text: /*
   * CDDL HEADER START
   *
   * The contents of this file are subject to the terms of the
   * Common Development and Distribution License (the "License").
   * You may not use this file except in compliance with the License.
   *
   * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   * or http://www.opensolaris.org/os/licensing.
   * See the License for the specific language governing permissions
   * and limitations under the License.
   *
   * When distributing Covered Code, include this CDDL HEADER in each
   * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
   * If applicable, add the following below this CDDL HEADER, with the
   * fields enclosed by brackets "[]" replaced with your own identifying
   * information: Portions Copyright [yyyy] [name of copyright owner]
   *
   * CDDL HEADER END
   */
  /*
   * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
  #include <sys/zfs_context.h>
  #include <sys/spa_impl.h>
  #include <sys/zio.h>
  #include <sys/zio_checksum.h>
  #include <sys/zio_compress.h>
  #include <sys/dmu.h>
  #include <sys/dmu_tx.h>
  #include <sys/zap.h>
  #include <sys/zil.h>
  #include <sys/vdev_impl.h>
  #include <sys/metaslab.h>
  #include <sys/uberblock_impl.h>
  #include <sys/txg.h>
  #include <sys/avl.h>
  #include <sys/unique.h>
  #include <sys/dsl_pool.h>
  #include <sys/dsl_dir.h>
  #include <sys/dsl_prop.h>
  #include <sys/dsl_scan.h>
  #include <sys/fs/zfs.h>
  #include <sys/metaslab_impl.h>
  #include <sys/arc.h>
  #include <sys/ddt.h>
  #include "zfs_prop.h"
  
  /*
   * SPA locking
   *
   * There are four basic locks for managing spa_t structures:
   *
   * spa_namespace_lock (global mutex)
   *
   *	This lock must be acquired to do any of the following:
   *
   *		- Lookup a spa_t by name
   *		- Add or remove a spa_t from the namespace
   *		- Increase spa_refcount from non-zero
   *		- Check if spa_refcount is zero
   *		- Rename a spa_t
   *		- add/remove/attach/detach devices
   *		- Held for the duration of create/destroy/import/export
   *
   *	It does not need to handle recursion.  A create or destroy may
   *	reference objects (files or zvols) in other pools, but by
   *	definition they must have an existing reference, and will never need
   *	to lookup a spa_t by name.
   *
   * spa_refcount (per-spa refcount_t protected by mutex)
   *
   *	This reference count keep track of any active users of the spa_t.  The
   *	spa_t cannot be destroyed or freed while this is non-zero.  Internally,
   *	the refcount is never really 'zero' - opening a pool implicitly keeps
   *	some references in the DMU.  Internally we check against spa_minref, but
   *	present the image of a zero/non-zero value to consumers.
   *
   * spa_config_lock[] (per-spa array of rwlocks)
   *
   *	This protects the spa_t from config changes, and must be held in
   *	the following circumstances:
   *
   *		- RW_READER to perform I/O to the spa
   *		- RW_WRITER to change the vdev config
   *
   * The locking order is fairly straightforward:
   *
   *		spa_namespace_lock	->	spa_refcount
   *
   *	The namespace lock must be acquired to increase the refcount from 0
   *	or to check if it is zero.
   *
   *		spa_refcount		->	spa_config_lock[]
   *
   *	There must be at least one valid reference on the spa_t to acquire
   *	the config lock.
   *
   *		spa_namespace_lock	->	spa_config_lock[]
   *
   *	The namespace lock must always be taken before the config lock.
   *
   *
   * The spa_namespace_lock can be acquired directly and is globally visible.
   *
   * The namespace is manipulated using the following functions, all of which
   * require the spa_namespace_lock to be held.
   *
   *	spa_lookup()		Lookup a spa_t by name.
   *
   *	spa_add()		Create a new spa_t in the namespace.
   *
   *	spa_remove()		Remove a spa_t from the namespace.  This also
   *				frees up any memory associated with the spa_t.
   *
   *	spa_next()		Returns the next spa_t in the system, or the
   *				first if NULL is passed.
   *
   *	spa_evict_all()		Shutdown and remove all spa_t structures in
   *				the system.
   *
   *	spa_guid_exists()	Determine whether a pool/device guid exists.
   *
   * The spa_refcount is manipulated using the following functions:
   *
   *	spa_open_ref()		Adds a reference to the given spa_t.  Must be
   *				called with spa_namespace_lock held if the
   *				refcount is currently zero.
   *
   *	spa_close()		Remove a reference from the spa_t.  This will
   *				not free the spa_t or remove it from the
   *				namespace.  No locking is required.
   *
   *	spa_refcount_zero()	Returns true if the refcount is currently
   *				zero.  Must be called with spa_namespace_lock
   *				held.
   *
   * The spa_config_lock[] is an array of rwlocks, ordered as follows:
   * SCL_CONFIG > SCL_STATE > SCL_ALLOC > SCL_ZIO > SCL_FREE > SCL_VDEV.
   * spa_config_lock[] is manipulated with spa_config_{enter,exit,held}().
   *
   * To read the configuration, it suffices to hold one of these locks as reader.
   * To modify the configuration, you must hold all locks as writer.  To modify
   * vdev state without altering the vdev tree's topology (e.g. online/offline),
   * you must hold SCL_STATE and SCL_ZIO as writer.
   *
   * We use these distinct config locks to avoid recursive lock entry.
   * For example, spa_sync() (which holds SCL_CONFIG as reader) induces
   * block allocations (SCL_ALLOC), which may require reading space maps
   * from disk (dmu_read() -> zio_read() -> SCL_ZIO).
   *
   * The spa config locks cannot be normal rwlocks because we need the
   * ability to hand off ownership.  For example, SCL_ZIO is acquired
   * by the issuing thread and later released by an interrupt thread.
   * They do, however, obey the usual write-wanted semantics to prevent
   * writer (i.e. system administrator) starvation.
   *
   * The lock acquisition rules are as follows:
   *
   * SCL_CONFIG
   *	Protects changes to the vdev tree topology, such as vdev
   *	add/remove/attach/detach.  Protects the dirty config list
   *	(spa_config_dirty_list) and the set of spares and l2arc devices.
   *
   * SCL_STATE
   *	Protects changes to pool state and vdev state, such as vdev
   *	online/offline/fault/degrade/clear.  Protects the dirty state list
   *	(spa_state_dirty_list) and global pool state (spa_state).
   *
   * SCL_ALLOC
   *	Protects changes to metaslab groups and classes.
   *	Held as reader by metaslab_alloc() and metaslab_claim().
   *
   * SCL_ZIO
   *	Held by bp-level zios (those which have no io_vd upon entry)
   *	to prevent changes to the vdev tree.  The bp-level zio implicitly
   *	protects all of its vdev child zios, which do not hold SCL_ZIO.
   *
   * SCL_FREE
   *	Protects changes to metaslab groups and classes.
   *	Held as reader by metaslab_free().  SCL_FREE is distinct from
   *	SCL_ALLOC, and lower than SCL_ZIO, so that we can safely free
   *	blocks in zio_done() while another i/o that holds either
   *	SCL_ALLOC or SCL_ZIO is waiting for this i/o to complete.
   *
   * SCL_VDEV
   *	Held as reader to prevent changes to the vdev tree during trivial
   *	inquiries such as bp_get_dsize().  SCL_VDEV is distinct from the
   *	other locks, and lower than all of them, to ensure that it's safe
   *	to acquire regardless of caller context.
   *
   * In addition, the following rules apply:
   *
   * (a)	spa_props_lock protects pool properties, spa_config and spa_config_list.
   *	The lock ordering is SCL_CONFIG > spa_props_lock.
   *
   * (b)	I/O operations on leaf vdevs.  For any zio operation that takes
   *	an explicit vdev_t argument -- such as zio_ioctl(), zio_read_phys(),
   *	or zio_write_phys() -- the caller must ensure that the config cannot
   *	cannot change in the interim, and that the vdev cannot be reopened.
   *	SCL_STATE as reader suffices for both.
   *
   * The vdev configuration is protected by spa_vdev_enter() / spa_vdev_exit().
   *
   *	spa_vdev_enter()	Acquire the namespace lock and the config lock
   *				for writing.
   *
   *	spa_vdev_exit()		Release the config lock, wait for all I/O
   *				to complete, sync the updated configs to the
   *				cache, and release the namespace lock.
   *
   * vdev state is protected by spa_vdev_state_enter() / spa_vdev_state_exit().
   * Like spa_vdev_enter/exit, these are convenience wrappers -- the actual
   * locking is, always, based on spa_namespace_lock and spa_config_lock[].
   *
   * spa_rename() is also implemented within this file since is requires
   * manipulation of the namespace.
   */
  
