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>

2 files changed, 30 insertions, 30 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 033745cd7fba..5e8fd1bace98 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1346,10 +1346,10 @@ static int tg_print_conf_uint(struct seq_file *sf, void *v)
         return 0;
 }
 
-static int tg_set_conf(struct cgroup_subsys_state *css, struct cftype *cft,
-                       const char *buf, bool is_u64)
+static ssize_t tg_set_conf(struct kernfs_open_file *of,
+                           char *buf, size_t nbytes, loff_t off, bool is_u64)
 {
-        struct blkcg *blkcg = css_to_blkcg(css);
+        struct blkcg *blkcg = css_to_blkcg(of_css(of));
         struct blkg_conf_ctx ctx;
         struct throtl_grp *tg;
         struct throtl_service_queue *sq;
@@ -1368,9 +1368,9 @@ static int tg_set_conf(struct cgroup_subsys_state *css, struct cftype *cft,
                 ctx.v = -1;
 
         if (is_u64)
-                *(u64 *)((void *)tg + cft->private) = ctx.v;
+                *(u64 *)((void *)tg + of_cft(of)->private) = ctx.v;
         else
-                *(unsigned int *)((void *)tg + cft->private) = ctx.v;
+                *(unsigned int *)((void *)tg + of_cft(of)->private) = ctx.v;
 
         throtl_log(&tg->service_queue,
                    "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
@@ -1404,19 +1404,19 @@ static int tg_set_conf(struct cgroup_subsys_state *css, struct cftype *cft,
         }
 
         blkg_conf_finish(&ctx);
-        return 0;
+        return nbytes;
 }
 
-static int tg_set_conf_u64(struct cgroup_subsys_state *css, struct cftype *cft,
-                           char *buf)
+static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
+                               char *buf, size_t nbytes, loff_t off)
 {
-        return tg_set_conf(css, cft, buf, true);
+        return tg_set_conf(of, buf, nbytes, off, true);
 }
 
-static int tg_set_conf_uint(struct cgroup_subsys_state *css, struct cftype *cft,
-                            char *buf)
+static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
+                                char *buf, size_t nbytes, loff_t off)
 {
-        return tg_set_conf(css, cft, buf, false);
+        return tg_set_conf(of, buf, nbytes, off, false);
 }
 
 static struct cftype throtl_files[] = {
@@ -1424,25 +1424,25 @@ static struct cftype throtl_files[] = {
                 .name = "throttle.read_bps_device",
                 .private = offsetof(struct throtl_grp, bps[READ]),
                 .seq_show = tg_print_conf_u64,
-                .write_string = tg_set_conf_u64,
+                .write = tg_set_conf_u64,
         },
         {
                 .name = "throttle.write_bps_device",
                 .private = offsetof(struct throtl_grp, bps[WRITE]),
                 .seq_show = tg_print_conf_u64,
-                .write_string = tg_set_conf_u64,
+                .write = tg_set_conf_u64,
         },
         {
                 .name = "throttle.read_iops_device",
                 .private = offsetof(struct throtl_grp, iops[READ]),
                 .seq_show = tg_print_conf_uint,
-                .write_string = tg_set_conf_uint,
+                .write = tg_set_conf_uint,
         },
         {
                 .name = "throttle.write_iops_device",
                 .private = offsetof(struct throtl_grp, iops[WRITE]),
                 .seq_show = tg_print_conf_uint,
-                .write_string = tg_set_conf_uint,
+                .write = tg_set_conf_uint,
         },
         {
                 .name = "throttle.io_service_bytes",
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e0985f1955e7..a73020b8c9af 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1670,11 +1670,11 @@ static int cfq_print_leaf_weight(struct seq_file *sf, void *v)
         return 0;
 }
 
-static int __cfqg_set_weight_device(struct cgroup_subsys_state *css,
-                                    struct cftype *cft, const char *buf,
-                                    bool is_leaf_weight)
+static ssize_t __cfqg_set_weight_device(struct kernfs_open_file *of,
+                                        char *buf, size_t nbytes, loff_t off,
+                                        bool is_leaf_weight)
 {
-        struct blkcg *blkcg = css_to_blkcg(css);
+        struct blkcg *blkcg = css_to_blkcg(of_css(of));
         struct blkg_conf_ctx ctx;
         struct cfq_group *cfqg;
         int ret;
@@ -1697,19 +1697,19 @@ static int __cfqg_set_weight_device(struct cgroup_subsys_state *css,
         }
 
         blkg_conf_finish(&ctx);
-        return ret;
+        return ret ?: nbytes;
 }
 
-static int cfqg_set_weight_device(struct cgroup_subsys_state *css,
-                                  struct cftype *cft, char *buf)
+static ssize_t cfqg_set_weight_device(struct kernfs_open_file *of,
+                                      char *buf, size_t nbytes, loff_t off)
 {
-        return __cfqg_set_weight_device(css, cft, buf, false);
+        return __cfqg_set_weight_device(of, buf, nbytes, off, false);
 }
 
-static int cfqg_set_leaf_weight_device(struct cgroup_subsys_state *css,
-                                       struct cftype *cft, char *buf)
+static ssize_t cfqg_set_leaf_weight_device(struct kernfs_open_file *of,
+                                           char *buf, size_t nbytes, loff_t off)
 {
-        return __cfqg_set_weight_device(css, cft, buf, true);
+        return __cfqg_set_weight_device(of, buf, nbytes, off, true);
 }
 
 static int __cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
@@ -1837,7 +1837,7 @@ static struct cftype cfq_blkcg_files[] = {
                 .name = "weight_device",
                 .flags = CFTYPE_ONLY_ON_ROOT,
                 .seq_show = cfqg_print_leaf_weight_device,
-                .write_string = cfqg_set_leaf_weight_device,
+                .write = cfqg_set_leaf_weight_device,
         },
         {
                 .name = "weight",
@@ -1851,7 +1851,7 @@ static struct cftype cfq_blkcg_files[] = {
                 .name = "weight_device",
                 .flags = CFTYPE_NOT_ON_ROOT,
                 .seq_show = cfqg_print_weight_device,
-                .write_string = cfqg_set_weight_device,
+                .write = cfqg_set_weight_device,
         },
         {
                 .name = "weight",
@@ -1863,7 +1863,7 @@ static struct cftype cfq_blkcg_files[] = {
         {
                 .name = "leaf_weight_device",
                 .seq_show = cfqg_print_leaf_weight_device,
-                .write_string = cfqg_set_leaf_weight_device,
+                .write = cfqg_set_leaf_weight_device,
         },
         {
                 .name = "leaf_weight",