From: Leon Yang <leon.gh.y...@gmail.com>
Each time the unmounted list is cleanup, synchronize_rcu() is
called, which is relatively costly. Scheduling the cleanup in a
workqueue, similar to what is being done in
net/core/net_namespace.c:cleanup_net, makes unmounting faster
without adding too much overhead. This is useful especially for
servers with many containers where mounting/unmounting happens a
lot.
Signed-off-by: Leon Yang <leon.gh.y...@gmail.com>
---
fs/namespace.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 3b601f1..864ce7e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -68,6 +68,7 @@ static int mnt_group_start = 1;
static struct hlist_head *mount_hashtable __read_mostly;
static struct hlist_head *mountpoint_hashtable __read_mostly;
static struct kmem_cache *mnt_cache __read_mostly;
+static struct workqueue_struct *unmounted_wq;
static DECLARE_RWSEM(namespace_sem);
/* /sys/fs */
@@ -1409,22 +1410,29 @@ EXPORT_SYMBOL(may_umount);
static HLIST_HEAD(unmounted); /* protected by namespace_sem */
-static void namespace_unlock(void)
+static void cleanup_unmounted(struct work_struct *work)
{
struct hlist_head head;
+ down_write(&namespace_sem);
hlist_move_list(&unmounted, &head);
up_write(&namespace_sem);
- if (likely(hlist_empty(&head)))
- return;
-
synchronize_rcu();
group_pin_kill(&head);
}
+static DECLARE_WORK(unmounted_cleanup_work, cleanup_unmounted);
+
+static void namespace_unlock(void)
+{
+ if (!likely(hlist_empty(&unmounted)))
+ queue_work(unmounted_wq, &unmounted_cleanup_work);
+ up_write(&namespace_sem);
+}
+
static inline void namespace_lock(void)
{
down_write(&namespace_sem);
@@ -3276,6 +3284,17 @@ void __init mnt_init(void)
init_mount_tree();
}
+static int __init unmounted_wq_init(void)
+{
+ /* Create workqueue for cleanup */
+ unmounted_wq = create_singlethread_workqueue("unmounted");
+ if (!unmounted_wq)
+ panic("Could not create unmounted workq");
+ return 0;
+}
+
+pure_initcall(unmounted_wq_init);
+
void put_mnt_ns(struct mnt_namespace *ns)
{
if (!atomic_dec_and_test(&ns->count))
--
2.7.4