  static avl_tree_t spa_namespace_avl;
  kmutex_t spa_namespace_lock;
  static kcondvar_t spa_namespace_cv;
  static int spa_active_count;
  int spa_max_replication_override = SPA_DVAS_PER_BP;
  
  static kmutex_t spa_spare_lock;
  static avl_tree_t spa_spare_avl;
  static kmutex_t spa_l2cache_lock;
  static avl_tree_t spa_l2cache_avl;
  
  kmem_cache_t *spa_buffer_pool;
  int spa_mode_global;
  
  #ifdef ZFS_DEBUG
  /* Everything except dprintf is on by default in debug builds */
  #ifdef _KERNEL
  int zfs_flags = ~ZFS_DEBUG_DPRINTF;
  #else
  int zfs_flags = ~0;
  #endif
  #else
  int zfs_flags = 0;
  #endif
  
  /*
   * zfs_recover can be set to nonzero to attempt to recover from
   * otherwise-fatal errors, typically caused by on-disk corruption.  When
   * set, calls to zfs_panic_recover() will turn into warning messages.
   */
  int zfs_recover = 0;
  
  
  /*
   * ==========================================================================
   * SPA config locking
   * ==========================================================================
   */
  static void
  spa_config_lock_init(spa_t *spa)
  {
  	for (int i = 0; i < SCL_LOCKS; i++) {
  		spa_config_lock_t *scl = &spa->spa_config_lock[i];
  		mutex_init(&scl->scl_lock, NULL, MUTEX_DEFAULT, NULL);
  		cv_init(&scl->scl_cv, NULL, CV_DEFAULT, NULL);
  		refcount_create(&scl->scl_count);
  		scl->scl_writer = NULL;
  		scl->scl_write_wanted = 0;
  	}
  }
  
  static void
  spa_config_lock_destroy(spa_t *spa)
  {
  	for (int i = 0; i < SCL_LOCKS; i++) {
  		spa_config_lock_t *scl = &spa->spa_config_lock[i];
  		mutex_destroy(&scl->scl_lock);
  		cv_destroy(&scl->scl_cv);
  		refcount_destroy(&scl->scl_count);
  		ASSERT(scl->scl_writer == NULL);
  		ASSERT(scl->scl_write_wanted == 0);
  	}
  }
  
  int
  spa_config_tryenter(spa_t *spa, int locks, void *tag, krw_t rw)
  {
  	for (int i = 0; i < SCL_LOCKS; i++) {
  		spa_config_lock_t *scl = &spa->spa_config_lock[i];
  		if (!(locks & (1 << i)))
  			continue;
  		mutex_enter(&scl->scl_lock);
  		if (rw == RW_READER) {
  			if (scl->scl_writer || scl->scl_write_wanted) {
  				mutex_exit(&scl->scl_lock);
  				spa_config_exit(spa, locks ^ (1 << i), tag);
  				return (0);
  			}
  		} else {
  			ASSERT(scl->scl_writer != curthread);
  			if (!refcount_is_zero(&scl->scl_count)) {
  				mutex_exit(&scl->scl_lock);
  				spa_config_exit(spa, locks ^ (1 << i), tag);
  				return (0);
  			}
  			scl->scl_writer = curthread;
  		}
  		(void) refcount_add(&scl->scl_count, tag);
  		mutex_exit(&scl->scl_lock);
  	}
  	return (1);
  }
  
  void
  spa_config_enter(spa_t *spa, int locks, void *tag, krw_t rw)
  {
  	int wlocks_held = 0;
  
  	for (int i = 0; i < SCL_LOCKS; i++) {
  		spa_config_lock_t *scl = &spa->spa_config_lock[i];
  		if (scl->scl_writer == curthread)
  			wlocks_held |= (1 << i);
  		if (!(locks & (1 << i)))
  			continue;
  		mutex_enter(&scl->scl_lock);
  		if (rw == RW_READER) {
  			while (scl->scl_writer || scl->scl_write_wanted) {
  				cv_wait(&scl->scl_cv, &scl->scl_lock);
  			}
  		} else {
  			ASSERT(scl->scl_writer != curthread);
  			while (!refcount_is_zero(&scl->scl_count)) {
  				scl->scl_write_wanted++;
  				cv_wait(&scl->scl_cv, &scl->scl_lock);
  				scl->scl_write_wanted--;
  			}
  			scl->scl_writer = curthread;
  		}
  		(void) refcount_add(&scl->scl_count, tag);
  		mutex_exit(&scl->scl_lock);
  	}
  	ASSERT(wlocks_held <= locks);
  }
  
