[PATCH -next] raid10: don't BUG_ON() in raise_barrier()

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

If raise_barrier() is called the first time in raid10_sync_request(), which
means the first non-normal io is handled, raise_barrier() should wait for
all dispatched normal io to be done. This ensures that normal io won't
starve.

However, BUG_ON() if this is broken is too aggressive. This patch replace
BUG_ON() with WARN and fall back to not force.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/raid10.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 4f8edb6ea3e2..a8b5fecef136 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -952,7 +952,9 @@ static void flush_pending_writes(struct r10conf *conf)
 static void raise_barrier(struct r10conf *conf, int force)
 {
 	write_seqlock_irq(&conf->resync_lock);
-	BUG_ON(force && !conf->barrier);
+
+	if (WARN_ON_ONCE(force && !conf->barrier))
+		force = false;
 
 	/* Wait until no block IO is waiting (unless 'force') */
 	wait_event_barrier(conf, force || !conf->nr_waiting);
-- 
2.31.1