1 files changed, 17 insertions, 1 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 7441bd93b732..8fe3ebd6ac00 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -412,6 +412,7 @@ static void wb_exit(struct bdi_writeback *wb)
  * protected.
  */
 static DEFINE_SPINLOCK(cgwb_lock);
+static struct workqueue_struct *cgwb_release_wq;
 
 /**
  * wb_congested_get_create - get or create a wb_congested
@@ -522,7 +523,7 @@ static void cgwb_release(struct percpu_ref *refcnt)
 {
         struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
                                                 refcnt);
-        schedule_work(&wb->release_work);
+        queue_work(cgwb_release_wq, &wb->release_work);
 }
 
 static void cgwb_kill(struct bdi_writeback *wb)
@@ -784,6 +785,21 @@ static void cgwb_bdi_register(struct backing_dev_info *bdi)
         spin_unlock_irq(&cgwb_lock);
 }
 
+static int __init cgwb_init(void)
+{
+        /*
+         * There can be many concurrent release work items overwhelming
+         * system_wq.  Put them in a separate wq and limit concurrency.
+         * There's no point in executing many of these in parallel.
+         */
+        cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
+        if (!cgwb_release_wq)
+                return -ENOMEM;
+
+        return 0;
+}
+subsys_initcall(cgwb_init);
+
 #else   /* CONFIG_CGROUP_WRITEBACK */
 
 static int cgwb_bdi_init(struct backing_dev_info *bdi)