[PATCH blktests] Make the NVMe tests more reliable

[Bart Van Assche <bvanassche@acm.org>]

When running blktests with kernel debugging enabled it can happen that
_find_nvme_loop_dev() returns before the NVMe block device has appeared
in sysfs. This patch avoids that the NVMe tests fail as follows:

+cat: /sys/block/nvme1n1/uuid: No such file or directory
+cat: /sys/block/nvme1n1/wwid: No such file or directory

Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 tests/nvme/rc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tests/nvme/rc b/tests/nvme/rc
index 348b4a3c2cbc..05dfc5915a13 100644
--- a/tests/nvme/rc
+++ b/tests/nvme/rc
@@ -169,8 +169,16 @@ _find_nvme_loop_dev() {
 		transport="$(cat "/sys/class/nvme/${dev}/transport")"
 		if [[ "$transport" == "loop" ]]; then
 			echo "$dev"
+			for ((i=0;i<10;i++)); do
+				[ -e /sys/block/$dev/uuid ] &&
+					[ -e /sys/block/$dev/wwid ] &&
+					return 0
+				sleep .1
+			done
+			return 1
 		fi
 	done
+	return 1
 }
 
 _filter_discovery() {
-- 
2.22.0.770.g0f2c4a37fd-goog