Handle some taskq_create() failures.

This commit attempts to handle taskq_create() failures and propagate
the error in the following functions:

	dsl_pool_open()
		dsl_pool_init()
		dsl_pool_create()

	zil_open()
		zfs_sb_setup()
		zvol_first_open()

Failures of taskq_create() were already handled in zvol_init().

The other major user of taskq_create() in which there is no error handling
is txg_dispatch_callbacks().

module/zfs/dsl_pool.c

@@ -170,6 +170,14 @@ dsl_pool_open_impl(spa_t *spa, uint64_t txg)
 
 	dp->dp_iput_taskq = taskq_create("zfs_iput_taskq", 1, minclsyspri,
 	    1, 4, 0);
+#ifdef _KERNEL
+	if (IS_ERR(dp->dp_iput_taskq)) {
+		dsl_pool_t *rval = (dsl_pool_t *)dp->dp_iput_taskq;
+		kmem_free(dp, sizeof (dsl_pool_t));
+		printk(KERN_INFO "%s: taskq_create() failed\n", FTAG);
+		return (rval);
+	}
+#endif
 
 	return (dp);
 }
@@ -180,6 +188,10 @@ dsl_pool_init(spa_t *spa, uint64_t txg, dsl_pool_t **dpp)
 	int err;
 	dsl_pool_t *dp = dsl_pool_open_impl(spa, txg);
 
+#ifdef _KERNEL
+	if (IS_ERR(dp))
+		return (PTR_ERR(dp));
+#endif
 	err = dmu_objset_open_impl(spa, NULL, &dp->dp_meta_rootbp,
 	    &dp->dp_meta_objset);
 	if (err != 0)
@@ -323,12 +335,19 @@ dsl_pool_t *
 dsl_pool_create(spa_t *spa, nvlist_t *zplprops, uint64_t txg)
 {
 	int err;
-	dsl_pool_t *dp = dsl_pool_open_impl(spa, txg);
-	dmu_tx_t *tx = dmu_tx_create_assigned(dp, txg);
+	dsl_pool_t *dp;
+	dmu_tx_t *tx;
 	objset_t *os;
 	dsl_dataset_t *ds;
 	uint64_t obj;
 
+	dp = dsl_pool_open_impl(spa, txg);
+#ifdef KERNEL
+	if (IS_ERR(dp))
+		return (dp);
+#endif
+	tx = dmu_tx_create_assigned(dp, txg);
+
 	rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG);
 
 	/* create and open the MOS (meta-objset) */

module/zfs/spa.c

@@ -3507,6 +3507,9 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 	spa_config_exit(spa, SCL_ALL, FTAG);
 
 	if (error != 0) {
+#ifdef _KERNEL
+	out:
+#endif
 		spa_unload(spa);
 		spa_deactivate(spa);
 		spa_remove(spa);
@@ -3546,6 +3549,12 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 
 	spa->spa_is_initializing = B_TRUE;
 	spa->spa_dsl_pool = dp = dsl_pool_create(spa, zplprops, txg);
+#ifdef _KERNEL
+	if (IS_ERR(dp)) {
+		error = PTR_ERR(dp);
+		goto out;
+	}
+#endif
 	spa->spa_meta_objset = dp->dp_meta_objset;
 	spa->spa_is_initializing = B_FALSE;
 

module/zfs/zfs_vfsops.c

@@ -816,6 +816,10 @@ zfs_sb_setup(zfs_sb_t *zsb, boolean_t mounting)
 	mutex_exit(&zsb->z_os->os_user_ptr_lock);
 
 	zsb->z_log = zil_open(zsb->z_os, zfs_get_data);
+	if (IS_ERR(zsb->z_log)) {
+		zfs_unregister_callbacks(zsb);
+		return (PTR_ERR(zsb->z_log));
+	}
 
 	/*
 	 * If we are not mounting (ie: online recv), then we don't

module/zfs/zil.c

@@ -1877,6 +1877,12 @@ zil_open(objset_t *os, zil_get_data_t *get_data)
 	zilog->zl_get_data = get_data;
 	zilog->zl_clean_taskq = taskq_create("zil_clean", 1, minclsyspri,
 	    2, 2, TASKQ_PREPOPULATE);
+#ifdef _KERNEL
+	if (IS_ERR(zilog->zl_clean_taskq)) {
+		printk(KERN_INFO "%s: taskq_create() failed\n", FTAG);
+		return ((zilog_t *)zilog->zl_clean_taskq);
+	}
+#endif
 
 	return (zilog);
 }

module/zfs/zvol.c

@@ -966,6 +966,10 @@ zvol_first_open(zvol_state_t *zv)
 	set_capacity(zv->zv_disk, volsize >> 9);
 	zv->zv_volsize = volsize;
 	zv->zv_zilog = zil_open(os, zvol_get_data);
+	if (IS_ERR(zv->zv_zilog)) {
+		error = PTR_ERR(zv->zv_zilog);
+		goto out_mutex;
+	}
 
 	VERIFY(dsl_prop_get_integer(zv->zv_name, "readonly", &ro, NULL) == 0);
 	if (ro || dmu_objset_is_snapshot(os) ||
@@ -1643,9 +1647,9 @@ zvol_init(void)
 
 	zvol_taskq = taskq_create(ZVOL_DRIVER, zvol_threads, maxclsyspri,
 	    zvol_threads, INT_MAX, TASKQ_PREPOPULATE);
-	if (zvol_taskq == NULL) {
-		printk(KERN_INFO "ZFS: taskq_create() failed\n");
-		error = -ENOMEM;
+	if (zvol_taskq == NULL || IS_ERR(zvol_taskq)) {
+		printk(KERN_INFO "ZFS: %s: taskq_create() failed\n", FTAG);
+		error = SET_ERROR(ENOMEM);
 		goto out1;
 	}