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-rw-r--r--mm/backing-dev.c66
1 files changed, 64 insertions, 2 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 576220acd686..271f2ca862c8 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -371,12 +371,16 @@ static void wb_exit(struct bdi_writeback *wb)
#include <linux/memcontrol.h>
/*
- * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, and memcg->cgwb_list.
- * bdi->cgwb_tree is also RCU protected.
+ * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, offline_cgwbs and
+ * memcg->cgwb_list. bdi->cgwb_tree is also RCU protected.
*/
static DEFINE_SPINLOCK(cgwb_lock);
static struct workqueue_struct *cgwb_release_wq;
+static LIST_HEAD(offline_cgwbs);
+static void cleanup_offline_cgwbs_workfn(struct work_struct *work);
+static DECLARE_WORK(cleanup_offline_cgwbs_work, cleanup_offline_cgwbs_workfn);
+
static void cgwb_release_workfn(struct work_struct *work)
{
struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
@@ -395,7 +399,13 @@ static void cgwb_release_workfn(struct work_struct *work)
fprop_local_destroy_percpu(&wb->memcg_completions);
percpu_ref_exit(&wb->refcnt);
+
+ spin_lock_irq(&cgwb_lock);
+ list_del(&wb->offline_node);
+ spin_unlock_irq(&cgwb_lock);
+
wb_exit(wb);
+ WARN_ON_ONCE(!list_empty(&wb->b_attached));
kfree_rcu(wb, rcu);
}
@@ -413,6 +423,7 @@ static void cgwb_kill(struct bdi_writeback *wb)
WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
list_del(&wb->memcg_node);
list_del(&wb->blkcg_node);
+ list_add(&wb->offline_node, &offline_cgwbs);
percpu_ref_kill(&wb->refcnt);
}
@@ -472,6 +483,7 @@ static int cgwb_create(struct backing_dev_info *bdi,
wb->memcg_css = memcg_css;
wb->blkcg_css = blkcg_css;
+ INIT_LIST_HEAD(&wb->b_attached);
INIT_WORK(&wb->release_work, cgwb_release_workfn);
set_bit(WB_registered, &wb->state);
@@ -633,6 +645,54 @@ static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
mutex_unlock(&bdi->cgwb_release_mutex);
}
+/*
+ * cleanup_offline_cgwbs_workfn - try to release dying cgwbs
+ *
+ * Try to release dying cgwbs by switching attached inodes to the nearest
+ * living ancestor's writeback. Processed wbs are placed at the end
+ * of the list to guarantee the forward progress.
+ */
+static void cleanup_offline_cgwbs_workfn(struct work_struct *work)
+{
+ struct bdi_writeback *wb;
+ LIST_HEAD(processed);
+
+ spin_lock_irq(&cgwb_lock);
+
+ while (!list_empty(&offline_cgwbs)) {
+ wb = list_first_entry(&offline_cgwbs, struct bdi_writeback,
+ offline_node);
+ list_move(&wb->offline_node, &processed);
+
+ /*
+ * If wb is dirty, cleaning up the writeback by switching
+ * attached inodes will result in an effective removal of any
+ * bandwidth restrictions, which isn't the goal. Instead,
+ * it can be postponed until the next time, when all io
+ * will be likely completed. If in the meantime some inodes
+ * will get re-dirtied, they should be eventually switched to
+ * a new cgwb.
+ */
+ if (wb_has_dirty_io(wb))
+ continue;
+
+ if (!wb_tryget(wb))
+ continue;
+
+ spin_unlock_irq(&cgwb_lock);
+ while (cleanup_offline_cgwb(wb))
+ cond_resched();
+ spin_lock_irq(&cgwb_lock);
+
+ wb_put(wb);
+ }
+
+ if (!list_empty(&processed))
+ list_splice_tail(&processed, &offline_cgwbs);
+
+ spin_unlock_irq(&cgwb_lock);
+}
+
/**
* wb_memcg_offline - kill all wb's associated with a memcg being offlined
* @memcg: memcg being offlined
@@ -649,6 +709,8 @@ void wb_memcg_offline(struct mem_cgroup *memcg)
cgwb_kill(wb);
memcg_cgwb_list->next = NULL; /* prevent new wb's */
spin_unlock_irq(&cgwb_lock);
+
+ queue_work(system_unbound_wq, &cleanup_offline_cgwbs_work);
}
/**