Drivers: hv: balloon: Execute balloon inflation in a separate context

Execute the balloon inflation operation in a separate work context.
This allows us to decouple the pressure reporting activity from the
ballooning activity. Testing has shown that this decoupling makes the
guest more reponsive.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 24 insertions, 10 deletions

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 7fb72dd05ba2..8dc406ccf10f 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -412,6 +412,11 @@ struct dm_info_msg {
  * End protocol definitions.
  */
 
+struct balloon_state {
+        __u32 num_pages;
+        struct work_struct wrk;
+};
+
 static bool hot_add;
 static bool do_hot_add;
 /*
@@ -459,7 +464,12 @@ struct hv_dynmem_device {
         unsigned int num_pages_ballooned;
 
         /*
-         * This thread handles both balloon/hot-add
+         * State to manage the ballooning (up) operation.
+         */
+        struct balloon_state balloon_wrk;
+
+        /*
+         * This thread handles hot-add
          * requests from the host as well as notifying
          * the host with regards to memory pressure in
          * the guest.
@@ -657,9 +667,9 @@ static int  alloc_balloon_pages(struct hv_dynmem_device *dm, int num_pages,
 
 
 
-static void balloon_up(struct hv_dynmem_device *dm, struct dm_balloon *req)
+static void balloon_up(struct work_struct *dummy)
 {
-        int num_pages = req->num_pages;
+        int num_pages = dm_device.balloon_wrk.num_pages;
         int num_ballooned = 0;
         struct dm_balloon_response *bl_resp;
         int alloc_unit;
@@ -684,14 +694,14 @@ static void balloon_up(struct hv_dynmem_device *dm, struct dm_balloon *req)
 
 
                 num_pages -= num_ballooned;
-                num_ballooned = alloc_balloon_pages(dm, num_pages,
+                num_ballooned = alloc_balloon_pages(&dm_device, num_pages,
                                                 bl_resp, alloc_unit,
                                                  &alloc_error);
 
                 if ((alloc_error) || (num_ballooned == num_pages)) {
                         bl_resp->more_pages = 0;
                         done = true;
-                        dm->state = DM_INITIALIZED;
+                        dm_device.state = DM_INITIALIZED;
                 }
 
                 /*
@@ -719,7 +729,7 @@ static void balloon_up(struct hv_dynmem_device *dm, struct dm_balloon *req)
                         pr_info("Balloon response failed\n");
 
                         for (i = 0; i < bl_resp->range_count; i++)
-                                free_balloon_pages(dm,
+                                free_balloon_pages(&dm_device,
                                                  &bl_resp->range_array[i]);
 
                         done = true;
@@ -775,9 +785,6 @@ static int dm_thread_func(void *dm_dev)
 
                 scan_start = jiffies;
                 switch (dm->state) {
-                case DM_BALLOON_UP:
-                        balloon_up(dm, (struct dm_balloon *)recv_buffer);
-                        break;
 
                 case DM_HOT_ADD:
                         hot_add_req(dm, (struct dm_hot_add *)recv_buffer);
@@ -861,6 +868,7 @@ static void balloon_onchannelcallback(void *context)
         struct dm_message *dm_msg;
         struct dm_header *dm_hdr;
         struct hv_dynmem_device *dm = hv_get_drvdata(dev);
+        struct dm_balloon *bal_msg;
 
         memset(recv_buffer, 0, sizeof(recv_buffer));
         vmbus_recvpacket(dev->channel, recv_buffer,
@@ -882,8 +890,12 @@ static void balloon_onchannelcallback(void *context)
                         break;
 
                 case DM_BALLOON_REQUEST:
+                        if (dm->state == DM_BALLOON_UP)
+                                pr_warn("Currently ballooning\n");
+                        bal_msg = (struct dm_balloon *)recv_buffer;
                         dm->state = DM_BALLOON_UP;
-                        complete(&dm->config_event);
+                        dm_device.balloon_wrk.num_pages = bal_msg->num_pages;
+                        schedule_work(&dm_device.balloon_wrk.wrk);
                         break;
 
                 case DM_UNBALLOON_REQUEST:
@@ -937,6 +949,7 @@ static int balloon_probe(struct hv_device *dev,
         dm_device.next_version = DYNMEM_PROTOCOL_VERSION_WIN7;
         init_completion(&dm_device.host_event);
         init_completion(&dm_device.config_event);
+        INIT_WORK(&dm_device.balloon_wrk.wrk, balloon_up);
 
         dm_device.thread =
                  kthread_run(dm_thread_func, &dm_device, "hv_balloon");
@@ -1048,6 +1061,7 @@ static int balloon_remove(struct hv_device *dev)
         if (dm->num_pages_ballooned != 0)
                 pr_warn("Ballooned pages: %d\n", dm->num_pages_ballooned);
 
+        cancel_work_sync(&dm->balloon_wrk.wrk);
         vmbus_close(dev->channel);
         kthread_stop(dm->thread);
         kfree(send_buffer);