cgroup: replace cftype->write_string() with cftype->write()

Convert all cftype->write_string() users to the new cftype->write()
which maps directly to kernfs write operation and has full access to
kernfs and cgroup contexts.  The conversions are mostly mechanical.

* @css and @cft are accessed using of_css() and of_cft() accessors
  respectively instead of being specified as arguments.

* Should return @nbytes on success instead of 0.

* @buf is not trimmed automatically.  Trim if necessary.  Note that
  blkcg and netprio don't need this as the parsers already handle
  whitespaces.

cftype->write_string() has no user left after the conversions and
removed.

While at it, remove unnecessary local variable @p in
cgroup_subtree_control_write() and stale comment about
CGROUP_LOCAL_BUFFER_SIZE in cgroup_freezer.c.

This patch doesn't introduce any visible behavior changes.

v2: netprio was missing from conversion.  Converted.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: "David S. Miller" <davem@davemloft.net>

1 files changed, 9 insertions, 7 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 37ca0a5c226d..2f4b08b8db24 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1603,13 +1603,15 @@ out_unlock:
 /*
  * Common handling for a write to a "cpus" or "mems" file.
  */
-static int cpuset_write_resmask(struct cgroup_subsys_state *css,
-                                struct cftype *cft, char *buf)
+static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
+                                    char *buf, size_t nbytes, loff_t off)
 {
-        struct cpuset *cs = css_cs(css);
+        struct cpuset *cs = css_cs(of_css(of));
         struct cpuset *trialcs;
         int retval = -ENODEV;
 
+        buf = strstrip(buf);
+
         /*
          * CPU or memory hotunplug may leave @cs w/o any execution
          * resources, in which case the hotplug code asynchronously updates
@@ -1633,7 +1635,7 @@ static int cpuset_write_resmask(struct cgroup_subsys_state *css,
                 goto out_unlock;
         }
 
-        switch (cft->private) {
+        switch (of_cft(of)->private) {
         case FILE_CPULIST:
                 retval = update_cpumask(cs, trialcs, buf);
                 break;
@@ -1648,7 +1650,7 @@ static int cpuset_write_resmask(struct cgroup_subsys_state *css,
         free_trial_cpuset(trialcs);
 out_unlock:
         mutex_unlock(&cpuset_mutex);
-        return retval;
+        return retval ?: nbytes;
 }
 
 /*
@@ -1750,7 +1752,7 @@ static struct cftype files[] = {
         {
                 .name = "cpus",
                 .seq_show = cpuset_common_seq_show,
-                .write_string = cpuset_write_resmask,
+                .write = cpuset_write_resmask,
                 .max_write_len = (100U + 6 * NR_CPUS),
                 .private = FILE_CPULIST,
         },
@@ -1758,7 +1760,7 @@ static struct cftype files[] = {
         {
                 .name = "mems",
                 .seq_show = cpuset_common_seq_show,
-                .write_string = cpuset_write_resmask,
+                .write = cpuset_write_resmask,
                 .max_write_len = (100U + 6 * MAX_NUMNODES),
                 .private = FILE_MEMLIST,
         },