linux-kernel - Re: [PATCH v3 01/11] mm/memory_hotplug: Simplify and fix check_hotplug_memory

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Message-ID: <20190701074202.GB6376@dhcp22.suse.cz>
Date:   Mon, 1 Jul 2019 09:42:02 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-ia64@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, akpm@...ux-foundation.org,
        Dan Williams <dan.j.williams@...el.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Qian Cai <cai@....pw>, Arun KS <arunks@...eaurora.org>,
        Mathieu Malaterre <malat@...ian.org>,
        Wei Yang <richardw.yang@...ux.intel.com>
Subject: Re: [PATCH v3 01/11] mm/memory_hotplug: Simplify and fix
 check_hotplug_memory_range()

[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@...ux-foundation.org>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Pavel Tatashin <pasha.tatashin@...een.com>
> Cc: Qian Cai <cai@....pw>
> Cc: Wei Yang <richard.weiyang@...il.com>
> Cc: Arun KS <arunks@...eaurora.org>
> Cc: Mathieu Malaterre <malat@...ian.org>
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> Reviewed-by: Wei Yang <richardw.yang@...ux.intel.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  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