  void
  spa_config_exit(spa_t *spa, int locks, void *tag)
  {
  	for (int i = SCL_LOCKS - 1; i >= 0; i--) {
  		spa_config_lock_t *scl = &spa->spa_config_lock[i];
  		if (!(locks & (1 << i)))
  			continue;
  		mutex_enter(&scl->scl_lock);
  		ASSERT(!refcount_is_zero(&scl->scl_count));
  		if (refcount_remove(&scl->scl_count, tag) == 0) {
  			ASSERT(scl->scl_writer == NULL ||
  			    scl->scl_writer == curthread);
  			scl->scl_writer = NULL;	/* OK in either case */
  			cv_broadcast(&scl->scl_cv);
  		}
  		mutex_exit(&scl->scl_lock);
  	}
  }
  
  int
  spa_config_held(spa_t *spa, int locks, krw_t rw)
  {
  	int locks_held = 0;
  
  	for (int i = 0; i < SCL_LOCKS; i++) {
  		spa_config_lock_t *scl = &spa->spa_config_lock[i];
  		if (!(locks & (1 << i)))
  			continue;
  		if ((rw == RW_READER && !refcount_is_zero(&scl->scl_count)) ||
  		    (rw == RW_WRITER && scl->scl_writer == curthread))
  			locks_held |= 1 << i;
  	}
  
  	return (locks_held);
  }
  
  /*
   * ==========================================================================
   * SPA namespace functions
   * ==========================================================================
   */
  
  /*
   * Lookup the named spa_t in the AVL tree.  The spa_namespace_lock must be held.
   * Returns NULL if no matching spa_t is found.
   */
  spa_t *
  spa_lookup(const char *name)
  {
  	static spa_t search;	/* spa_t is large; don't allocate on stack */
  	spa_t *spa;
  	avl_index_t where;
  	char c;
  	char *cp;
  
  	ASSERT(MUTEX_HELD(&spa_namespace_lock));
  
  	/*
  	 * If it's a full dataset name, figure out the pool name and
  	 * just use that.
  	 */
  	cp = strpbrk(name, "/@");
  	if (cp) {
  		c = *cp;
  		*cp = '\0';
  	}
  
  	(void) strlcpy(search.spa_name, name, sizeof (search.spa_name));
  	spa = avl_find(&spa_namespace_avl, &search, &where);
  
  	if (cp)
  		*cp = c;
  
  	return (spa);
  }
  
  /*
   * Create an uninitialized spa_t with the given name.  Requires
   * spa_namespace_lock.  The caller must ensure that the spa_t doesn't already
   * exist by calling spa_lookup() first.
   */
  spa_t *
  spa_add(const char *name, nvlist_t *config, const char *altroot)
  {
  	spa_t *spa;
  	spa_config_dirent_t *dp;
  
  	ASSERT(MUTEX_HELD(&spa_namespace_lock));
  
  	spa = kmem_zalloc(sizeof (spa_t), KM_SLEEP);
  
  	mutex_init(&spa->spa_async_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa->spa_scrub_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa->spa_errlog_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa->spa_errlist_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa->spa_history_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa->spa_props_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa->spa_suspend_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa->spa_vdev_top_lock, NULL, MUTEX_DEFAULT, NULL);
  
  	cv_init(&spa->spa_async_cv, NULL, CV_DEFAULT, NULL);
  	cv_init(&spa->spa_scrub_io_cv, NULL, CV_DEFAULT, NULL);
  	cv_init(&spa->spa_suspend_cv, NULL, CV_DEFAULT, NULL);
  
  	for (int t = 0; t < TXG_SIZE; t++)
  		bplist_init(&spa->spa_free_bplist[t]);
  	bplist_init(&spa->spa_deferred_bplist);
  
  	(void) strlcpy(spa->spa_name, name, sizeof (spa->spa_name));
  	spa->spa_state = POOL_STATE_UNINITIALIZED;
  	spa->spa_freeze_txg = UINT64_MAX;
  	spa->spa_final_txg = UINT64_MAX;
  	spa->spa_load_max_txg = UINT64_MAX;
  
  	refcount_create(&spa->spa_refcount);
  	spa_config_lock_init(spa);
  
  	avl_add(&spa_namespace_avl, spa);
  
  	/*
  	 * Set the alternate root, if there is one.
  	 */
  	if (altroot) {
  		spa->spa_root = spa_strdup(altroot);
  		spa_active_count++;
  	}
  
  	/*
  	 * Every pool starts with the default cachefile
  	 */
  	list_create(&spa->spa_config_list, sizeof (spa_config_dirent_t),
  	    offsetof(spa_config_dirent_t, scd_link));
  
  	dp = kmem_zalloc(sizeof (spa_config_dirent_t), KM_SLEEP);
  	dp->scd_path = altroot ? NULL : spa_strdup(spa_config_path);
  	list_insert_head(&spa->spa_config_list, dp);
  
  	if (config != NULL)
  		VERIFY(nvlist_dup(config, &spa->spa_config, 0) == 0);
  
  	return (spa);
  }
  
  /*
   * Removes a spa_t from the namespace, freeing up any memory used.  Requires
   * spa_namespace_lock.  This is called only after the spa_t has been closed and
   * deactivated.
   */
  void
  spa_remove(spa_t *spa)
  {
  	spa_config_dirent_t *dp;
  
  	ASSERT(MUTEX_HELD(&spa_namespace_lock));
  	ASSERT(spa->spa_state == POOL_STATE_UNINITIALIZED);
  
  	nvlist_free(spa->spa_config_splitting);
  
  	avl_remove(&spa_namespace_avl, spa);
  	cv_broadcast(&spa_namespace_cv);
  
  	if (spa->spa_root) {
  		spa_strfree(spa->spa_root);
  		spa_active_count--;
  	}
  
  	while ((dp = list_head(&spa->spa_config_list)) != NULL) {
  		list_remove(&spa->spa_config_list, dp);
  		if (dp->scd_path != NULL)
  			spa_strfree(dp->scd_path);
  		kmem_free(dp, sizeof (spa_config_dirent_t));
  	}
  
  	list_destroy(&spa->spa_config_list);
  
  	spa_config_set(spa, NULL);
  
  	refcount_destroy(&spa->spa_refcount);
  
  	spa_config_lock_destroy(spa);
  
  	for (int t = 0; t < TXG_SIZE; t++)
  		bplist_fini(&spa->spa_free_bplist[t]);
  	bplist_fini(&spa->spa_deferred_bplist);
  
  	cv_destroy(&spa->spa_async_cv);
  	cv_destroy(&spa->spa_scrub_io_cv);
  	cv_destroy(&spa->spa_suspend_cv);
  
  	mutex_destroy(&spa->spa_async_lock);
  	mutex_destroy(&spa->spa_scrub_lock);
  	mutex_destroy(&spa->spa_errlog_lock);
  	mutex_destroy(&spa->spa_errlist_lock);
  	mutex_destroy(&spa->spa_history_lock);
  	mutex_destroy(&spa->spa_props_lock);
  	mutex_destroy(&spa->spa_suspend_lock);
  	mutex_destroy(&spa->spa_vdev_top_lock);
  
  	kmem_free(spa, sizeof (spa_t));
  }
  
  /*
   * Given a pool, return the next pool in the namespace, or NULL if there is
   * none.  If 'prev' is NULL, return the first pool.
   */
  spa_t *
  spa_next(spa_t *prev)
  {
  	ASSERT(MUTEX_HELD(&spa_namespace_lock));
  
  	if (prev)
  		return (AVL_NEXT(&spa_namespace_avl, prev));
  	else
  		return (avl_first(&spa_namespace_avl));
  }
  
