X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=blobdiff_plain;f=module%2Fzfs%2Fzvol.c;h=e35c91bc184ea2c91c89ee25f7611df645a0b98e;hb=91604b298c24c84fe03bc6c028abb961ca3e6fcf;hp=9dda04077e7d0073dddcb2ce6c63b5160d261974;hpb=56c34bac44d47898809c46db3e5444511bbe0ef6;p=zfs.git

diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index 9dda040..e35c91b 100644
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -46,8 +46,10 @@
 #include <sys/zvol.h>
 #include <linux/blkdev_compat.h>
 
+unsigned int zvol_inhibit_dev = 0;
 unsigned int zvol_major = ZVOL_MAJOR;
-unsigned int zvol_threads = 0;
+unsigned int zvol_threads = 32;
+unsigned long zvol_max_discard_blocks = 16384;
 
 static taskq_t *zvol_taskq;
 static kmutex_t zvol_state_lock;
@@ -139,6 +141,29 @@ zvol_find_by_name(const char *name)
 	return NULL;
 }
 
+
+/*
+ * Given a path, return TRUE if path is a ZVOL.
+ */
+boolean_t
+zvol_is_zvol(const char *device)
+{
+	struct block_device *bdev;
+	unsigned int major;
+
+	bdev = lookup_bdev(device);
+	if (IS_ERR(bdev))
+		return (B_FALSE);
+
+	major = MAJOR(bdev->bd_dev);
+	bdput(bdev);
+
+	if (major == zvol_major)
+            return (B_TRUE);
+
+	return (B_FALSE);
+}
+
 /*
  * ZFS_IOC_CREATE callback handles dmu zvol and zap object creation.
  */
@@ -428,20 +453,20 @@ zvol_replay_err(zvol_state_t *zv, lr_t *lr, boolean_t byteswap)
  * Callback vectors for replaying records.
  * Only TX_WRITE is needed for zvol.
  */
-zil_replay_func_t *zvol_replay_vector[TX_MAX_TYPE] = {
-	(zil_replay_func_t *)zvol_replay_err,	/* no such transaction type */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_CREATE */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_MKDIR */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_MKXATTR */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_SYMLINK */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_REMOVE */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_RMDIR */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_LINK */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_RENAME */
-	(zil_replay_func_t *)zvol_replay_write,	/* TX_WRITE */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_TRUNCATE */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_SETATTR */
-	(zil_replay_func_t *)zvol_replay_err,	/* TX_ACL */
+zil_replay_func_t zvol_replay_vector[TX_MAX_TYPE] = {
+	(zil_replay_func_t)zvol_replay_err,	/* no such transaction type */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_CREATE */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_MKDIR */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_MKXATTR */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_SYMLINK */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_REMOVE */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_RMDIR */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_LINK */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_RENAME */
+	(zil_replay_func_t)zvol_replay_write,	/* TX_WRITE */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_TRUNCATE */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_SETATTR */
+	(zil_replay_func_t)zvol_replay_err,	/* TX_ACL */
 };
 
 /*
@@ -459,11 +484,15 @@ zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx,
 	uint32_t blocksize = zv->zv_volblocksize;
 	zilog_t *zilog = zv->zv_zilog;
 	boolean_t slogging;
+	ssize_t immediate_write_sz;
 
 	if (zil_replaying(zilog, tx))
 		return;
 
-	slogging = spa_has_slogs(zilog->zl_spa);
+	immediate_write_sz = (zilog->zl_logbias == ZFS_LOGBIAS_THROUGHPUT)
+		? 0 : zvol_immediate_write_sz;
+	slogging = spa_has_slogs(zilog->zl_spa) &&
+		(zilog->zl_logbias == ZFS_LOGBIAS_LATENCY);
 
 	while (size) {
 		itx_t *itx;
@@ -475,7 +504,7 @@ zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx,
 		 * Unlike zfs_log_write() we can be called with
 		 * up to DMU_MAX_ACCESS/2 (5MB) writes.
 		 */
-		if (blocksize > zvol_immediate_write_sz && !slogging &&
+		if (blocksize > immediate_write_sz && !slogging &&
 		    size >= blocksize && offset % blocksize == 0) {
 			write_state = WR_INDIRECT; /* uses dmu_sync */
 			len = blocksize;
@@ -534,6 +563,25 @@ zvol_write(void *arg)
 	dmu_tx_t *tx;
 	rl_t *rl;
 
