Add callback for zfs_multihost_interval

Add a callback to wake all running mmp threads when
zfs_multihost_interval is changed.

This is necessary when the interval is changed from a very large value
to a significantly lower one, while pools are imported that have the
multihost property enabled.

Without this commit, the mmp thread does not wake up and detect the new
interval until after it has waited the old multihost interval time.  A
user monitoring mmp writes via the provided kstat would be led to
believe that the changed setting did not work.

Added a test in the ZTS under mmp to verify the new functionality is
working.

Added a test to ztest which starts and stops mmp threads, and calls into
the code to signal sleeping mmp threads, to test for deadlocks or
similar locking issues.

Reviewed-by: Giuseppe Di Natale <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Olaf Faaland <[email protected]>
Closes #6387

1 files changed, 43 insertions, 0 deletions

diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index b4cedbdba..788e6aa6a 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -326,6 +326,7 @@ ztest_func_t ztest_spa_create_destroy;
 ztest_func_t ztest_fault_inject;
 ztest_func_t ztest_ddt_repair;
 ztest_func_t ztest_dmu_snapshot_hold;
+ztest_func_t ztest_mmp_enable_disable;
 ztest_func_t ztest_spa_rename;
 ztest_func_t ztest_scrub;
 ztest_func_t ztest_dsl_dataset_promote_busy;
@@ -375,6 +376,7 @@ ztest_info_t ztest_info[] = {
 	ZTI_INIT(ztest_fault_inject, 1, &zopt_sometimes),
 	ZTI_INIT(ztest_ddt_repair, 1, &zopt_sometimes),
 	ZTI_INIT(ztest_dmu_snapshot_hold, 1, &zopt_sometimes),
+	ZTI_INIT(ztest_mmp_enable_disable, 1, &zopt_sometimes),
 	ZTI_INIT(ztest_reguid, 1, &zopt_rarely),
 	ZTI_INIT(ztest_spa_rename, 1, &zopt_rarely),
 	ZTI_INIT(ztest_scrub, 1, &zopt_rarely),
@@ -2660,6 +2662,47 @@ ztest_spa_create_destroy(ztest_ds_t *zd, uint64_t id)
 	(void) rw_unlock(&ztest_name_lock);
 }
 
+/*
+ * Start and then stop the MMP threads to ensure the startup and shutdown code
+ * works properly.  Actual protection and property-related code tested via ZTS.
+ */
+/* ARGSUSED */
+void
+ztest_mmp_enable_disable(ztest_ds_t *zd, uint64_t id)
+{
+	ztest_shared_opts_t *zo = &ztest_opts;
+	spa_t *spa = ztest_spa;
+
+	if (zo->zo_mmp_test)
+		return;
+
+	spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
+	mutex_enter(&spa->spa_props_lock);
+
+	if (!spa_multihost(spa)) {
+		spa->spa_multihost = B_TRUE;
+		mmp_thread_start(spa);
+	}
+
+	mutex_exit(&spa->spa_props_lock);
+	spa_config_exit(spa, SCL_CONFIG, FTAG);
+
+	txg_wait_synced(spa_get_dsl(spa), 0);
+	mmp_signal_all_threads();
+	txg_wait_synced(spa_get_dsl(spa), 0);
+
+	spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
+	mutex_enter(&spa->spa_props_lock);
+
+	if (spa_multihost(spa)) {
+		mmp_thread_stop(spa);
+		spa->spa_multihost = B_FALSE;
+	}
+
+	mutex_exit(&spa->spa_props_lock);
+	spa_config_exit(spa, SCL_CONFIG, FTAG);
+}
+
 /* ARGSUSED */
 void
 ztest_spa_upgrade(ztest_ds_t *zd, uint64_t id)