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Date:      Fri, 28 Aug 2020 13:15:13 +0000 (UTC)
From:      Andriy Gapon <avg@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org
Subject:   svn commit: r364917 - in stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys
Message-ID:  <202008281315.07SDFDcC034359@repo.freebsd.org>

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Author: avg
Date: Fri Aug 28 13:15:13 2020
New Revision: 364917
URL: https://svnweb.freebsd.org/changeset/base/364917

Log:
  MFC r362047,r362048: rework how ZVOLs are updated in response to DSL operations

Modified:
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_destroy.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/spa_impl.h
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zvol.h
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c
  stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c	Fri Aug 28 13:15:13 2020	(r364917)
@@ -1053,6 +1053,9 @@ dmu_objset_create_sync(void *arg, dmu_tx_t *tx)
 		    doca->doca_cred, tx);
 	}
 
+#if defined(__FreeBSD__) && defined(_KERNEL)
+	zvol_create_minors(dp->dp_spa, doca->doca_name);
+#endif
 	spa_history_log_internal_ds(ds, "create", tx, "");
 	dsl_dataset_rele(ds, FTAG);
 	dsl_dir_rele(pdd, FTAG);
@@ -1148,6 +1151,9 @@ dmu_objset_clone_sync(void *arg, dmu_tx_t *tx)
 
 	VERIFY0(dsl_dataset_hold_obj(pdd->dd_pool, obj, FTAG, &ds));
 	dsl_dataset_name(origin, namebuf);
+#if defined(__FreeBSD__) && defined(_KERNEL)
+	zvol_create_minors(dp->dp_spa, doca->doca_clone);
+#endif
 	spa_history_log_internal_ds(ds, "clone", tx,
 	    "origin=%s (%llu)", namebuf, origin->ds_object);
 	dsl_dataset_rele(ds, FTAG);

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c	Fri Aug 28 13:15:13 2020	(r364917)
@@ -57,6 +57,9 @@
 #include <sys/dsl_bookmark.h>
 #include <sys/zfeature.h>
 #include <sys/bqueue.h>
+#ifdef __FreeBSD__
+#include <sys/zvol.h>
+#endif
 
 #ifdef __FreeBSD__
 #undef dump_write
@@ -3445,6 +3448,11 @@ dmu_recv_end_sync(void *arg, dmu_tx_t *tx)
 		drc->drc_newsnapobj =
 		    dsl_dataset_phys(drc->drc_ds)->ds_prev_snap_obj;
 	}
+
+#if defined(__FreeBSD__) && defined(_KERNEL)
+	zvol_create_minors(dp->dp_spa, drc->drc_tofs);
+#endif
+
 	/*
 	 * Release the hold from dmu_recv_begin.  This must be done before
 	 * we return to open context, so that when we free the dataset's dnode,

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c	Fri Aug 28 13:15:13 2020	(r364917)
@@ -1572,6 +1572,9 @@ dsl_dataset_snapshot_sync(void *arg, dmu_tx_t *tx)
 			dsl_props_set_sync_impl(ds->ds_prev,
 			    ZPROP_SRC_LOCAL, ddsa->ddsa_props, tx);
 		}
+#if defined(__FreeBSD__) && defined(_KERNEL)
+		zvol_create_minors(dp->dp_spa, name);
+#endif
 		dsl_dataset_rele(ds, FTAG);
 	}
 }
@@ -1646,17 +1649,6 @@ dsl_dataset_snapshot(nvlist_t *snaps, nvlist_t *props,
 		fnvlist_free(suspended);
 	}
 
-#ifdef __FreeBSD__
-#ifdef _KERNEL
-	if (error == 0) {
-		for (pair = nvlist_next_nvpair(snaps, NULL); pair != NULL;
-		    pair = nvlist_next_nvpair(snaps, pair)) {
-			char *snapname = nvpair_name(pair);
-			zvol_create_minors(snapname);
-		}
-	}
-#endif
-#endif
 	return (error);
 }
 
@@ -2535,7 +2527,7 @@ dsl_dataset_rename_snapshot_sync_impl(dsl_pool_t *dp,
 	snprintf(newname, ZFS_MAX_DATASET_NAME_LEN, "%s@%s",
 	    ddrsa->ddrsa_fsname, ddrsa->ddrsa_newsnapname);
 	zfsvfs_update_fromname(oldname, newname);
-	zvol_rename_minors(oldname, newname);
+	zvol_rename_minors(dp->dp_spa, oldname, newname);
 	kmem_free(newname, ZFS_MAX_DATASET_NAME_LEN);
 	kmem_free(oldname, ZFS_MAX_DATASET_NAME_LEN);
 #endif
@@ -3087,9 +3079,6 @@ dsl_dataset_promote_sync(void *arg, dmu_tx_t *tx)
 	}
 
