zfs: merge openzfs/zfs@1f940de07

[FreeBSD/FreeBSD.git] / sys / contrib / openzfs / module / zfs / vdev_trim.c

/*
 * 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 https://opensource.org/licenses/CDDL-1.0.
 * 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 (c) 2016, 2024 by Delphix. All rights reserved.
 * Copyright (c) 2019 by Lawrence Livermore National Security, LLC.
 * Copyright (c) 2021 Hewlett Packard Enterprise Development LP
 * Copyright 2023 RackTop Systems, Inc.
 */

#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/txg.h>
#include <sys/vdev_impl.h>
#include <sys/vdev_trim.h>
#include <sys/metaslab_impl.h>
#include <sys/dsl_synctask.h>
#include <sys/zap.h>
#include <sys/dmu_tx.h>
#include <sys/arc_impl.h>

/*
 * TRIM is a feature which is used to notify a SSD that some previously
 * written space is no longer allocated by the pool.  This is useful because
 * writes to a SSD must be performed to blocks which have first been erased.
 * Ensuring the SSD always has a supply of erased blocks for new writes
 * helps prevent the performance from deteriorating.
 *
 * There are two supported TRIM methods; manual and automatic.
 *
 * Manual TRIM:
 *
 * A manual TRIM is initiated by running the 'zpool trim' command.  A single
 * 'vdev_trim' thread is created for each leaf vdev, and it is responsible for
 * managing that vdev TRIM process.  This involves iterating over all the
 * metaslabs, calculating the unallocated space ranges, and then issuing the
 * required TRIM I/Os.
 *
 * While a metaslab is being actively trimmed it is not eligible to perform
 * new allocations.  After traversing all of the metaslabs the thread is
 * terminated.  Finally, both the requested options and current progress of
 * the TRIM are regularly written to the pool.  This allows the TRIM to be
 * suspended and resumed as needed.
 *
 * Automatic TRIM:
 *
 * An automatic TRIM is enabled by setting the 'autotrim' pool property
 * to 'on'.  When enabled, a `vdev_autotrim' thread is created for each
 * top-level (not leaf) vdev in the pool.  These threads perform the same
 * core TRIM process as a manual TRIM, but with a few key differences.
 *
 * 1) Automatic TRIM happens continuously in the background and operates
 *    solely on recently freed blocks (ms_trim not ms_allocatable).
 *
 * 2) Each thread is associated with a top-level (not leaf) vdev.  This has
 *    the benefit of simplifying the threading model, it makes it easier
 *    to coordinate administrative commands, and it ensures only a single
 *    metaslab is disabled at a time.  Unlike manual TRIM, this means each
 *    'vdev_autotrim' thread is responsible for issuing TRIM I/Os for its
 *    children.
 *
 * 3) There is no automatic TRIM progress information stored on disk, nor
 *    is it reported by 'zpool status'.
 *
 * While the automatic TRIM process is highly effective it is more likely
 * than a manual TRIM to encounter tiny ranges.  Ranges less than or equal to
 * 'zfs_trim_extent_bytes_min' (32k) are considered too small to efficiently
 * TRIM and are skipped.  This means small amounts of freed space may not
 * be automatically trimmed.
 *
 * Furthermore, devices with attached hot spares and devices being actively
 * replaced are skipped.  This is done to avoid adding additional stress to
 * a potentially unhealthy device and to minimize the required rebuild time.
 *
 * For this reason it may be beneficial to occasionally manually TRIM a pool
 * even when automatic TRIM is enabled.
 */

/*
 * Maximum size of TRIM I/O, ranges will be chunked in to 128MiB lengths.
 */
static unsigned int zfs_trim_extent_bytes_max = 128 * 1024 * 1024;

/*
 * Minimum size of TRIM I/O, extents smaller than 32Kib will be skipped.
 */
static unsigned int zfs_trim_extent_bytes_min = 32 * 1024;