+	/*
+	 * Annotate this call path with a flag that indicates that it is
+	 * unsafe to use KM_SLEEP during memory allocations due to the
+	 * potential for a deadlock.  KM_PUSHPAGE should be used instead.
+	 */
+	ASSERT(!(current->flags & PF_NOFS));
+	current->flags |= PF_NOFS;
+
+	if (req->cmd_flags & VDEV_REQ_FLUSH)
+		zil_commit(zv->zv_zilog, ZVOL_OBJ);
+
+	/*
+	 * Some requests are just for flush and nothing else.
+	 */
+	if (size == 0) {
+		blk_end_request(req, 0, size);
+		goto out;
+	}
+
 	rl = zfs_range_lock(&zv->zv_znode, offset, size, RL_WRITER);
 
 	tx = dmu_tx_create(zv->zv_objset);
@@ -545,21 +593,80 @@ zvol_write(void *arg)
 		dmu_tx_abort(tx);
 		zfs_range_unlock(rl);
 		blk_end_request(req, -error, size);
-		return;
+		goto out;
 	}
 
 	error = dmu_write_req(zv->zv_objset, ZVOL_OBJ, req, tx);
 	if (error == 0)
-		zvol_log_write(zv, tx, offset, size, rq_is_sync(req));
+		zvol_log_write(zv, tx, offset, size,
+		    req->cmd_flags & VDEV_REQ_FUA);
 
 	dmu_tx_commit(tx);
 	zfs_range_unlock(rl);
 
-	if (rq_is_sync(req) || zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS)
+	if ((req->cmd_flags & VDEV_REQ_FUA) ||
+	    zv->zv_objset->os_sync == ZFS_SYNC_ALWAYS)
 		zil_commit(zv->zv_zilog, ZVOL_OBJ);
 
 	blk_end_request(req, -error, size);
+out:
+	current->flags &= ~PF_NOFS;
+}
+
+#ifdef HAVE_BLK_QUEUE_DISCARD
+static void
+zvol_discard(void *arg)
+{
+	struct request *req = (struct request *)arg;
+	struct request_queue *q = req->q;
+	zvol_state_t *zv = q->queuedata;
+	uint64_t start = blk_rq_pos(req) << 9;
+	uint64_t end = start + blk_rq_bytes(req);
+	int error;
+	rl_t *rl;
+
+	/*
+	 * Annotate this call path with a flag that indicates that it is
+	 * unsafe to use KM_SLEEP during memory allocations due to the
+	 * potential for a deadlock.  KM_PUSHPAGE should be used instead.
+	 */
+	ASSERT(!(current->flags & PF_NOFS));
+	current->flags |= PF_NOFS;
+
+	if (end > zv->zv_volsize) {
+		blk_end_request(req, -EIO, blk_rq_bytes(req));
+		goto out;
+	}
+
+	/*
+	 * Align the request to volume block boundaries. If we don't,
+	 * then this will force dnode_free_range() to zero out the
+	 * unaligned parts, which is slow (read-modify-write) and
+	 * useless since we are not freeing any space by doing so.
+	 */
+	start = P2ROUNDUP(start, zv->zv_volblocksize);
+	end = P2ALIGN(end, zv->zv_volblocksize);
+
+	if (start >= end) {
+		blk_end_request(req, 0, blk_rq_bytes(req));
+		goto out;
+	}
+
+	rl = zfs_range_lock(&zv->zv_znode, start, end - start, RL_WRITER);
+
+	error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, start, end - start);
+
+	/*
+	 * TODO: maybe we should add the operation to the log.
+	 */
+
+	zfs_range_unlock(rl);
+
+	blk_end_request(req, -error, blk_rq_bytes(req));
+out:
+	current->flags &= ~PF_NOFS;
 }
+#endif /* HAVE_BLK_QUEUE_DISCARD */
 
 /*
  * Common read path running under the zvol taskq context.  This function
@@ -578,6 +685,11 @@ zvol_read(void *arg)
 	int error;
 	rl_t *rl;
 