  /*
   * ==========================================================================
   * SPA refcount functions
   * ==========================================================================
   */
  
  /*
   * Add a reference to the given spa_t.  Must have at least one reference, or
   * have the namespace lock held.
   */
  void
  spa_open_ref(spa_t *spa, void *tag)
  {
  	ASSERT(refcount_count(&spa->spa_refcount) >= spa->spa_minref ||
  	    MUTEX_HELD(&spa_namespace_lock));
  	(void) refcount_add(&spa->spa_refcount, tag);
  }
  
  /*
   * Remove a reference to the given spa_t.  Must have at least one reference, or
   * have the namespace lock held.
   */
  void
  spa_close(spa_t *spa, void *tag)
  {
  	ASSERT(refcount_count(&spa->spa_refcount) > spa->spa_minref ||
  	    MUTEX_HELD(&spa_namespace_lock));
  	(void) refcount_remove(&spa->spa_refcount, tag);
  }
  
  /*
   * Check to see if the spa refcount is zero.  Must be called with
   * spa_namespace_lock held.  We really compare against spa_minref, which is the
   * number of references acquired when opening a pool
   */
  boolean_t
  spa_refcount_zero(spa_t *spa)
  {
  	ASSERT(MUTEX_HELD(&spa_namespace_lock));
  
  	return (refcount_count(&spa->spa_refcount) == spa->spa_minref);
  }
  
  /*
   * ==========================================================================
   * SPA spare and l2cache tracking
   * ==========================================================================
   */
  
  /*
   * Hot spares and cache devices are tracked using the same code below,
   * for 'auxiliary' devices.
   */
  
  typedef struct spa_aux {
  	uint64_t	aux_guid;
  	uint64_t	aux_pool;
  	avl_node_t	aux_avl;
  	int		aux_count;
  } spa_aux_t;
  
  static int
  spa_aux_compare(const void *a, const void *b)
  {
  	const spa_aux_t *sa = a;
  	const spa_aux_t *sb = b;
  
  	if (sa->aux_guid < sb->aux_guid)
  		return (-1);
  	else if (sa->aux_guid > sb->aux_guid)
  		return (1);
  	else
  		return (0);
  }
  
  void
  spa_aux_add(vdev_t *vd, avl_tree_t *avl)
  {
  	avl_index_t where;
  	spa_aux_t search;
  	spa_aux_t *aux;
  
  	search.aux_guid = vd->vdev_guid;
  	if ((aux = avl_find(avl, &search, &where)) != NULL) {
  		aux->aux_count++;
  	} else {
  		aux = kmem_zalloc(sizeof (spa_aux_t), KM_SLEEP);
  		aux->aux_guid = vd->vdev_guid;
  		aux->aux_count = 1;
  		avl_insert(avl, aux, where);
  	}
  }
  
  void
  spa_aux_remove(vdev_t *vd, avl_tree_t *avl)
  {
  	spa_aux_t search;
  	spa_aux_t *aux;
  	avl_index_t where;
  
  	search.aux_guid = vd->vdev_guid;
  	aux = avl_find(avl, &search, &where);
  
  	ASSERT(aux != NULL);
  
  	if (--aux->aux_count == 0) {
  		avl_remove(avl, aux);
  		kmem_free(aux, sizeof (spa_aux_t));
  	} else if (aux->aux_pool == spa_guid(vd->vdev_spa)) {
  		aux->aux_pool = 0ULL;
  	}
  }
  
  boolean_t
  spa_aux_exists(uint64_t guid, uint64_t *pool, int *refcnt, avl_tree_t *avl)
  {
  	spa_aux_t search, *found;
  
  	search.aux_guid = guid;
  	found = avl_find(avl, &search, NULL);
  
  	if (pool) {
  		if (found)
  			*pool = found->aux_pool;
  		else
  			*pool = 0ULL;
  	}
  
  	if (refcnt) {
  		if (found)
  			*refcnt = found->aux_count;
  		else
  			*refcnt = 0;
  	}
  
  	return (found != NULL);
  }
  
  void
  spa_aux_activate(vdev_t *vd, avl_tree_t *avl)
  {
  	spa_aux_t search, *found;
  	avl_index_t where;
  
  	search.aux_guid = vd->vdev_guid;
  	found = avl_find(avl, &search, &where);
  	ASSERT(found != NULL);
  	ASSERT(found->aux_pool == 0ULL);
  
  	found->aux_pool = spa_guid(vd->vdev_spa);
  }
  
  /*
   * Spares are tracked globally due to the following constraints:
   *
   *	- A spare may be part of multiple pools.
   *	- A spare may be added to a pool even if it's actively in use within
   *	  another pool.
   *	- A spare in use in any pool can only be the source of a replacement if
   *	  the target is a spare in the same pool.
   *
   * We keep track of all spares on the system through the use of a reference
   * counted AVL tree.  When a vdev is added as a spare, or used as a replacement
   * spare, then we bump the reference count in the AVL tree.  In addition, we set
   * the 'vdev_isspare' member to indicate that the device is a spare (active or
   * inactive).  When a spare is made active (used to replace a device in the
   * pool), we also keep track of which pool its been made a part of.
   *
   * The 'spa_spare_lock' protects the AVL tree.  These functions are normally
   * called under the spa_namespace lock as part of vdev reconfiguration.  The
   * separate spare lock exists for the status query path, which does not need to
   * be completely consistent with respect to other vdev configuration changes.
   */
  
  static int
  spa_spare_compare(const void *a, const void *b)
  {
  	return (spa_aux_compare(a, b));
  }
  
