memory cgroup enhancements: add- pre_destroy() handler (4fca88c8) · Commits · 戴 / test

Add a handler "pre_destroy" to cgroup_subsys. It is called before cgroup_rmdir() checks all subsys's refcnt. I think this is useful for subsys which have some extra refs even if there are no tasks in cgroup. By adding pre_destroy(), the kernel keeps the rule "destroy() against subsystem is called only when refcnt=0." and allows css ref to be used by other objects than tasks. Signed-off-by:

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: David Rientjes <rientjes@google.com> Cc: Herbert Poetzl <herbert@13thfloor.at> Cc: Kirill Korotaev <dev@sw.ru> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Paul Menage <menage@google.com> Cc: Pavel Emelianov <xemul@openvz.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Signed-off-by:

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

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/cgroup.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -233,6 +233,7 @@ int cgroup_is_descendant(const struct cgroup *cont);
		struct cgroup_subsys {
		struct cgroup_subsys_state (create)(struct cgroup_subsys *ss,
		struct cgroup *cont);
		void (pre_destroy)(struct cgroup_subsys ss, struct cgroup *cont);
		void (destroy)(struct cgroup_subsys ss, struct cgroup *cont);
		int (can_attach)(struct cgroup_subsys ss,
		struct cgroup cont, struct task_struct tsk);

kernel/cgroup.c

+22 −0

Original line number	Diff line number	Diff line
		@@ -586,6 +586,21 @@ static struct inode cgroup_new_inode(mode_t mode, struct super_block sb)
		return inode;
		}

		/*
		* Call subsys's pre_destroy handler.
		* This is called before css refcnt check.
		*/

		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])
		ss->pre_destroy(ss, cgrp);
		return;
		}


		static void cgroup_diput(struct dentry dentry, struct inode inode)
		{
		/* is dentry a directory ? if so, kfree() associated cgroup */
		@@ -2160,6 +2175,13 @@ static int cgroup_rmdir(struct inode unused_dir, struct dentry dentry)
		parent = cgrp->parent;
		root = cgrp->root;
		sb = root->sb;
		/*
		* Call pre_destroy handlers of subsys
		*/
		cgroup_call_pre_destroy(cgrp);
		/*
		* Notify subsyses that rmdir() request comes.
		*/

		if (cgroup_has_css_refs(cgrp)) {
		mutex_unlock(&cgroup_mutex);

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