/*
 * Skip uninitialized metaslabs during the TRIM process.  This option is
 * useful for pools constructed from large thinly-provisioned devices where
 * TRIM operations are slow.  As a pool ages an increasing fraction of
 * the pools metaslabs will be initialized progressively degrading the
 * usefulness of this option.  This setting is stored when starting a
 * manual TRIM and will persist for the duration of the requested TRIM.
 */
unsigned int zfs_trim_metaslab_skip = 0;

/*
 * Maximum number of queued TRIM I/Os per leaf vdev.  The number of
 * concurrent TRIM I/Os issued to the device is controlled by the
 * zfs_vdev_trim_min_active and zfs_vdev_trim_max_active module options.
 */
static unsigned int zfs_trim_queue_limit = 10;

/*
 * The minimum number of transaction groups between automatic trims of a
 * metaslab.  This setting represents a trade-off between issuing more
 * efficient TRIM operations, by allowing them to be aggregated longer,
 * and issuing them promptly so the trimmed space is available.  Note
 * that this value is a minimum; metaslabs can be trimmed less frequently
 * when there are a large number of ranges which need to be trimmed.
 *
 * Increasing this value will allow frees to be aggregated for a longer
 * time.  This can result is larger TRIM operations, and increased memory
 * usage in order to track the ranges to be trimmed.  Decreasing this value
 * has the opposite effect.  The default value of 32 was determined though
 * testing to be a reasonable compromise.
 */
static unsigned int zfs_trim_txg_batch = 32;

/*
 * The trim_args are a control structure which describe how a leaf vdev
 * should be trimmed.  The core elements are the vdev, the metaslab being
 * trimmed and a range tree containing the extents to TRIM.  All provided
 * ranges must be within the metaslab.
 */
typedef struct trim_args {
        /*
         * These fields are set by the caller of vdev_trim_ranges().
         */
        vdev_t          *trim_vdev;             /* Leaf vdev to TRIM */
        metaslab_t      *trim_msp;              /* Disabled metaslab */
        range_tree_t    *trim_tree;             /* TRIM ranges (in metaslab) */
        trim_type_t     trim_type;              /* Manual or auto TRIM */
        uint64_t        trim_extent_bytes_max;  /* Maximum TRIM I/O size */
        uint64_t        trim_extent_bytes_min;  /* Minimum TRIM I/O size */
        enum trim_flag  trim_flags;             /* TRIM flags (secure) */

        /*
         * These fields are updated by vdev_trim_ranges().
         */
        hrtime_t        trim_start_time;        /* Start time */
        uint64_t        trim_bytes_done;        /* Bytes trimmed */
} trim_args_t;

/*
 * Determines whether a vdev_trim_thread() should be stopped.
 */
static boolean_t
vdev_trim_should_stop(vdev_t *vd)
{
        return (vd->vdev_trim_exit_wanted || !vdev_writeable(vd) ||
            vd->vdev_detached || vd->vdev_top->vdev_removing ||
            vd->vdev_top->vdev_rz_expanding);
}

/*
 * Determines whether a vdev_autotrim_thread() should be stopped.
 */
static boolean_t
vdev_autotrim_should_stop(vdev_t *tvd)
{
        return (tvd->vdev_autotrim_exit_wanted ||
            !vdev_writeable(tvd) || tvd->vdev_removing ||
            tvd->vdev_rz_expanding ||
            spa_get_autotrim(tvd->vdev_spa) == SPA_AUTOTRIM_OFF);
}

/*
 * Wait for given number of kicks, return true if the wait is aborted due to
 * vdev_autotrim_exit_wanted.
 */
static boolean_t
vdev_autotrim_wait_kick(vdev_t *vd, int num_of_kick)
{
        mutex_enter(&vd->vdev_autotrim_lock);
        for (int i = 0; i < num_of_kick; i++) {
                if (vd->vdev_autotrim_exit_wanted)
                        break;
                cv_wait_idle(&vd->vdev_autotrim_kick_cv,
                    &vd->vdev_autotrim_lock);
        }
        boolean_t exit_wanted = vd->vdev_autotrim_exit_wanted;
        mutex_exit(&vd->vdev_autotrim_lock);

