[PATCH v2 09/29] virtio-mem: factor out handling of fake-offline pages in memory notifier

David Hildenbrand
2020-11-12T13:39:04Z

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>
---
drivers/virtio/virtio_mem.c | 73 +++++++++++++++++++++++++------------
1 file changed, 50 insertions(+), 23 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index fedfea27967e..c24055248f9d 100644
--- 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);
--
2.26.2