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

cftype->trigger() is pointless.  It's trivial to ignore the input
buffer from a regular ->write() operation.  Convert all ->trigger()
users to ->write() and remove ->trigger().

This patch doesn't introduce any visible behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>

5 files changed, 35 insertions, 43 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index aecdc84fe128..08eb71ee600b 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -500,14 +500,6 @@ struct cftype {
                          s64 val);
 
         /*
-         * trigger() callback can be used to get some kick from the
-         * userspace, when the actual string written is not important
-         * at all. The private field can be used to determine the
-         * kick type for multiplexing.
-         */
-        int (*trigger)(struct cgroup_subsys_state *css, unsigned int event);
-
-        /*
          * write() is the generic write callback which maps directly to
          * kernfs write operation and overrides all other operations.
          * Maximum write size is determined by ->max_write_len.  Use
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2a88ce7b24b6..2f16aab03493 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1034,8 +1034,7 @@ static umode_t cgroup_file_mode(const struct cftype *cft)
         if (cft->read_u64 || cft->read_s64 || cft->seq_show)
                 mode |= S_IRUGO;
 
-        if (cft->write_u64 || cft->write_s64 || cft->write ||
-            cft->trigger)
+        if (cft->write_u64 || cft->write_s64 || cft->write)
                 mode |= S_IWUSR;
 
         return mode;
@@ -2750,8 +2749,6 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
                 ret = kstrtoll(buf, 0, &v);
                 if (!ret)
                         ret = cft->write_s64(css, cft, v);
-        } else if (cft->trigger) {
-                ret = cft->trigger(css, (unsigned int)cft->private);
         } else {
                 ret = -EINVAL;
         }
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 191de26b0148..a380681ab3cf 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -284,14 +284,14 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
         return ret ?: nbytes;
 }
 
-static int hugetlb_cgroup_reset(struct cgroup_subsys_state *css,
-                                unsigned int event)
+static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of,
+                                    char *buf, size_t nbytes, loff_t off)
 {
         int idx, name, ret = 0;
-        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);
+        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));
 
-        idx = MEMFILE_IDX(event);
-        name = MEMFILE_ATTR(event);
+        idx = MEMFILE_IDX(of_cft(of)->private);
+        name = MEMFILE_ATTR(of_cft(of)->private);
 
         switch (name) {
         case RES_MAX_USAGE:
@@ -304,7 +304,7 @@ static int hugetlb_cgroup_reset(struct cgroup_subsys_state *css,
                 ret = -EINVAL;
                 break;
         }
-        return ret;
+        return ret ?: nbytes;
 }
 
 static char *mem_fmt(char *buf, int size, unsigned long hsize)
@@ -344,14 +344,14 @@ static void __init __hugetlb_cgroup_file_init(int idx)
         cft = &h->cgroup_files[2];
         snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf);
         cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE);
-        cft->trigger = hugetlb_cgroup_reset;
+        cft->write = hugetlb_cgroup_reset;
         cft->read_u64 = hugetlb_cgroup_read_u64;
 
         /* Add the failcntfile */
         cft = &h->cgroup_files[3];
         snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf);
         cft->private  = MEMFILE_PRIVATE(idx, RES_FAILCNT);
-        cft->trigger  = hugetlb_cgroup_reset;
+        cft->write = hugetlb_cgroup_reset;
         cft->read_u64 = hugetlb_cgroup_read_u64;
 
         /* NULL terminate the last cft */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7098a43f7447..b638a79209ee 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4887,14 +4887,15 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
         return 0;
 }
 
-static int mem_cgroup_force_empty_write(struct cgroup_subsys_state *css,
-                                        unsigned int event)
+static ssize_t mem_cgroup_force_empty_write(struct kernfs_open_file *of,
+                                            char *buf, size_t nbytes,
+                                            loff_t off)
 {
-        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
+        struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
 
         if (mem_cgroup_is_root(memcg))
                 return -EINVAL;
-        return mem_cgroup_force_empty(memcg);
+        return mem_cgroup_force_empty(memcg) ?: nbytes;
 }
 
 static u64 mem_cgroup_hierarchy_read(struct cgroup_subsys_state *css,
@@ -5220,14 +5221,15 @@ out:
         *memsw_limit = min_memsw_limit;
 }
 
-static int mem_cgroup_reset(struct cgroup_subsys_state *css, unsigned int event)
+static ssize_t mem_cgroup_reset(struct kernfs_open_file *of, char *buf,
+                                size_t nbytes, loff_t off)
 {
-        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
+        struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
         int name;
         enum res_type type;
 
