bcache: correct dirty data statistics

commit 2e17a262a2371d38d2ec03614a2675a32cef9912 upstream.

When bcache device is clean, dirty keys may still exist after
journal replay, so we need to count these dirty keys even
device in clean status, otherwise after writeback, the amount
of dirty data would be incorrect.
Signed-off-by: NTang Junhui <tang.junhui.linux@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NColy Li <colyli@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/md/bcache/super.c

@@ -1148,11 +1148,12 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
 	}
 
 	if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
-		bch_sectors_dirty_init(&dc->disk);
 		atomic_set(&dc->has_dirty, 1);
 		bch_writeback_queue(dc);
 	}
 
+	bch_sectors_dirty_init(&dc->disk);
+
 	bch_cached_dev_run(dc);
 	bcache_device_link(&dc->disk, c, "bdev");
 	atomic_inc(&c->attached_dev_nr);