diff --git a/scripts/kernel/generate-kernel-patch b/scripts/kernel/generate-kernel-patch
index 12374e86b..6f649d861 100755
--- a/scripts/kernel/generate-kernel-patch
+++ b/scripts/kernel/generate-kernel-patch
@@ -314,6 +314,7 @@ scst/src/scst_copy_mgr.c scst/src/scst_dlm.c scst/src/scst_dlm.h \
 scst/src/scst_event.c scst/src/scst_event_priv.h scst/src/scst_no_dlm.c \
 scst/src/scst_test.h \
 scst/src/scst_event_test.h \
+scst/src/scst_dlm_test.h \
 scst/src/scst_copy_mgr_test.h"
 scst_05_targ="scst/src/scst_targ.c scst/src/scst_local_cmd.c \
 scst/src/scst_local_cmd.h \
diff --git a/scst/src/kunit/lib/suites/scst_kunit_lib.c b/scst/src/kunit/lib/suites/scst_kunit_lib.c
index 0747cc9f3..0d910c1d6 100644
--- a/scst/src/kunit/lib/suites/scst_kunit_lib.c
+++ b/scst/src/kunit/lib/suites/scst_kunit_lib.c
@@ -8,6 +8,8 @@
 #endif
 
 #include "../../../scst_lib_test.h"
+#include "../../../scst_dlm.h"
+#include "../../../scst_dlm_test.h"
 
 struct scst_port_id_fixture {
 	unsigned int free_id;
@@ -137,7 +139,69 @@ static void scst_empty_explicit_sg_buffers(struct kunit *test)
 	KUNIT_EXPECT_NULL(test, buf);
 }
 
+#if (defined(CONFIG_DLM) || defined(CONFIG_DLM_MODULE)) && !defined(CONFIG_SCST_NO_DLM)
+static int scst_dlm_read_nodeids_error(char **entries)
+{
+	struct kunit *test = kunit_get_current_test();
+	const int *error = test->priv;
+
+	/* An empty partial result must not replace an established membership. */
+	*entries = *error == -ENOMEM ? NULL : kzalloc(1, GFP_KERNEL);
+	KUNIT_EXPECT_TRUE(test, *error == -ENOMEM || *entries);
+	return *error;
+}
+
+static void scst_dlm_directory_error_preserves_membership(struct kunit *test)
+{
+	static const int errors[] = { -EIO, -EACCES, -ENOMEM };
+	struct scst_pr_dlm_data *dlm;
+	u32 *nodeids;
+	unsigned int i;
+	int error;
+
+	dlm = kunit_kzalloc(test, sizeof(*dlm), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, dlm);
+	mutex_init(&dlm->ls_mutex);
+	kunit_activate_static_stub(test, scst_dlm_read_nodeids, scst_dlm_read_nodeids_error);
+	for (i = 0; i < ARRAY_SIZE(errors); i++) {
+		int ret;
+
+		/* The production update owns and may reallocate this array. */
+		nodeids = kmalloc_array(2, sizeof(*nodeids), GFP_KERNEL);
+		KUNIT_ASSERT_NOT_NULL(test, nodeids);
+		nodeids[0] = 17;
+		nodeids[1] = 23;
+		dlm->nodeid = nodeids;
+		dlm->participants = 2;
+		dlm->local_nodeid = 17;
+		error = errors[i];
+		test->priv = &error;
+
+		mutex_lock(&dlm->ls_mutex);
+		ret = scst_dlm_update_nodeids(dlm);
+		mutex_unlock(&dlm->ls_mutex);
+		KUNIT_EXPECT_EQ(test, ret, errors[i]);
+		KUNIT_EXPECT_PTR_EQ(test, dlm->nodeid, nodeids);
+		KUNIT_EXPECT_EQ(test, dlm->participants, 2);
+		KUNIT_EXPECT_EQ(test, dlm->local_nodeid, 17U);
+		if (dlm->nodeid == nodeids) {
+			KUNIT_EXPECT_EQ(test, nodeids[0], 17U);
+			KUNIT_EXPECT_EQ(test, nodeids[1], 23U);
+		}
+		/* Also tolerate the old bug freeing/replacing nodeids. */
+		kfree(dlm->nodeid);
+		dlm->nodeid = NULL;
+	}
+	kunit_deactivate_static_stub(test, scst_dlm_read_nodeids);
+	test->priv = NULL;
+	mutex_destroy(&dlm->ls_mutex);
+}
+#endif
+
 static struct kunit_case scst_lib_cases[] = {
+#if (defined(CONFIG_DLM) || defined(CONFIG_DLM_MODULE)) && !defined(CONFIG_SCST_NO_DLM)
+	KUNIT_CASE(scst_dlm_directory_error_preserves_membership),
+#endif
 	KUNIT_CASE(scst_port_id_boundaries),
 	KUNIT_CASE(scst_lun_flat_encoding),
 	KUNIT_CASE(scst_explicit_sg_buffers),
diff --git a/scst/src/scst_dlm.c b/scst/src/scst_dlm.c
index 42cbc547d..127eed628 100644
--- a/scst/src/scst_dlm.c
+++ b/scst/src/scst_dlm.c
@@ -29,6 +29,7 @@
 #include "scst_priv.h"
 #include "scst_pres.h"
 #include "scst_dlm.h"
+#include "scst_dlm_test.h"
 
