Re: [RFC] mm/hotplug: Make get_nid_for_pfn() work with HAVE_ARCH_PFN_VALID

From: Michal Hocko <mhocko@kernel.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	logang@deltatee.com, osalvador@suse.de, hannes@cmpxchg.org,
	akpm@linux-foundation.org, richard.weiyang@gmail.com,
	rientjes@google.com, zi.yan@cs.rutgers.edu
Subject: Re: [RFC] mm/hotplug: Make get_nid_for_pfn() work with HAVE_ARCH_PFN_VALID
Date: Tue, 26 Mar 2019 13:25:22 +0100	[thread overview]
Message-ID: <20190326122522.GO28406@dhcp22.suse.cz> (raw)
In-Reply-To: <65a4b160-a654-8bd3-8022-491094cf6b8f@arm.com>

On Tue 26-03-19 17:33:19, Anshuman Khandual wrote:
[...]
> I could get it working with the following re-order of memblock_[free|remove] and
> arch_remove_memory(). I did not observe any other adverse side affect because of
> this change. Does it look okay ?

Memblock should only work with physical memory ranges without touching
struct pages so this should be safe. But you should double check of
course.

> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1863,11 +1863,11 @@ void __ref __remove_memory(int nid, u64 start, u64 size)
>  
>         /* remove memmap entry */
>         firmware_map_remove(start, start + size, "System RAM");
> +       arch_remove_memory(nid, start, size, NULL);
> +
>         memblock_free(start, size);
>         memblock_remove(start, size);
>  
> -       arch_remove_memory(nid, start, size, NULL);
> -
>         try_offline_node(nid);
>  
>         mem_hotplug_done();

-- 
Michal Hocko
SUSE Labs