[v1] mm: memory hot(un)plug and SPARSEMEM cleanups

[PATCH 04/14] mm/memory_hotplug: simplify check_pfn_span()

Posted by David Hildenbrand (Arm) 2 weeks, 6 days ago

We now always have CONFIG_SPARSEMEM_VMEMMAP, so remove the dead code.

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/memory_hotplug.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 3495d94587e7..70e620496cec 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -320,21 +320,13 @@ static void release_memory_resource(struct resource *res)
 static int check_pfn_span(unsigned long pfn, unsigned long nr_pages)
 {
 	/*
-	 * Disallow all operations smaller than a sub-section and only
-	 * allow operations smaller than a section for
-	 * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
-	 * enforces a larger memory_block_size_bytes() granularity for
-	 * memory that will be marked online, so this check should only
-	 * fire for direct arch_{add,remove}_memory() users outside of
-	 * add_memory_resource().
+	 * Disallow all operations smaller than a sub-section.
+	 * Note that check_hotplug_memory_range() enforces a larger
+	 * memory_block_size_bytes() granularity for memory that will be marked
+	 * online, so this check should only fire for direct
+	 * arch_{add,remove}_memory() users outside of add_memory_resource().
 	 */
-	unsigned long min_align;
-
-	if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
-		min_align = PAGES_PER_SUBSECTION;
-	else
-		min_align = PAGES_PER_SECTION;
-	if (!IS_ALIGNED(pfn | nr_pages, min_align))
+	if (!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SUBSECTION))
 		return -EINVAL;
 	return 0;
 }
-- 
2.43.0

Re: [PATCH 04/14] mm/memory_hotplug: simplify check_pfn_span()

Posted by Mike Rapoport 2 weeks, 5 days ago

On Tue, Mar 17, 2026 at 05:56:42PM +0100, David Hildenbrand (Arm) wrote:
> We now always have CONFIG_SPARSEMEM_VMEMMAP, so remove the dead code.
> 
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  mm/memory_hotplug.c | 20 ++++++--------------
>  1 file changed, 6 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3495d94587e7..70e620496cec 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -320,21 +320,13 @@ static void release_memory_resource(struct resource *res)
>  static int check_pfn_span(unsigned long pfn, unsigned long nr_pages)
>  {
>  	/*
> -	 * Disallow all operations smaller than a sub-section and only
> -	 * allow operations smaller than a section for
> -	 * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
> -	 * enforces a larger memory_block_size_bytes() granularity for
> -	 * memory that will be marked online, so this check should only
> -	 * fire for direct arch_{add,remove}_memory() users outside of
> -	 * add_memory_resource().
> +	 * Disallow all operations smaller than a sub-section.
> +	 * Note that check_hotplug_memory_range() enforces a larger
> +	 * memory_block_size_bytes() granularity for memory that will be marked
> +	 * online, so this check should only fire for direct
> +	 * arch_{add,remove}_memory() users outside of add_memory_resource().
>  	 */
> -	unsigned long min_align;
> -
> -	if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
> -		min_align = PAGES_PER_SUBSECTION;
> -	else
> -		min_align = PAGES_PER_SECTION;
> -	if (!IS_ALIGNED(pfn | nr_pages, min_align))
> +	if (!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SUBSECTION))
>  		return -EINVAL;
>  	return 0;
>  }
> -- 
> 2.43.0
> 

-- 
Sincerely yours,
Mike.

Re: [PATCH 04/14] mm/memory_hotplug: simplify check_pfn_span()

Posted by Lorenzo Stoakes (Oracle) 2 weeks, 6 days ago

On Tue, Mar 17, 2026 at 05:56:42PM +0100, David Hildenbrand (Arm) wrote:
> We now always have CONFIG_SPARSEMEM_VMEMMAP, so remove the dead code.
>
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

It's a sparse patch but that's ok, so:

Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>

> ---
>  mm/memory_hotplug.c | 20 ++++++--------------
>  1 file changed, 6 insertions(+), 14 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 3495d94587e7..70e620496cec 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -320,21 +320,13 @@ static void release_memory_resource(struct resource *res)
>  static int check_pfn_span(unsigned long pfn, unsigned long nr_pages)
>  {
>  	/*
> -	 * Disallow all operations smaller than a sub-section and only
> -	 * allow operations smaller than a section for
> -	 * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
> -	 * enforces a larger memory_block_size_bytes() granularity for
> -	 * memory that will be marked online, so this check should only
> -	 * fire for direct arch_{add,remove}_memory() users outside of
> -	 * add_memory_resource().
> +	 * Disallow all operations smaller than a sub-section.
> +	 * Note that check_hotplug_memory_range() enforces a larger
> +	 * memory_block_size_bytes() granularity for memory that will be marked
> +	 * online, so this check should only fire for direct
> +	 * arch_{add,remove}_memory() users outside of add_memory_resource().
>  	 */
> -	unsigned long min_align;
> -
> -	if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
> -		min_align = PAGES_PER_SUBSECTION;
> -	else
> -		min_align = PAGES_PER_SECTION;
> -	if (!IS_ALIGNED(pfn | nr_pages, min_align))
> +	if (!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SUBSECTION))
>  		return -EINVAL;
>  	return 0;
>  }
> --
> 2.43.0
>