Re: [PATCH 07/20] io-controller: Export disk time used and nr sectors dipatched through cgroups

Gui Jianfeng
2009-06-23T12:13:17Z

Vivek Goyal wrote:
...
> +
> +static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
> + struct cftype *cftype, struct seq_file *m)
> +{
> + struct io_cgroup *iocg;
> + struct io_group *iog;
> + struct hlist_node *n;
> +
> + if (!cgroup_lock_live_group(cgroup))
> + return -ENODEV;
> +
> + iocg = cgroup_to_io_cgroup(cgroup);
> +
> + spin_lock_irq(&iocg->lock);

It's better to make use of rcu_read_lock instead since it's
a read action.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
---
block/elevator-fq.c | 12 ++++++------
1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 2ad40eb..d779282 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -1418,7 +1418,7 @@ static int io_cgroup_disk_time_read(struct cgroup *cgroup,

iocg = cgroup_to_io_cgroup(cgroup);

- spin_lock_irq(&iocg->lock);
+ rcu_read_lock();
hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
/*
* There might be groups which are not functional and
@@ -1430,7 +1430,7 @@ static int io_cgroup_disk_time_read(struct cgroup *cgroup,
iog->entity.total_service);
}
}
- spin_unlock_irq(&iocg->lock);
+ rcu_read_unlock();
cgroup_unlock();

return 0;
@@ -1448,7 +1448,7 @@ static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,

iocg = cgroup_to_io_cgroup(cgroup);

- spin_lock_irq(&iocg->lock);
+ rcu_read_lock();
hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
/*
* There might be groups which are not functional and
@@ -1460,7 +1460,7 @@ static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
iog->entity.total_sector_service);
}
}
- spin_unlock_irq(&iocg->lock);
+ rcu_read_unlock();
cgroup_unlock();

return 0;
@@ -1478,7 +1478,7 @@ static int io_cgroup_disk_queue_read(struct cgroup *cgroup,
return -ENODEV;

iocg = cgroup_to_io_cgroup(cgroup);
- spin_lock_irq(&iocg->lock);
+ rcu_read_lock();
/* Loop through all the io groups and print statistics */
hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
/*
@@ -1491,7 +1491,7 @@ static int io_cgroup_disk_queue_read(struct cgroup *cgroup,
iog->queue_duration);
}
}
- spin_unlock_irq(&iocg->lock);
+ rcu_read_unlock();
cgroup_unlock();

return 0;
--
1.5.4.rc3

> + hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
> + /*
> + * There might be groups which are not functional and
> + * waiting to be reclaimed upon cgoup deletion.
> + */
> + if (iog->key) {
> + seq_printf(m, "%u %u %lu\n", MAJOR(iog->dev),
> + MINOR(iog->dev),
> + iog->entity.total_sector_service);
> + }
> + }
> + spin_unlock_irq(&iocg->lock);
> + cgroup_unlock();
> +
> + return 0;
> +}
> +
>