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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 <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: 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: Charan Teja Reddy <charante@codeaurora.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20200819175957.28465-3-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2020-10-15 20:07:50 -07:00 committed by Linus Torvalds
parent 73a11c9658
commit 4986fac160
1 changed files with 10 additions and 0 deletions
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10
mm/memory_hotplug.c
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@ -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();
/*