linux-kernel - Re: [PATCH 4/6] mm/hotplug: Reorder arch_remove_memory() call in __remove

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Date:   Wed, 3 Apr 2019 10:45:12 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org, will.deacon@....com,
        catalin.marinas@....com, mhocko@...e.com,
        mgorman@...hsingularity.net, james.morse@....com,
        mark.rutland@....com, robin.murphy@....com, cpandya@...eaurora.org,
        arunks@...eaurora.org, dan.j.williams@...el.com,
        logang@...tatee.com, pasha.tatashin@...cle.com, david@...hat.com,
        cai@....pw
Subject: Re: [PATCH 4/6] mm/hotplug: Reorder arch_remove_memory() call in
 __remove_memory()

On Wed, Apr 03, 2019 at 10:00:04AM +0530, Anshuman Khandual wrote:
> Re-ordering arch_remove_memory() with memblock_[free|remove] solves the
> problem on arm64 as pfn_valid() behaves correctly and returns positive
> as memblock for the address range still exists. arch_remove_memory()
> removes applicable memory sections from zone with __remove_pages() and
> tears down kernel linear mapping. Removing memblock regions afterwards
> is consistent.
> 
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>

Yes, I cannot see a way of those two colliding with each other, and
a testing on my box did not raise anything spooky either.

Reviewed-by: Oscar Salvador <osalvador@...e.de>

> ---
>  mm/memory_hotplug.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 0082d69..71d0d79 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1872,11 +1872,10 @@ 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();
> -- 
> 2.7.4
> 

-- 
Oscar Salvador
SUSE L3