+	if (size == 0) {
+		blk_end_request(req, 0, size);
+		return;
+	}
+
 	rl = zfs_range_lock(&zv->zv_znode, offset, size, RL_READER);
 
 	error = dmu_read_req(zv->zv_objset, ZVOL_OBJ, req);
@@ -627,7 +739,7 @@ zvol_request(struct request_queue *q)
 	while ((req = blk_fetch_request(q)) != NULL) {
 		size = blk_rq_bytes(req);
 
-		if (blk_rq_pos(req) + blk_rq_sectors(req) >
+		if (size != 0 && blk_rq_pos(req) + blk_rq_sectors(req) >
 		    get_capacity(zv->zv_disk)) {
 			printk(KERN_INFO
 			       "%s: bad access: block=%llu, count=%lu\n",
@@ -656,6 +768,13 @@ zvol_request(struct request_queue *q)
 				break;
 			}
 
+#ifdef HAVE_BLK_QUEUE_DISCARD
+			if (req->cmd_flags & VDEV_REQ_DISCARD) {
+				zvol_dispatch(zvol_discard, req);
+				break;
+			}
+#endif /* HAVE_BLK_QUEUE_DISCARD */
+
 			zvol_dispatch(zvol_write, req);
 			break;
 		default:
@@ -698,7 +817,7 @@ zvol_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio)
 	ASSERT(zio != NULL);
 	ASSERT(size != 0);
 
-	zgd = (zgd_t *)kmem_zalloc(sizeof (zgd_t), KM_SLEEP);
+	zgd = (zgd_t *)kmem_zalloc(sizeof (zgd_t), KM_PUSHPAGE);
 	zgd->zgd_zilog = zv->zv_zilog;
 	zgd->zgd_rl = zfs_range_lock(&zv->zv_znode, offset, size, RL_READER);
 
@@ -772,25 +891,49 @@ zvol_first_open(zvol_state_t *zv)
 {
 	objset_t *os;
 	uint64_t volsize;
+	int locked = 0;
 	int error;
 	uint64_t ro;
 
+	/*
+	 * In all other cases the spa_namespace_lock is taken before the
+	 * bdev->bd_mutex lock.  But in this case the Linux __blkdev_get()
+	 * function calls fops->open() with the bdev->bd_mutex lock held.
+	 *
+	 * To avoid a potential lock inversion deadlock we preemptively
+	 * try to take the spa_namespace_lock().  Normally it will not
+	 * be contended and this is safe because spa_open_common() handles
+	 * the case where the caller already holds the spa_namespace_lock.
+	 *
+	 * When it is contended we risk a lock inversion if we were to
+	 * block waiting for the lock.  Luckily, the __blkdev_get()
+	 * function allows us to return -ERESTARTSYS which will result in
+	 * bdev->bd_mutex being dropped, reacquired, and fops->open() being
+	 * called again.  This process can be repeated safely until both
+	 * locks are acquired.
+	 */
+	if (!mutex_owned(&spa_namespace_lock)) {
+		locked = mutex_tryenter(&spa_namespace_lock);
+		if (!locked)
+			return (-ERESTARTSYS);
+	}
+
 	/* lie and say we're read-only */
 	error = dmu_objset_own(zv->zv_name, DMU_OST_ZVOL, 1, zvol_tag, &os);
 	if (error)
-		return (-error);
+		goto out_mutex;
 
 	error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize);
 	if (error) {
-	        dmu_objset_disown(os, zvol_tag);
-	        return (-error);
+		dmu_objset_disown(os, zvol_tag);
+		goto out_mutex;
 	}
 
 	zv->zv_objset = os;
 	error = dmu_bonus_hold(os, ZVOL_OBJ, zvol_tag, &zv->zv_dbuf);
 	if (error) {
-	        dmu_objset_disown(os, zvol_tag);
-	        return (-error);
+		dmu_objset_disown(os, zvol_tag);
+		goto out_mutex;
 	}
 
 	set_capacity(zv->zv_disk, volsize >> 9);
@@ -798,14 +941,19 @@ zvol_first_open(zvol_state_t *zv)
 	zv->zv_zilog = zil_open(os, zvol_get_data);
 
