Commit 2ef6f4bd authored Oct 13, 2020 by Xiubo Li Committed by Greg Kroah-Hartman Nov 05, 2020

nbd: make the config put is called before the notifying the waiter



[ Upstream commit 87aac3a80af5cbad93e63250e8a1e19095ba0d30 ]

There has one race case for ceph's rbd-nbd tool. When do mapping
it may fail with EBUSY from ioctl(nbd, NBD_DO_IT), but actually
the nbd device has already unmaped.

It dues to if just after the wake_up(), the recv_work() is scheduled
out and defers calling the nbd_config_put(), though the map process
has exited the "nbd->recv_task" is not cleared.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent c151f684

drivers/block/nbd.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -740,9 +740,9 @@ static void recv_work(struct work_struct *work)

		blk_mq_complete_request(blk_mq_rq_from_pdu(cmd));
		}
		nbd_config_put(nbd);
		atomic_dec(&config->recv_threads);
		wake_up(&config->recv_wq);
		nbd_config_put(nbd);
		kfree(args);
		}