_init_one_section() warns because its mem_map parameter
> shadows the global mem_map declaration in linux/mmzone.h.
> 
> Rename it to section_mem_map to make that scope explicit and avoid the
> shadowing warning.

I suspect that the comment in mmzone.h saying that mem_map is must be
declared for SPARSEMEM is stale and it can be guarded by #ifdef
CONFIG_FLATMEM which will be a more correct fix.
 
> No functional change.
> 
> Signed-off-by: Anuradha Weeraman <anuradha@debian.org>
> ---
>  mm/internal.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/internal.h b/mm/internal.h
> index 181e79f1d6a2..4943def97167 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -957,7 +957,7 @@ void sparse_init(void);
>  int sparse_index_init(unsigned long section_nr, int nid);
>  
>  static inline void sparse_init_one_section(struct mem_section *ms,
> -		unsigned long pnum, struct page *mem_map,
> +		unsigned long pnum, struct page *section_mem_map,
>  		struct mem_section_usage *usage, unsigned long flags)
>  {
>  	unsigned long coded_mem_map;
> @@ -969,7 +969,7 @@ static inline void sparse_init_one_section(struct mem_section *ms,
>  	 * page_to_pfn() on !CONFIG_SPARSEMEM_VMEMMAP can simply subtract it
>  	 * from the page pointer to obtain the PFN.
>  	 */
> -	coded_mem_map = (unsigned long)(mem_map - section_nr_to_pfn(pnum));
> +	coded_mem_map = (unsigned long)(section_mem_map - section_nr_to_pfn(pnum));
>  	VM_WARN_ON_ONCE(coded_mem_map & ~SECTION_MAP_MASK);
>  
>  	ms->section_mem_map &= ~SECTION_MAP_MASK;
> -- 
> 2.53.0
> 
> 

-- 
Sincerely yours,
Mike.

Re: [PATCH] mm: avoid shadowing global mem_map in sparse_init_one_section()

[David Hildenbrand (Arm)]

On 7/5/26 11:17, Mike Rapoport wrote:
> On Sat, Jul 04, 2026 at 11:54:51PM +0530, Anuradha Weeraman wrote:
>> With W=2, sparse_init_one_section() warns because its mem_map parameter
>> shadows the global mem_map declaration in linux/mmzone.h.
>>
>> Rename it to section_mem_map to make that scope explicit and avoid the
>> shadowing warning.
> 
> I suspect that the comment in mmzone.h saying that mem_map is must be
> declared for SPARSEMEM is stale and it can be guarded by #ifdef
> CONFIG_FLATMEM which will be a more correct fix.
>  

Unrelated to that, I thought we don't particularly care about W=2 stuff unless
it uncovers a real bug?

-- 
Cheers,

David