Commit 75139b82 authored by Li Zefan's avatar Li Zefan Committed by Linus Torvalds
Browse files

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: default avatarLi 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 18e7f1f0

kernel/cgroup.c

+7 −22
Original line number Diff line number Diff line
@@ -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])

		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. */

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