cgroup files: move notify_on_release file to separate write handler

This patch moves the write handler for the cgroups notify_on_release
file into a separate handler. This handler requires no cgroups locking
since it relies on atomic bitops for synchronization.

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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 8 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a14122ecaa5e..d597d3015786 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1474,13 +1474,6 @@ static ssize_t cgroup_common_file_write(struct cgroup *cgrp,
         case FILE_TASKLIST:
                 retval = attach_task_by_pid(cgrp, buffer);
                 break;
-        case FILE_NOTIFY_ON_RELEASE:
-                clear_bit(CGRP_RELEASABLE, &cgrp->flags);
-                if (simple_strtoul(buffer, NULL, 10) != 0)
-                        set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
-                else
-                        clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
-                break;
         default:
                 retval = -EINVAL;
                 goto out2;
@@ -2252,6 +2245,18 @@ static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
         return notify_on_release(cgrp);
 }
 
+static int cgroup_write_notify_on_release(struct cgroup *cgrp,
+                                          struct cftype *cft,
+                                          u64 val)
+{
+        clear_bit(CGRP_RELEASABLE, &cgrp->flags);
+        if (val)
+                set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
+        else
+                clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
+        return 0;
+}
+
 /*
  * for the common functions, 'private' gives the type of file
  */
@@ -2268,7 +2273,7 @@ static struct cftype files[] = {
         {
                 .name = "notify_on_release",
                 .read_u64 = cgroup_read_notify_on_release,
-                .write = cgroup_common_file_write,
+                .write_u64 = cgroup_write_notify_on_release,
                 .private = FILE_NOTIFY_ON_RELEASE,
         },
 };