[PATCH V2 0/3] Drivers: hv: hv_balloon

[PATCH V2 0/3] Drivers: hv: hv_balloon

[K. Y. Srinivasan]

Some bug fixes for the balloon driver. In this version,
based on Dan Carpenter's comment, I have added some additional
information to the change log.

K. Y. Srinivasan (3):
  Drivers: hv: hv_balloon: Make adjustments in computing the floor
  Drivers: hv: hv_balloon: Fix a locking bug in the balloon driver
  Drivers: hv: hv_balloon: Don't post pressure status from interrupt
    context

 drivers/hv/hv_balloon.c |   89 ++++++++++++++++++++++++++++++++++++++--------
 1 files changed, 73 insertions(+), 16 deletions(-)

-- 
1.7.4.1

[PATCH V2 1/3] Drivers: hv: hv_balloon: Make adjustments in computing the floor

[K. Y. Srinivasan]

Make adjustments in computing the balloon floor. The current computation
of the balloon floor was not appropriate for virtual machines with more than
10 GB of assigned memory - we would get into situations where the host would
agressively balloon down the guest and leave the guest in an unusable state.
This patch fixes the issue by raising the floor.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/hv_balloon.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index b958ded..9cbbb83 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -928,9 +928,8 @@ static unsigned long compute_balloon_floor(void)
 	 *     128        72    (1/2)
 	 *     512       168    (1/4)
 	 *    2048       360    (1/8)
-	 *    8192       552    (1/32)
-	 *   32768      1320
-	 *  131072      4392
+	 *    8192       768    (1/16)
+	 *   32768      1536	(1/32)
 	 */
 	if (totalram_pages < MB2PAGES(128))
 		min_pages = MB2PAGES(8) + (totalram_pages >> 1);
@@ -938,8 +937,10 @@ static unsigned long compute_balloon_floor(void)
 		min_pages = MB2PAGES(40) + (totalram_pages >> 2);
 	else if (totalram_pages < MB2PAGES(2048))
 		min_pages = MB2PAGES(104) + (totalram_pages >> 3);
+	else if (totalram_pages < MB2PAGES(8192))
+		min_pages = MB2PAGES(256) + (totalram_pages >> 4);
 	else
-		min_pages = MB2PAGES(296) + (totalram_pages >> 5);
+		min_pages = MB2PAGES(512) + (totalram_pages >> 5);
 #undef MB2PAGES
 	return min_pages;
 }
-- 
1.7.4.1

[PATCH V2 2/3] Drivers: hv: hv_balloon: Fix a locking bug in the balloon driver

[K. Y. Srinivasan]

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>
---
 drivers/hv/hv_balloon.c |   69 +++++++++++++++++++++++++++++++++++++++++++---
 1 files changed, 64 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 9cbbb83..2c610ec 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -533,6 +533,9 @@ struct hv_dynmem_device {
 	 */
 	struct task_struct *thread;
 
+	struct mutex ha_region_mutex;
+	struct completion waiter_event;
+
 	/*
 	 * A list of hot-add regions.
 	 */
@@ -549,7 +552,60 @@ struct hv_dynmem_device {
 static struct hv_dynmem_device dm_device;
 
 static void post_status(struct hv_dynmem_device *dm);
+
+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);
+	}
+}
+
+
 #ifdef CONFIG_MEMORY_HOTPLUG
+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 +647,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size,
 		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 +676,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size,
 		 * 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 +690,6 @@ static void hv_online_page(struct page *pg)
 	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 +887,7 @@ static void hot_add_req(struct work_struct *dummy)
 	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 +919,7 @@ static void hot_add_req(struct work_struct *dummy)
 	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 +1443,9 @@ 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_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 +1459,7 @@ static int balloon_probe(struct hv_device *dev,
 
 #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 +1578,7 @@ static int balloon_remove(struct hv_device *dev)
 	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);
-- 
1.7.4.1

[PATCH V2 3/3] Drivers: hv: hv_balloon: Don't post pressure status from interrupt context

[K. Y. Srinivasan]

We currently release memory (balloon down) in the interrupt context and we also
post memory status while releasing memory. Rather than posting the status
in the interrupt context, wakeup the status posting thread to post the status.
This will address the inconsistent lock state that Sitsofe Wheeler <sitsofe@gmail.com>
reported:

http://lkml.iu.edu/hypermail/linux/kernel/1411.1/00075.html

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reported-by: Sitsofe Wheeler <sitsofe@gmail.com>
---
 drivers/hv/hv_balloon.c |   11 ++++-------
 1 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 2c610ec..afdb0d5 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1227,7 +1227,7 @@ static void balloon_down(struct hv_dynmem_device *dm,
 
 	for (i = 0; i < range_count; i++) {
 		free_balloon_pages(dm, &range_array[i]);
-		post_status(&dm_device);
+		complete(&dm_device.config_event);
 	}
 
 	if (req->more_pages == 1)
@@ -1251,19 +1251,16 @@ static void balloon_onchannelcallback(void *context);
 static int dm_thread_func(void *dm_dev)
 {
 	struct hv_dynmem_device *dm = dm_dev;
-	int t;
 
 	while (!kthread_should_stop()) {
-		t = wait_for_completion_interruptible_timeout(
+		wait_for_completion_interruptible_timeout(
 						&dm_device.config_event, 1*HZ);
 		/*
 		 * The host expects us to post information on the memory
 		 * pressure every second.
 		 */
-
-		if (t == 0)
-			post_status(dm);
-
+		reinit_completion(&dm_device.config_event);
+		post_status(dm);
 	}
 
 	return 0;
-- 
1.7.4.1