From: Xiubo Li xiubli@redhat.com
[ Upstream commit 862488105b84ca744b3d8ff131e0fcfe10644be1 ]
1. nbd_put takes the mutex and drops nbd->ref to 0. It then does idr_remove and drops the mutex.
2. nbd_genl_connect takes the mutex. idr_find/idr_for_each fails to find an existing device, so it does nbd_dev_add.
3. just before the nbd_put could call nbd_dev_remove or not finished totally, but if nbd_dev_add try to add_disk, we can hit:
debugfs: Directory 'nbd1' with parent 'block' already present!
This patch will make sure all the disk add/remove stuff are done by holding the nbd_index_mutex lock.
Reported-by: Mike Christie mchristi@redhat.com Reviewed-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Xiubo Li xiubli@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/nbd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index bc2fa4e85f0ca..d445195945618 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -228,8 +228,8 @@ static void nbd_put(struct nbd_device *nbd) if (refcount_dec_and_mutex_lock(&nbd->refs, &nbd_index_mutex)) { idr_remove(&nbd_index_idr, nbd->index); - mutex_unlock(&nbd_index_mutex); nbd_dev_remove(nbd); + mutex_unlock(&nbd_index_mutex); } }