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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: Kirill A. Shutemov <kirill@shutemov.name>
Acked-by: KAMEZAWA 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2010-05-26 14:42:46 -07:00 committed by Linus Torvalds
parent ac39cf8cb8
commit 907860ed38
3 changed files with 42 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/cgroup.h
View File

@ -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);
};

1
kernel/cgroup.c
View File

@ -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);

65
mm/memcontrol.c
View File

@ -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,