Re: [PATCH v8 4/8] mm,memory_hotplug: Allocate memmap from the added memory range

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-int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
-		       int online_type, int nid)
+int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages,
+			      struct zone *zone)
+{
+	unsigned long end_pfn = pfn + nr_pages;
+	int ret;
+
+	ret = kasan_add_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
+	if (ret)
+		return ret;
+
+	/*
+	 * Initialize vmemmap pages with the corresponding node, zone links set.

The "set" sounds weird. I'd remove that comment completely.

+	 */
+	move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_UNMOVABLE);
+
+	/*
+	 * It might be that the vmemmap_pages fully span sections. If that is
+	 * the case, mark those sections online here as otherwise they will be
+	 * left offline.
+	 */
+	if (nr_pages >= PAGES_PER_SECTION)
+	        online_mem_sections(pfn, ALIGN_DOWN(end_pfn, PAGES_PER_SECTION));
+
+	return ret;
+}
+
+void mhp_deinit_memmap_on_memory(unsigned long pfn, unsigned long nr_pages)
+{
+	unsigned long end_pfn = pfn + nr_pages;
+        /*
+	 * The pages associated with this vmemmap have been offlined, so
+	 * we can reset its state here.
+	 */
+	remove_pfn_range_from_zone(page_zone(pfn_to_page(pfn)), pfn, nr_pages);
+	kasan_remove_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
+
+	/*
+	 * It might be that the vmemmap_pages fully span sections. If that is
+	 * the case, mark those sections offline here as otherwise they will be
+	 * left online.
+	 */
+	if (nr_pages >= PAGES_PER_SECTION)
+		offline_mem_sections(pfn, ALIGN_DOWN(end_pfn, PAGES_PER_SECTION));

It's usually best if you undo stuff in the complete opposite order. For example at this point, the memmap might already have been poisoned, yet pfn_to_online_page() would return true. You should do that first.

Apart from that, nothing jumped at me :)

Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>

--
Thanks,

David / dhildenb





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