Protect against CPU exhaust by event/x process during
errors by adding some delays in scheduling next event
and retry count limit.
Signed-off-by: Daniel Kiper <dkiper@xxxxxxxxxxxx>
---
drivers/xen/balloon.c | 107 +++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 90 insertions(+), 17 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 4223f64..6bae013 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -66,6 +66,22 @@
#define BALLOON_CLASS_NAME "xen_memory"
+/*
+ * balloon_process() state:
+ *
+ * BP_DONE: done or nothing to do,
+ * BP_EAGAIN: error, go to sleep,
+ * BP_ECANCELED: error, balloon operation canceled.
+ */
+
+enum bp_state {
+ BP_DONE,
+ BP_EAGAIN,
+ BP_ECANCELED
+};
+
+#define RETRY_UNLIMITED 0
+
struct balloon_stats {
/* We aim for 'current allocation' == 'target allocation'. */
unsigned long current_pages;
@@ -73,6 +89,10 @@ struct balloon_stats {
/* Number of pages in high- and low-memory balloons. */
unsigned long balloon_low;
unsigned long balloon_high;
+ unsigned long schedule_delay;
+ unsigned long max_schedule_delay;
+ unsigned long retry_count;
+ unsigned long max_retry_count;
};
static DEFINE_MUTEX(balloon_mutex);
@@ -171,6 +191,36 @@ static struct page *balloon_next_page(struct page *page)
return list_entry(next, struct page, lru);
}
+static enum bp_state update_schedule(enum bp_state state)
+{
+ if (state == BP_DONE) {
+ balloon_stats.schedule_delay = 1;
+ balloon_stats.retry_count = 1;
+ return BP_DONE;
+ }
+
+ pr_info("xen_balloon: Retry count: %lu/%lu\n", balloon_stats.retry_count,
+ balloon_stats.max_retry_count);
+
+ ++balloon_stats.retry_count;
+
+ if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
+ balloon_stats.retry_count > balloon_stats.max_retry_count) {
+ pr_info("xen_balloon: Retry count limit exceeded\n"
+ "xen_balloon: Balloon operation canceled\n");
+ balloon_stats.schedule_delay = 1;
+ balloon_stats.retry_count = 1;
+ return BP_ECANCELED;
+ }
+
+ balloon_stats.schedule_delay <<= 1;
+
+ if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
+ balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
+
+ return BP_EAGAIN;
+}
+
static unsigned long current_target(void)
{
unsigned long target = balloon_stats.target_pages;
@@ -183,11 +233,11 @@ static unsigned long current_target(void)
return target;
}
-static int increase_reservation(unsigned long nr_pages)
+static enum bp_state increase_reservation(unsigned long nr_pages)
{
+ int rc;
unsigned long pfn, i;
struct page *page;
- long rc;
struct xen_memory_reservation reservation = {
.address_bits = 0,
.extent_order = 0,
@@ -199,7 +249,10 @@ static int increase_reservation(unsigned long nr_pages)
page = balloon_first_page();
for (i = 0; i < nr_pages; i++) {
- BUG_ON(page == NULL);
+ if (!page) {
+ nr_pages = i;
+ break;
+ }
frame_list[i] = page_to_pfn(page);
page = balloon_next_page(page);
}
@@ -207,8 +260,10 @@ static int increase_reservation(unsigned long nr_pages)
set_xen_guest_handle(reservation.extent_start, frame_list);
reservation.nr_extents = nr_pages;
rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
- if (rc < 0)
- goto out;
+ if (rc <= 0) {
+ pr_info("xen_balloon: %s: Cannot allocate memory\n", __func__);
+ return BP_EAGAIN;
+ }
for (i = 0; i < rc; i++) {
page = balloon_retrieve();
@@ -238,15 +293,14 @@ static int increase_reservation(unsigned long nr_pages)
balloon_stats.current_pages += rc;
- out:
- return rc < 0 ? rc : rc != nr_pages;
+ return BP_DONE;
}
-static int decrease_reservation(unsigned long nr_pages)
+static enum bp_state decrease_reservation(unsigned long nr_pages)
{
+ enum bp_state state = BP_DONE;
unsigned long pfn, i;
struct page *page;
- int need_sleep = 0;
int ret;
struct xen_memory_reservation reservation = {
.address_bits = 0,
@@ -259,8 +313,9 @@ static int decrease_reservation(unsigned long nr_pages)
for (i = 0; i < nr_pages; i++) {
if ((page = alloc_page(GFP_BALLOON)) == NULL) {
+ pr_info("xen_balloon: %s: Cannot allocate memory\n", __func__);
nr_pages = i;
- need_sleep = 1;
+ state = BP_EAGAIN;
break;
}
@@ -296,7 +351,7 @@ static int decrease_reservation(unsigned long nr_pages)
balloon_stats.current_pages -= nr_pages;
- return need_sleep;
+ return state;
}
/*
@@ -307,27 +362,31 @@ static int decrease_reservation(unsigned long nr_pages)
*/
static void balloon_process(struct work_struct *work)
{
- int need_sleep = 0;
+ enum bp_state state = BP_DONE;
long credit;
mutex_lock(&balloon_mutex);
do {
credit = current_target() - balloon_stats.current_pages;
+
if (credit > 0)
- need_sleep = (increase_reservation(credit) != 0);
+ state = increase_reservation(credit);
+
if (credit < 0)
- need_sleep = (decrease_reservation(-credit) != 0);
+ state = decrease_reservation(-credit);
+
+ state = update_schedule(state);
#ifndef CONFIG_PREEMPT
if (need_resched())
schedule();
#endif
- } while ((credit != 0) && !need_sleep);
+ } while (credit && state == BP_DONE);
/* Schedule more work if there is some still to be done. */
- if (current_target() != balloon_stats.current_pages)
- schedule_delayed_work(&balloon_worker, HZ);
+ if (state == BP_EAGAIN)
+ schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
mutex_unlock(&balloon_mutex);
}
@@ -394,6 +453,11 @@ static int __init balloon_init(void)
balloon_stats.balloon_low = 0;
balloon_stats.balloon_high = 0;
+ balloon_stats.schedule_delay = 1;
+ balloon_stats.max_schedule_delay = 32;
+ balloon_stats.retry_count = 1;
+ balloon_stats.max_retry_count = 16;
+
register_balloon(&balloon_sysdev);
/*
@@ -447,6 +511,11 @@ BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
+static SYSDEV_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
+static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
+static SYSDEV_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
+static SYSDEV_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
+
static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
char *buf)
{
@@ -508,6 +577,10 @@ static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
static struct sysdev_attribute *balloon_attrs[] = {
&attr_target_kb,
&attr_target,
+ &attr_schedule_delay.attr,
+ &attr_max_schedule_delay.attr,
+ &attr_retry_count.attr,
+ &attr_max_retry_count.attr
};
static struct attribute *balloon_info_attrs[] = {
--
1.5.6.5
--
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