        return (exit_wanted);
}

/*
 * The sync task for updating the on-disk state of a manual TRIM.  This
 * is scheduled by vdev_trim_change_state().
 */
static void
vdev_trim_zap_update_sync(void *arg, dmu_tx_t *tx)
{
        /*
         * We pass in the guid instead of the vdev_t since the vdev may
         * have been freed prior to the sync task being processed.  This
         * happens when a vdev is detached as we call spa_config_vdev_exit(),
         * stop the trimming thread, schedule the sync task, and free
         * the vdev. Later when the scheduled sync task is invoked, it would
         * find that the vdev has been freed.
         */
        uint64_t guid = *(uint64_t *)arg;
        uint64_t txg = dmu_tx_get_txg(tx);
        kmem_free(arg, sizeof (uint64_t));

        vdev_t *vd = spa_lookup_by_guid(tx->tx_pool->dp_spa, guid, B_FALSE);
        if (vd == NULL || vd->vdev_top->vdev_removing ||
            !vdev_is_concrete(vd) || vd->vdev_top->vdev_rz_expanding)
                return;

        uint64_t last_offset = vd->vdev_trim_offset[txg & TXG_MASK];
        vd->vdev_trim_offset[txg & TXG_MASK] = 0;

        VERIFY3U(vd->vdev_leaf_zap, !=, 0);

        objset_t *mos = vd->vdev_spa->spa_meta_objset;

        if (last_offset > 0 || vd->vdev_trim_last_offset == UINT64_MAX) {

                if (vd->vdev_trim_last_offset == UINT64_MAX)
                        last_offset = 0;

                vd->vdev_trim_last_offset = last_offset;
                VERIFY0(zap_update(mos, vd->vdev_leaf_zap,
                    VDEV_LEAF_ZAP_TRIM_LAST_OFFSET,
                    sizeof (last_offset), 1, &last_offset, tx));
        }

        if (vd->vdev_trim_action_time > 0) {
                uint64_t val = (uint64_t)vd->vdev_trim_action_time;
                VERIFY0(zap_update(mos, vd->vdev_leaf_zap,
                    VDEV_LEAF_ZAP_TRIM_ACTION_TIME, sizeof (val),
                    1, &val, tx));
        }

        if (vd->vdev_trim_rate > 0) {
                uint64_t rate = (uint64_t)vd->vdev_trim_rate;

                if (rate == UINT64_MAX)
                        rate = 0;

                VERIFY0(zap_update(mos, vd->vdev_leaf_zap,
                    VDEV_LEAF_ZAP_TRIM_RATE, sizeof (rate), 1, &rate, tx));
        }

        uint64_t partial = vd->vdev_trim_partial;
        if (partial == UINT64_MAX)
                partial = 0;

        VERIFY0(zap_update(mos, vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_PARTIAL,
            sizeof (partial), 1, &partial, tx));

        uint64_t secure = vd->vdev_trim_secure;
        if (secure == UINT64_MAX)
                secure = 0;

        VERIFY0(zap_update(mos, vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_SECURE,
            sizeof (secure), 1, &secure, tx));


        uint64_t trim_state = vd->vdev_trim_state;
        VERIFY0(zap_update(mos, vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_STATE,
            sizeof (trim_state), 1, &trim_state, tx));
}

/*
 * Update the on-disk state of a manual TRIM.  This is called to request
 * that a TRIM be started/suspended/canceled, or to change one of the
 * TRIM options (partial, secure, rate).
 */
static void
vdev_trim_change_state(vdev_t *vd, vdev_trim_state_t new_state,
    uint64_t rate, boolean_t partial, boolean_t secure)
{
        ASSERT(MUTEX_HELD(&vd->vdev_trim_lock));
        spa_t *spa = vd->vdev_spa;

        if (new_state == vd->vdev_trim_state)
                return;

        /*
         * Copy the vd's guid, this will be freed by the sync task.
         */
        uint64_t *guid = kmem_zalloc(sizeof (uint64_t), KM_SLEEP);
        *guid = vd->vdev_guid;

        /*
         * If we're suspending, then preserve the original start time.
         */
        if (vd->vdev_trim_state != VDEV_TRIM_SUSPENDED) {
                vd->vdev_trim_action_time = gethrestime_sec();
        }

