On 10.03.20 12:43, Michal Hocko wrote:
> On Mon 02-03-20 14:49:37, David Hildenbrand wrote:
> [...]
>> +static void virtio_mem_notify_going_offline(struct virtio_mem *vm,
>> + unsigned long mb_id)
>> +{
>> + const unsigned long nr_pages = PFN_DOWN(vm->subblock_size);
>> + unsigned long pfn;
>> + int sb_id, i;
>> +
>> + for (sb_id = 0; sb_id < vm->nb_sb_per_mb; sb_id++) {
>> + if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
>> + continue;
>> + /*
>> + * Drop our reference to the pages so the memory can get
>> + * offlined and add the unplugged pages to the managed
>> + * page counters (so offlining code can correctly subtract
>> + * them again).
>> + */
>> + pfn = PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) +
>> + sb_id * vm->subblock_size);
>> + adjust_managed_page_count(pfn_to_page(pfn), nr_pages);
>> + for (i = 0; i < nr_pages; i++)
>> + page_ref_dec(pfn_to_page(pfn + i));
>
> Is there ever situation this might be a different than 1->0 transition?
Only if some other code would be taking a reference. At least not from
virtio-mem perspective.
--
Thanks,
David / dhildenb
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