  void
  spa_spare_add(vdev_t *vd)
  {
  	mutex_enter(&spa_spare_lock);
  	ASSERT(!vd->vdev_isspare);
  	spa_aux_add(vd, &spa_spare_avl);
  	vd->vdev_isspare = B_TRUE;
  	mutex_exit(&spa_spare_lock);
  }
  
  void
  spa_spare_remove(vdev_t *vd)
  {
  	mutex_enter(&spa_spare_lock);
  	ASSERT(vd->vdev_isspare);
  	spa_aux_remove(vd, &spa_spare_avl);
  	vd->vdev_isspare = B_FALSE;
  	mutex_exit(&spa_spare_lock);
  }
  
  boolean_t
  spa_spare_exists(uint64_t guid, uint64_t *pool, int *refcnt)
  {
  	boolean_t found;
  
  	mutex_enter(&spa_spare_lock);
  	found = spa_aux_exists(guid, pool, refcnt, &spa_spare_avl);
  	mutex_exit(&spa_spare_lock);
  
  	return (found);
  }
  
  void
  spa_spare_activate(vdev_t *vd)
  {
  	mutex_enter(&spa_spare_lock);
  	ASSERT(vd->vdev_isspare);
  	spa_aux_activate(vd, &spa_spare_avl);
  	mutex_exit(&spa_spare_lock);
  }
  
  /*
   * Level 2 ARC devices are tracked globally for the same reasons as spares.
   * Cache devices currently only support one pool per cache device, and so
   * for these devices the aux reference count is currently unused beyond 1.
   */
  
  static int
  spa_l2cache_compare(const void *a, const void *b)
  {
  	return (spa_aux_compare(a, b));
  }
  
  void
  spa_l2cache_add(vdev_t *vd)
  {
  	mutex_enter(&spa_l2cache_lock);
  	ASSERT(!vd->vdev_isl2cache);
  	spa_aux_add(vd, &spa_l2cache_avl);
  	vd->vdev_isl2cache = B_TRUE;
  	mutex_exit(&spa_l2cache_lock);
  }
  
  void
  spa_l2cache_remove(vdev_t *vd)
  {
  	mutex_enter(&spa_l2cache_lock);
  	ASSERT(vd->vdev_isl2cache);
  	spa_aux_remove(vd, &spa_l2cache_avl);
  	vd->vdev_isl2cache = B_FALSE;
  	mutex_exit(&spa_l2cache_lock);
  }
  
  boolean_t
  spa_l2cache_exists(uint64_t guid, uint64_t *pool)
  {
  	boolean_t found;
  
  	mutex_enter(&spa_l2cache_lock);
  	found = spa_aux_exists(guid, pool, NULL, &spa_l2cache_avl);
  	mutex_exit(&spa_l2cache_lock);
  
  	return (found);
  }
  
  void
  spa_l2cache_activate(vdev_t *vd)
  {
  	mutex_enter(&spa_l2cache_lock);
  	ASSERT(vd->vdev_isl2cache);
  	spa_aux_activate(vd, &spa_l2cache_avl);
  	mutex_exit(&spa_l2cache_lock);
  }
  
  /*
   * ==========================================================================
   * SPA vdev locking
   * ==========================================================================
   */
  
  /*
   * Lock the given spa_t for the purpose of adding or removing a vdev.
   * Grabs the global spa_namespace_lock plus the spa config lock for writing.
   * It returns the next transaction group for the spa_t.
   */
  uint64_t
  spa_vdev_enter(spa_t *spa)
  {
  	mutex_enter(&spa->spa_vdev_top_lock);
  	mutex_enter(&spa_namespace_lock);
  	return (spa_vdev_config_enter(spa));
  }
  
  /*
   * Internal implementation for spa_vdev_enter().  Used when a vdev
   * operation requires multiple syncs (i.e. removing a device) while
   * keeping the spa_namespace_lock held.
   */
  uint64_t
  spa_vdev_config_enter(spa_t *spa)
  {
  	ASSERT(MUTEX_HELD(&spa_namespace_lock));
  
  	spa_config_enter(spa, SCL_ALL, spa, RW_WRITER);
  
  	return (spa_last_synced_txg(spa) + 1);
  }
  
  /*
   * Used in combination with spa_vdev_config_enter() to allow the syncing
   * of multiple transactions without releasing the spa_namespace_lock.
   */
  void
  spa_vdev_config_exit(spa_t *spa, vdev_t *vd, uint64_t txg, int error, char *tag)
  {
  	ASSERT(MUTEX_HELD(&spa_namespace_lock));
  
  	int config_changed = B_FALSE;
  
  	ASSERT(txg > spa_last_synced_txg(spa));
  
  	spa->spa_pending_vdev = NULL;
  
  	/*
  	 * Reassess the DTLs.
  	 */
  	vdev_dtl_reassess(spa->spa_root_vdev, 0, 0, B_FALSE);
  
  	/*
  	 * If the config changed, notify the scrub that it must restart.
  	 * This will initiate a resilver if needed.
  	 */
  	if (error == 0 && !list_is_empty(&spa->spa_config_dirty_list)) {
  		config_changed = B_TRUE;
  		spa->spa_config_generation++;
  	}
  
  	/*
  	 * Verify the metaslab classes.
  	 */
  	ASSERT(metaslab_class_validate(spa_normal_class(spa)) == 0);
  	ASSERT(metaslab_class_validate(spa_log_class(spa)) == 0);
  
  	spa_config_exit(spa, SCL_ALL, spa);
  
  	/*
  	 * Panic the system if the specified tag requires it.  This
  	 * is useful for ensuring that configurations are updated
  	 * transactionally.
  	 */
  	if (zio_injection_enabled)
  		zio_handle_panic_injection(spa, tag, 0);
  
  	/*
  	 * Note: this txg_wait_synced() is important because it ensures
  	 * that there won't be more than one config change per txg.
  	 * This allows us to use the txg as the generation number.
  	 */
  	if (error == 0)
  		txg_wait_synced(spa->spa_dsl_pool, txg);
  
  	if (vd != NULL) {
  		ASSERT(!vd->vdev_detached || vd->vdev_dtl_smo.smo_object == 0);
  		spa_config_enter(spa, SCL_ALL, spa, RW_WRITER);
  		vdev_free(vd);
  		spa_config_exit(spa, SCL_ALL, spa);
  	}
  
  	/*
  	 * If the config changed, update the config cache.
  	 */
  	if (config_changed)
  		spa_config_sync(spa, B_FALSE, B_TRUE);
  }
  
