From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/memory_hotplug: make sure the pfn is aligned to the order when onlining
Commit a9cd410a3d29 ("mm/page_alloc.c: memory hotplug: free pages as
higher order") assumed that any PFN we get via memory resources is aligned
to to MAX_ORDER - 1, I am not convinced that is always true. Let's play
safe, check the alignment and fallback to single pages.
akpm: warn in this situation so we get to find out if and why this ever
occurs.
[akpm@xxxxxxxxxxxxxxxxxxxx: add WARN_ON_ONCE()]
Link: http://lkml.kernel.org/r/20190814154109.3448-5-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Arun KS <arunks@xxxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Nadav Amit <namit@xxxxxxxxxx>
Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 3 +++
1 file changed, 3 insertions(+)
--- a/mm/memory_hotplug.c~mm-memory_hotplug-make-sure-the-pfn-is-aligned-to-the-order-when-onlining
+++ a/mm/memory_hotplug.c
@@ -646,6 +646,9 @@ static int online_pages_range(unsigned l
*/
for (pfn = start_pfn; pfn < end_pfn; pfn += 1ul << order) {
order = min(MAX_ORDER - 1, get_order(PFN_PHYS(end_pfn - pfn)));
+ /* __free_pages_core() wants pfns to be aligned to the order */
+ if (WARN_ON_ONCE(!IS_ALIGNED(pfn, 1ul << order)))
+ order = 0;
(*online_page_callback)(pfn_to_page(pfn), order);
}
_
