Drivers: hv: hv_balloon: Fix a locking bug in the balloon driver
We support memory hot-add in the Hyper-V balloon driver by hot adding an appropriately
sized and aligned region and controlling the on-lining of pages within that region
based on the pages that the host wants us to online. We do this because the
granularity and alignment requirements in Linux are different from what Windows
expects. The state to manage the onlining of pages needs to be correctly
protected. Fix this bug.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 9cbbb83..8e30415 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -533,6 +533,9 @@
*/
struct task_struct *thread;
+ struct mutex ha_region_mutex;
+ struct completion waiter_event;
+
/*
* A list of hot-add regions.
*/
@@ -549,7 +552,59 @@
static struct hv_dynmem_device dm_device;
static void post_status(struct hv_dynmem_device *dm);
+
#ifdef CONFIG_MEMORY_HOTPLUG
+static void acquire_region_mutex(bool trylock)
+{
+ if (trylock) {
+ reinit_completion(&dm_device.waiter_event);
+ while (!mutex_trylock(&dm_device.ha_region_mutex))
+ wait_for_completion(&dm_device.waiter_event);
+ } else {
+ mutex_lock(&dm_device.ha_region_mutex);
+ }
+}
+
+static void release_region_mutex(bool trylock)
+{
+ if (trylock) {
+ mutex_unlock(&dm_device.ha_region_mutex);
+ } else {
+ mutex_unlock(&dm_device.ha_region_mutex);
+ complete(&dm_device.waiter_event);
+ }
+}
+
+static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
+ void *v)
+{
+ switch (val) {
+ case MEM_GOING_ONLINE:
+ acquire_region_mutex(true);
+ break;
+
+ case MEM_ONLINE:
+ case MEM_CANCEL_ONLINE:
+ release_region_mutex(true);
+ if (dm_device.ha_waiting) {
+ dm_device.ha_waiting = false;
+ complete(&dm_device.ol_waitevent);
+ }
+ break;
+
+ case MEM_GOING_OFFLINE:
+ case MEM_OFFLINE:
+ case MEM_CANCEL_OFFLINE:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block hv_memory_nb = {
+ .notifier_call = hv_memory_notifier,
+ .priority = 0
+};
+
static void hv_bring_pgs_online(unsigned long start_pfn, unsigned long size)
{
@@ -591,6 +646,7 @@
init_completion(&dm_device.ol_waitevent);
dm_device.ha_waiting = true;
+ release_region_mutex(false);
nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));
ret = add_memory(nid, PFN_PHYS((start_pfn)),
(HA_CHUNK << PAGE_SHIFT));
@@ -619,6 +675,7 @@
* have not been "onlined" within the allowed time.
*/
wait_for_completion_timeout(&dm_device.ol_waitevent, 5*HZ);
+ acquire_region_mutex(false);
post_status(&dm_device);
}
@@ -632,11 +689,6 @@
unsigned long cur_start_pgp;
unsigned long cur_end_pgp;
- if (dm_device.ha_waiting) {
- dm_device.ha_waiting = false;
- complete(&dm_device.ol_waitevent);
- }
-
list_for_each(cur, &dm_device.ha_region_list) {
has = list_entry(cur, struct hv_hotadd_state, list);
cur_start_pgp = (unsigned long)
@@ -834,6 +886,7 @@
resp.hdr.size = sizeof(struct dm_hot_add_response);
#ifdef CONFIG_MEMORY_HOTPLUG
+ acquire_region_mutex(false);
pg_start = dm->ha_wrk.ha_page_range.finfo.start_page;
pfn_cnt = dm->ha_wrk.ha_page_range.finfo.page_cnt;
@@ -865,6 +918,7 @@
if (do_hot_add)
resp.page_count = process_hot_add(pg_start, pfn_cnt,
rg_start, rg_sz);
+ release_region_mutex(false);
#endif
/*
* The result field of the response structure has the
@@ -1388,7 +1442,9 @@
dm_device.next_version = DYNMEM_PROTOCOL_VERSION_WIN7;
init_completion(&dm_device.host_event);
init_completion(&dm_device.config_event);
+ init_completion(&dm_device.waiter_event);
INIT_LIST_HEAD(&dm_device.ha_region_list);
+ mutex_init(&dm_device.ha_region_mutex);
INIT_WORK(&dm_device.balloon_wrk.wrk, balloon_up);
INIT_WORK(&dm_device.ha_wrk.wrk, hot_add_req);
dm_device.host_specified_ha_region = false;
@@ -1402,6 +1458,7 @@
#ifdef CONFIG_MEMORY_HOTPLUG
set_online_page_callback(&hv_online_page);
+ register_memory_notifier(&hv_memory_nb);
#endif
hv_set_drvdata(dev, &dm_device);
@@ -1520,6 +1577,7 @@
kfree(send_buffer);
#ifdef CONFIG_MEMORY_HOTPLUG
restore_online_page_callback(&hv_online_page);
+ unregister_memory_notifier(&hv_memory_nb);
#endif
list_for_each_safe(cur, tmp, &dm->ha_region_list) {
has = list_entry(cur, struct hv_hotadd_state, list);