btrfs: warn for any missed cleanup at btrfs_close_one_device

During my recent search for the root cause of a reported bug, I realized
that it's a good idea to issue a warning for missed cleanup instead of
using debug-only assertions. Since most installations run with debug off,
missed cleanups and premature calls to close could go unnoticed. However,
these issues are serious enough to warrant reporting and fixing.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: asj

fs/btrfs/volumes.c

@@ -1150,10 +1150,10 @@ static void btrfs_close_one_device(struct btrfs_device *device)
 	device->last_flush_error = 0;
 
 	/* Verify the device is back in a pristine state  */
-	ASSERT(!test_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state));
-	ASSERT(!test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state));
-	ASSERT(list_empty(&device->dev_alloc_list));
-	ASSERT(list_empty(&device->post_commit_list));
+	WARN_ON(test_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state));
+	WARN_ON(test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state));
+	WARN_ON(!list_empty(&device->dev_alloc_list));
+	WARN_ON(!list_empty(&device->post_commit_list));
 }
 
 static void close_fs_devices(struct btrfs_fs_devices *fs_devices)