[dm-devel] [PATCH] Fix Null pointer Exception

[Stefan Raspl]

Here's a trivial patch for the kernel panics that we reported last week
when testing various ways to forcefully disconnect or temporarily disable
DASD disks from an IBM System z machine. We ran into NULL pointer exceptions
at the respective places.


Signed-off-by: Stefan Raspl <raspl at linux.vnet.ibm.com>


---
 drivers/md/dm-table.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -943,7 +943,8 @@ int dm_table_any_congested(struct dm_tab
 
 	list_for_each_entry(dd, devices, list) {
 		struct request_queue *q = bdev_get_queue(dd->bdev);
-		r |= bdi_congested(&q->backing_dev_info, bdi_bits);
+		if (q)
+			r |= bdi_congested(&q->backing_dev_info, bdi_bits);
 	}
 
 	return r;
@@ -957,7 +958,8 @@ void dm_table_unplug_all(struct dm_table
 	list_for_each_entry(dd, devices, list) {
 		struct request_queue *q = bdev_get_queue(dd->bdev);
 
-		blk_unplug(q);
+		if (q)
+			blk_unplug(q);
 	}
 }