iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

xen/balloon: Protect against CPU exhaust by event/x process

Browse Source 
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 2011-03-08 22:48:24 +01:00 committed by Konrad Rzeszutek Wilk
parent 95170b2e23
commit 95d2ac4a0c
1 changed files with 90 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

107
drivers/xen/balloon.c
View File

@ -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[] = {