cgroup: replace cftype->read_seq_string() with cftype->seq_show()

In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs.  This patch
replaces cftype->read_seq_string() with cftype->seq_show() which is
not limited to single_open() operation and will map directcly to
kernfs seq_file interface.

The conversions are mechanical.  As ->seq_show() doesn't have @css and
@cft, the functions which make use of them are converted to use
seq_css() and seq_cft() respectively.  In several occassions, e.f. if
it has seq_string in its name, the function name is updated to fit the
new method better.

This patch does not introduce any behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 498710d..56cbb69 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -173,14 +173,14 @@
 	return css->cgroup->id;
 }
 
-static int read_priomap(struct cgroup_subsys_state *css, struct cftype *cft,
-			struct seq_file *sf)
+static int read_priomap(struct seq_file *sf, void *v)
 {
 	struct net_device *dev;
 
 	rcu_read_lock();
 	for_each_netdev_rcu(&init_net, dev)
-		seq_printf(sf, "%s %u\n", dev->name, netprio_prio(css, dev));
+		seq_printf(sf, "%s %u\n", dev->name,
+			   netprio_prio(seq_css(sf), dev));
 	rcu_read_unlock();
 	return 0;
 }
@@ -238,7 +238,7 @@
 	},
 	{
 		.name = "ifpriomap",
-		.read_seq_string = read_priomap,
+		.seq_show = read_priomap,
 		.write_string = write_priomap,
 	},
 	{ }	/* terminate */