From b8a9ae779f2c7049071034661e09cb7e1e82250c Mon Sep 17 00:00:00 2001
From: Jens Axboe <jens.axboe@oracle.com>
Date: Fri, 11 Sep 2009 22:44:29 +0200
Subject: [PATCH] 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>
---
block/blk-sysfs.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index d3aa2aadb3e0..b78c9c3e2670 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -40,7 +40,12 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count)
{
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;