Drivers: hv: balloon: Execute hot-add code in a separate context

Execute the hot-add operation in a separate work context.
This allows us to decouple the pressure reporting activity from the
"hot-add" activity. Testing has shown that this makes the guest more
responsive to hot add requests.

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, 23 insertions, 18 deletions

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 8dc406ccf10f..13fda3807bfb 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -417,6 +417,11 @@ struct balloon_state {
         struct work_struct wrk;
 };
 
+struct hot_add_wrk {
+        union dm_mem_page_range ha_page_range;
+        struct work_struct wrk;
+};
+
 static bool hot_add;
 static bool do_hot_add;
 /*
@@ -469,6 +474,11 @@ struct hv_dynmem_device {
         struct balloon_state balloon_wrk;
 
         /*
+         * State to execute the "hot-add" operation.
+         */
+        struct hot_add_wrk ha_wrk;
+
+        /*
          * This thread handles hot-add
          * requests from the host as well as notifying
          * the host with regards to memory pressure in
@@ -486,7 +496,7 @@ struct hv_dynmem_device {
 
 static struct hv_dynmem_device dm_device;
 
-static void hot_add_req(struct hv_dynmem_device *dm, struct dm_hot_add *msg)
+static void hot_add_req(struct work_struct *dummy)
 {
 
         struct dm_hot_add_response resp;
@@ -509,8 +519,8 @@ static void hot_add_req(struct hv_dynmem_device *dm, struct dm_hot_add *msg)
         resp.page_count = 0;
         resp.result = 0;
 
-        dm->state = DM_INITIALIZED;
-        vmbus_sendpacket(dm->dev->channel, &resp,
+        dm_device.state = DM_INITIALIZED;
+        vmbus_sendpacket(dm_device.dev->channel, &resp,
                         sizeof(struct dm_hot_add_response),
                         (unsigned long)NULL,
                         VM_PKT_DATA_INBAND, 0);
@@ -771,7 +781,6 @@ static int dm_thread_func(void *dm_dev)
 {
         struct hv_dynmem_device *dm = dm_dev;
         int t;
-        unsigned long  scan_start;
 
         while (!kthread_should_stop()) {
                 t = wait_for_completion_timeout(&dm_device.config_event, 1*HZ);
@@ -783,19 +792,6 @@ static int dm_thread_func(void *dm_dev)
                 if (t == 0)
                         post_status(dm);
 
-                scan_start = jiffies;
-                switch (dm->state) {
-
-                case DM_HOT_ADD:
-                        hot_add_req(dm, (struct dm_hot_add *)recv_buffer);
-                        break;
-                default:
-                        break;
-                }
-
-                if (!time_in_range(jiffies, scan_start, scan_start + HZ))
-                        post_status(dm);
-
         }
 
         return 0;
@@ -869,6 +865,8 @@ static void balloon_onchannelcallback(void *context)
         struct dm_header *dm_hdr;
         struct hv_dynmem_device *dm = hv_get_drvdata(dev);
         struct dm_balloon *bal_msg;
+        struct dm_hot_add *ha_msg;
+        union dm_mem_page_range *ha_pg_range;
 
         memset(recv_buffer, 0, sizeof(recv_buffer));
         vmbus_recvpacket(dev->channel, recv_buffer,
@@ -905,8 +903,13 @@ static void balloon_onchannelcallback(void *context)
                         break;
 
                 case DM_MEM_HOT_ADD_REQUEST:
+                        if (dm->state == DM_HOT_ADD)
+                                pr_warn("Currently hot-adding\n");
                         dm->state = DM_HOT_ADD;
-                        complete(&dm->config_event);
+                        ha_msg = (struct dm_hot_add *)recv_buffer;
+                        ha_pg_range = &ha_msg->range;
+                        dm_device.ha_wrk.ha_page_range = *ha_pg_range;
+                        schedule_work(&dm_device.ha_wrk.wrk);
                         break;
 
                 case DM_INFO_MESSAGE:
@@ -950,6 +953,7 @@ static int balloon_probe(struct hv_device *dev,
         init_completion(&dm_device.host_event);
         init_completion(&dm_device.config_event);
         INIT_WORK(&dm_device.balloon_wrk.wrk, balloon_up);
+        INIT_WORK(&dm_device.ha_wrk.wrk, hot_add_req);
 
         dm_device.thread =
                  kthread_run(dm_thread_func, &dm_device, "hv_balloon");
@@ -1062,6 +1066,7 @@ static int balloon_remove(struct hv_device *dev)
                 pr_warn("Ballooned pages: %d\n", dm->num_pages_ballooned);
 
         cancel_work_sync(&dm->balloon_wrk.wrk);
+        cancel_work_sync(&dm->ha_wrk.wrk);
         vmbus_close(dev->channel);
         kthread_stop(dm->thread);
         kfree(send_buffer);