  /*
   * Unlock the spa_t after adding or removing a vdev.  Besides undoing the
   * locking of spa_vdev_enter(), we also want make sure the transactions have
   * synced to disk, and then update the global configuration cache with the new
   * information.
   */
  int
  spa_vdev_exit(spa_t *spa, vdev_t *vd, uint64_t txg, int error)
  {
  	spa_vdev_config_exit(spa, vd, txg, error, FTAG);
  	mutex_exit(&spa_namespace_lock);
  	mutex_exit(&spa->spa_vdev_top_lock);
  
  	return (error);
  }
  
  /*
   * Lock the given spa_t for the purpose of changing vdev state.
   */
  void
  spa_vdev_state_enter(spa_t *spa, int oplocks)
  {
  	int locks = SCL_STATE_ALL | oplocks;
  
  	spa_config_enter(spa, locks, spa, RW_WRITER);
  	spa->spa_vdev_locks = locks;
  }
  
  int
  spa_vdev_state_exit(spa_t *spa, vdev_t *vd, int error)
  {
  	boolean_t config_changed = B_FALSE;
  
  	if (vd != NULL || error == 0)
  		vdev_dtl_reassess(vd ? vd->vdev_top : spa->spa_root_vdev,
  		    0, 0, B_FALSE);
  
  	if (vd != NULL) {
  		vdev_state_dirty(vd->vdev_top);
  		config_changed = B_TRUE;
  		spa->spa_config_generation++;
  	}
  
  	ASSERT3U(spa->spa_vdev_locks, >=, SCL_STATE_ALL);
  	spa_config_exit(spa, spa->spa_vdev_locks, spa);
  
  	/*
  	 * If anything changed, wait for it to sync.  This ensures that,
  	 * from the system administrator's perspective, zpool(1M) commands
  	 * are synchronous.  This is important for things like zpool offline:
  	 * when the command completes, you expect no further I/O from ZFS.
  	 */
  	if (vd != NULL)
  		txg_wait_synced(spa->spa_dsl_pool, 0);
  
  	/*
  	 * If the config changed, update the config cache.
  	 */
  	if (config_changed) {
  		mutex_enter(&spa_namespace_lock);
  		spa_config_sync(spa, B_FALSE, B_TRUE);
  		mutex_exit(&spa_namespace_lock);
  	}
  
  	return (error);
  }
  
  /*
   * ==========================================================================
   * Miscellaneous functions
   * ==========================================================================
   */
  
  /*
   * Rename a spa_t.
   */
  int
  spa_rename(const char *name, const char *newname)
  {
  	spa_t *spa;
  	int err;
  
  	/*
  	 * Lookup the spa_t and grab the config lock for writing.  We need to
  	 * actually open the pool so that we can sync out the necessary labels.
  	 * It's OK to call spa_open() with the namespace lock held because we
  	 * allow recursive calls for other reasons.
  	 */
  	mutex_enter(&spa_namespace_lock);
  	if ((err = spa_open(name, &spa, FTAG)) != 0) {
  		mutex_exit(&spa_namespace_lock);
  		return (err);
  	}
  
  	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
  
  	avl_remove(&spa_namespace_avl, spa);
  	(void) strlcpy(spa->spa_name, newname, sizeof (spa->spa_name));
  	avl_add(&spa_namespace_avl, spa);
  
  	/*
  	 * Sync all labels to disk with the new names by marking the root vdev
  	 * dirty and waiting for it to sync.  It will pick up the new pool name
  	 * during the sync.
  	 */
  	vdev_config_dirty(spa->spa_root_vdev);
  
  	spa_config_exit(spa, SCL_ALL, FTAG);
  
  	txg_wait_synced(spa->spa_dsl_pool, 0);
  
  	/*
  	 * Sync the updated config cache.
  	 */
  	spa_config_sync(spa, B_FALSE, B_TRUE);
  
  	spa_close(spa, FTAG);
  
  	mutex_exit(&spa_namespace_lock);
  
  	return (0);
  }
  
  /*
   * Determine whether a pool with given pool_guid exists.  If device_guid is
   * non-zero, determine whether the pool exists *and* contains a device with the
   * specified device_guid.
   */
  boolean_t
  spa_guid_exists(uint64_t pool_guid, uint64_t device_guid)
  {
  	spa_t *spa;
  	avl_tree_t *t = &spa_namespace_avl;
  
  	ASSERT(MUTEX_HELD(&spa_namespace_lock));
  
  	for (spa = avl_first(t); spa != NULL; spa = AVL_NEXT(t, spa)) {
  		if (spa->spa_state == POOL_STATE_UNINITIALIZED)
  			continue;
  		if (spa->spa_root_vdev == NULL)
  			continue;
  		if (spa_guid(spa) == pool_guid) {
  			if (device_guid == 0)
  				break;
  
  			if (vdev_lookup_by_guid(spa->spa_root_vdev,
  			    device_guid) != NULL)
  				break;
  
  			/*
  			 * Check any devices we may be in the process of adding.
  			 */
  			if (spa->spa_pending_vdev) {
  				if (vdev_lookup_by_guid(spa->spa_pending_vdev,
  				    device_guid) != NULL)
  					break;
  			}
  		}
  	}
  
  	return (spa != NULL);
  }
  
  char *
  spa_strdup(const char *s)
  {
  	size_t len;
  	char *new;
  
  	len = strlen(s);
  	new = kmem_alloc(len + 1, KM_SLEEP);
  	bcopy(s, new, len);
  	new[len] = '\0';
  
  	return (new);
  }
  
  void
  spa_strfree(char *s)
  {
  	kmem_free(s, strlen(s) + 1);
  }
  
  uint64_t
  spa_get_random(uint64_t range)
  {
  	uint64_t r;
  
  	ASSERT(range != 0);
  
  	(void) random_get_pseudo_bytes((void *)&r, sizeof (uint64_t));
  
  	return (r % range);
  }
  
  uint64_t
  spa_generate_guid(spa_t *spa)
  {
  	uint64_t guid = spa_get_random(-1ULL);
  
  	if (spa != NULL) {
  		while (guid == 0 || spa_guid_exists(spa_guid(spa), guid))
  			guid = spa_get_random(-1ULL);
  	} else {
  		while (guid == 0 || spa_guid_exists(guid, 0))
  			guid = spa_get_random(-1ULL);
  	}
  
  	return (guid);
  }
  
  void
  sprintf_blkptr(char *buf, const blkptr_t *bp)
  {
  	char *type = NULL;
  	char *checksum = NULL;
  	char *compress = NULL;
  
  	if (bp != NULL) {
  		type = dmu_ot[BP_GET_TYPE(bp)].ot_name;
  		checksum = zio_checksum_table[BP_GET_CHECKSUM(bp)].ci_name;
  		compress = zio_compress_table[BP_GET_COMPRESS(bp)].ci_name;
  	}
  
