[PATCH blktests v2] nvme/068: check module reference count with patience

The test case nvme/068 fails depending on the system it runs on with
the failure message below:

   nvme/068 (tr=rdma) (NVMe multipath delayed removal test)     [failed]
       runtime    ...  11.357s
       --- tests/nvme/068.out    2026-08-03 17:24:32.394566266 +0000
       +++ /home/runner/blktests/results/nodev_tr_rdma/nvme/068.out.bad  2026-08-03 18:15:17.461243816 +0000
       @@ -1,3 +1,4 @@
        Running nvme/068
        pwrite: Input/output error
       +module refcount not as original
        Test complete

The test case checks the reference count of the nvme_core module. If the
count is not the expected value, it fails with the error message.
However, when the test system is slow, it takes some time until the
reference count gets updated. When the check is too early, the count
mismatch happens. To avoid the unexpected failure, repeat the reference
count check.

Signed-off-by: Shin'ichiro Kawasaki <[email protected]>
---
I ran the test case nvme/068 with the patch using the kernel that does
not include the commit below:

  3f150f0f010f ("nvme-multipath: put module reference when delayed removal work is canceled")

And I observed the test case failed. When the kernel includes the commit,
the test case passes. This indicates the patch does not break the
reference count sanity check capability of the test case.

Changes from v1:
- Per review comments, handled empty "$refcnt" case and explicit 0 return

 tests/nvme/068 | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/tests/nvme/068 b/tests/nvme/068
index 4aee95b..cab57cd 100755
--- a/tests/nvme/068
+++ b/tests/nvme/068
@@ -27,6 +27,19 @@ _delayed_nvme_reconnect_ctrl() {
 	_nvme_connect_subsys
 }
 
+_check_nvme_core_ref_count() {
+	local refcnt i
+
+	for ((i = 0; i < 10; i++)); do
+		refcnt=$(_module_use_count nvme_core)
+		if [ "$refcnt" == "" ] || [ "$refcnt" -eq "$refcnt_orig" ]; then
+			return 0
+		fi
+		sleep 1
+	done
+	return 1
+}
+
 test() {
 	echo "Running ${TEST_NAME}"
 
@@ -98,8 +111,7 @@ test() {
 	if ! _nvmf_wait_for_state "${def_subsysnqn}" "live" ; then
 		echo "subsystem did not return"
 	fi
-	refcnt=$(_module_use_count nvme_core)
-	if [ "$refcnt" != "" ] && [ "$refcnt" -ne "$refcnt_orig" ]; then
+	if ! _check_nvme_core_ref_count; then
 		echo "module refcount not as original"
 	fi
 
-- 
2.54.0