block: don't assume device has a request list backing in nr_requests store
Stacked devices do not. For now, just error out with -EINVAL. Later
we could make the limit apply on stacked devices too, for throttling
reasons.
This fixes
5a54cd13353bb3b88887604e2c980aa01e314309
and should go into 2.6.31 stable as well.
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index d3aa2aa..b78c9c3 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -40,7 +40,12 @@
{
struct request_list *rl = &q->rq;
unsigned long nr;
- int ret = queue_var_store(&nr, page, count);
+ int ret;
+
+ if (!q->request_fn)
+ return -EINVAL;
+
+ ret = queue_var_store(&nr, page, count);
if (nr < BLKDEV_MIN_RQ)
nr = BLKDEV_MIN_RQ;