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Commit 0bec1cea authored by Juergen Gross's avatar Juergen Gross Committed by Greg Kroah-Hartman
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xen/balloon: fix cancelled balloon action 



commit 319933a80fd4f07122466a77f93e5019d71be74c upstream.

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.

While at it introduce a short wait for the BP_WAIT case.

Cc: stable@vger.kernel.org
Fixes: 8480ed9c2bbd56 ("xen/balloon: use a kernel thread instead a workqueue")
Reported-by: default avatarMarek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Tested-by: default avatarJason Andryuk <jandryuk@gmail.com>
Reviewed-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20211005133433.32008-1-jgross@suse.com


Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5520f147

drivers/xen/balloon.c

+15 −6
Original line number Diff line number Diff line
@@ -508,12 +508,12 @@ 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();
@@ -533,10 +533,19 @@ 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,