Commit c268e994 authored by Daisuke Nishimura's avatar Daisuke Nishimura Committed by Linus Torvalds
Browse files

memcg: fix hierarchical reclaim 



If root_mem has no children, last_scaned_child is set to root_mem itself.
But after some children added to root_mem, mem_cgroup_get_next_node can
mem_cgroup_put the root_mem although root_mem has not been mem_cgroup_get.

This patch fixes this behavior by:

- Set last_scanned_child to NULL if root_mem has no children or DFS
  search has returned to root_mem itself(root_mem is not a "child" of
  root_mem).  Make mem_cgroup_get_first_node return root_mem in this case.
   There are no mem_cgroup_get/put for root_mem.

- Rename mem_cgroup_get_next_node to __mem_cgroup_get_next_node, and
  mem_cgroup_get_first_node to mem_cgroup_get_next_node.  Make
  mem_cgroup_hierarchical_reclaim call only new mem_cgroup_get_next_node.

Signed-off-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 40d58138

mm/memcontrol.c

+36 −32
Original line number Diff line number Diff line
@@ -633,7 +633,7 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan, 
 * called with hierarchy_mutex held

 */

static struct mem_cgroup *

mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem)

__mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem)

{

	struct cgroup *cgroup, *curr_cgroup, *root_cgroup;
@@ -644,19 +644,16 @@ mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) 
		/*

		 * Walk down to children

		 */

		mem_cgroup_put(curr);

		cgroup = list_entry(curr_cgroup->children.next,

						struct cgroup, sibling);

		curr = mem_cgroup_from_cont(cgroup);

		mem_cgroup_get(curr);

		goto done;

	}



visit_parent:

	if (curr_cgroup == root_cgroup) {

		mem_cgroup_put(curr);

		curr = root_mem;

		mem_cgroup_get(curr);

		/* caller handles NULL case */

		curr = NULL;

		goto done;

	}
@@ -664,11 +661,9 @@ visit_parent: 
	 * Goto next sibling

	 */

	if (curr_cgroup->sibling.next != &curr_cgroup->parent->children) {

		mem_cgroup_put(curr);

		cgroup = list_entry(curr_cgroup->sibling.next, struct cgroup,

						sibling);

		curr = mem_cgroup_from_cont(cgroup);

		mem_cgroup_get(curr);

		goto done;

	}
@@ -679,7 +674,6 @@ visit_parent: 
	goto visit_parent;



done:

	root_mem->last_scanned_child = curr;

	return curr;

}
@@ -689,40 +683,46 @@ done: 
 * that to reclaim free pages from.

 */

static struct mem_cgroup *

mem_cgroup_get_first_node(struct mem_cgroup *root_mem)

mem_cgroup_get_next_node(struct mem_cgroup *root_mem)

{

	struct cgroup *cgroup;

	struct mem_cgroup *ret;

	struct mem_cgroup *orig, *next;

	bool obsolete;



	obsolete = mem_cgroup_is_obsolete(root_mem->last_scanned_child);



	/*

	 * Scan all children under the mem_cgroup mem

	 */

	mutex_lock(&mem_cgroup_subsys.hierarchy_mutex);



	orig = root_mem->last_scanned_child;

	obsolete = mem_cgroup_is_obsolete(orig);



	if (list_empty(&root_mem->css.cgroup->children)) {

		ret = root_mem;

		/*

		 * root_mem might have children before and last_scanned_child

		 * may point to one of them. We put it later.

		 */

		if (orig)

			VM_BUG_ON(!obsolete);

		next = NULL;

		goto done;

	}



	if (!root_mem->last_scanned_child || obsolete) {



		if (obsolete && root_mem->last_scanned_child)

			mem_cgroup_put(root_mem->last_scanned_child);



	if (!orig || obsolete) {

		cgroup = list_first_entry(&root_mem->css.cgroup->children,

				struct cgroup, sibling);

		ret = mem_cgroup_from_cont(cgroup);

		mem_cgroup_get(ret);

		next = mem_cgroup_from_cont(cgroup);

	} else

		ret = mem_cgroup_get_next_node(root_mem->last_scanned_child,

						root_mem);

		next = __mem_cgroup_get_next_node(orig, root_mem);



done:

	root_mem->last_scanned_child = ret;

	if (next)

		mem_cgroup_get(next);

	root_mem->last_scanned_child = next;

	if (orig)

		mem_cgroup_put(orig);

	mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex);

	return ret;

	return (next) ? next : root_mem;

}



static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem)
@@ -780,21 +780,18 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem, 
	if (!root_mem->use_hierarchy)

		return ret;



	next_mem = mem_cgroup_get_first_node(root_mem);

	next_mem = mem_cgroup_get_next_node(root_mem);



	while (next_mem != root_mem) {

		if (mem_cgroup_is_obsolete(next_mem)) {

			mem_cgroup_put(next_mem);

			next_mem = mem_cgroup_get_first_node(root_mem);

			next_mem = mem_cgroup_get_next_node(root_mem);

			continue;

		}

		ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap,

						   get_swappiness(next_mem));

		if (mem_cgroup_check_under_limit(root_mem))

			return 0;

		mutex_lock(&mem_cgroup_subsys.hierarchy_mutex);

		next_mem = mem_cgroup_get_next_node(next_mem, root_mem);

		mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex);

		next_mem = mem_cgroup_get_next_node(root_mem);

	}

	return ret;

}
@@ -2254,7 +2251,14 @@ static void mem_cgroup_pre_destroy(struct cgroup_subsys *ss, 
static void mem_cgroup_destroy(struct cgroup_subsys *ss,

				struct cgroup *cont)

{

	mem_cgroup_put(mem_cgroup_from_cont(cont));

	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);

	struct mem_cgroup *last_scanned_child = mem->last_scanned_child;



	if (last_scanned_child) {

		VM_BUG_ON(!mem_cgroup_is_obsolete(last_scanned_child));

		mem_cgroup_put(last_scanned_child);

	}

	mem_cgroup_put(mem);

}



static int mem_cgroup_populate(struct cgroup_subsys *ss,

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