[PATCH] mm/memory_hotplug: Factor out altmap freeing checks

[PATCH] mm/memory_hotplug: Factor out altmap freeing checks

[Muchun Song]

Use a small helper to centralize altmap freeing after verifying that all
vmemmap pages were released. This keeps the check consistent between the
normal teardown path and the memory hotplug error paths.

Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 mm/memory_hotplug.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 462d8dcd636d..af5489f03771 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1403,6 +1403,12 @@ bool mhp_supports_memmap_on_memory(void)
 }
 EXPORT_SYMBOL_GPL(mhp_supports_memmap_on_memory);
 
+static void altmap_free(struct vmem_altmap *altmap)
+{
+	WARN_ONCE(altmap->alloc, "Altmap not fully unmapped");
+	kfree(altmap);
+}
+
 static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
 {
 	unsigned long memblock_size = memory_block_size_bytes();
@@ -1427,12 +1433,8 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
 		put_device(&mem->dev);
 
 		remove_memory_block_devices(cur_start, memblock_size);
-
 		arch_remove_memory(cur_start, memblock_size, altmap, NULL);
-
-		/* Verify that all vmemmap pages have actually been freed. */
-		WARN(altmap->alloc, "Altmap not fully unmapped");
-		kfree(altmap);
+		altmap_free(altmap);
 	}
 }
 
@@ -1463,7 +1465,7 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group,
 		/* call arch's memory hotadd */
 		ret = arch_add_memory(nid, cur_start, memblock_size, &params);
 		if (ret < 0) {
-			kfree(params.altmap);
+			altmap_free(params.altmap);
 			goto out;
 		}
 
@@ -1472,7 +1474,7 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group,
 						  params.altmap, group);
 		if (ret) {
 			arch_remove_memory(cur_start, memblock_size, params.altmap, NULL);
-			kfree(params.altmap);
+			altmap_free(params.altmap);
 			goto out;
 		}
 	}

base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
-- 
2.20.1

Re: [PATCH] mm/memory_hotplug: Factor out altmap freeing checks

[David Hildenbrand (Arm)]

On 5/11/26 10:43, Muchun Song wrote:
> Use a small helper to centralize altmap freeing after verifying that all
> vmemmap pages were released. This keeps the check consistent between the
> normal teardown path and the memory hotplug error paths.
> 
> Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David

Re: [PATCH] mm/memory_hotplug: Factor out altmap freeing checks

[Oscar Salvador]

On Mon, May 11, 2026 at 04:43:07PM +0800, Muchun Song wrote:
> Use a small helper to centralize altmap freeing after verifying that all
> vmemmap pages were released. This keeps the check consistent between the
> normal teardown path and the memory hotplug error paths.
> 
> Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>

Acked-by: Oscar Salvador <osalvador@suse.de>

 

-- 
Oscar Salvador
SUSE Labs

Re: [PATCH] mm/memory_hotplug: Factor out altmap freeing checks

[Donet Tom]

On 5/11/26 2:13 PM, Muchun Song wrote:
> Use a small helper to centralize altmap freeing after verifying that all
> vmemmap pages were released. This keeps the check consistent between the
> normal teardown path and the memory hotplug error paths.
>
> Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>


looks good to me.

Reviewed-by: Donet Tom <donettom@linux.ibm.com>

-Donet

> ---
>   mm/memory_hotplug.c | 16 +++++++++-------
>   1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 462d8dcd636d..af5489f03771 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1403,6 +1403,12 @@ bool mhp_supports_memmap_on_memory(void)
>   }
>   EXPORT_SYMBOL_GPL(mhp_supports_memmap_on_memory);
>   
> +static void altmap_free(struct vmem_altmap *altmap)
> +{
> +	WARN_ONCE(altmap->alloc, "Altmap not fully unmapped");
> +	kfree(altmap);
> +}
> +
>   static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
>   {
>   	unsigned long memblock_size = memory_block_size_bytes();
> @@ -1427,12 +1433,8 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
>   		put_device(&mem->dev);
>   
>   		remove_memory_block_devices(cur_start, memblock_size);
> -
>   		arch_remove_memory(cur_start, memblock_size, altmap, NULL);
> -
> -		/* Verify that all vmemmap pages have actually been freed. */
> -		WARN(altmap->alloc, "Altmap not fully unmapped");
> -		kfree(altmap);
> +		altmap_free(altmap);
>   	}
>   }
>   
> @@ -1463,7 +1465,7 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group,
>   		/* call arch's memory hotadd */
>   		ret = arch_add_memory(nid, cur_start, memblock_size, &params);
>   		if (ret < 0) {
> -			kfree(params.altmap);
> +			altmap_free(params.altmap);
>   			goto out;
>   		}
>   
> @@ -1472,7 +1474,7 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group,
>   						  params.altmap, group);
>   		if (ret) {
>   			arch_remove_memory(cur_start, memblock_size, params.altmap, NULL);
> -			kfree(params.altmap);
> +			altmap_free(params.altmap);
>   			goto out;
>   		}
>   	}
>
> base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83