Patch "Drivers: hv: balloon: keep track of where ha_region starts" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

Drivers: hv: balloon: keep track of where ha_region starts

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drivers-hv-balloon-keep-track-of-where-ha_region-starts.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Vitaly Kuznetsov <[email protected]>
Date: Wed, 24 Aug 2016 16:23:09 -0700
Subject: Drivers: hv: balloon: keep track of where ha_region starts

From: Vitaly Kuznetsov <[email protected]>

commit 7cf3b79ec85ee1a5bbaaf936bb1d050dc652983b upstream.

Windows 2012 (non-R2) does not specify hot add region in hot add requests and the logic in hot_add_req() is trying to find a 128Mb-aligned region covering the request. It may also happen that host's requests are not 128Mb aligned and the created ha_region will start before the first specified PFN. We can't online these non-present pages but we don't remember the real start of the region.

This is a regression introduced by the commit 5abbbb75d733 ("Drivers: hv:
hv_balloon: don't lose memory when onlining order is not natural"). While the idea of keeping the 'moving window' was wrong (as there is no guarantee that hot add requests come ordered) we should still keep track of covered_start_pfn. This is not a revert, the logic is different.

---
 drivers/hv/hv_balloon.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

@@ -430,13 +430,14 @@ struct dm_info_msg {
  * currently hot added. We hot add in multiples of 128M
  * chunks; it is possible that we may not be able to bring
  * online all the pages in the region. The range
- * covered_end_pfn defines the pages that can
+ * covered_start_pfn:covered_end_pfn defines the pages that can
  * be brough online.
  */
 
 struct hv_hotadd_state {
 	struct list_head list;
 	unsigned long start_pfn;
+	unsigned long covered_start_pfn;
 	unsigned long covered_end_pfn;
 	unsigned long ha_end_pfn;
 	unsigned long end_pfn;

@@ -682,7 +683,8 @@ static void hv_online_page(struct page *
 
 	list_for_each(cur, &dm_device.ha_region_list) {
 		has = list_entry(cur, struct hv_hotadd_state, list);
-		cur_start_pgp = (unsigned long)pfn_to_page(has->start_pfn);
+		cur_start_pgp = (unsigned long)
+			pfn_to_page(has->covered_start_pfn);
 		cur_end_pgp = (unsigned long)pfn_to_page(has->covered_end_pfn);
 
 		if (((unsigned long)pg >= cur_start_pgp) &&

@@ -854,6 +856,7 @@ static unsigned long process_hot_add(uns
 		list_add_tail(&ha_region->list, &dm_device.ha_region_list);
 		ha_region->start_pfn = rg_start;
 		ha_region->ha_end_pfn = rg_start;
+		ha_region->covered_start_pfn = pg_start;
 		ha_region->covered_end_pfn = pg_start;
 		ha_region->end_pfn = rg_start + rg_size;
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/drivers-hv-balloon-keep-track-of-where-ha_region-starts.patch queue-4.4/drivers-hv-get-rid-of-timeout-in-vmbus_open.patch queue-4.4/hv-don-t-reset-hv_context.tsc_page-on-crash.patch queue-4.4/drivers-hv-don-t-leak-memory-in-vmbus_establish_gpadl.patch queue-4.4/tools-hv-kvp-ensure-kvp-device-fd-is-closed-on-exec.patch queue-4.4/drivers-hv-balloon-account-for-gaps-in-hot-add-regions.patch