 #if (defined(CONFIG_DLM) || defined(CONFIG_DLM_MODULE)) && \
 	!defined(CONFIG_SCST_NO_DLM)
@@ -744,43 +745,59 @@ out:
 #endif
 }
 
-/*
- * scst_dlm_update_nodeids - Update the Corosync node ID array pr_dlm->nodeid[]
- */
-static int scst_dlm_update_nodeids(struct scst_pr_dlm_data *pr_dlm)
+static const char scst_dlm_comms_dir[] = "/sys/kernel/config/dlm/cluster/comms";
+
+/* The caller owns *entries even when reading the directory fails. */
+SCST_KUNIT_VISIBLE
+int scst_dlm_read_nodeids(char **entries)
 {
-	static const char comms_dir[] = "/sys/kernel/config/dlm/cluster/comms";
 	struct file *comms;
-	char *p, *entries = kzalloc(1, GFP_KERNEL);
-	unsigned long nodeid;
-	uint32_t *new;
-	int i, ret, num_nodes;
-	char path[256], buf[64];
+	int ret;
 
-	lockdep_assert_held(&pr_dlm->ls_mutex);
+	SCST_KUNIT_REDIRECT(scst_dlm_read_nodeids, entries);
 
-	num_nodes = 0;
+	*entries = kzalloc(1, GFP_KERNEL);
+	if (!*entries)
+		return -ENOMEM;
 
-	comms = filp_open(comms_dir, 0, 0400);
-	if (IS_ERR(comms)) {
-		ret = PTR_ERR(comms);
-		goto out;
-	}
+	comms = filp_open(scst_dlm_comms_dir, 0, 0400);
+	if (IS_ERR(comms))
+		return PTR_ERR(comms);
 #ifndef HAVE_ITERATE_DIR
-	ret = vfs_readdir(comms, scst_dlm_filldir, &entries);
+	ret = vfs_readdir(comms, scst_dlm_filldir, entries);
 #else
 	{
 		struct scst_dlm_readdir_context ctx = {
 			.ctx = {
 				.actor = scst_dlm_filldir,
 			},
-			.entries = entries,
+			.entries = *entries,
 		};
 		ret = iterate_dir(comms, &ctx.ctx);
-		entries = ctx.entries;
+		*entries = ctx.entries;
 	}
 #endif
 	filp_close(comms, NULL);
+	return ret;
+}
+
+/*
+ * scst_dlm_update_nodeids - Update the Corosync node ID array pr_dlm->nodeid[]
+ */
+SCST_KUNIT_VISIBLE
+int scst_dlm_update_nodeids(struct scst_pr_dlm_data *pr_dlm)
+{
+	char *p, *entries = NULL;
+	unsigned long nodeid;
+	u32 *new;
+	int i, ret, num_nodes = 0;
+	char path[256], buf[64];
+
+	lockdep_assert_held(&pr_dlm->ls_mutex);
+
+	ret = scst_dlm_read_nodeids(&entries);
+	if (ret < 0)
+		goto out;
 	ret = -ENOMEM;
 	if (!entries)
 		goto out;
@@ -796,7 +813,7 @@ static int scst_dlm_update_nodeids(struct scst_pr_dlm_data *pr_dlm)
 		ret = kstrtoul(p, 0, &nodeid);
 		if (WARN_ON_ONCE(ret < 0))
 			continue;
-		snprintf(path, sizeof(path), "%s/%s/local", comms_dir, p);
+		snprintf(path, sizeof(path), "%s/%s/local", scst_dlm_comms_dir, p);
 		if (scst_read_file(path, buf, sizeof(buf)) >= 0 &&
 		    strcmp(buf, "1\n") == 0)
 			pr_dlm->local_nodeid = nodeid;
diff --git a/scst/src/scst_dlm_test.h b/scst/src/scst_dlm_test.h
new file mode 100644
index 000000000..806d14ba2
--- /dev/null
+++ b/scst/src/scst_dlm_test.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef SCST_DLM_TEST_H
+#define SCST_DLM_TEST_H
+
+#include "scst_test.h"
+
+#ifdef SCST_KUNIT_ENABLED
+struct scst_pr_dlm_data;
+
+int scst_dlm_read_nodeids(char **entries);
+int scst_dlm_update_nodeids(struct scst_pr_dlm_data *pr_dlm);
+#endif
+
+#endif /* SCST_DLM_TEST_H */