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>

kernel/cpuset.c

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 032929f..4410ac6 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1732,12 +1732,10 @@
  * and since these maps can change value dynamically, one could read
  * gibberish by doing partial reads while a list was changing.
  */
-static int cpuset_common_read_seq_string(struct cgroup_subsys_state *css,
-					 struct cftype *cft,
-					 struct seq_file *sf)
+static int cpuset_common_seq_show(struct seq_file *sf, void *v)
 {
-	struct cpuset *cs = css_cs(css);
-	cpuset_filetype_t type = cft->private;
+	struct cpuset *cs = css_cs(seq_css(sf));
+	cpuset_filetype_t type = seq_cft(sf)->private;
 	ssize_t count;
 	char *buf, *s;
 	int ret = 0;
@@ -1824,7 +1822,7 @@
 static struct cftype files[] = {
 	{
 		.name = "cpus",
-		.read_seq_string = cpuset_common_read_seq_string,
+		.seq_show = cpuset_common_seq_show,
 		.write_string = cpuset_write_resmask,
 		.max_write_len = (100U + 6 * NR_CPUS),
 		.private = FILE_CPULIST,
@@ -1832,7 +1830,7 @@
 
 	{
 		.name = "mems",
-		.read_seq_string = cpuset_common_read_seq_string,
+		.seq_show = cpuset_common_seq_show,
 		.write_string = cpuset_write_resmask,
 		.max_write_len = (100U + 6 * MAX_NUMNODES),
 		.private = FILE_MEMLIST,