cgroups: remove some redundant NULL checks

- In cgroup_clone(), if vfs_mkdir() returns successfully,
  dentry->d_fsdata will be the pointer to the newly created
  cgroup and won't be NULL.

- a cgroup file's dentry->d_fsdata won't be NULL, guaranteed
  by cgroup_add_file().

- When walking through the subsystems of a cgroup_fs (using
  for_each_subsys), cgrp->subsys[ss->subsys_id] won't be NULL,
  guaranteed by cgroup_create().

(Also remove 2 unused variables in cgroup_rmdir().

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index f221446..220e0fd 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -586,7 +586,7 @@ static void cgroup_call_pre_destroy(struct cgroup *cgrp)
 {
        struct cgroup_subsys *ss;
        for_each_subsys(cgrp->root, ss)
-               if (ss->pre_destroy && cgrp->subsys[ss->subsys_id])
+               if (ss->pre_destroy)
                        ss->pre_destroy(ss, cgrp);
        return;
 }
@@ -610,10 +610,8 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
                /*
                 * Release the subsystem state objects.
                 */
-               for_each_subsys(cgrp->root, ss) {
-                       if (cgrp->subsys[ss->subsys_id])
-                               ss->destroy(ss, cgrp);
-               }
+               for_each_subsys(cgrp->root, ss)
+                       ss->destroy(ss, cgrp);
 
                cgrp->root->number_of_cgroups--;
                mutex_unlock(&cgroup_mutex);
@@ -1445,7 +1443,7 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
        struct cftype *cft = __d_cft(file->f_dentry);
        struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
 
-       if (!cft || cgroup_is_removed(cgrp))
+       if (cgroup_is_removed(cgrp))
                return -ENODEV;
        if (cft->write)
                return cft->write(cgrp, cft, file, buf, nbytes, ppos);
@@ -1490,7 +1488,7 @@ static ssize_t cgroup_file_read(struct file *file, char __user *buf,
        struct cftype *cft = __d_cft(file->f_dentry);
        struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
 
-       if (!cft || cgroup_is_removed(cgrp))
+       if (cgroup_is_removed(cgrp))
                return -ENODEV;
 
        if (cft->read)
@@ -1554,10 +1552,8 @@ static int cgroup_file_open(struct inode *inode, struct file *file)
        err = generic_file_open(inode, file);
        if (err)
                return err;
-
        cft = __d_cft(file->f_dentry);
-       if (!cft)
-               return -ENODEV;
+
        if (cft->read_map || cft->read_seq_string) {
                struct cgroup_seqfile_state *state =
                        kzalloc(sizeof(*state), GFP_USER);
@@ -2463,8 +2459,6 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
        struct cgroup *cgrp = dentry->d_fsdata;
        struct dentry *d;
        struct cgroup *parent;
-       struct super_block *sb;
-       struct cgroupfs_root *root;
 
        /* the vfs holds both inode->i_mutex already */
 
@@ -2487,8 +2481,6 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
 
        mutex_lock(&cgroup_mutex);
        parent = cgrp->parent;
-       root = cgrp->root;
-       sb = root->sb;
 
        if (atomic_read(&cgrp->count)
            || !list_empty(&cgrp->children)
@@ -2937,7 +2929,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
        }
 
        /* Create the cgroup directory, which also creates the cgroup */
-       ret = vfs_mkdir(inode, dentry, S_IFDIR | 0755);
+       ret = vfs_mkdir(inode, dentry, 0755);
        child = __d_cgrp(dentry);
        dput(dentry);
        if (ret) {
@@ -2947,13 +2939,6 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
                goto out_release;
        }
 
-       if (!child) {
-               printk(KERN_INFO
-                      "Couldn't find new cgroup %s\n", nodename);
-               ret = -ENOMEM;
-               goto out_release;
-       }
-
        /* The cgroup now exists. Retake cgroup_mutex and check
         * that we're still in the same state that we thought we
         * were. */