From 9ba00538ada7ecb4fb8bd71ba734a8eada987817 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@cse.unsw.edu.au>
Date: Fri, 9 Sep 2005 16:23:57 -0700
Subject: [PATCH] [PATCH] md: ensure bitmap_writeback_daemon handles shutdown
 properly.

mddev->bitmap gets clearred before the writeback daemon is stopped.  So the
write_back daemon needs to be careful not to dereference the 'bitmap' if it is
NULL.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
 drivers/md/bitmap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 90fe70d76a3..87145faac49 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1156,6 +1156,9 @@ static void bitmap_writeback_daemon(mddev_t *mddev)
 		err = -EINTR;
 		goto out;
 	}
+	if (bitmap == NULL)
+		/* about to be stopped. */
+		return;
 
 	PRINTK("%s: bitmap writeback daemon woke up...\n", bmname(bitmap));
 	/* wait on bitmap page writebacks */
-- 
2.41.1