[ndctl PATCH 2/2] daxctl, util/sysfs: skip module probe-insert when driver is builtin or live

[Chen Pei <cp0613@linux.alibaba.com>]

kmod_module_probe_insert_module() is supposed to return 0 for builtin
modules, but only when libkmod can locate the modules.builtin index. If
the index is missing or out of sync, libkmod falls through to the real
init_module() syscall and returns an error such as -ENOENT, producing a
spurious "insert failure" even though the driver is already part of the
running kernel.

Pre-check kmod_module_get_initstate() and short-circuit when the module
is KMOD_MODULE_BUILTIN or KMOD_MODULE_LIVE, matching the pattern used by
ndctl's own test/core.c.

For builtin modules the local kmod reference is dropped because builtin
drivers cannot be unloaded; for live modules the reference is retained
in dev->module, matching the post-probe-success behavior.

Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
---
 daxctl/lib/libdaxctl.c | 18 ++++++++++++++++--
 util/sysfs.c           | 17 +++++++++++------
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/daxctl/lib/libdaxctl.c b/daxctl/lib/libdaxctl.c
index ffc81eb..42bfc39 100644
--- a/daxctl/lib/libdaxctl.c
+++ b/daxctl/lib/libdaxctl.c
@@ -910,7 +910,7 @@ static int daxctl_insert_kmod_for_mode(struct daxctl_dev *dev,
 	const char *devname = daxctl_dev_get_devname(dev);
 	struct daxctl_ctx *ctx = daxctl_dev_get_ctx(dev);
 	struct kmod_module *kmod;
-	int rc;
+	int state, rc;
 
 	rc = kmod_module_new_from_name(ctx->kmod_ctx, mod_name, &kmod);
 	if (rc < 0) {
@@ -919,7 +919,21 @@ static int daxctl_insert_kmod_for_mode(struct daxctl_dev *dev,
 		return rc;
 	}
 
-	/* if the driver is builtin, this Just Works */
+	/* If the driver is builtin or already live, skip probe-insert. */
+	state = kmod_module_get_initstate(kmod);
+	if (state == KMOD_MODULE_BUILTIN) {
+		dbg(ctx, "%s: module %s is builtin\n", devname,
+			kmod_module_get_name(kmod));
+		kmod_module_unref(kmod);
+		return 0;
+	}
+	if (state == KMOD_MODULE_LIVE) {
+		dbg(ctx, "%s: module %s already loaded\n", devname,
+			kmod_module_get_name(kmod));
+		dev->module = kmod;
+		return 0;
+	}
+
 	dbg(ctx, "%s inserting module: %s\n", devname,
 		kmod_module_get_name(kmod));
 	rc = kmod_module_probe_insert_module(kmod,
diff --git a/util/sysfs.c b/util/sysfs.c
index e027e38..641b86d 100644
--- a/util/sysfs.c
+++ b/util/sysfs.c
@@ -183,12 +183,17 @@ int __util_bind(const char *devname, struct kmod_module *module,
 	}
 
 	if (module) {
-		rc = kmod_module_probe_insert_module(module,
-						     KMOD_PROBE_APPLY_BLACKLIST,
-						     NULL, NULL, NULL, NULL);
-		if (rc < 0) {
-			log_err(ctx, "%s: insert failure: %d\n", __func__, rc);
-			return rc;
+		/* Skip probe-insert when the module is already builtin or live. */
+		int state = kmod_module_get_initstate(module);
+
+		if (state != KMOD_MODULE_BUILTIN && state != KMOD_MODULE_LIVE) {
+			rc = kmod_module_probe_insert_module(module,
+							     KMOD_PROBE_APPLY_BLACKLIST,
+							     NULL, NULL, NULL, NULL);
+			if (rc < 0) {
+				log_err(ctx, "%s: insert failure: %d\n", __func__, rc);
+				return rc;
+			}
 		}
 	}
 
-- 
2.43.0