  	SPRINTF_BLKPTR(snprintf, ' ', buf, bp, type, checksum, compress);
  }
  
  void
  spa_freeze(spa_t *spa)
  {
  	uint64_t freeze_txg = 0;
  
  	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
  	if (spa->spa_freeze_txg == UINT64_MAX) {
  		freeze_txg = spa_last_synced_txg(spa) + TXG_SIZE;
  		spa->spa_freeze_txg = freeze_txg;
  	}
  	spa_config_exit(spa, SCL_ALL, FTAG);
  	if (freeze_txg != 0)
  		txg_wait_synced(spa_get_dsl(spa), freeze_txg);
  }
  
  void
  zfs_panic_recover(const char *fmt, ...)
  {
  	va_list adx;
  
  	va_start(adx, fmt);
  	vcmn_err(zfs_recover ? CE_WARN : CE_PANIC, fmt, adx);
  	va_end(adx);
  }
  
  /*
   * This is a stripped-down version of strtoull, suitable only for converting
   * lowercase hexidecimal numbers that don't overflow.
   */
  uint64_t
  strtonum(const char *str, char **nptr)
  {
  	uint64_t val = 0;
  	char c;
  	int digit;
  
  	while ((c = *str) != '\0') {
  		if (c >= '0' && c <= '9')
  			digit = c - '0';
  		else if (c >= 'a' && c <= 'f')
  			digit = 10 + c - 'a';
  		else
  			break;
  
  		val *= 16;
  		val += digit;
  
  		str++;
  	}
  
  	if (nptr)
  		*nptr = (char *)str;
  
  	return (val);
  }
  
  /*
   * ==========================================================================
   * Accessor functions
   * ==========================================================================
   */
  
  boolean_t
  spa_shutting_down(spa_t *spa)
  {
  	return (spa->spa_async_suspended);
  }
  
  dsl_pool_t *
  spa_get_dsl(spa_t *spa)
  {
  	return (spa->spa_dsl_pool);
  }
  
  blkptr_t *
  spa_get_rootblkptr(spa_t *spa)
  {
  	return (&spa->spa_ubsync.ub_rootbp);
  }
  
  void
  spa_set_rootblkptr(spa_t *spa, const blkptr_t *bp)
  {
  	spa->spa_uberblock.ub_rootbp = *bp;
  }
  
  void
  spa_altroot(spa_t *spa, char *buf, size_t buflen)
  {
  	if (spa->spa_root == NULL)
  		buf[0] = '\0';
  	else
  		(void) strncpy(buf, spa->spa_root, buflen);
  }
  
  int
  spa_sync_pass(spa_t *spa)
  {
  	return (spa->spa_sync_pass);
  }
  
  char *
  spa_name(spa_t *spa)
  {
  	return (spa->spa_name);
  }
  
  uint64_t
  spa_guid(spa_t *spa)
  {
  	/*
  	 * If we fail to parse the config during spa_load(), we can go through
  	 * the error path (which posts an ereport) and end up here with no root
  	 * vdev.  We stash the original pool guid in 'spa_load_guid' to handle
  	 * this case.
  	 */
  	if (spa->spa_root_vdev != NULL)
  		return (spa->spa_root_vdev->vdev_guid);
  	else
  		return (spa->spa_load_guid);
  }
  
  uint64_t
  spa_last_synced_txg(spa_t *spa)
  {
  	return (spa->spa_ubsync.ub_txg);
  }
  
  uint64_t
  spa_first_txg(spa_t *spa)
  {
  	return (spa->spa_first_txg);
  }
  
  uint64_t
  spa_syncing_txg(spa_t *spa)
  {
  	return (spa->spa_syncing_txg);
  }
  
  pool_state_t
  spa_state(spa_t *spa)
  {
  	return (spa->spa_state);
  }
  
  spa_load_state_t
  spa_load_state(spa_t *spa)
  {
  	return (spa->spa_load_state);
  }
  
  uint64_t
  spa_freeze_txg(spa_t *spa)
  {
  	return (spa->spa_freeze_txg);
  }
  
  /* ARGSUSED */
  uint64_t
  spa_get_asize(spa_t *spa, uint64_t lsize)
  {
  	/*
  	 * The worst case is single-sector max-parity RAID-Z blocks, in which
  	 * case the space requirement is exactly (VDEV_RAIDZ_MAXPARITY + 1)
  	 * times the size; so just assume that.  Add to this the fact that
  	 * we can have up to 3 DVAs per bp, and one more factor of 2 because
  	 * the block may be dittoed with up to 3 DVAs by ddt_sync().
  	 */
  	return (lsize * (VDEV_RAIDZ_MAXPARITY + 1) * SPA_DVAS_PER_BP * 2);
  }
  
  uint64_t
  spa_get_dspace(spa_t *spa)
  {
  	return (spa->spa_dspace);
  }
  
  void
  spa_update_dspace(spa_t *spa)
  {
  	spa->spa_dspace = metaslab_class_get_dspace(spa_normal_class(spa)) +
  	    ddt_get_dedup_dspace(spa);
  }
  
  /*
   * Return the failure mode that has been set to this pool. The default
   * behavior will be to block all I/Os when a complete failure occurs.
   */
  uint8_t
  spa_get_failmode(spa_t *spa)
  {
  	return (spa->spa_failmode);
  }
  
  boolean_t
  spa_suspended(spa_t *spa)
  {
  	return (spa->spa_suspended);
  }
  
  uint64_t
  spa_version(spa_t *spa)
  {
  	return (spa->spa_ubsync.ub_version);
  }
  
  boolean_t
  spa_deflate(spa_t *spa)
  {
  	return (spa->spa_deflate);
  }
  
  metaslab_class_t *
  spa_normal_class(spa_t *spa)
  {
  	return (spa->spa_normal_class);
  }
  
  metaslab_class_t *
  spa_log_class(spa_t *spa)
  {
  	return (spa->spa_log_class);
  }
  
  int
  spa_max_replication(spa_t *spa)
  {
  	/*
  	 * As of SPA_VERSION == SPA_VERSION_DITTO_BLOCKS, we are able to
  	 * handle BPs with more than one DVA allocated.  Set our max
  	 * replication level accordingly.
  	 */
  	if (spa_version(spa) < SPA_VERSION_DITTO_BLOCKS)
  		return (1);
  	return (MIN(SPA_DVAS_PER_BP, spa_max_replication_override));
  }
  
  int
  spa_prev_software_version(spa_t *spa)
  {
  	return (spa->spa_prev_software_version);
  }
  
  uint64_t
  dva_get_dsize_sync(spa_t *spa, const dva_t *dva)
  {
  	uint64_t asize = DVA_GET_ASIZE(dva);
  	uint64_t dsize = asize;
  