        /*
         * If we're activating, then preserve the requested rate and trim
         * method.  Setting the last offset and rate to UINT64_MAX is used
         * as a sentinel to indicate they should be reset to default values.
         */
        if (new_state == VDEV_TRIM_ACTIVE) {
                if (vd->vdev_trim_state == VDEV_TRIM_COMPLETE ||
                    vd->vdev_trim_state == VDEV_TRIM_CANCELED) {
                        vd->vdev_trim_last_offset = UINT64_MAX;
                        vd->vdev_trim_rate = UINT64_MAX;
                        vd->vdev_trim_partial = UINT64_MAX;
                        vd->vdev_trim_secure = UINT64_MAX;
                }

                if (rate != 0)
                        vd->vdev_trim_rate = rate;

                if (partial != 0)
                        vd->vdev_trim_partial = partial;

                if (secure != 0)
                        vd->vdev_trim_secure = secure;
        }

        vdev_trim_state_t old_state = vd->vdev_trim_state;
        boolean_t resumed = (old_state == VDEV_TRIM_SUSPENDED);
        vd->vdev_trim_state = new_state;

        dmu_tx_t *tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir);
        VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
        dsl_sync_task_nowait(spa_get_dsl(spa), vdev_trim_zap_update_sync,
            guid, tx);

        switch (new_state) {
        case VDEV_TRIM_ACTIVE:
                spa_event_notify(spa, vd, NULL,
                    resumed ? ESC_ZFS_TRIM_RESUME : ESC_ZFS_TRIM_START);
                spa_history_log_internal(spa, "trim", tx,
                    "vdev=%s activated", vd->vdev_path);
                break;
        case VDEV_TRIM_SUSPENDED:
                spa_event_notify(spa, vd, NULL, ESC_ZFS_TRIM_SUSPEND);
                spa_history_log_internal(spa, "trim", tx,
                    "vdev=%s suspended", vd->vdev_path);
                break;
        case VDEV_TRIM_CANCELED:
                if (old_state == VDEV_TRIM_ACTIVE ||
                    old_state == VDEV_TRIM_SUSPENDED) {
                        spa_event_notify(spa, vd, NULL, ESC_ZFS_TRIM_CANCEL);
                        spa_history_log_internal(spa, "trim", tx,
                            "vdev=%s canceled", vd->vdev_path);
                }
                break;
        case VDEV_TRIM_COMPLETE:
                spa_event_notify(spa, vd, NULL, ESC_ZFS_TRIM_FINISH);
                spa_history_log_internal(spa, "trim", tx,
                    "vdev=%s complete", vd->vdev_path);
                break;
        default:
                panic("invalid state %llu", (unsigned long long)new_state);
        }

        dmu_tx_commit(tx);

        if (new_state != VDEV_TRIM_ACTIVE)
                spa_notify_waiters(spa);
}

/*
 * The zio_done_func_t done callback for each manual TRIM issued.  It is
 * responsible for updating the TRIM stats, reissuing failed TRIM I/Os,
 * and limiting the number of in flight TRIM I/Os.
 */
static void
vdev_trim_cb(zio_t *zio)
{
        vdev_t *vd = zio->io_vd;

        mutex_enter(&vd->vdev_trim_io_lock);
        if (zio->io_error == ENXIO && !vdev_writeable(vd)) {
                /*
                 * The I/O failed because the vdev was unavailable; roll the
                 * last offset back. (This works because spa_sync waits on
                 * spa_txg_zio before it runs sync tasks.)
                 */
                uint64_t *offset =
                    &vd->vdev_trim_offset[zio->io_txg & TXG_MASK];
                *offset = MIN(*offset, zio->io_offset);
        } else {
                if (zio->io_error != 0) {
                        vd->vdev_stat.vs_trim_errors++;
                        spa_iostats_trim_add(vd->vdev_spa, TRIM_TYPE_MANUAL,
                            0, 0, 0, 0, 1, zio->io_orig_size);
                } else {
                        spa_iostats_trim_add(vd->vdev_spa, TRIM_TYPE_MANUAL,
                            1, zio->io_orig_size, 0, 0, 0, 0);
                }

