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hv_balloon: fix bugs in num_pages_onlined accounting

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Our num_pages_onlined accounting is buggy:
1) In case we're offlining a memory block which was present at boot (e.g.
   when there was no hotplug at all) we subtract 32k from 0 and as
   num_pages_onlined is unsigned get a very big positive number.

2) Commit 6df8d9aaf3 ("Drivers: hv: balloon: Correctly update onlined
   page count") made num_pages_onlined counter accurate on onlining but
   totally incorrect on offlining for partly populated regions: no matter
   how many pages were onlined and what was actually added to
   num_pages_onlined counter we always subtract the full region (32k) so
   again, num_pages_onlined can wrap around zero. By onlining/offlining
   the same partly populated region multiple times we can make the
   situation worse.

Solve these issues by doing accurate accounting on offlining: walk HAS
list, check for covered range and gaps.

Fixes: 6df8d9aaf3 ("Drivers: hv: balloon: Correctly update onlined page count")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vitaly Kuznetsov 2018-03-04 22:17:21 -07:00 committed by Greg Kroah-Hartman
parent 4f098af514
commit bba072d162
1 changed files with 69 additions and 13 deletions
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82
drivers/hv/hv_balloon.c
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@ -576,11 +576,65 @@ static struct hv_dynmem_device dm_device;
static void post_status(struct hv_dynmem_device *dm);
#ifdef CONFIG_MEMORY_HOTPLUG
static inline bool has_pfn_is_backed(struct hv_hotadd_state *has,
unsigned long pfn)
{
struct hv_hotadd_gap *gap;
/* The page is not backed. */
if ((pfn < has->covered_start_pfn) || (pfn >= has->covered_end_pfn))
return false;
/* Check for gaps. */
list_for_each_entry(gap, &has->gap_list, list) {
if ((pfn >= gap->start_pfn) && (pfn < gap->end_pfn))
return false;
}
return true;
}
static unsigned long hv_page_offline_check(unsigned long start_pfn,
unsigned long nr_pages)
{
unsigned long pfn = start_pfn, count = 0;
struct hv_hotadd_state *has;
bool found;
while (pfn < start_pfn + nr_pages) {
/*
* Search for HAS which covers the pfn and when we find one
* count how many consequitive PFNs are covered.
*/
found = false;
list_for_each_entry(has, &dm_device.ha_region_list, list) {
while ((pfn >= has->start_pfn) &&
(pfn < has->end_pfn) &&
(pfn < start_pfn + nr_pages)) {
found = true;
if (has_pfn_is_backed(has, pfn))
count++;
pfn++;
}
}
/*
* This PFN is not in any HAS (e.g. we're offlining a region
* which was present at boot), no need to account for it. Go
* to the next one.
*/
if (!found)
pfn++;
}
return count;
}
static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
void *v)
{
struct memory_notify *mem = (struct memory_notify *)v;
unsigned long flags;
unsigned long flags, pfn_count;
switch (val) {
case MEM_ONLINE:
@ -593,7 +647,19 @@ static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
case MEM_OFFLINE:
spin_lock_irqsave(&dm_device.ha_lock, flags);
dm_device.num_pages_onlined -= mem->nr_pages;
pfn_count = hv_page_offline_check(mem->start_pfn,
mem->nr_pages);
if (pfn_count <= dm_device.num_pages_onlined) {
dm_device.num_pages_onlined -= pfn_count;
} else {
/*
* We're offlining more pages than we managed to online.
* This is unexpected. In any case don't let
* num_pages_onlined wrap around zero.
*/
WARN_ON_ONCE(1);
dm_device.num_pages_onlined = 0;
}
spin_unlock_irqrestore(&dm_device.ha_lock, flags);
break;
case MEM_GOING_ONLINE:
@ -612,19 +678,9 @@ static struct notifier_block hv_memory_nb = {
/* Check if the particular page is backed and can be onlined and online it. */
static void hv_page_online_one(struct hv_hotadd_state *has, struct page *pg)
{
struct hv_hotadd_gap *gap;
unsigned long pfn = page_to_pfn(pg);
/* The page is not backed. */
if ((pfn < has->covered_start_pfn) || (pfn >= has->covered_end_pfn))
if (!has_pfn_is_backed(has, page_to_pfn(pg)))
return;
/* Check for gaps. */
list_for_each_entry(gap, &has->gap_list, list) {
if ((pfn >= gap->start_pfn) && (pfn < gap->end_pfn))
return;
}
/* This frame is currently backed; online the page. */
__online_page_set_limits(pg);
__online_page_increment_counters(pg);