  	ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);
  
  	if (asize != 0 && spa->spa_deflate) {
  		vdev_t *vd = vdev_lookup_top(spa, DVA_GET_VDEV(dva));
  		dsize = (asize >> SPA_MINBLOCKSHIFT) * vd->vdev_deflate_ratio;
  	}
  
  	return (dsize);
  }
  
  uint64_t
  bp_get_dsize_sync(spa_t *spa, const blkptr_t *bp)
  {
  	uint64_t dsize = 0;
  
  	for (int d = 0; d < SPA_DVAS_PER_BP; d++)
  		dsize += dva_get_dsize_sync(spa, &bp->blk_dva[d]);
  
  	return (dsize);
  }
  
  uint64_t
  bp_get_dsize(spa_t *spa, const blkptr_t *bp)
  {
  	uint64_t dsize = 0;
  
  	spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
  
  	for (int d = 0; d < SPA_DVAS_PER_BP; d++)
  		dsize += dva_get_dsize_sync(spa, &bp->blk_dva[d]);
  
  	spa_config_exit(spa, SCL_VDEV, FTAG);
  
  	return (dsize);
  }
  
  /*
   * ==========================================================================
   * Initialization and Termination
   * ==========================================================================
   */
  
  static int
  spa_name_compare(const void *a1, const void *a2)
  {
  	const spa_t *s1 = a1;
  	const spa_t *s2 = a2;
  	int s;
  
  	s = strcmp(s1->spa_name, s2->spa_name);
  	if (s > 0)
  		return (1);
  	if (s < 0)
  		return (-1);
  	return (0);
  }
  
  int
  spa_busy(void)
  {
  	return (spa_active_count);
  }
  
  void
  spa_boot_init()
  {
  	spa_config_load();
  }
  
  void
  spa_init(int mode)
  {
  	mutex_init(&spa_namespace_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa_spare_lock, NULL, MUTEX_DEFAULT, NULL);
  	mutex_init(&spa_l2cache_lock, NULL, MUTEX_DEFAULT, NULL);
  	cv_init(&spa_namespace_cv, NULL, CV_DEFAULT, NULL);
  
  	avl_create(&spa_namespace_avl, spa_name_compare, sizeof (spa_t),
  	    offsetof(spa_t, spa_avl));
  
  	avl_create(&spa_spare_avl, spa_spare_compare, sizeof (spa_aux_t),
  	    offsetof(spa_aux_t, aux_avl));
  
  	avl_create(&spa_l2cache_avl, spa_l2cache_compare, sizeof (spa_aux_t),
  	    offsetof(spa_aux_t, aux_avl));
  
  	spa_mode_global = mode;
  
  	refcount_init();
  	unique_init();
  	zio_init();
  	dmu_init();
  	zil_init();
  	vdev_cache_stat_init();
  	zfs_prop_init();
  	zpool_prop_init();
  	spa_config_load();
  	l2arc_start();
  }
  
  void
  spa_fini(void)
  {
  	l2arc_stop();
  
  	spa_evict_all();
  
  	vdev_cache_stat_fini();
  	zil_fini();
  	dmu_fini();
  	zio_fini();
  	unique_fini();
  	refcount_fini();
  
  	avl_destroy(&spa_namespace_avl);
  	avl_destroy(&spa_spare_avl);
  	avl_destroy(&spa_l2cache_avl);
  
  	cv_destroy(&spa_namespace_cv);
  	mutex_destroy(&spa_namespace_lock);
  	mutex_destroy(&spa_spare_lock);
  	mutex_destroy(&spa_l2cache_lock);
  }
  
  /*
   * Return whether this pool has slogs. No locking needed.
   * It's not a problem if the wrong answer is returned as it's only for
   * performance and not correctness
   */
  boolean_t
  spa_has_slogs(spa_t *spa)
  {
  	return (spa->spa_log_class->mc_rotor != NULL);
  }
  
  spa_log_state_t
  spa_get_log_state(spa_t *spa)
  {
  	return (spa->spa_log_state);
  }
  
  void
  spa_set_log_state(spa_t *spa, spa_log_state_t state)
  {
  	spa->spa_log_state = state;
  }
  
  boolean_t
  spa_is_root(spa_t *spa)
  {
  	return (spa->spa_is_root);
  }
  
  boolean_t
  spa_writeable(spa_t *spa)
  {
  	return (!!(spa->spa_mode & FWRITE));
  }
  
  int
  spa_mode(spa_t *spa)
  {
  	return (spa->spa_mode);
  }
  
  uint64_t
  spa_bootfs(spa_t *spa)
  {
  	return (spa->spa_bootfs);
  }
  
  uint64_t
  spa_delegation(spa_t *spa)
  {
  	return (spa->spa_delegation);
  }
  
  objset_t *
  spa_meta_objset(spa_t *spa)
  {
  	return (spa->spa_meta_objset);
  }
  
  enum zio_checksum
  spa_dedup_checksum(spa_t *spa)
  {
  	return (spa->spa_dedup_checksum);
  }
  
  /*
   * Reset pool scan stat per scan pass (or reboot).
   */
  void
  spa_scan_stat_init(spa_t *spa)
  {
  	/* data not stored on disk */
  	spa->spa_scan_pass_start = gethrestime_sec();
  	spa->spa_scan_pass_exam = 0;
  	vdev_scan_stat_init(spa->spa_root_vdev);
  }
  
  /*
   * Get scan stats for zpool status reports
   */
  int
  spa_scan_get_stats(spa_t *spa, pool_scan_stat_t *ps)
  {
  	dsl_scan_t *scn = spa->spa_dsl_pool ? spa->spa_dsl_pool->dp_scan : NULL;
  
  	if (scn == NULL || scn->scn_phys.scn_func == POOL_SCAN_NONE)
  		return (ENOENT);
  	bzero(ps, sizeof (pool_scan_stat_t));
  
  	/* data stored on disk */
  	ps->pss_func = scn->scn_phys.scn_func;
  	ps->pss_start_time = scn->scn_phys.scn_start_time;
  	ps->pss_end_time = scn->scn_phys.scn_end_time;
  	ps->pss_to_examine = scn->scn_phys.scn_to_examine;
  	ps->pss_examined = scn->scn_phys.scn_examined;
  	ps->pss_to_process = scn->scn_phys.scn_to_process;
  	ps->pss_processed = scn->scn_phys.scn_processed;
  	ps->pss_errors = scn->scn_phys.scn_errors;
  	ps->pss_state = scn->scn_phys.scn_state;
  
  	/* data not stored on disk */
  	ps->pss_pass_start = spa->spa_scan_pass_start;
  	ps->pss_pass_exam = spa->spa_scan_pass_exam;
  
  	return (0);
  }
  