xen/balloon: Protect against CPU exhaust by event/x process
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@net-space.pl> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Daniel Kiper
Konrad Rzeszutek Wilk
parent
95170b2e23
commit
95d2ac4a0c
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@ -66,6 +66,22 @@
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#define BALLOON_CLASS_NAME "xen_memory"
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/*
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* balloon_process() state:
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*
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* BP_DONE: done or nothing to do,
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* BP_EAGAIN: error, go to sleep,
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* BP_ECANCELED: error, balloon operation canceled.
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*/
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enum bp_state {
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BP_DONE,
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BP_EAGAIN,
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BP_ECANCELED
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};
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#define RETRY_UNLIMITED 0
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struct balloon_stats {
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/* We aim for 'current allocation' == 'target allocation'. */
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unsigned long current_pages;
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@ -73,6 +89,10 @@ struct balloon_stats {
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/* Number of pages in high- and low-memory balloons. */
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unsigned long balloon_low;
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unsigned long balloon_high;
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unsigned long schedule_delay;
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unsigned long max_schedule_delay;
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unsigned long retry_count;
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unsigned long max_retry_count;
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};
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static DEFINE_MUTEX(balloon_mutex);
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@ -171,6 +191,36 @@ static struct page *balloon_next_page(struct page *page)
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return list_entry(next, struct page, lru);
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}
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static enum bp_state update_schedule(enum bp_state state)
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{
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if (state == BP_DONE) {
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balloon_stats.schedule_delay = 1;
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balloon_stats.retry_count = 1;
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return BP_DONE;
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}
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pr_info("xen_balloon: Retry count: %lu/%lu\n", balloon_stats.retry_count,
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balloon_stats.max_retry_count);
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++balloon_stats.retry_count;
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if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
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balloon_stats.retry_count > balloon_stats.max_retry_count) {
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pr_info("xen_balloon: Retry count limit exceeded\n"
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"xen_balloon: Balloon operation canceled\n");
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balloon_stats.schedule_delay = 1;
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balloon_stats.retry_count = 1;
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return BP_ECANCELED;
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}
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balloon_stats.schedule_delay <<= 1;
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if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
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balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
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return BP_EAGAIN;
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}
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static unsigned long current_target(void)
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{
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unsigned long target = balloon_stats.target_pages;
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@ -183,11 +233,11 @@ static unsigned long current_target(void)
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return target;
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}
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static int increase_reservation(unsigned long nr_pages)
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static enum bp_state increase_reservation(unsigned long nr_pages)
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{
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int rc;
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unsigned long pfn, i;
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struct page *page;
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long rc;
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struct xen_memory_reservation reservation = {
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.address_bits = 0,
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.extent_order = 0,
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@ -199,7 +249,10 @@ static int increase_reservation(unsigned long nr_pages)
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page = balloon_first_page();
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for (i = 0; i < nr_pages; i++) {
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BUG_ON(page == NULL);
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if (!page) {
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nr_pages = i;
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break;
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}
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frame_list[i] = page_to_pfn(page);
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page = balloon_next_page(page);
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}
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@ -207,8 +260,10 @@ static int increase_reservation(unsigned long nr_pages)
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set_xen_guest_handle(reservation.extent_start, frame_list);
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reservation.nr_extents = nr_pages;
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rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
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if (rc < 0)
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goto out;
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if (rc <= 0) {
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pr_info("xen_balloon: %s: Cannot allocate memory\n", __func__);
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return BP_EAGAIN;
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}
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for (i = 0; i < rc; i++) {
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page = balloon_retrieve();
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@ -238,15 +293,14 @@ static int increase_reservation(unsigned long nr_pages)
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balloon_stats.current_pages += rc;
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out:
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return rc < 0 ? rc : rc != nr_pages;
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return BP_DONE;
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}
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static int decrease_reservation(unsigned long nr_pages)
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static enum bp_state decrease_reservation(unsigned long nr_pages)
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{
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enum bp_state state = BP_DONE;
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unsigned long pfn, i;
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struct page *page;
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int need_sleep = 0;
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int ret;
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struct xen_memory_reservation reservation = {
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.address_bits = 0,
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@ -259,8 +313,9 @@ static int decrease_reservation(unsigned long nr_pages)
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for (i = 0; i < nr_pages; i++) {
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if ((page = alloc_page(GFP_BALLOON)) == NULL) {
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pr_info("xen_balloon: %s: Cannot allocate memory\n", __func__);
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nr_pages = i;
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need_sleep = 1;
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state = BP_EAGAIN;
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break;
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}
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@ -296,7 +351,7 @@ static int decrease_reservation(unsigned long nr_pages)
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balloon_stats.current_pages -= nr_pages;
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return need_sleep;
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return state;
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}
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/*
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@ -307,27 +362,31 @@ static int decrease_reservation(unsigned long nr_pages)
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*/
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static void balloon_process(struct work_struct *work)
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{
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int need_sleep = 0;
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enum bp_state state = BP_DONE;
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long credit;
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mutex_lock(&balloon_mutex);
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do {
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credit = current_target() - balloon_stats.current_pages;
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if (credit > 0)
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need_sleep = (increase_reservation(credit) != 0);
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state = increase_reservation(credit);
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if (credit < 0)
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need_sleep = (decrease_reservation(-credit) != 0);
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state = decrease_reservation(-credit);
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state = update_schedule(state);
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#ifndef CONFIG_PREEMPT
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if (need_resched())
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schedule();
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#endif
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} while ((credit != 0) && !need_sleep);
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} while (credit && state == BP_DONE);
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/* Schedule more work if there is some still to be done. */
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if (current_target() != balloon_stats.current_pages)
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schedule_delayed_work(&balloon_worker, HZ);
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if (state == BP_EAGAIN)
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schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
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mutex_unlock(&balloon_mutex);
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}
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@ -394,6 +453,11 @@ static int __init balloon_init(void)
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balloon_stats.balloon_low = 0;
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balloon_stats.balloon_high = 0;
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balloon_stats.schedule_delay = 1;
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balloon_stats.max_schedule_delay = 32;
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balloon_stats.retry_count = 1;
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balloon_stats.max_retry_count = 16;
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register_balloon(&balloon_sysdev);
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/*
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@ -447,6 +511,11 @@ BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
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BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
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BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
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static SYSDEV_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
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static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
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static SYSDEV_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
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static SYSDEV_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
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static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
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char *buf)
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{
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@ -508,6 +577,10 @@ static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
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static struct sysdev_attribute *balloon_attrs[] = {
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&attr_target_kb,
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&attr_target,
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&attr_schedule_delay.attr,
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&attr_max_schedule_delay.attr,
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&attr_retry_count.attr,
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&attr_max_retry_count.attr
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};
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static struct attribute *balloon_info_attrs[] = {
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