bcache: fix race between setting bdev state to none and new write request direct to backing
There is a race condition in detaching as below:
A. detaching B. Write request
(1) writing back
(2) write back done, set bdev
state to clean.
(3) cached_dev_put() and
schedule_work(&dc->detach);
(4) write data [0 - 4K] directly
into backing and ack to user.
(5) power-failure...
When we restart this bcache device, this bdev is clean but not detached,
and read [0 - 4K], we will get unexpected old data from cache device.
To fix this problem, set the bdev state to none when we writeback done
in detaching, and then if power-failure happened as above, the data in
cache will not be used in next bcache device starting, it's detached, we
will read the correct data from backing derectly.
Signed-off-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 3c74996..a129e4d 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -705,6 +705,15 @@ static int bch_writeback_thread(void *arg)
* bch_cached_dev_detach().
*/
if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
+ struct closure cl;
+
+ closure_init_stack(&cl);
+ memset(&dc->sb.set_uuid, 0, 16);
+ SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE);
+
+ bch_write_bdev_super(dc, &cl);
+ closure_sync(&cl);
+
up_write(&dc->writeback_lock);
break;
}
