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, 7 insertions, 7 deletions

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 9134dbf70d3e..7dbac4061b1c 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -767,27 +767,27 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
         return rc;
 }
 
-static int devcgroup_access_write(struct cgroup_subsys_state *css,
-                                  struct cftype *cft, char *buffer)
+static ssize_t devcgroup_access_write(struct kernfs_open_file *of,
+                                      char *buf, size_t nbytes, loff_t off)
 {
         int retval;
 
         mutex_lock(&devcgroup_mutex);
-        retval = devcgroup_update_access(css_to_devcgroup(css),
-                                         cft->private, buffer);
+        retval = devcgroup_update_access(css_to_devcgroup(of_css(of)),
+                                         of_cft(of)->private, strstrip(buf));
         mutex_unlock(&devcgroup_mutex);
-        return retval;
+        return retval ?: nbytes;
 }
 
 static struct cftype dev_cgroup_files[] = {
         {
                 .name = "allow",
-                .write_string  = devcgroup_access_write,
+                .write = devcgroup_access_write,
                 .private = DEVCG_ALLOW,
         },
         {
                 .name = "deny",
-                .write_string = devcgroup_access_write,
+                .write = devcgroup_access_write,
                 .private = DEVCG_DENY,
         },
         {