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From: Oscar Salvador <osalvador@techadventures.net>
To: 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, david@redhat.com,
	dave.jiang@intel.com, linux-mm@kvack.org,
	alexander.h.duyck@linux.intel.com,
	Oscar Salvador <osalvador@suse.de>
Subject: [PATCH 3/5] mm/memory_hotplug: Check for IORESOURCE_SYSRAM in release_mem_region_adjustable
Date: Mon, 15 Oct 2018 17:30:32 +0200	[thread overview]
Message-ID: <20181015153034.32203-4-osalvador@techadventures.net> (raw)
In-Reply-To: <20181015153034.32203-1-osalvador@techadventures.net>

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;
 
-- 
2.13.6


  parent reply	other threads:[~2018-10-15 15:31 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 ` Oscar Salvador [this message]
2018-10-16  9:54   ` [PATCH 3/5] mm/memory_hotplug: Check for IORESOURCE_SYSRAM in release_mem_region_adjustable David Hildenbrand
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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