 	VERIFY(dsl_prop_get_integer(zv->zv_name, "readonly", &ro, NULL) == 0);
-	if (ro || dmu_objset_is_snapshot(os)) {
-                set_disk_ro(zv->zv_disk, 1);
-	        zv->zv_flags |= ZVOL_RDONLY;
+	if (ro || dmu_objset_is_snapshot(os) ||
+	    !spa_writeable(dmu_objset_spa(os))) {
+		set_disk_ro(zv->zv_disk, 1);
+		zv->zv_flags |= ZVOL_RDONLY;
 	} else {
-                set_disk_ro(zv->zv_disk, 0);
-	        zv->zv_flags &= ~ZVOL_RDONLY;
+		set_disk_ro(zv->zv_disk, 0);
+		zv->zv_flags &= ~ZVOL_RDONLY;
 	}
 
+out_mutex:
+	if (locked)
+		mutex_exit(&spa_namespace_lock);
+
 	return (-error);
 }
 
@@ -814,8 +962,18 @@ zvol_last_close(zvol_state_t *zv)
 {
 	zil_close(zv->zv_zilog);
 	zv->zv_zilog = NULL;
+
 	dmu_buf_rele(zv->zv_dbuf, zvol_tag);
 	zv->zv_dbuf = NULL;
+
+	/*
+	 * Evict cached data
+	 */
+	if (dsl_dataset_is_dirty(dmu_objset_ds(zv->zv_objset)) &&
+	    !(zv->zv_flags & ZVOL_RDONLY))
+		txg_wait_synced(dmu_objset_pool(zv->zv_objset), 0);
+	(void) dmu_objset_evict_dbufs(zv->zv_objset);
+
 	dmu_objset_disown(zv->zv_objset, zvol_tag);
 	zv->zv_objset = NULL;
 }
@@ -978,7 +1136,7 @@ zvol_probe(dev_t dev, int *part, void *arg)
 
 	mutex_enter(&zvol_state_lock);
 	zv = zvol_find_by_dev(dev);
-	kobj = zv ? get_disk(zv->zv_disk) : ERR_PTR(-ENOENT);
+	kobj = zv ? get_disk(zv->zv_disk) : NULL;
 	mutex_exit(&zvol_state_lock);
 
 	return kobj;
@@ -1053,15 +1211,32 @@ static zvol_state_t *
 zvol_alloc(dev_t dev, const char *name)
 {
 	zvol_state_t *zv;
+	int error = 0;
 
 	zv = kmem_zalloc(sizeof (zvol_state_t), KM_SLEEP);
-	if (zv == NULL)
-		goto out;
+
+	spin_lock_init(&zv->zv_lock);
+	list_link_init(&zv->zv_next);
 
 	zv->zv_queue = blk_init_queue(zvol_request, &zv->zv_lock);
 	if (zv->zv_queue == NULL)
 		goto out_kmem;
 
+#ifdef HAVE_ELEVATOR_CHANGE
+	error = elevator_change(zv->zv_queue, "noop");
+#endif /* HAVE_ELEVATOR_CHANGE */
+	if (error) {
+		printk("ZFS: Unable to set \"%s\" scheduler for zvol %s: %d\n",
+		    "noop", name, error);
+		goto out_queue;
+	}
+
+#ifdef HAVE_BLK_QUEUE_FLUSH
+	blk_queue_flush(zv->zv_queue, VDEV_REQ_FLUSH | VDEV_REQ_FUA);
+#else
+	blk_queue_ordered(zv->zv_queue, QUEUE_ORDERED_DRAIN, NULL);
+#endif /* HAVE_BLK_QUEUE_FLUSH */
+
 	zv->zv_disk = alloc_disk(ZVOL_MINORS);
 	if (zv->zv_disk == NULL)
 		goto out_queue;
@@ -1076,9 +1251,6 @@ zvol_alloc(dev_t dev, const char *name)
 	    sizeof (rl_t), offsetof(rl_t, r_node));
 	zv->zv_znode.z_is_zvol = TRUE;
 
