[SRU][linux-aws-xenial][PATCH 2/2] block: don't show io_timeout if driver has no timeout handler

[Kamal Mostafa]

From: Weiping Zhang <zhangweiping at didiglobal.com>

BugLink: https://bugs.launchpad.net/bugs/1841461

If the low level driver has no timeout handler, the
/sys/block/<disk>/queue/io_timeout will not be displayed.

Reviewed-by: Bart Van Assche <bvanassche at acm.org>
Signed-off-by: Weiping Zhang <zhangweiping at didiglobal.com>
Signed-off-by: Jens Axboe <axboe at kernel.dk>
(backported from commit 4d25339e32a1b6e1f490bb78b1e5b0fa9eb3e073)
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 block/blk-sysfs.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 5da33f8d1d53..0507c1d25134 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -505,7 +505,7 @@ static struct queue_sysfs_entry queue_io_timeout_entry = {
 	.store = queue_io_timeout_store,
 };
 
-static struct attribute *default_attrs[] = {
+static struct attribute *queue_attrs[] = {
 	&queue_requests_entry.attr,
 	&queue_ra_entry.attr,
 	&queue_max_hw_sectors_entry.attr,
@@ -534,6 +534,25 @@ static struct attribute *default_attrs[] = {
 	NULL,
 };
 
+static umode_t queue_attr_visible(struct kobject *kobj, struct attribute *attr,
+				int n)
+{
+	struct request_queue *q =
+		container_of(kobj, struct request_queue, kobj);
+
+	if (attr == &queue_io_timeout_entry.attr &&
+		(!q->mq_ops || !q->mq_ops->timeout))
+			return 0;
+
+	return attr->mode;
+}
+
+static struct attribute_group queue_attr_group = {
+	.attrs = queue_attrs,
+	.is_visible = queue_attr_visible,
+};
+
+
 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
 
 static ssize_t
@@ -641,7 +660,6 @@ static const struct sysfs_ops queue_sysfs_ops = {
 
 struct kobj_type blk_queue_ktype = {
 	.sysfs_ops	= &queue_sysfs_ops,
-	.default_attrs	= default_attrs,
 	.release	= blk_release_queue,
 };
 
@@ -679,6 +697,14 @@ int blk_register_queue(struct gendisk *disk)
 		return ret;
 	}
 
+	ret = sysfs_create_group(&q->kobj, &queue_attr_group);
+	if (ret) {
+		blk_trace_remove_sysfs(dev);
+		kobject_del(&q->kobj);
+		kobject_put(&dev->kobj);
+		return ret;
+	}
+
 	kobject_uevent(&q->kobj, KOBJ_ADD);
 
 	if (q->mq_ops)
-- 
2.17.1