1 files changed, 34 insertions, 2 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 54d0db116153..e85c4013e8a2 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -135,6 +135,25 @@ static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
 	return queue_var_show(max_hw_sectors_kb, (page));
 }
 
+static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
+{
+	return queue_var_show(blk_queue_nomerges(q), page);
+}
+
+static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
+				    size_t count)
+{
+	unsigned long nm;
+	ssize_t ret = queue_var_store(&nm, page, count);
+
+	if (nm)
+	       set_bit(QUEUE_FLAG_NOMERGES, &q->queue_flags);
+	else
+	       clear_bit(QUEUE_FLAG_NOMERGES, &q->queue_flags);
+
+	return ret;
+}
+
 
 static struct queue_sysfs_entry queue_requests_entry = {
 	.attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
@@ -170,6 +189,12 @@ static struct queue_sysfs_entry queue_hw_sector_size_entry = {
 	.show = queue_hw_sector_size_show,
 };
 
+static struct queue_sysfs_entry queue_nomerges_entry = {
+	.attr = {.name = "nomerges", .mode = S_IRUGO | S_IWUSR },
+	.show = queue_nomerges_show,
+	.store = queue_nomerges_store,
+};
+
 static struct attribute *default_attrs[] = {
 	&queue_requests_entry.attr,
 	&queue_ra_entry.attr,
@@ -177,6 +202,7 @@ static struct attribute *default_attrs[] = {
 	&queue_max_sectors_entry.attr,
 	&queue_iosched_entry.attr,
 	&queue_hw_sector_size_entry.attr,
+	&queue_nomerges_entry.attr,
 	NULL,
 };
 
@@ -276,9 +302,12 @@ int blk_register_queue(struct gendisk *disk)
 
 	struct request_queue *q = disk->queue;
 
-	if (!q || !q->request_fn)
+	if (WARN_ON(!q))
 		return -ENXIO;
 
+	if (!q->request_fn)
+		return 0;
+
 	ret = kobject_add(&q->kobj, kobject_get(&disk->dev.kobj),
 			  "%s", "queue");
 	if (ret < 0)
@@ -300,7 +329,10 @@ void blk_unregister_queue(struct gendisk *disk)
 {
 	struct request_queue *q = disk->queue;
 
-	if (q && q->request_fn) {
+	if (WARN_ON(!q))
+		return;
+
+	if (q->request_fn) {
 		elv_unregister_queue(q);
 
 		kobject_uevent(&q->kobj, KOBJ_REMOVE);