[Devel] [PATCH hci-8.1 v6 4/7] dm/push_backup: fix mod_timer() usage

[Andrey Zhadchenko]

mod_timer() takes an absolute jiffies value, but all callers pass a
relative one, which is always in the past. The timer fires and re-arms
on every tick while a write is delayed. It has worked so far because
pb_timer_func() checks pb->deadline_jiffies each time.

Fixes: 62e07487348e ("dm: Add push backup driver")
https://virtuozzo.atlassian.net/browse/VSTOR-152912

Feature: dm-backup: push backup target driver
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
Reviewed-by: Alexander Ivanov <alexander.ivanov at virtuozzo.com>
---
v2: no changes
v3: no changes
v4: added Fixes: tag
v5: moved before "do not re-arm deadline timer", so it also fixes
    the mod_timer() in push_backup_write(); commit message: the
    relative expiry is always in the past, not only after 5 min
v6: subject prefix changed to dm/push_backup, added Feature: tag

 drivers/md/dm-push-backup.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-push-backup.c b/drivers/md/dm-push-backup.c
index 5c4f3d625fb82..b6d1629245235 100644
--- a/drivers/md/dm-push-backup.c
+++ b/drivers/md/dm-push-backup.c
@@ -244,7 +244,7 @@ static void pb_timer_func(struct timer_list *timer)
 	spin_unlock_irqrestore(&pb->lock, flags);
 
 	if (unlikely(time_before64(now, deadline)))
-		mod_timer(timer, deadline - now + 1);
+		mod_timer(timer, jiffies + (deadline - now) + 1);
 	else
 		queue_work(pb->wq, &pb->worker);
 }
@@ -278,7 +278,7 @@ static int postpone_if_required_for_backup(struct push_backup *pb,
 	spin_unlock_irqrestore(&pb->lock, flags);
 
 	if (queue_timer)
-		mod_timer(&pb->deadline_timer, pb->timeout_in_jiffies + 1);
+		mod_timer(&pb->deadline_timer, jiffies + pb->timeout_in_jiffies + 1);
 	rcu_read_unlock();
 
 	if (queue_timer)
@@ -532,7 +532,7 @@ static int push_backup_write(struct push_backup *pb,
 	if (!list_empty(&pbio_list)) {
 		resubmit_pbios(pb, &pbio_list);
 		if (has_more)
-			mod_timer(&pb->deadline_timer, pb->timeout_in_jiffies + 1);
+			mod_timer(&pb->deadline_timer, jiffies + pb->timeout_in_jiffies + 1);
 	}
 
 	return 0;
-- 
2.43.5