Commit cc9cb219 authored Jun 05, 2008 by Pavel Emelyanov Committed by Linus Torvalds Jun 06, 2008

devscgroup: relax task to dev_cgroup conversion



Two functions, that need to get a device_cgroup from a task (they are
devcgroup_inode_permission and devcgroup_inode_mknod) make it in a strange
way:

They get a css_set from task, then a subsys_state from css_set, then a
cgroup from the state and then a subsys_state again from the cgroup.
Besides, the devices_subsys_id is read from memory, whilst there's a
enum-ed constant for it.

Optimize this part a bit:
1. Get the subsys_stats form the task and be done - no 2 extra
   dereferences,
2. Use the device_subsys_id constant, not the value from memory
   (i.e. one less dereference).

Found while preparing 2.6.26 OpenVZ port.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Paul Menage <menage@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: James Morris <jmorris@namei.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent b66862f7

security/device_cgroup.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -506,7 +506,6 @@ struct cgroup_subsys devices_subsys = {

		int devcgroup_inode_permission(struct inode *inode, int mask)
		{
		struct cgroup *cgroup;
		struct dev_cgroup *dev_cgroup;
		struct dev_whitelist_item *wh;

		@@ -515,8 +514,8 @@ int devcgroup_inode_permission(struct inode *inode, int mask)
		return 0;
		if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))
		return 0;
		cgroup = task_cgroup(current, devices_subsys.subsys_id);
		dev_cgroup = cgroup_to_devcgroup(cgroup);
		dev_cgroup = css_to_devcgroup(task_subsys_state(current,
		devices_subsys_id));
		if (!dev_cgroup)
		return 0;

		@@ -547,12 +546,11 @@ int devcgroup_inode_permission(struct inode *inode, int mask)

		int devcgroup_inode_mknod(int mode, dev_t dev)
		{
		struct cgroup *cgroup;
		struct dev_cgroup *dev_cgroup;
		struct dev_whitelist_item *wh;

		cgroup = task_cgroup(current, devices_subsys.subsys_id);
		dev_cgroup = cgroup_to_devcgroup(cgroup);
		dev_cgroup = css_to_devcgroup(task_subsys_state(current,
		devices_subsys_id));
		if (!dev_cgroup)
		return 0;