Commit 907860ed authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

cgroups: make cftype.unregister_event() void-returning 



Since we are unable to handle an error returned by
cftype.unregister_event() properly, let's make the callback
void-returning.

mem_cgroup_unregister_event() has been rewritten to be a "never fail"
function.  On mem_cgroup_usage_register_event() we save old buffer for
thresholds array and reuse it in mem_cgroup_usage_unregister_event() to
avoid allocation.

Signed-off-by: default avatarKirill A. Shutemov <kirill@shutemov.name>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ac39cf8c

include/linux/cgroup.h

+1 −1
Original line number Diff line number Diff line
@@ -397,7 +397,7 @@ struct cftype { 
	 * This callback must be implemented, if you want provide

	 * notification functionality.

	 */

	int (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,

	void (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,

			struct eventfd_ctx *eventfd);

};

kernel/cgroup.c

+0 −1
Original line number Diff line number Diff line
@@ -2994,7 +2994,6 @@ static void cgroup_event_remove(struct work_struct *work) 
			remove);

	struct cgroup *cgrp = event->cgrp;



	/* TODO: check return code */

	event->cft->unregister_event(cgrp, event->cft, event->eventfd);



	eventfd_ctx_put(event->eventfd);

mm/memcontrol.c

+41 −24
Original line number Diff line number Diff line
@@ -226,9 +226,19 @@ struct mem_cgroup { 
	/* thresholds for memory usage. RCU-protected */

	struct mem_cgroup_threshold_ary *thresholds;



	/*

	 * Preallocated buffer to be used in mem_cgroup_unregister_event()

	 * to make it "never fail".

	 * It must be able to store at least thresholds->size - 1 entries.

	 */

	struct mem_cgroup_threshold_ary *__thresholds;



	/* thresholds for mem+swap usage. RCU-protected */

	struct mem_cgroup_threshold_ary *memsw_thresholds;



	/* the same as __thresholds, but for memsw_thresholds */

	struct mem_cgroup_threshold_ary *__memsw_thresholds;



	/* For oom notifier event fd */

	struct list_head oom_notify;
@@ -3604,17 +3614,27 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp, 
	else

		rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new);



	/* To be sure that nobody uses thresholds before freeing it */

	/* To be sure that nobody uses thresholds */

	synchronize_rcu();



	kfree(thresholds);

	/*

	 * Free old preallocated buffer and use thresholds as new

	 * preallocated buffer.

	 */

	if (type == _MEM) {

		kfree(memcg->__thresholds);

		memcg->__thresholds = thresholds;

	} else {

		kfree(memcg->__memsw_thresholds);

		memcg->__memsw_thresholds = thresholds;

	}

unlock:

	mutex_unlock(&memcg->thresholds_lock);



	return ret;

}



static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp,

static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,

	struct cftype *cft, struct eventfd_ctx *eventfd)

{

	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
@@ -3622,7 +3642,7 @@ static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, 
	int type = MEMFILE_TYPE(cft->private);

	u64 usage;

	int size = 0;

	int i, j, ret = 0;

	int i, j;



	mutex_lock(&memcg->thresholds_lock);

	if (type == _MEM)
@@ -3649,20 +3669,19 @@ static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, 
			size++;

	}



	/* Use preallocated buffer for new array of thresholds */

	if (type == _MEM)

		thresholds_new = memcg->__thresholds;

	else

		thresholds_new = memcg->__memsw_thresholds;



	/* Set thresholds array to NULL if we don't have thresholds */

	if (!size) {

		kfree(thresholds_new);

		thresholds_new = NULL;

		goto assign;

		goto swap_buffers;

	}



	/* Allocate memory for new array of thresholds */

	thresholds_new = kmalloc(sizeof(*thresholds_new) +

			size * sizeof(struct mem_cgroup_threshold),

			GFP_KERNEL);

	if (!thresholds_new) {

		ret = -ENOMEM;

		goto unlock;

	}

	thresholds_new->size = size;



	/* Copy thresholds and find current threshold */
@@ -3683,20 +3702,20 @@ static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, 
		j++;

	}



assign:

	if (type == _MEM)

swap_buffers:

	/* Swap thresholds array and preallocated buffer */

	if (type == _MEM) {

		memcg->__thresholds = thresholds;

		rcu_assign_pointer(memcg->thresholds, thresholds_new);

	else

	} else {

		memcg->__memsw_thresholds = thresholds;

		rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new);

	}



	/* To be sure that nobody uses thresholds before freeing it */

	/* To be sure that nobody uses thresholds */

	synchronize_rcu();



	kfree(thresholds);

unlock:

	mutex_unlock(&memcg->thresholds_lock);



	return ret;

}



static int mem_cgroup_oom_register_event(struct cgroup *cgrp,
@@ -3724,7 +3743,7 @@ static int mem_cgroup_oom_register_event(struct cgroup *cgrp, 
	return 0;

}



static int mem_cgroup_oom_unregister_event(struct cgroup *cgrp,

static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp,

	struct cftype *cft, struct eventfd_ctx *eventfd)

{

	struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
@@ -3743,8 +3762,6 @@ static int mem_cgroup_oom_unregister_event(struct cgroup *cgrp, 
	}



	mutex_unlock(&memcg_oom_mutex);



	return 0;

}



static int mem_cgroup_oom_control_read(struct cgroup *cgrp,

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