-	spin_lock_init(&zv->zv_lock);
-	list_link_init(&zv->zv_next);
-
 	zv->zv_disk->major = zvol_major;
 	zv->zv_disk->first_minor = (dev & MINORMASK);
 	zv->zv_disk->fops = &zvol_ops;
@@ -1093,7 +1265,7 @@ out_queue:
 	blk_cleanup_queue(zv->zv_queue);
 out_kmem:
 	kmem_free(zv, sizeof (zvol_state_t));
-out:
+
 	return NULL;
 }
 
@@ -1114,7 +1286,28 @@ zvol_free(zvol_state_t *zv)
 }
 
 static int
-__zvol_create_minor(const char *name)
+__zvol_snapdev_hidden(const char *name)
+{
+        uint64_t snapdev;
+        char *parent;
+        char *atp;
+        int error = 0;
+
+        parent = kmem_alloc(MAXPATHLEN, KM_SLEEP);
+        (void) strlcpy(parent, name, MAXPATHLEN);
+
+        if ((atp = strrchr(parent, '@')) != NULL) {
+                *atp = '\0';
+                error = dsl_prop_get_integer(parent, "snapdev", &snapdev, NULL);
+                if ((error == 0) && (snapdev == ZFS_SNAPDEV_HIDDEN))
+                        error = ENODEV;
+        }
+        kmem_free(parent, MAXPATHLEN);
+        return (error);
+}
+
+static int
+__zvol_create_minor(const char *name, boolean_t ignore_snapdev)
 {
 	zvol_state_t *zv;
 	objset_t *os;
@@ -1131,6 +1324,12 @@ __zvol_create_minor(const char *name)
 		goto out;
 	}
 
+	if (ignore_snapdev == B_FALSE) {
+		error = __zvol_snapdev_hidden(name);
+		if (error)
+			goto out;
+	}
+
 	doi = kmem_alloc(sizeof(dmu_object_info_t), KM_SLEEP);
 
 	error = dmu_objset_own(name, DMU_OST_ZVOL, B_TRUE, zvol_tag, &os);
@@ -1164,14 +1363,31 @@ __zvol_create_minor(const char *name)
 
 	set_capacity(zv->zv_disk, zv->zv_volsize >> 9);
 
-	if (zil_replay_disable)
-		zil_destroy(dmu_objset_zil(os), B_FALSE);
-	else
-		zil_replay(os, zv, zvol_replay_vector);
+	blk_queue_max_hw_sectors(zv->zv_queue, UINT_MAX);
+	blk_queue_max_segments(zv->zv_queue, UINT16_MAX);
+	blk_queue_max_segment_size(zv->zv_queue, UINT_MAX);
+	blk_queue_physical_block_size(zv->zv_queue, zv->zv_volblocksize);
+	blk_queue_io_opt(zv->zv_queue, zv->zv_volblocksize);
+#ifdef HAVE_BLK_QUEUE_DISCARD
+	blk_queue_max_discard_sectors(zv->zv_queue,
+	    (zvol_max_discard_blocks * zv->zv_volblocksize) >> 9);
+	blk_queue_discard_granularity(zv->zv_queue, zv->zv_volblocksize);
+	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zv->zv_queue);
+#endif
+#ifdef HAVE_BLK_QUEUE_NONROT
+	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zv->zv_queue);
+#endif
+
+	if (spa_writeable(dmu_objset_spa(os))) {
+		if (zil_replay_disable)
+			zil_destroy(dmu_objset_zil(os), B_FALSE);
+		else
+			zil_replay(os, zv, zvol_replay_vector);
+	}
 
+	zv->zv_objset = NULL;
 out_dmu_objset_disown:
 	dmu_objset_disown(os, zvol_tag);
-	zv->zv_objset = NULL;
 out_doi:
 	kmem_free(doi, sizeof(dmu_object_info_t));
 out:
@@ -1195,7 +1411,7 @@ zvol_create_minor(const char *name)
 	int error;
 
 	mutex_enter(&zvol_state_lock);
-	error = __zvol_create_minor(name);
+	error = __zvol_create_minor(name, B_FALSE);
 	mutex_exit(&zvol_state_lock);
 
 	return (error);
@@ -1243,7 +1459,7 @@ zvol_create_minors_cb(spa_t *spa, uint64_t dsobj,
 	if (strchr(dsname, '/') == NULL)
 		return 0;
 
-	(void) __zvol_create_minor(dsname);
+	(void) __zvol_create_minor(dsname, B_FALSE);
 	return (0);
 }
 