-        type = MEMFILE_TYPE(event);
-        name = MEMFILE_ATTR(event);
+        type = MEMFILE_TYPE(of_cft(of)->private);
+        name = MEMFILE_ATTR(of_cft(of)->private);
 
         switch (name) {
         case RES_MAX_USAGE:
@@ -5252,7 +5254,7 @@ static int mem_cgroup_reset(struct cgroup_subsys_state *css, unsigned int event)
                 break;
         }
 
-        return 0;
+        return nbytes;
 }
 
 static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css,
@@ -6105,7 +6107,7 @@ static struct cftype mem_cgroup_files[] = {
         {
                 .name = "max_usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
-                .trigger = mem_cgroup_reset,
+                .write = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read_u64,
         },
         {
@@ -6123,7 +6125,7 @@ static struct cftype mem_cgroup_files[] = {
         {
                 .name = "failcnt",
                 .private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
-                .trigger = mem_cgroup_reset,
+                .write = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read_u64,
         },
         {
@@ -6132,7 +6134,7 @@ static struct cftype mem_cgroup_files[] = {
         },
         {
                 .name = "force_empty",
-                .trigger = mem_cgroup_force_empty_write,
+                .write = mem_cgroup_force_empty_write,
         },
         {
                 .name = "use_hierarchy",
@@ -6186,13 +6188,13 @@ static struct cftype mem_cgroup_files[] = {
         {
                 .name = "kmem.failcnt",
                 .private = MEMFILE_PRIVATE(_KMEM, RES_FAILCNT),
-                .trigger = mem_cgroup_reset,
+                .write = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read_u64,
         },
         {
                 .name = "kmem.max_usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_KMEM, RES_MAX_USAGE),
-                .trigger = mem_cgroup_reset,
+                .write = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read_u64,
         },
 #ifdef CONFIG_SLABINFO
@@ -6215,7 +6217,7 @@ static struct cftype memsw_cgroup_files[] = {
         {
                 .name = "memsw.max_usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
-                .trigger = mem_cgroup_reset,
+                .write = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read_u64,
         },
         {
@@ -6227,7 +6229,7 @@ static struct cftype memsw_cgroup_files[] = {
         {
                 .name = "memsw.failcnt",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
-                .trigger = mem_cgroup_reset,
+                .write = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read_u64,
         },
         { },    /* terminate */
diff --git a/net/ipv4/tcp_memcontrol.c b/net/ipv4/tcp_memcontrol.c
index 841fd3fa937a..f7a2ec3ac584 100644
--- a/net/ipv4/tcp_memcontrol.c
+++ b/net/ipv4/tcp_memcontrol.c
@@ -170,17 +170,18 @@ static u64 tcp_cgroup_read(struct cgroup_subsys_state *css, struct cftype *cft)
         return val;
 }
 
-static int tcp_cgroup_reset(struct cgroup_subsys_state *css, unsigned int event)
+static ssize_t tcp_cgroup_reset(struct kernfs_open_file *of,
+                                char *buf, size_t nbytes, loff_t off)
 {
         struct mem_cgroup *memcg;
         struct cg_proto *cg_proto;
 
-        memcg = mem_cgroup_from_css(css);
+        memcg = mem_cgroup_from_css(of_css(of));
         cg_proto = tcp_prot.proto_cgroup(memcg);
         if (!cg_proto)
-                return 0;
+                return nbytes;
 
-        switch (event) {
+        switch (of_cft(of)->private) {
         case RES_MAX_USAGE:
                 res_counter_reset_max(&cg_proto->memory_allocated);
                 break;
@@ -189,7 +190,7 @@ static int tcp_cgroup_reset(struct cgroup_subsys_state *css, unsigned int event)
                 break;
         }
 
-        return 0;
+        return nbytes;
 }
 
 static struct cftype tcp_files[] = {
@@ -207,13 +208,13 @@ static struct cftype tcp_files[] = {
         {
                 .name = "kmem.tcp.failcnt",
                 .private = RES_FAILCNT,
-                .trigger = tcp_cgroup_reset,
+                .write = tcp_cgroup_reset,
                 .read_u64 = tcp_cgroup_read,
         },
         {
                 .name = "kmem.tcp.max_usage_in_bytes",
                 .private = RES_MAX_USAGE,
-                .trigger = tcp_cgroup_reset,
+                .write = tcp_cgroup_reset,
                 .read_u64 = tcp_cgroup_read,
         },
         { }     /* terminate */