UBI: add UBI devices reference counting

This is one more step on the way to "removable" UBI devices. It
adds reference counting for UBI devices. Every time a volume on
this device is opened - the device's refcount is increased. It
is also increased if someone is reading any sysfs file of this
UBI device or of one of its volumes.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 7d32f71d6f1e..bfc64c824165 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -1303,6 +1303,7 @@ int ubi_wl_flush(struct ubi_device *ubi)
          * Make sure all the works which have been done in parallel are
          * finished.
          */
+        ubi_assert(ubi->ref_count > 0);
         down_write(&ubi->work_sem);
         up_write(&ubi->work_sem);