GitLab

Explicitly check show_devname method return code and bail out in case
of an error.  This fixes regression introduced by commit 9d4d6574

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Cc: stable@vger.kernel.org
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>