                vd->vdev_trim_bytes_done += zio->io_orig_size;
        }

        ASSERT3U(vd->vdev_trim_inflight[TRIM_TYPE_MANUAL], >, 0);
        vd->vdev_trim_inflight[TRIM_TYPE_MANUAL]--;
        cv_broadcast(&vd->vdev_trim_io_cv);
        mutex_exit(&vd->vdev_trim_io_lock);

        spa_config_exit(vd->vdev_spa, SCL_STATE_ALL, vd);
}

/*
 * The zio_done_func_t done callback for each automatic TRIM issued.  It
 * is responsible for updating the TRIM stats and limiting the number of
 * in flight TRIM I/Os.  Automatic TRIM I/Os are best effort and are
 * never reissued on failure.
 */
static void
vdev_autotrim_cb(zio_t *zio)
{
        vdev_t *vd = zio->io_vd;

        mutex_enter(&vd->vdev_trim_io_lock);

        if (zio->io_error != 0) {
                vd->vdev_stat.vs_trim_errors++;
                spa_iostats_trim_add(vd->vdev_spa, TRIM_TYPE_AUTO,
                    0, 0, 0, 0, 1, zio->io_orig_size);
        } else {
                spa_iostats_trim_add(vd->vdev_spa, TRIM_TYPE_AUTO,
                    1, zio->io_orig_size, 0, 0, 0, 0);
        }

        ASSERT3U(vd->vdev_trim_inflight[TRIM_TYPE_AUTO], >, 0);
        vd->vdev_trim_inflight[TRIM_TYPE_AUTO]--;
        cv_broadcast(&vd->vdev_trim_io_cv);
        mutex_exit(&vd->vdev_trim_io_lock);

        spa_config_exit(vd->vdev_spa, SCL_STATE_ALL, vd);
}

/*
 * The zio_done_func_t done callback for each TRIM issued via
 * vdev_trim_simple(). It is responsible for updating the TRIM stats and
 * limiting the number of in flight TRIM I/Os.  Simple TRIM I/Os are best
 * effort and are never reissued on failure.
 */
static void
vdev_trim_simple_cb(zio_t *zio)
{
        vdev_t *vd = zio->io_vd;

        mutex_enter(&vd->vdev_trim_io_lock);

        if (zio->io_error != 0) {
                vd->vdev_stat.vs_trim_errors++;
                spa_iostats_trim_add(vd->vdev_spa, TRIM_TYPE_SIMPLE,
                    0, 0, 0, 0, 1, zio->io_orig_size);
        } else {
                spa_iostats_trim_add(vd->vdev_spa, TRIM_TYPE_SIMPLE,
                    1, zio->io_orig_size, 0, 0, 0, 0);
        }

        ASSERT3U(vd->vdev_trim_inflight[TRIM_TYPE_SIMPLE], >, 0);
        vd->vdev_trim_inflight[TRIM_TYPE_SIMPLE]--;
        cv_broadcast(&vd->vdev_trim_io_cv);
        mutex_exit(&vd->vdev_trim_io_lock);

        spa_config_exit(vd->vdev_spa, SCL_STATE_ALL, vd);
}
/*
 * Returns the average trim rate in bytes/sec for the ta->trim_vdev.
 */
static uint64_t
vdev_trim_calculate_rate(trim_args_t *ta)
{
        return (ta->trim_bytes_done * 1000 /
            (NSEC2MSEC(gethrtime() - ta->trim_start_time) + 1));
}

/*
 * Issues a physical TRIM and takes care of rate limiting (bytes/sec)
 * and number of concurrent TRIM I/Os.
 */
static int
vdev_trim_range(trim_args_t *ta, uint64_t start, uint64_t size)
{
        vdev_t *vd = ta->trim_vdev;
        spa_t *spa = vd->vdev_spa;
        void *cb;

        mutex_enter(&vd->vdev_trim_io_lock);

