virtio-mem: prioritize unplug from ZONE_MOVABLE in Big Block Mode

Let's handle unplug in Big Block Mode similar to Sub Block Mode --
prioritize memory blocks onlined to ZONE_MOVABLE.

We won't care further about big blocks with mixed zones, as it's
rather a corner case that won't matter in practice.

Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20210602185720.31821-8-david@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 43199389c41436ee737c837e61fb10ab136e5603..d3e874b6b50b42bae192d9731c826a1a489138db 100644 (file)
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -2121,6 +2121,29 @@ static bool virtio_mem_bbm_bb_is_offline(struct virtio_mem *vm,
        return true;
 }
 
+/*
+ * Test if a big block is completely onlined to ZONE_MOVABLE (or offline).
+ */
+static bool virtio_mem_bbm_bb_is_movable(struct virtio_mem *vm,
+                                        unsigned long bb_id)
+{
+       const unsigned long start_pfn = PFN_DOWN(virtio_mem_bb_id_to_phys(vm, bb_id));
+       const unsigned long nr_pages = PFN_DOWN(vm->bbm.bb_size);
+       struct page *page;
+       unsigned long pfn;
+
+       for (pfn = start_pfn; pfn < start_pfn + nr_pages;
+            pfn += PAGES_PER_SECTION) {
+               page = pfn_to_online_page(pfn);
+               if (!page)
+                       continue;
+               if (page_zonenum(page) != ZONE_MOVABLE)
+                       return false;
+       }
+
+       return true;
+}
+
 static int virtio_mem_bbm_unplug_request(struct virtio_mem *vm, uint64_t diff)
 {
        uint64_t nb_bb = diff / vm->bbm.bb_size;
@@ -2134,7 +2157,7 @@ static int virtio_mem_bbm_unplug_request(struct virtio_mem *vm, uint64_t diff)
         * Try to unplug big blocks. Similar to SBM, start with offline
         * big blocks.
         */
-       for (i = 0; i < 2; i++) {
+       for (i = 0; i < 3; i++) {
                virtio_mem_bbm_for_each_bb_rev(vm, bb_id, VIRTIO_MEM_BBM_BB_ADDED) {
                        cond_resched();
 
@@ -2144,6 +2167,8 @@ static int virtio_mem_bbm_unplug_request(struct virtio_mem *vm, uint64_t diff)
                         */
                        if (i == 0 && !virtio_mem_bbm_bb_is_offline(vm, bb_id))
                                continue;
+                       if (i == 1 && !virtio_mem_bbm_bb_is_movable(vm, bb_id))
+                               continue;
                        rc = virtio_mem_bbm_offline_remove_and_unplug_bb(vm, bb_id);
                        if (rc == -EBUSY)
                                continue;