block: Unregister bdi on last reference drop

Most users will want to unregister bdi when dropping last reference to a bdi. Only a few users (like block devices) want to play more complex tricks with bdi registration and unregistration. So unregister bdi when the last reference to bdi is dropped and just make sure we don't unregister the bdi the second time if it is already unregistered. Reviewed-by: Christoph Hellwig <[email protected]> Signed-off-by: Jan Kara <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
sudhin-joseph · Apr 20, 2017 · 5af110b · 5af110b
1 parent baf7a61
commit 5af110b
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
@@ -961,6 +961,8 @@ static void release_bdi(struct kref *ref)
 	struct backing_dev_info *bdi =
 			container_of(ref, struct backing_dev_info, refcnt);
 
+	if (test_bit(WB_registered, &bdi->wb.state))
+		bdi_unregister(bdi);
 	bdi_exit(bdi);
 	kfree(bdi);
 }