 #if defined(__FreeBSD__) && defined(_KERNEL)
-	/* Take the spa_namespace_lock early so zvol renames don't deadlock. */
-	mutex_enter(&spa_namespace_lock);
-
 	oldname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 	newname = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
 #endif
@@ -3135,7 +3124,7 @@ dsl_dataset_promote_sync(void *arg, dmu_tx_t *tx)
 #if defined(__FreeBSD__) && defined(_KERNEL)
 		dsl_dataset_name(ds, newname);
 		zfsvfs_update_fromname(oldname, newname);
-		zvol_rename_minors(oldname, newname);
+		zvol_rename_minors(dp->dp_spa, oldname, newname);
 #endif
 
 		/* move any clone references */
@@ -3177,8 +3166,6 @@ dsl_dataset_promote_sync(void *arg, dmu_tx_t *tx)
 	}
 
 #if defined(__FreeBSD__) && defined(_KERNEL)
-	mutex_exit(&spa_namespace_lock);
-
 	kmem_free(newname, ZFS_MAX_DATASET_NAME_LEN);
 	kmem_free(oldname, ZFS_MAX_DATASET_NAME_LEN);
 #endif

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_destroy.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_destroy.c	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_destroy.c	Fri Aug 28 13:15:13 2020	(r364917)
@@ -43,7 +43,11 @@
 #include <sys/dsl_deleg.h>
 #include <sys/dmu_impl.h>
 #include <sys/zcp.h>
+#if defined(__FreeBSD__) && defined(_KERNEL)
+#include <sys/zvol.h>
+#endif
 
+
 int
 dsl_destroy_snapshot_check_impl(dsl_dataset_t *ds, boolean_t defer)
 {
@@ -489,6 +493,14 @@ dsl_destroy_snapshot_sync_impl(dsl_dataset_t *ds, bool
 	if (dsl_dataset_phys(ds)->ds_userrefs_obj != 0)
 		VERIFY0(zap_destroy(mos, dsl_dataset_phys(ds)->ds_userrefs_obj,
 		    tx));
+
+#if defined(__FreeBSD__) && defined(_KERNEL)
+	char dsname[ZFS_MAX_DATASET_NAME_LEN];
+
+	dsl_dataset_name(ds, dsname);
+	zvol_remove_minors(dp->dp_spa, dsname);
+#endif
+
 	dsl_dir_rele(ds->ds_dir, ds);
 	ds->ds_dir = NULL;
 	dmu_object_free_zapified(mos, obj, tx);
@@ -979,6 +991,9 @@ dsl_destroy_head_sync(void *arg, dmu_tx_t *tx)
 
 	VERIFY0(dsl_dataset_hold(dp, ddha->ddha_name, FTAG, &ds));
 	dsl_destroy_head_sync_impl(ds, tx);
+#if defined(__FreeBSD__) && defined(_KERNEL)
+	zvol_remove_minors(dp->dp_spa, ddha->ddha_name);
+#endif
 	dsl_dataset_rele(ds, FTAG);
 }
 

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c	Fri Aug 28 13:15:13 2020	(r364917)
@@ -2093,7 +2093,7 @@ dsl_dir_rename_sync(void *arg, dmu_tx_t *tx)
 #ifdef __FreeBSD__
 #ifdef _KERNEL
 	zfsvfs_update_fromname(ddra->ddra_oldname, ddra->ddra_newname);
-	zvol_rename_minors(ddra->ddra_oldname, ddra->ddra_newname);
+	zvol_rename_minors(dp->dp_spa, ddra->ddra_oldname, ddra->ddra_newname);
 #endif
 #endif
 

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c	Fri Aug 28 13:15:13 2020	(r364917)
@@ -32,6 +32,7 @@
  * Copyright (c) 2017, Intel Corporation.
  * Copyright (c) 2017 Datto Inc.
  * Copyright 2018 OmniOS Community Edition (OmniOSce) Association.
+ * Copyright (c) 2016 Actifio, Inc. All rights reserved.
  */
 
 /*
@@ -1280,6 +1281,24 @@ spa_activate(spa_t *spa, int mode)
 	 */
 	trim_thread_create(spa);
 