        /*
         * Limit manual TRIM I/Os to the requested rate.  This does not
         * apply to automatic TRIM since no per vdev rate can be specified.
         */
        if (ta->trim_type == TRIM_TYPE_MANUAL) {
                while (vd->vdev_trim_rate != 0 && !vdev_trim_should_stop(vd) &&
                    vdev_trim_calculate_rate(ta) > vd->vdev_trim_rate) {
                        cv_timedwait_idle(&vd->vdev_trim_io_cv,
                            &vd->vdev_trim_io_lock, ddi_get_lbolt() +
                            MSEC_TO_TICK(10));
                }
        }
        ta->trim_bytes_done += size;

        /* Limit in flight trimming I/Os */
        while (vd->vdev_trim_inflight[0] + vd->vdev_trim_inflight[1] +
            vd->vdev_trim_inflight[2] >= zfs_trim_queue_limit) {
                cv_wait(&vd->vdev_trim_io_cv, &vd->vdev_trim_io_lock);
        }
        vd->vdev_trim_inflight[ta->trim_type]++;
        mutex_exit(&vd->vdev_trim_io_lock);

        dmu_tx_t *tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir);
        VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
        uint64_t txg = dmu_tx_get_txg(tx);

        spa_config_enter(spa, SCL_STATE_ALL, vd, RW_READER);
        mutex_enter(&vd->vdev_trim_lock);

        if (ta->trim_type == TRIM_TYPE_MANUAL &&
            vd->vdev_trim_offset[txg & TXG_MASK] == 0) {
                uint64_t *guid = kmem_zalloc(sizeof (uint64_t), KM_SLEEP);
                *guid = vd->vdev_guid;

                /* This is the first write of this txg. */
                dsl_sync_task_nowait(spa_get_dsl(spa),
                    vdev_trim_zap_update_sync, guid, tx);
        }

        /*
         * We know the vdev_t will still be around since all consumers of
         * vdev_free must stop the trimming first.
         */
        if ((ta->trim_type == TRIM_TYPE_MANUAL &&
            vdev_trim_should_stop(vd)) ||
            (ta->trim_type == TRIM_TYPE_AUTO &&
            vdev_autotrim_should_stop(vd->vdev_top))) {
                mutex_enter(&vd->vdev_trim_io_lock);
                vd->vdev_trim_inflight[ta->trim_type]--;
                mutex_exit(&vd->vdev_trim_io_lock);
                spa_config_exit(vd->vdev_spa, SCL_STATE_ALL, vd);
                mutex_exit(&vd->vdev_trim_lock);
                dmu_tx_commit(tx);
                return (SET_ERROR(EINTR));
        }
        mutex_exit(&vd->vdev_trim_lock);

        if (ta->trim_type == TRIM_TYPE_MANUAL)
                vd->vdev_trim_offset[txg & TXG_MASK] = start + size;

        if (ta->trim_type == TRIM_TYPE_MANUAL) {
                cb = vdev_trim_cb;
        } else if (ta->trim_type == TRIM_TYPE_AUTO) {
                cb = vdev_autotrim_cb;
        } else {
                cb = vdev_trim_simple_cb;
        }

        zio_nowait(zio_trim(spa->spa_txg_zio[txg & TXG_MASK], vd,
            start, size, cb, NULL, ZIO_PRIORITY_TRIM, ZIO_FLAG_CANFAIL,
            ta->trim_flags));
        /* vdev_trim_cb and vdev_autotrim_cb release SCL_STATE_ALL */

        dmu_tx_commit(tx);

        return (0);
}

/*
 * Issues TRIM I/Os for all ranges in the provided ta->trim_tree range tree.
 * Additional parameters describing how the TRIM should be performed must
 * be set in the trim_args structure.  See the trim_args definition for
 * additional information.
 */
static int
vdev_trim_ranges(trim_args_t *ta)
{
        vdev_t *vd = ta->trim_vdev;
        zfs_btree_t *t = &ta->trim_tree->rt_root;
        zfs_btree_index_t idx;
        uint64_t extent_bytes_max = ta->trim_extent_bytes_max;
        uint64_t extent_bytes_min = ta->trim_extent_bytes_min;
        spa_t *spa = vd->vdev_spa;
        int error = 0;

        ta->trim_start_time = gethrtime();
        ta->trim_bytes_done = 0;

        for (range_seg_t *rs = zfs_btree_first(t, &idx); rs != NULL;
            rs = zfs_btree_next(t, &idx, &idx)) {
                uint64_t size = rs_get_end(rs, ta->trim_tree) - rs_get_start(rs,
                    ta->trim_tree);

                if (extent_bytes_min && size < extent_bytes_min) {
                        spa_iostats_trim_add(spa, ta->trim_type,
                            0, 0, 1, size, 0, 0);
                        continue;
                }

