cgroup files: convert res_counter_write() to be a cgroups write_string() handler

Currently res_counter_write() is a raw file handler even though it's
ultimately taking a number, since in some cases it wants to
pre-process the string when converting it to a number.

This patch converts res_counter_write() from a raw file handler to a
write_string() handler; this allows some of the boilerplate
copying/locking/checking to be removed, and simplies the cleanup path,
since these functions are now performed by the cgroups framework.

[lizf@cn.fujitsu.com: build fix]
Signed-off-by: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 19 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e46451e1d9b7..7385d58fb061 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -838,32 +838,18 @@ out:
         return ret;
 }
 
-static int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp)
-{
-        *tmp = memparse(buf, &buf);
-        if (*buf != '\0')
-                return -EINVAL;
-
-        /*
-         * Round up the value to the closest page size
-         */
-        *tmp = ((*tmp + PAGE_SIZE - 1) >> PAGE_SHIFT) << PAGE_SHIFT;
-        return 0;
-}
-
 static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
 {
         return res_counter_read_u64(&mem_cgroup_from_cont(cont)->res,
                                     cft->private);
 }
 
-static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
-                                struct file *file, const char __user *userbuf,
-                                size_t nbytes, loff_t *ppos)
+static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
+                            const char *buffer)
 {
         return res_counter_write(&mem_cgroup_from_cont(cont)->res,
-                                cft->private, userbuf, nbytes, ppos,
-                                mem_cgroup_write_strategy);
+                                 cft->private, buffer,
+                                 res_counter_memparse_write_strategy);
 }
 
 static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
@@ -940,7 +926,7 @@ static struct cftype mem_cgroup_files[] = {
         {
                 .name = "limit_in_bytes",
                 .private = RES_LIMIT,
-                .write = mem_cgroup_write,
+                .write_string = mem_cgroup_write,
                 .read_u64 = mem_cgroup_read,
         },
         {