+	/*
+	 * This taskq is used to perform zvol-minor-related tasks
+	 * asynchronously. This has several advantages, including easy
+	 * resolution of various deadlocks (zfsonlinux bug #3681).
+	 *
+	 * The taskq must be single threaded to ensure tasks are always
+	 * processed in the order in which they were dispatched.
+	 *
+	 * A taskq per pool allows one to keep the pools independent.
+	 * This way if one pool is suspended, it will not impact another.
+	 *
+	 * The preferred location to dispatch a zvol minor task is a sync
+	 * task. In this context, there is easy access to the spa_t and minimal
+	 * error handling is required because the sync task must succeed.
+	 */
+	spa->spa_zvol_taskq = taskq_create("z_zvol", 1, minclsyspri,
+	    1, INT_MAX, 0);
+
 	for (size_t i = 0; i < TXG_SIZE; i++) {
 		spa->spa_txg_zio[i] = zio_root(spa, NULL, NULL,
 		    ZIO_FLAG_CANFAIL);
@@ -1323,6 +1342,11 @@ spa_deactivate(spa_t *spa)
 
 	spa_evicting_os_wait(spa);
 
+	if (spa->spa_zvol_taskq) {
+		taskq_destroy(spa->spa_zvol_taskq);
+		spa->spa_zvol_taskq = NULL;
+	}
+
 	txg_list_destroy(&spa->spa_vdev_txg_list);
 
 	list_destroy(&spa->spa_config_dirty_list);
@@ -4614,7 +4638,7 @@ spa_open_common(const char *pool, spa_t **spapp, void 
 #ifdef __FreeBSD__
 #ifdef _KERNEL
 		if (firstopen)
-			zvol_create_minors(spa->spa_name);
+			zvol_create_minors(spa, spa->spa_name);
 #endif
 #endif
 	}
@@ -5970,7 +5994,7 @@ spa_import(const char *pool, nvlist_t *config, nvlist_
 
 #ifdef __FreeBSD__
 #ifdef _KERNEL
-	zvol_create_minors(pool);
+	zvol_create_minors(spa, pool);
 #endif
 #endif
 	return (0);
@@ -6119,6 +6143,12 @@ spa_export_common(char *pool, int new_state, nvlist_t 
 	spa_open_ref(spa, FTAG);
 	mutex_exit(&spa_namespace_lock);
 	spa_async_suspend(spa);
+	if (spa->spa_zvol_taskq) {
+#ifdef _KERNEL
+		zvol_remove_minors(spa, spa_name(spa));
+#endif
+		taskq_wait(spa->spa_zvol_taskq);
+	}
 	mutex_enter(&spa_namespace_lock);
 	spa_close(spa, FTAG);
 

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/spa_impl.h
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/spa_impl.h	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/spa_impl.h	Fri Aug 28 13:15:13 2020	(r364917)
@@ -27,6 +27,7 @@
  * Copyright 2013 Saso Kiselkov. All rights reserved.
  * Copyright (c) 2017 Datto Inc.
  * Copyright (c) 2017, Intel Corporation.
+ * Copyright (c) 2016 Actifio, Inc. All rights reserved.
  */
 
 #ifndef _SYS_SPA_IMPL_H
@@ -398,6 +399,8 @@ struct spa {
 	uint64_t	spa_lowmem_last_txg;	/* txg window start */
 
 	hrtime_t	spa_ccw_fail_time;	/* Conf cache write fail time */
+
+	taskq_t		*spa_zvol_taskq;	/* Taskq for minor management */
 
 	uint64_t	spa_multihost;		/* multihost aware (mmp) */
 	mmp_thread_t	spa_mmp;		/* multihost mmp thread */

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zvol.h
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zvol.h	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/zvol.h	Fri Aug 28 13:15:13 2020	(r364917)
@@ -21,6 +21,7 @@
 
 /*
  * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016 Actifio, Inc. All rights reserved.
  */
 
 #ifndef	_SYS_ZVOL_H
@@ -40,9 +41,6 @@ extern int zvol_check_volsize(uint64_t volsize, uint64
 extern int zvol_check_volblocksize(uint64_t volblocksize);
 extern int zvol_get_stats(objset_t *os, nvlist_t *nv);
 extern void zvol_create_cb(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx);
-extern int zvol_create_minor(const char *);
-extern int zvol_remove_minor(const char *);
-extern void zvol_remove_minors(const char *);
 extern int zvol_set_volsize(const char *, uint64_t);
 
