Re: [PATCH v5 7/7] mm/hotplug: Enable runtime update of memmap_on_memory parameter

[David Hildenbrand <david@redhat.com>]

On 25.07.23 12:02, Aneesh Kumar K.V wrote:
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>   mm/memory_hotplug.c | 27 +++++++++++++++------------
>   1 file changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 96e794f39313..6cb6eac1aee5 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -95,7 +95,12 @@ static int set_memmap_mode(const char *val, const struct kernel_param *kp)
>   		mode =  MEMMAP_ON_MEMORY_DISABLE;
>   
>   matched:
> +	/*
> +	 * Avoid changing memmap mode during hotplug.
> +	 */
> +	get_online_mems();
>   	*((int *)kp->arg) =  mode;
> +	put_online_mems();
>   	if (mode == MEMMAP_ON_MEMORY_FORCE) {
>   		unsigned long memmap_pages = memory_block_memmap_on_memory_pages();
>   
> @@ -116,7 +121,7 @@ static const struct kernel_param_ops memmap_mode_ops = {
>   	.set = set_memmap_mode,
>   	.get = get_memmap_mode,
>   };
> -module_param_cb(memmap_on_memory, &memmap_mode_ops, &memmap_mode, 0444);
> +module_param_cb(memmap_on_memory, &memmap_mode_ops, &memmap_mode, 0644);
>   MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug\n"
>   		 "With value \"force\" it could result in memory wastage due "
>   		 "to memmap size limitations (Y/N/force)");
> @@ -2175,18 +2180,16 @@ static int __ref try_remove_memory(u64 start, u64 size)
>   	 * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in
>   	 * the same granularity it was added - a single memory block.
>   	 */
> -	if (mhp_memmap_on_memory()) {
> -		ret = walk_memory_blocks(start, size, &mhp_altmap,
> -					 get_vmemmap_altmap_cb);
> -		if (ret) {
> -			if (size != memory_block_size_bytes()) {
> -				pr_warn("Refuse to remove %#llx - %#llx,"
> -					"wrong granularity\n",
> -					start, start + size);
> -				return -EINVAL;
> -			}
> -			altmap = &mhp_altmap;
> +	ret = walk_memory_blocks(start, size, &mhp_altmap,
> +				 get_vmemmap_altmap_cb);
> +	if (ret) {
> +		if (size != memory_block_size_bytes()) {
> +			pr_warn("Refuse to remove %#llx - %#llx,"
> +				"wrong granularity\n",
> +				start, start + size);
> +			return -EINVAL;
>   		}
> +		altmap = &mhp_altmap;
>   	}
>   
>   	/* remove memmap entry */


Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb