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From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, David Hildenbrand <david@redhat.com>,
	Michal Hocko <mhocko@suse.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Wei Yang <richard.weiyang@linux.alibaba.com>,
	Baoquan He <bhe@redhat.com>,
	Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
	Oscar Salvador <osalvador@suse.de>
Subject: [PATCH v2 02/10] mm/memory_hotplug: enforce section granularity when onlining/offlining
Date: Wed, 19 Aug 2020 19:59:49 +0200	[thread overview]
Message-ID: <20200819175957.28465-3-david@redhat.com> (raw)
In-Reply-To: <20200819175957.28465-1-david@redhat.com>

Already two people (including me) tried to offline subsections, because
the function looks like it can deal with it. But we really can only
online/offline full sections that are properly aligned (e.g., we can only
mark full sections online/offline via SECTION_IS_ONLINE).

Add a simple safety net to document the restriction now. Current users
(core and powernv/memtrace) respect these restrictions.

Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/memory_hotplug.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c781d386d87f9..6856702af68d9 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -801,6 +801,11 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
 	int ret;
 	struct memory_notify arg;
 
+	/* We can only online full sections (e.g., SECTION_IS_ONLINE) */
+	if (WARN_ON_ONCE(!nr_pages ||
+			 !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)))
+		return -EINVAL;
+
 	mem_hotplug_begin();
 
 	/* associate pfn range with the zone */
@@ -1483,6 +1488,11 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 	struct memory_notify arg;
 	char *reason;
 
+	/* We can only offline full sections (e.g., SECTION_IS_ONLINE) */
+	if (WARN_ON_ONCE(!nr_pages ||
+			 !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION)))
+		return -EINVAL;
+
 	mem_hotplug_begin();
 
 	/*
-- 
2.26.2


  parent reply	other threads:[~2020-08-19 18:00 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-19 17:59 [PATCH v2 00/10] mm/memory_hotplug: online_pages()/offline_pages() cleanups David Hildenbrand
2020-08-19 17:59 ` [PATCH v2 01/10] mm/memory_hotplug: inline __offline_pages() into offline_pages() David Hildenbrand
2020-08-24 10:26   ` Oscar Salvador
2020-08-31 10:05   ` Pankaj Gupta
2020-08-19 17:59 ` David Hildenbrand [this message]
2020-08-24 10:39   ` [PATCH v2 02/10] mm/memory_hotplug: enforce section granularity when onlining/offlining Oscar Salvador
2020-08-25  2:11     ` Wei Yang
2020-09-08  9:14       ` David Hildenbrand
2020-08-19 17:59 ` [PATCH v2 03/10] mm/memory_hotplug: simplify page offlining David Hildenbrand
2020-08-24 10:44   ` Oscar Salvador
2020-09-03 21:58   ` Andrew Morton
2020-09-04  5:47     ` David Hildenbrand
2020-09-04  7:46       ` Michal Hocko
2020-09-04 19:21       ` Andrew Morton
2020-09-07  6:45         ` Michal Hocko
2020-09-08  9:10           ` David Hildenbrand
2020-08-19 17:59 ` [PATCH v2 04/10] mm/page_alloc: simplify __offline_isolated_pages() David Hildenbrand
2020-08-24 10:48   ` Oscar Salvador
2020-08-19 17:59 ` [PATCH v2 05/10] mm/memory_hotplug: drop nr_isolate_pageblock in offline_pages() David Hildenbrand
2020-08-24 10:49   ` Oscar Salvador
2020-08-19 17:59 ` [PATCH v2 06/10] mm/page_isolation: simplify return value of start_isolate_page_range() David Hildenbrand
2020-08-24 10:51   ` Oscar Salvador
2020-08-19 17:59 ` [PATCH v2 07/10] mm/memory_hotplug: simplify page onlining David Hildenbrand
2020-08-24 10:55   ` Oscar Salvador
2020-08-19 17:59 ` [PATCH v2 08/10] mm/page_alloc: drop stale pageblock comment in memmap_init_zone*() David Hildenbrand
2020-08-24 10:58   ` Oscar Salvador
2020-08-19 17:59 ` [PATCH v2 09/10] mm: pass migratetype into memmap_init_zone() and move_pfn_range_to_zone() David Hildenbrand
2020-08-24 11:59   ` Oscar Salvador
2020-08-19 17:59 ` [PATCH v2 10/10] mm/memory_hotplug: mark pageblocks MIGRATE_ISOLATE while onlining memory David Hildenbrand
2020-08-24 12:07   ` Oscar Salvador

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