 #ifdef illumos
@@ -72,8 +70,10 @@ extern void zvol_log_write_minor(void *minor_hdl, dmu_
 #endif	/* illumos */
 
 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
-extern int zvol_create_minors(const char *name);
-extern void zvol_rename_minors(const char *oldname, const char *newname);
+extern void zvol_create_minors(spa_t *spa, const char *name);
+extern void zvol_remove_minors(spa_t *spa, const char *name);
+extern void zvol_rename_minors(spa_t *spa, const char *oldname,
+    const char *newname);
 #endif
 
 #endif	/* _KERNEL */

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c	Fri Aug 28 13:15:13 2020	(r364917)
@@ -1642,8 +1642,10 @@ zfs_ioc_pool_destroy(zfs_cmd_t *zc)
 	int error;
 	zfs_log_history(zc);
 	error = spa_destroy(zc->zc_name);
+#ifndef __FreeBSD__
 	if (error == 0)
 		zvol_remove_minors(zc->zc_name);
+#endif
 	return (error);
 }
 
@@ -1694,8 +1696,10 @@ zfs_ioc_pool_export(zfs_cmd_t *zc)
 
 	zfs_log_history(zc);
 	error = spa_export(zc->zc_name, NULL, force, hardforce);
+#ifndef __FreeBSD__
 	if (error == 0)
 		zvol_remove_minors(zc->zc_name);
+#endif
 	return (error);
 }
 
@@ -3395,13 +3399,23 @@ zfs_ioc_create(const char *fsname, nvlist_t *innvl, nv
 	if (error == 0) {
 		error = zfs_set_prop_nvlist(fsname, ZPROP_SRC_LOCAL,
 		    nvprops, outnvl);
+#if defined(__FreeBSD__) && defined(_KERNEL)
+		/*
+		 * Wait for ZVOL operations to settle down before destroying.
+		 */
+		if (error != 0) {
+			spa_t *spa;
+
+			if (spa_open(fsname, &spa, FTAG) == 0) {
+				taskqueue_drain_all(
+				    spa->spa_zvol_taskq->tq_queue);
+				spa_close(spa, FTAG);
+			}
+		}
+#endif
 		if (error != 0)
 			(void) dsl_destroy_head(fsname);
 	}
-#ifdef __FreeBSD__
-	if (error == 0 && type == DMU_OST_ZVOL)
-		zvol_create_minors(fsname);
-#endif
 	return (error);
 }
 
@@ -3443,10 +3457,6 @@ zfs_ioc_clone(const char *fsname, nvlist_t *innvl, nvl
 		if (error != 0)
 			(void) dsl_destroy_head(fsname);
 	}
-#ifdef __FreeBSD__
-	if (error == 0)
-		zvol_create_minors(fsname);
-#endif
 	return (error);
 }
 
@@ -3738,9 +3748,6 @@ zfs_ioc_destroy_snaps(const char *poolname, nvlist_t *
 			return (SET_ERROR(EXDEV));
 
 		zfs_unmount_snap(nvpair_name(pair));
-#if defined(__FreeBSD__)
-		zvol_remove_minors(name);
-#endif
 	}
 
 	return (dsl_destroy_snapshots_nvl(snaps, defer, outnvl));
@@ -3924,10 +3931,8 @@ zfs_ioc_destroy(zfs_cmd_t *zc)
 		err = dsl_destroy_snapshot(zc->zc_name, zc->zc_defer_destroy);
 	else
 		err = dsl_destroy_head(zc->zc_name);
+#ifndef __FreeBSD__
 	if (ost == DMU_OST_ZVOL && err == 0)
-#ifdef __FreeBSD__
-		zvol_remove_minors(zc->zc_name);
-#else
 		(void) zvol_remove_minor(zc->zc_name);
 #endif
 	return (err);
@@ -4813,11 +4818,6 @@ zfs_ioc_recv(zfs_cmd_t *zc)
 	}
 #endif
 
