mm/balloon_compaction: add vmstat counters and kpageflags bit

Always mark pages with PageBalloon even if balloon compaction is disabled
and expose this mark in /proc/kpageflags as KPF_BALLOON.

Also this patch adds three counters into /proc/vmstat: "balloon_inflate",
"balloon_deflate" and "balloon_migrate".  They accumulate balloon
activity.  Current size of balloon is (balloon_inflate - balloon_deflate)
pages.

All generic balloon code now gathered under option CONFIG_MEMORY_BALLOON.
It should be selected by ballooning driver which wants use this feature.
Currently virtio-balloon is the only user.

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 2 insertions, 0 deletions

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index c6683f2e396c..00b228638274 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -25,6 +25,7 @@ config VIRTIO_PCI
 config VIRTIO_BALLOON
         tristate "Virtio balloon driver"
         depends on VIRTIO
+        select MEMORY_BALLOON
         ---help---
          This driver supports increasing and decreasing the amount
          of memory within a KVM guest.
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 2bad7f9dd2ac..f893148a107b 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -396,6 +396,7 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
         balloon_page_insert(vb_dev_info, newpage);
         vb_dev_info->isolated_pages--;
+        __count_vm_event(BALLOON_MIGRATE);
         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
         set_page_pfns(vb->pfns, newpage);