[Devel] [PATCH vz7] Create debugfs file with virtio balloon usage information

[Alexander Atanasov]

Allow the guest to know how much it is ballooned by the host.
Depending on options the ballooned memory is accounted in two ways.
If deflate on oom is enabled - ballooned memory is accounted as used.
If deflate on oom is not enabled - ballooned memory is subtracted
from total ram.

https://jira.sw.ru/browse/PSBM-140407
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
 drivers/virtio/virtio_balloon.c | 52 +++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 142719d05dc5..e8cefeea4f22 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -23,6 +23,7 @@
 #include <linux/virtio_balloon.h>
 #include <linux/swap.h>
 #include <linux/workqueue.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/module.h>
@@ -447,6 +448,54 @@ static int init_vqs(struct virtio_balloon *vb)
 	return 0;
 }
 
+/*
+ * DEBUGFS Interface
+ */
+#ifdef CONFIG_DEBUG_FS
+
+static int virtio_balloon_debug_show(struct seq_file *f, void *offset)
+{
+	struct virtio_balloon *vb = f->private;
+	u64 inflated_kb = vb->num_pages << (VIRTIO_BALLOON_PFN_SHIFT - 10);
+	u64 inflated_total = 0;
+	u64 inflated_free = 0;
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+		inflated_free = inflated_kb;
+	else
+		inflated_total = inflated_kb;
+
+	seq_printf(f, "InflatedTotal: %lld kB\n", inflated_total);
+	seq_printf(f, "InflatedFree: %lld kB\n", inflated_free);
+
+	return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(virtio_balloon_debug);
+
+static void  virtio_balloon_debugfs_init(struct virtio_balloon *b)
+{
+	debugfs_create_file("virtio-balloon", 0444, NULL, b,
+				&virtio_balloon_debug_fops);
+}
+
+static void  virtio_balloon_debugfs_exit(struct virtio_balloon *b)
+{
+	debugfs_remove(debugfs_lookup("virtio-balloon", NULL));
+}
+
+#else
+
+static inline void virtio_balloon_debugfs_init(struct virtio_balloon *b)
+{
+}
+
+static inline void virtio_balloon_debugfs_exit(struct virtio_balloon *b)
+{
+}
+
+#endif /* CONFIG_DEBUG_FS */
+
 #ifdef CONFIG_BALLOON_COMPACTION
 /*
  * virtballoon_migratepage - perform the balloon page migration on behalf of
@@ -568,6 +617,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
 
 	if (towards_target(vb))
 		virtballoon_changed(vdev);
+	virtio_balloon_debugfs_init(vb);
+
 	return 0;
 
 out_oom_notify:
@@ -595,6 +646,7 @@ static void virtballoon_remove(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;
 
+	virtio_balloon_debugfs_exit(vb);
 	unregister_oom_notifier(&vb->nb);
 
 	spin_lock_irq(&vb->stop_update_lock);
-- 
2.31.1