>>> Ok, I seems to understand the logic now. >>> >>> But how we prevent ONLINE_PARTIAL memory block get offlined? There are three >>> calls in virtio_mem_set_fake_offline(), while all of them adjust page's flag. >>> How they hold reference to struct page? >> >> Sorry, I should have given you the right pointer. (similar to my other >> reply) >> >> We hold a reference either via >> >> 1. alloc_contig_range() > > I am not familiar with this one, need to spend some time to look into. Each individual page will have a pagecount of 1. > >> 2. memmap init code, when not calling generic_online_page(). > > I may miss some code here. Before online pages, memmaps are allocated in > section_activate(). They are supposed to be zero-ed. (I don't get the exact > code line.) I am not sure when we grab a refcount here. Best to refer to __init_single_page() -> init_page_count(). Each page that wasn't onlined via generic_online_page() has a refcount of 1 and looks like allocated. -- Thanks, David / dhildenb
