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Commit b326f9d0 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: clean up find_css_set() and friends 



find_css_set() passes uninitialized on-stack template[] array to
find_existing_css_set() which sets the entries for all subsystems.
Passing around an uninitialized array is a bit icky and we want to
introduce an iterator which only iterates loaded subsystems.  Let's
initialize it on definition.

While at it, also make the following cosmetic cleanups.

* Convert to proper /** comments.

* Reorder variable declarations.

* Replace comment on synchronization with lockdep_assert_held().

This patch doesn't make any functional differences.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent a8a648c4

kernel/cgroup.c

+17 −21
Original line number Diff line number Diff line
@@ -434,7 +434,7 @@ static inline void put_css_set_taskexit(struct css_set *cset) 
	__put_css_set(cset, 1);

}



/*

/**

 * compare_css_sets - helper function for find_existing_css_set().

 * @cset: candidate css_set being tested

 * @old_cset: existing css_set for a task
@@ -506,27 +506,20 @@ static bool compare_css_sets(struct css_set *cset, 
	return true;

}



/*

 * find_existing_css_set() is a helper for

 * find_css_set(), and checks to see whether an existing

 * css_set is suitable.

 *

 * oldcg: the cgroup group that we're using before the cgroup

 * transition

 *

 * cgrp: the cgroup that we're moving into

 *

 * template: location in which to build the desired set of subsystem

 * state objects for the new cgroup group

/**

 * find_existing_css_set - init css array and find the matching css_set

 * @old_cset: the css_set that we're using before the cgroup transition

 * @cgrp: the cgroup that we're moving into

 * @template: out param for the new set of csses, should be clear on entry

 */

static struct css_set *find_existing_css_set(struct css_set *old_cset,

					struct cgroup *cgrp,

					struct cgroup_subsys_state *template[])

{

	int i;

	struct cgroupfs_root *root = cgrp->root;

	struct css_set *cset;

	unsigned long key;

	int i;



	/*

	 * Build the set of subsystem state objects that we want to see in the
@@ -618,22 +611,25 @@ static void link_css_set(struct list_head *tmp_links, struct css_set *cset, 
	list_add_tail(&link->cgrp_link, &cset->cgrp_links);

}



/*

 * find_css_set() takes an existing cgroup group and a

 * cgroup object, and returns a css_set object that's

 * equivalent to the old group, but with the given cgroup

 * substituted into the appropriate hierarchy. Must be called with

 * cgroup_mutex held

/**

 * find_css_set - return a new css_set with one cgroup updated

 * @old_cset: the baseline css_set

 * @cgrp: the cgroup to be updated

 *

 * Return a new css_set that's equivalent to @old_cset, but with @cgrp

 * substituted into the appropriate hierarchy.

 */

static struct css_set *find_css_set(struct css_set *old_cset,

				    struct cgroup *cgrp)

{

	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };

	struct css_set *cset;

	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];

	struct list_head tmp_links;

	struct cgrp_cset_link *link;

	unsigned long key;



	lockdep_assert_held(&cgroup_mutex);



	/* First see if we already have a cgroup group that matches

	 * the desired set */

	read_lock(&css_set_lock);