virtio-mem: factor out handling of fake-offline pages in memory notifier

Let's factor out the core pieces and place the implementation next to
virtio_mem_fake_offline(). We'll reuse this functionality soon.

Reviewed-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20201112133815.13332-10-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 fedfea27967e990c8cceb12dc06884850c87f835..c24055248f9d92663783f7e4dea7f4b08f1f6ef6 100644 (file)
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -160,6 +160,10 @@ static DEFINE_MUTEX(virtio_mem_mutex);
 static LIST_HEAD(virtio_mem_devices);
 
 static void virtio_mem_online_page_cb(struct page *page, unsigned int order);
+static void virtio_mem_fake_offline_going_offline(unsigned long pfn,
+                                                 unsigned long nr_pages);
+static void virtio_mem_fake_offline_cancel_offline(unsigned long pfn,
+                                                  unsigned long nr_pages);
 
 /*
  * Register a virtio-mem device so it will be considered for the online_page
@@ -586,27 +590,15 @@ 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);
-       struct page *page;
        unsigned long pfn;
-       int sb_id, i;
+       int sb_id;
 
        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 = pfn_to_page(pfn + i);
-                       if (WARN_ON(!page_ref_dec_and_test(page)))
-                               dump_page(page, "unplugged page referenced");
-               }
+               virtio_mem_fake_offline_going_offline(pfn, nr_pages);
        }
 }
 
@@ -615,21 +607,14 @@ static void virtio_mem_notify_cancel_offline(struct virtio_mem *vm,
 {
        const unsigned long nr_pages = PFN_DOWN(vm->subblock_size);
        unsigned long pfn;
-       int sb_id, i;
+       int sb_id;
 
        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;
-               /*
-                * Get the reference we dropped when going offline and
-                * subtract the unplugged pages from the managed page
-                * counters.
-                */
                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_inc(pfn_to_page(pfn + i));
+               virtio_mem_fake_offline_cancel_offline(pfn, nr_pages);
        }
 }
 
@@ -814,6 +799,48 @@ static int virtio_mem_fake_offline(unsigned long pfn, unsigned long nr_pages)
        return 0;
 }
 
+/*
+ * Handle fake-offline pages when memory is going offline - such that the
+ * pages can be skipped by mm-core when offlining.
+ */
+static void virtio_mem_fake_offline_going_offline(unsigned long pfn,
+                                                 unsigned long nr_pages)
+{
+       struct page *page;
+       unsigned long i;
+
+       /*
+        * 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).
+        */
+       adjust_managed_page_count(pfn_to_page(pfn), nr_pages);
+       /* Drop our reference to the pages so the memory can get offlined. */
+       for (i = 0; i < nr_pages; i++) {
+               page = pfn_to_page(pfn + i);
+               if (WARN_ON(!page_ref_dec_and_test(page)))
+                       dump_page(page, "fake-offline page referenced");
+       }
+}
+
+/*
+ * Handle fake-offline pages when memory offlining is canceled - to undo
+ * what we did in virtio_mem_fake_offline_going_offline().
+ */
+static void virtio_mem_fake_offline_cancel_offline(unsigned long pfn,
+                                                  unsigned long nr_pages)
+{
+       unsigned long i;
+
+       /*
+        * Get the reference we dropped when going offline and subtract the
+        * unplugged pages from the managed page counters.
+        */
+       adjust_managed_page_count(pfn_to_page(pfn), -nr_pages);
+       for (i = 0; i < nr_pages; i++)
+               page_ref_inc(pfn_to_page(pfn + i));
+}
+
 static void virtio_mem_online_page_cb(struct page *page, unsigned int order)
 {
        const unsigned long addr = page_to_phys(page);