Re: [PATCH v2 4/8] powernv/memtrace: always online added memory blocks

From: Michael Ellerman <mpe@ellerman.id.au>
To: David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
	linux-hyperv@vger.kernel.org,
	David Hildenbrand <david@redhat.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Michal Hocko <mhocko@kernel.org>,
	Oscar Salvador <osalvador@suse.de>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Baoquan He <bhe@redhat.com>, Wei Yang <richard.weiyang@gmail.com>
Subject: Re: [PATCH v2 4/8] powernv/memtrace: always online added memory blocks
Date: Thu, 19 Mar 2020 20:49:47 +1100	[thread overview]
Message-ID: <8736a4eksk.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20200317104942.11178-5-david@redhat.com>

David Hildenbrand <david@redhat.com> writes:
> Let's always try to online the re-added memory blocks. In case add_memory()
> already onlined the added memory blocks, the first device_online() call
> will fail and stop processing the remaining memory blocks.
>
> This avoids manually having to check memhp_auto_online.
>
> Note: PPC always onlines all hotplugged memory directly from the kernel
> as well - something that is handled by user space on other
> architectures.
>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Wei Yang <richard.weiyang@gmail.com>
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  arch/powerpc/platforms/powernv/memtrace.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)

Fine by me.

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers

> diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
> index d6d64f8718e6..13b369d2cc45 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/arch/powerpc/platforms/powernv/memtrace.c
> @@ -231,16 +231,10 @@ static int memtrace_online(void)
>  			continue;
>  		}
>  
> -		/*
> -		 * If kernel isn't compiled with the auto online option
> -		 * we need to online the memory ourselves.
> -		 */
> -		if (!memhp_auto_online) {
> -			lock_device_hotplug();
> -			walk_memory_blocks(ent->start, ent->size, NULL,
> -					   online_mem_block);
> -			unlock_device_hotplug();
> -		}
> +		lock_device_hotplug();
> +		walk_memory_blocks(ent->start, ent->size, NULL,
> +				   online_mem_block);
> +		unlock_device_hotplug();
>  
>  		/*
>  		 * Memory was added successfully so clean up references to it
> -- 
> 2.24.1