From: Olaf Faaland <faaland1@llnl.gov>
Date: Fri, 11 May 2018 19:46:07 +0000 (-0700)
Subject: module param callbacks check for initialized spa
X-Git-Tag: zfs-0.7.10~22
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3eef58c9b6753fac47cd0640207873b83432efc7;p=zfs

module param callbacks check for initialized spa

Callbacks provided for module parameters are executed both
after the module is loaded, when a user alters it via sysfs, e.g
	echo bar > /sys/modules/zfs/parameters/foo

as well as when the module is loaded with an argument, e.g.
	modprobe zfs foo=bar

In the latter case, the init functions likely have not run yet,
including spa_init() which initializes the namespace lock so it is safe
to use.

Instead of immediately taking the namespace lock and attemping to
iterate over initialized spa structures, check whether spa_mode_global
is nonzero.  This is set by spa_init() after it has initialized the
namespace lock.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #7496
Closes #7521
---

diff --git a/module/zfs/mmp.c b/module/zfs/mmp.c
index 3b74a6b61..7523310cd 100644
--- a/module/zfs/mmp.c
+++ b/module/zfs/mmp.c
@@ -607,7 +607,8 @@ param_set_multihost_interval(const char *val, zfs_kernel_param_t *kp)
 	if (ret < 0)
 		return (ret);
 
-	mmp_signal_all_threads();
+	if (spa_mode_global != 0)
+		mmp_signal_all_threads();
 
 	return (ret);
 }
diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
index d62128353..6761e755a 100644
--- a/module/zfs/vdev_disk.c
+++ b/module/zfs/vdev_disk.c
@@ -815,19 +815,21 @@ param_set_vdev_scheduler(const char *val, zfs_kernel_param_t *kp)
 	if ((p = strchr(val, '\n')) != NULL)
 		*p = '\0';
 
-	mutex_enter(&spa_namespace_lock);
-	while ((spa = spa_next(spa)) != NULL) {
-		if (spa_state(spa) != POOL_STATE_ACTIVE ||
-		    !spa_writeable(spa) || spa_suspended(spa))
-			continue;
-
-		spa_open_ref(spa, FTAG);
-		mutex_exit(&spa_namespace_lock);
-		vdev_elevator_switch(spa->spa_root_vdev, (char *)val);
+	if (spa_mode_global != 0) {
 		mutex_enter(&spa_namespace_lock);
-		spa_close(spa, FTAG);
+		while ((spa = spa_next(spa)) != NULL) {
+			if (spa_state(spa) != POOL_STATE_ACTIVE ||
+			    !spa_writeable(spa) || spa_suspended(spa))
+				continue;
+
+			spa_open_ref(spa, FTAG);
+			mutex_exit(&spa_namespace_lock);
+			vdev_elevator_switch(spa->spa_root_vdev, (char *)val);
+			mutex_enter(&spa_namespace_lock);
+			spa_close(spa, FTAG);
+		}
+		mutex_exit(&spa_namespace_lock);
 	}
-	mutex_exit(&spa_namespace_lock);
 
 	return (param_set_charp(val, kp));
 }