-#ifdef __FreeBSD__
-	if (error == 0)
-		zvol_create_minors(tofs);
-#endif
-
 	/*
 	 * On error, restore the original props.
 	 */
@@ -6958,6 +6958,24 @@ zfsdev_ioctl(struct cdev *dev, u_long zcmd, caddr_t ar
 
 out:
 	nvlist_free(innvl);
+
+#if defined(__FreeBSD__) && defined(_KERNEL)
+	/*
+	 * Wait for ZVOL changes to get applied.
+	 * NB: taskqueue_drain_all() does less than taskq_wait(),
+	 * but enough for what we want.
+	 * And there is no equivalent illumos API.
+	 */
+	if (error == 0) {
+		spa_t *spa;
+
+		if (spa_open(saved_poolname, &spa, FTAG) == 0) {
+			taskqueue_drain_all(
+			    spa->spa_zvol_taskq->tq_queue);
+			spa_close(spa, FTAG);
+		}
+	}
+#endif
 
 #ifdef illumos
 	rc = ddi_copyout(zc, (void *)arg, sizeof (zfs_cmd_t), flag);

Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
==============================================================================
--- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c	Fri Aug 28 10:33:19 2020	(r364916)
+++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c	Fri Aug 28 13:15:13 2020	(r364917)
@@ -30,6 +30,7 @@
  * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright (c) 2014 Integros [integros.com]
+ * Copyright (c) 2016 Actifio, Inc. All rights reserved.
  */
 
 /* Portions Copyright 2011 Martin Matuska <mm@FreeBSD.org> */
@@ -184,6 +185,20 @@ typedef struct zvol_state {
 #endif
 } zvol_state_t;
 
+typedef enum {
+	ZVOL_ASYNC_CREATE_MINORS,
+	ZVOL_ASYNC_REMOVE_MINORS,
+	ZVOL_ASYNC_RENAME_MINORS,
+	ZVOL_ASYNC_MAX
+} zvol_async_op_t;
+
+typedef struct {
+	zvol_async_op_t op;
+	char pool[ZFS_MAX_DATASET_NAME_LEN];
+	char name1[ZFS_MAX_DATASET_NAME_LEN];
+	char name2[ZFS_MAX_DATASET_NAME_LEN];
+} zvol_task_t;
+
 #ifndef illumos
 static LIST_HEAD(, zvol_state) all_zvols;
 #endif
@@ -606,7 +621,7 @@ zvol_name2minor(const char *name, minor_t *minor)
 /*
  * Create a minor node (plus a whole lot more) for the specified volume.
  */
-int
+static int
 zvol_create_minor(const char *name)
 {
 	zfs_soft_state_t *zs;
@@ -690,7 +705,6 @@ zvol_create_minor(const char *name)
 	if (error != 0 || mode == ZFS_VOLMODE_DEFAULT)
 		mode = volmode;
 
-	DROP_GIANT();
 	zv->zv_volmode = mode;
 	if (zv->zv_volmode == ZFS_VOLMODE_GEOM) {
 		g_topology_lock();
@@ -765,7 +779,6 @@ zvol_create_minor(const char *name)
 		zvol_geom_run(zv);
 		g_topology_unlock();
 	}
-	PICKUP_GIANT();
 
 	ZFS_LOG(1, "ZVOL %s created.", name);
 #endif
@@ -819,22 +832,6 @@ zvol_remove_zv(zvol_state_t *zv)
 }
 
 int
-zvol_remove_minor(const char *name)
-{
-	zvol_state_t *zv;
-	int rc;
-
-	mutex_enter(&zfsdev_state_lock);
-	if ((zv = zvol_minor_lookup(name)) == NULL) {
-		mutex_exit(&zfsdev_state_lock);
-		return (SET_ERROR(ENXIO));
-	}
-	rc = zvol_remove_zv(zv);
-	mutex_exit(&zfsdev_state_lock);
-	return (rc);
-}
-
-int
 zvol_first_open(zvol_state_t *zv)
 {
 	dmu_object_info_t doi;
@@ -975,7 +972,7 @@ zvol_update_volsize(objset_t *os, uint64_t volsize)
 }
 
 void
-zvol_remove_minors(const char *name)
+zvol_remove_minors_impl(const char *name)
 {
 #ifdef illumos
 	zvol_state_t *zv;
@@ -1003,7 +1000,6 @@ zvol_remove_minors(const char *name)
 
 	namelen = strlen(name);
 
-	DROP_GIANT();
 	mutex_enter(&zfsdev_state_lock);
 
