bdi_unregister() should be called after bdi_register() is called,
so we should check whether WB_registered flag is set.
For example of the situation, error path in device driver may call
blk_cleanup_queue() before the driver calls bdi_register().
Signed-off-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
---
mm/backing-dev.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 8fde443..f8b07d4 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -853,6 +853,9 @@ static void bdi_remove_from_list(struct backing_dev_info *bdi)
void bdi_unregister(struct backing_dev_info *bdi)
{
+ if (!test_bit(WB_registered, &bdi->wb.state))
+ return;
+
/* make sure nobody finds us on the bdi_list anymore */
bdi_remove_from_list(bdi);
wb_shutdown(&bdi->wb);
--
1.8.3.1
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