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

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Message-ID: <20200317105818.GK26018@dhcp22.suse.cz>
Date:   Tue, 17 Mar 2020 11:58:18 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org, linux-hyperv@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Baoquan He <bhe@...hat.com>,
        Wei Yang <richard.weiyang@...il.com>
Subject: Re: [PATCH v2 4/8] powernv/memtrace: always online added memory
 blocks

On Tue 17-03-20 11:49:38, David Hildenbrand wrote:
> 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@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Cc: Baoquan He <bhe@...hat.com>
> Cc: Wei Yang <richard.weiyang@...il.com>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Signed-off-by: David Hildenbrand <david@...hat.com>

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

> ---
>  arch/powerpc/platforms/powernv/memtrace.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> 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

-- 
Michal Hocko
SUSE Labs