From 4986fac160b3eb1432ca9970d51c55f4f93b1a2e Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 15 Oct 2020 20:07:50 -0700 Subject: mm/memory_hotplug: enforce section granularity when onlining/offlining 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. Signed-off-by: David Hildenbrand Signed-off-by: Andrew Morton Reviewed-by: Oscar Salvador Acked-by: Michal Hocko Cc: Wei Yang Cc: Baoquan He Cc: Pankaj Gupta Cc: Charan Teja Reddy Cc: Dan Williams Cc: Fenghua Yu Cc: Logan Gunthorpe Cc: "Matthew Wilcox (Oracle)" Cc: Mel Gorman Cc: Mel Gorman Cc: Michel Lespinasse Cc: Mike Rapoport Cc: Tony Luck Link: https://lkml.kernel.org/r/20200819175957.28465-3-david@redhat.com Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'mm/memory_hotplug.c') diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index ba201ab4c0e4..03a8825c5620 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -809,6 +809,11 @@ 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 */ @@ -1494,6 +1499,11 @@ 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(); /* -- cgit