@@ -1257,6 +1473,9 @@ zvol_create_minors(const char *pool)
 	spa_t *spa = NULL;
 	int error = 0;
 
+	if (zvol_inhibit_dev)
+		return (0);
+
 	mutex_enter(&zvol_state_lock);
 	if (pool) {
 		error = dmu_objset_find_spa(NULL, pool, zvol_create_minors_cb,
@@ -1286,6 +1505,9 @@ zvol_remove_minors(const char *pool)
 	zvol_state_t *zv, *zv_next;
 	char *str;
 
+	if (zvol_inhibit_dev)
+		return;
+
 	str = kmem_zalloc(MAXNAMELEN, KM_SLEEP);
 	if (pool) {
 		(void) strncpy(str, pool, strlen(pool));
@@ -1305,38 +1527,70 @@ zvol_remove_minors(const char *pool)
 	kmem_free(str, MAXNAMELEN);
 }
 
+static int
+snapdev_snapshot_changed_cb(const char *dsname, void *arg) {
+	uint64_t snapdev = *(uint64_t *) arg;
+
+	if (strchr(dsname, '@') == NULL)
+		return 0;
+
+	switch (snapdev) {
+		case ZFS_SNAPDEV_VISIBLE:
+			mutex_enter(&zvol_state_lock);
+			(void) __zvol_create_minor(dsname, B_TRUE);
+			mutex_exit(&zvol_state_lock);
+			break;
+		case ZFS_SNAPDEV_HIDDEN:
+			(void) zvol_remove_minor(dsname);
+			break;
+	}
+	return 0;
+}
+
+int
+zvol_set_snapdev(const char *dsname, uint64_t snapdev) {
+	(void) dmu_objset_find((char *) dsname, snapdev_snapshot_changed_cb,
+		&snapdev, DS_FIND_SNAPSHOTS | DS_FIND_CHILDREN);
+	/* caller should continue to modify snapdev property */
+	return (-1);
+}
+
+
 int
 zvol_init(void)
 {
 	int error;
 
-	if (!zvol_threads)
-		zvol_threads = num_online_cpus();
+	list_create(&zvol_state_list, sizeof (zvol_state_t),
+	            offsetof(zvol_state_t, zv_next));
+	mutex_init(&zvol_state_lock, NULL, MUTEX_DEFAULT, NULL);
 
 	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");
-		return (-ENOMEM);
+		error = -ENOMEM;
+		goto out1;
 	}
 
 	error = register_blkdev(zvol_major, ZVOL_DRIVER);
 	if (error) {
 		printk(KERN_INFO "ZFS: register_blkdev() failed %d\n", error);
-		taskq_destroy(zvol_taskq);
-		return (error);
+		goto out2;
 	}
 
 	blk_register_region(MKDEV(zvol_major, 0), 1UL << MINORBITS,
 	                    THIS_MODULE, zvol_probe, NULL, NULL);
 
-	mutex_init(&zvol_state_lock, NULL, MUTEX_DEFAULT, NULL);
-	list_create(&zvol_state_list, sizeof (zvol_state_t),
-	            offsetof(zvol_state_t, zv_next));
+	return (0);
 
-	(void) zvol_create_minors(NULL);
+out2:
+	taskq_destroy(zvol_taskq);
+out1:
+	mutex_destroy(&zvol_state_lock);
+	list_destroy(&zvol_state_list);
 
-	return (0);
+	return (error);
 }
 
 void
@@ -1350,8 +1604,14 @@ zvol_fini(void)
 	list_destroy(&zvol_state_list);
 }
 
+module_param(zvol_inhibit_dev, uint, 0644);
+MODULE_PARM_DESC(zvol_inhibit_dev, "Do not create zvol device nodes");
+
 module_param(zvol_major, uint, 0444);
 MODULE_PARM_DESC(zvol_major, "Major number for zvol device");
 
 module_param(zvol_threads, uint, 0444);
 MODULE_PARM_DESC(zvol_threads, "Number of threads for zvol device");
+
+module_param(zvol_max_discard_blocks, ulong, 0444);
+MODULE_PARM_DESC(zvol_max_discard_blocks, "Max number of blocks to discard at once");