Add "xen/balloon: fix cancelled balloon action" patch

Fix xen-balloon thread using 100% CPU

0001-xen-balloon-fix-cancelled-balloon-action.patch

@@ -0,0 +1,67 @@
+From c0901b425d5939b7f3ce6c3f4bb7a0161b819745 Mon Sep 17 00:00:00 2001
+From: Juergen Gross <[email protected]>
+Date: Mon, 4 Oct 2021 17:05:48 +0200
+Subject: [PATCH] xen/balloon: fix cancelled balloon action
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+In case a ballooning action is cancelled the new kernel thread handling
+the ballooning might end up in a busy loop.
+
+Fix that by handling the cancelled action gracefully.
+
+Cc: [email protected]
+Fixes: 8480ed9c2bbd56 ("xen/balloon: use a kernel thread instead a workqueue")
+Reported-by: Marek Marczykowski-Górecki <[email protected]>
+Signed-off-by: Juergen Gross <[email protected]>
+---
+ drivers/xen/balloon.c | 21 +++++++++++++++------
+ 1 file changed, 15 insertions(+), 6 deletions(-)
+
+diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
+index 43ebfe36ac27..3a50f097ed3e 100644
+--- a/drivers/xen/balloon.c
++++ b/drivers/xen/balloon.c
+@@ -491,12 +491,12 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
+ }
+
+ /*
+- * Stop waiting if either state is not BP_EAGAIN and ballooning action is
+- * needed, or if the credit has changed while state is BP_EAGAIN.
++ * Stop waiting if either state is BP_DONE and ballooning action is
++ * needed, or if the credit has changed while state is not BP_DONE.
+  */
+ static bool balloon_thread_cond(enum bp_state state, long credit)
+ {
+-	if (state != BP_EAGAIN)
++	if (state == BP_DONE)
+ 		credit = 0;
+
+ 	return current_credit() != credit || kthread_should_stop();
+@@ -516,10 +516,19 @@ static int balloon_thread(void *unused)
+
+ 	set_freezable();
+ 	for (;;) {
+-		if (state == BP_EAGAIN)
+-			timeout = balloon_stats.schedule_delay * HZ;
+-		else
++		switch (state) {
++		case BP_DONE:
++		case BP_ECANCELED:
+ 			timeout = 3600 * HZ;
++			break;
++		case BP_EAGAIN:
++			timeout = balloon_stats.schedule_delay * HZ;
++			break;
++		case BP_WAIT:
++			timeout = HZ;
++			break;
++		}
++
+ 		credit = current_credit();
+
+ 		wait_event_freezable_timeout(balloon_thread_wq,
+-- 
+2.26.2
+

kernel.spec.in

@@ -131,6 +131,7 @@ Patch11: 0012-xen-blkfront-prepare-request-locally-only-then-put-i.patch
 Patch12: 0013-xen-pcifront-pciback-Update-pciif.h-with-err-and-res.patch
 Patch14: 0001-Revert-xen-netback-Check-for-hotplug-status-existenc.patch
 Patch15: 0002-Revert-xen-netback-remove-hotplug-status-once-it-has.patch
+Patch16: 0001-xen-balloon-fix-cancelled-balloon-action.patch
 
 %description
 Qubes Dom0 kernel.