From: Xiubo Li <xiubli@xxxxxxxxxx> When calling the ioctl(), fget() will be called on this fd, and nbd_release() is only called when the fd's refcount drops to zero. With this we can make sure that the nbd_release() won't be called before the ioctl() finished. So there won't have the double lock issue for the "config_lock", which has already been held by nbd_ioctl(). Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx> --- drivers/block/nbd.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 3bb8281bb753..48f36b003bf5 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1345,6 +1345,17 @@ static void nbd_clear_sock_ioctl(struct nbd_device *nbd, sock_shutdown(nbd); __invalidate_device(bdev, true); nbd_bdev_reset(bdev); + + /* + * When calling the ioctl(), fget() will be called on this + * fd, and nbd_release() is only called when the fd's refcount + * drops to zero. With this we can make sure that the + * nbd_release() won't be called before the ioctl() finished. + * + * So there won't have the double lock issue if it will + * call the nbd_config_put() here for the "config_lock", which + * has already been held by nbd_ioctl(). + */ if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, &nbd->config->runtime_flags)) nbd_config_put(nbd); -- 2.18.4
