Re: [PATCH v3 01/11] mm/memory_hotplug: Simplify and fix check_hotplug_memory_range()

[Michal Hocko]

[Sorry for a really late response]

On Mon 27-05-19 13:11:42, David Hildenbrand wrote:
> By converting start and size to page granularity, we actually ignore
> unaligned parts within a page instead of properly bailing out with an
> error.

I do not expect any code path would ever provide an unaligned address
and even if it did then rounding that to a pfn doesn't sound like a
terrible thing to do. Anyway this removes few lines so why not.
> 
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Oscar Salvador <osalvador@xxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
> Cc: Qian Cai <cai@xxxxxx>
> Cc: Wei Yang <richard.weiyang@xxxxxxxxx>
> Cc: Arun KS <arunks@xxxxxxxxxxxxxx>
> Cc: Mathieu Malaterre <malat@xxxxxxxxxx>
> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Reviewed-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  mm/memory_hotplug.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index e096c987d261..762887b2358b 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1051,16 +1051,11 @@ int try_online_node(int nid)
>  
>  static int check_hotplug_memory_range(u64 start, u64 size)
>  {
> -	unsigned long block_sz = memory_block_size_bytes();
> -	u64 block_nr_pages = block_sz >> PAGE_SHIFT;
> -	u64 nr_pages = size >> PAGE_SHIFT;
> -	u64 start_pfn = PFN_DOWN(start);
> -
>  	/* memory range must be block size aligned */
> -	if (!nr_pages || !IS_ALIGNED(start_pfn, block_nr_pages) ||
> -	    !IS_ALIGNED(nr_pages, block_nr_pages)) {
> +	if (!size || !IS_ALIGNED(start, memory_block_size_bytes()) ||
> +	    !IS_ALIGNED(size, memory_block_size_bytes())) {
>  		pr_err("Block size [%#lx] unaligned hotplug range: start %#llx, size %#llx",
> -		       block_sz, start, size);
> +		       memory_block_size_bytes(), start, size);
>  		return -EINVAL;
>  	}
>  
> -- 
> 2.20.1
> 

-- 
Michal Hocko
SUSE Labs