WIP: Remove spa_namespace_lock from zpool status

TEST

@@ -35,7 +35,7 @@
 #TEST_ZFSTESTS_ITERS="1"
 #TEST_ZFSTESTS_OPTIONS="-vx"
 #TEST_ZFSTESTS_RUNFILE="linux.run"
-#TEST_ZFSTESTS_TAGS="functional"
+TEST_ZFSTESTS_TAGS="zpool_import,zpool_export,zpool_status,zpool_add"
 
 ### zfsstress
 #TEST_ZFSSTRESS_SKIP="yes"

include/sys/spa.h

@@ -842,6 +842,22 @@ extern kmutex_t spa_namespace_lock;
 extern avl_tree_t spa_namespace_avl;
 extern kcondvar_t spa_namespace_cv;
 
+extern krwlock_t spa_namespace_lite_lock;
+
+extern uint_t spa_namespace_delay_ms;
+/*
+ * Special version of mutex_enter() used for testing the spa_namespace_lock.
+ * It inserts an artificial delay after acquiring the lock to simulate a failure
+ * while holding the lock.  The delay is controlled by the
+ * spa_namespace_lock_delay module param and is only to be used by ZTS.
+ */
+#define	mutex_enter_ns(lock) do { \
+	ASSERT(lock == &spa_namespace_lock); \
+	mutex_enter(lock); \
+	if (unlikely(spa_namespace_delay_ms != 0)) \
+		zfs_msleep(spa_namespace_delay_ms); \
+	} while (0);
+
 /*
  * SPA configuration functions in spa_config.c
  */
@@ -866,9 +882,11 @@ extern int spa_config_parse(spa_t *spa, vdev_t **vdp, nvlist_t *nv,
 
 /* Namespace manipulation */
 extern spa_t *spa_lookup(const char *name);
+extern spa_t *spa_lookup_lite(const char *name);
 extern spa_t *spa_add(const char *name, nvlist_t *config, const char *altroot);
 extern void spa_remove(spa_t *spa);
 extern spa_t *spa_next(spa_t *prev);
+extern spa_t *spa_next_lite(spa_t *prev);
 
 /* Refcount functions */
 extern void spa_open_ref(spa_t *spa, const void *tag);

include/sys/spa_impl.h

@@ -484,6 +484,7 @@ struct spa {
 extern char *spa_config_path;
 extern const char *zfs_deadman_failmode;
 extern uint_t spa_slop_shift;
+extern uint_t spa_namespace_delay_ms;
 extern void spa_taskq_dispatch(spa_t *spa, zio_type_t t, zio_taskq_type_t q,
     task_func_t *func, zio_t *zio, boolean_t cutinline);
 extern void spa_load_spares(spa_t *spa);

include/sys/zfs_context.h

@@ -769,6 +769,8 @@ void ksiddomain_rele(ksiddomain_t *);
 		(void) nanosleep(&ts, NULL);				\
 	} while (0)
 
+#define	zfs_msleep(ms) zfs_sleep_until(gethrtime() + (MSEC2NSEC(ms)))
+
 typedef int fstrans_cookie_t;
 
 extern fstrans_cookie_t spl_fstrans_mark(void);

include/sys/zfs_delay.h

@@ -37,5 +37,6 @@
 			usleep_range(delta_us, delta_us + 100);		\
 		}							\
 	} while (0)
+#define	zfs_msleep(ms) zfs_sleep_until(gethrtime() + (MSEC2NSEC(ms)))
 
 #endif	/* _SYS_FS_ZFS_DELAY_H */

module/os/freebsd/zfs/spa_os.c

@@ -192,7 +192,7 @@ spa_import_rootpool(const char *name, bool checkpointrewind)
 	 */
 	config = spa_generate_rootconf(name);
 
-	mutex_enter(&spa_namespace_lock);
+	mutex_enter_ns(&spa_namespace_lock);
 	if (config != NULL) {
 		pname = fnvlist_lookup_string(config, ZPOOL_CONFIG_POOL_NAME);
 		VERIFY0(strcmp(name, pname));

module/os/freebsd/zfs/zfs_ioctl_os.c

@@ -107,7 +107,7 @@ zfs_ioc_nextboot(const char *unused, nvlist_t *innvl, nvlist_t *outnvl)
 	    "command", &command) != 0)
 		return (EINVAL);
 
-	mutex_enter(&spa_namespace_lock);
+	mutex_enter_ns(&spa_namespace_lock);
 	spa = spa_by_guid(pool_guid, vdev_guid);
 	if (spa != NULL)
 		strcpy(name, spa_name(spa));

module/zfs/arc.c

@@ -8205,7 +8205,7 @@ l2arc_dev_get_next(void)
 	 * of cache devices (l2arc_dev_mtx).  Once a device has been selected,
 	 * both locks will be dropped and a spa config lock held instead.
 	 */
-	mutex_enter(&spa_namespace_lock);
+	mutex_enter_ns(&spa_namespace_lock);
 	mutex_enter(&l2arc_dev_mtx);
 
 	/* if there are no vdevs, there is nothing to do */

module/zfs/mmp.c

@@ -728,7 +728,7 @@ mmp_signal_all_threads(void)
 {
 	spa_t *spa = NULL;
 
-	mutex_enter(&spa_namespace_lock);
+	mutex_enter_ns(&spa_namespace_lock);
 	while ((spa = spa_next(spa))) {
 		if (spa->spa_state == POOL_STATE_ACTIVE)
 			mmp_signal_thread(spa);