 	LIST_FOREACH_SAFE(zv, &all_zvols, zv_links, tzv) {
@@ -1016,7 +1012,6 @@ zvol_remove_minors(const char *name)
 	}
 
 	mutex_exit(&zfsdev_state_lock);
-	PICKUP_GIANT();
 #endif	/* illumos */
 }
 
@@ -2919,7 +2914,7 @@ zvol_create_snapshots(objset_t *os, const char *name)
 }
 
 int
-zvol_create_minors(const char *name)
+zvol_create_minors_impl(const char *name)
 {
 	uint64_t cookie;
 	objset_t *os;
@@ -2975,7 +2970,7 @@ zvol_create_minors(const char *name)
 	while (dmu_dir_list_next(os, MAXPATHLEN - (p - osname), p, NULL,
 	    &cookie) == 0) {
 		dmu_objset_rele(os, FTAG);
-		(void)zvol_create_minors(osname);
+		(void)zvol_create_minors_impl(osname);
 		if ((error = dmu_objset_hold(name, FTAG, &os)) != 0) {
 			printf("ZFS WARNING: Unable to put hold on %s (error=%d).\n",
 			    name, error);
@@ -3044,7 +3039,7 @@ zvol_rename_minor(zvol_state_t *zv, const char *newnam
 }
 
 void
-zvol_rename_minors(const char *oldname, const char *newname)
+zvol_rename_minors_impl(const char *oldname, const char *newname)
 {
 	char name[MAXPATHLEN];
 	struct g_provider *pp;
@@ -3057,7 +3052,6 @@ zvol_rename_minors(const char *oldname, const char *ne
 	oldnamelen = strlen(oldname);
 	newnamelen = strlen(newname);
 
-	DROP_GIANT();
 	/* See comment in zvol_open(). */
 	if (!MUTEX_HELD(&zfsdev_state_lock)) {
 		mutex_enter(&zfsdev_state_lock);
@@ -3079,7 +3073,88 @@ zvol_rename_minors(const char *oldname, const char *ne
 
 	if (locked)
 		mutex_exit(&zfsdev_state_lock);
-	PICKUP_GIANT();
+}
+
+static zvol_task_t *
+zvol_task_alloc(zvol_async_op_t op, const char *name1, const char *name2)
+{
+	zvol_task_t *task;
+	char *delim;
+
+	task = kmem_zalloc(sizeof (zvol_task_t), KM_SLEEP);
+	task->op = op;
+	delim = strchr(name1, '/');
+	strlcpy(task->pool, name1, delim ? (delim - name1 + 1) : MAXNAMELEN);
+
+	strlcpy(task->name1, name1, MAXNAMELEN);
+	if (name2 != NULL)
+		strlcpy(task->name2, name2, MAXNAMELEN);
+
+	return (task);
+}
+
+static void
+zvol_task_free(zvol_task_t *task)
+{
+	kmem_free(task, sizeof (zvol_task_t));
+}
+
+/*
+ * The worker thread function performed asynchronously.
+ */
+static void
+zvol_task_cb(void *param)
+{
+	zvol_task_t *task = (zvol_task_t *)param;
+
+	switch (task->op) {
+	case ZVOL_ASYNC_CREATE_MINORS:
+		(void) zvol_create_minors_impl(task->name1);
+		break;
+	case ZVOL_ASYNC_REMOVE_MINORS:
+		zvol_remove_minors_impl(task->name1);
+		break;
+	case ZVOL_ASYNC_RENAME_MINORS:
+		zvol_rename_minors_impl(task->name1, task->name2);
+		break;
+	default:
+		VERIFY(0);
+		break;
+	}
+
+	zvol_task_free(task);
+}
+
+static void
+zvol_minors_helper(spa_t *spa, zvol_async_op_t op, const char *name1,
+    const char *name2)
+{
+	zvol_task_t *task;
+
+	if (dataset_name_hidden(name1))
+		return;
+	if (name2 != NULL && dataset_name_hidden(name2))
+		return;
+	task = zvol_task_alloc(op, name1, name2);
+	(void)taskq_dispatch(spa->spa_zvol_taskq, zvol_task_cb, task, TQ_SLEEP);
+}
+
+void
+zvol_create_minors(spa_t *spa, const char *name)
+{
+	zvol_minors_helper(spa, ZVOL_ASYNC_CREATE_MINORS, name, NULL);
+}
+
+void
+zvol_remove_minors(spa_t *spa, const char *name)
+{
+	zvol_minors_helper(spa, ZVOL_ASYNC_REMOVE_MINORS, name, NULL);
+}
+
+void
+zvol_rename_minors(spa_t *spa, const char *oldname, const char *newname)
+{
+	zvol_minors_helper(spa, ZVOL_ASYNC_RENAME_MINORS, oldname, newname);
 }
 
 static int



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