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From: David Hildenbrand <david@redhat.com>
To: Oscar Salvador <osalvador@techadventures.net>, akpm@linux-foundation.org
Cc: mhocko@suse.com, dan.j.williams@intel.com,
	yasu.isimatu@gmail.com, rppt@linux.vnet.ibm.com,
	malat@debian.org, linux-kernel@vger.kernel.org,
	pavel.tatashin@microsoft.com, jglisse@redhat.com,
	Jonathan.Cameron@huawei.com, rafael@kernel.org,
	dave.jiang@intel.com, linux-mm@kvack.org,
	alexander.h.duyck@linux.intel.com,
	Oscar Salvador <osalvador@suse.de>
Subject: Re: [PATCH 3/5] mm/memory_hotplug: Check for IORESOURCE_SYSRAM in release_mem_region_adjustable
Date: Tue, 16 Oct 2018 11:54:45 +0200	[thread overview]
Message-ID: <a7421c75-e26d-f830-8d7a-8afad269f5de@redhat.com> (raw)
In-Reply-To: <20181015153034.32203-4-osalvador@techadventures.net>

On 15/10/2018 17:30, Oscar Salvador wrote:
> From: Oscar Salvador <osalvador@suse.de>
> 
> This is a preparation for the next patch.
> 
> Currently, we only call release_mem_region_adjustable() in __remove_pages
> if the zone is not ZONE_DEVICE, because resources that belong to
> HMM/devm are being released by themselves with devm_release_mem_region.
> 
> Since we do not want to touch any zone/page stuff during the removing
> of the memory (but during the offlining), we do not want to check for
> the zone here.
> So we need another way to tell release_mem_region_adjustable() to not
> realease the resource in case it belongs to HMM/devm.
> 
> HMM/devm acquires/releases a resource through
> devm_request_mem_region/devm_release_mem_region.
> 
> These resources have the flag IORESOURCE_MEM, while resources acquired by
> hot-add memory path (register_memory_resource()) contain
> IORESOURCE_SYSTEM_RAM.
> 
> So, we can check for this flag in release_mem_region_adjustable, and if
> the resource does not contain such flag, we know that we are dealing with
> a HMM/devm resource, so we can back off.
> 
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> ---
>  kernel/resource.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 81937830a42f..c45decd7d6af 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1272,6 +1272,22 @@ int release_mem_region_adjustable(struct resource *parent,
>  			continue;
>  		}
>  
> +		/*
> +		 * All memory regions added from memory-hotplug path
> +		 * have the flag IORESOURCE_SYSTEM_RAM.
> +		 * If the resource does not have this flag, we know that
> +		 * we are dealing with a resource coming from HMM/devm.
> +		 * HMM/devm use another mechanism to add/release a resource.
> +		 * This goes via devm_request_mem_region and
> +		 * devm_release_mem_region.
> +		 * HMM/devm take care to release their resources when they want,
> +		 * so if we are dealing with them, let us just back off here.
> +		 */
> +		if (!(res->flags & IORESOURCE_SYSRAM)) {
> +			ret = 0;
> +			break;
> +		}
> +
>  		if (!(res->flags & IORESOURCE_MEM))
>  			break;
>  
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 

Thanks,

David / dhildenb

  reply	other threads:[~2018-10-16  9:54 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-15 15:30 [PATCH 0/5] Do not touch pages/zones during hot-remove path Oscar Salvador
2018-10-15 15:30 ` [PATCH 1/5] mm/memory_hotplug: Add nid parameter to arch_remove_memory Oscar Salvador
2018-11-12 18:52   ` Pavel Tatashin
2018-10-15 15:30 ` [PATCH 2/5] mm/memory_hotplug: Create add/del_device_memory functions Oscar Salvador
2018-10-16  8:55   ` David Hildenbrand
2018-10-17  9:33     ` Oscar Salvador
2018-10-17  9:45       ` David Hildenbrand
2018-10-18  6:57         ` Oscar Salvador
2018-11-12 19:14   ` Pavel Tatashin
2018-11-12 19:21   ` Dan Williams
2018-11-12 21:28     ` Pavel Tatashin
2018-11-16 13:06       ` osalvador
2018-11-16 13:03     ` osalvador
2018-10-15 15:30 ` [PATCH 3/5] mm/memory_hotplug: Check for IORESOURCE_SYSRAM in release_mem_region_adjustable Oscar Salvador
2018-10-16  9:54   ` David Hildenbrand [this message]
2018-11-12 19:27   ` Pavel Tatashin
2018-10-15 15:30 ` [PATCH 4/5] mm/memory_hotplug: Move zone/pages handling to offline stage Oscar Salvador
2018-10-15 15:30 ` [PATCH 5/5] mm/memory-hotplug: Rework unregister_mem_sect_under_nodes Oscar Salvador
2018-10-18 14:24   ` Jonathan Cameron
2018-10-18 15:02     ` Oscar Salvador
2018-10-18 15:38       ` Jonathan Cameron

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