                /* Split range into legally-sized physical chunks */
                uint64_t writes_required = ((size - 1) / extent_bytes_max) + 1;

                for (uint64_t w = 0; w < writes_required; w++) {
                        error = vdev_trim_range(ta, VDEV_LABEL_START_SIZE +
                            rs_get_start(rs, ta->trim_tree) +
                            (w *extent_bytes_max), MIN(size -
                            (w * extent_bytes_max), extent_bytes_max));
                        if (error != 0) {
                                goto done;
                        }
                }
        }

done:
        /*
         * Make sure all TRIMs for this metaslab have completed before
         * returning. TRIM zios have lower priority over regular or syncing
         * zios, so all TRIM zios for this metaslab must complete before the
         * metaslab is re-enabled. Otherwise it's possible write zios to
         * this metaslab could cut ahead of still queued TRIM zios for this
         * metaslab causing corruption if the ranges overlap.
         */
        mutex_enter(&vd->vdev_trim_io_lock);
        while (vd->vdev_trim_inflight[0] > 0) {
                cv_wait(&vd->vdev_trim_io_cv, &vd->vdev_trim_io_lock);
        }
        mutex_exit(&vd->vdev_trim_io_lock);

        return (error);
}

static void
vdev_trim_xlate_last_rs_end(void *arg, range_seg64_t *physical_rs)
{
        uint64_t *last_rs_end = (uint64_t *)arg;

        if (physical_rs->rs_end > *last_rs_end)
                *last_rs_end = physical_rs->rs_end;
}

static void
vdev_trim_xlate_progress(void *arg, range_seg64_t *physical_rs)
{
        vdev_t *vd = (vdev_t *)arg;

        uint64_t size = physical_rs->rs_end - physical_rs->rs_start;
        vd->vdev_trim_bytes_est += size;

        if (vd->vdev_trim_last_offset >= physical_rs->rs_end) {
                vd->vdev_trim_bytes_done += size;
        } else if (vd->vdev_trim_last_offset > physical_rs->rs_start &&
            vd->vdev_trim_last_offset <= physical_rs->rs_end) {
                vd->vdev_trim_bytes_done +=
                    vd->vdev_trim_last_offset - physical_rs->rs_start;
        }
}

/*
 * Calculates the completion percentage of a manual TRIM.
 */
static void
vdev_trim_calculate_progress(vdev_t *vd)
{
        ASSERT(spa_config_held(vd->vdev_spa, SCL_CONFIG, RW_READER) ||
            spa_config_held(vd->vdev_spa, SCL_CONFIG, RW_WRITER));
        ASSERT(vd->vdev_leaf_zap != 0);

        vd->vdev_trim_bytes_est = 0;
        vd->vdev_trim_bytes_done = 0;

        for (uint64_t i = 0; i < vd->vdev_top->vdev_ms_count; i++) {
                metaslab_t *msp = vd->vdev_top->vdev_ms[i];
                mutex_enter(&msp->ms_lock);

                uint64_t ms_free = (msp->ms_size -
                    metaslab_allocated_space(msp)) /
                    vdev_get_ndisks(vd->vdev_top);

                /*
                 * Convert the metaslab range to a physical range
                 * on our vdev. We use this to determine if we are
                 * in the middle of this metaslab range.
                 */
                range_seg64_t logical_rs, physical_rs, remain_rs;
                logical_rs.rs_start = msp->ms_start;
                logical_rs.rs_end = msp->ms_start + msp->ms_size;

                /* Metaslab space after this offset has not been trimmed. */
                vdev_xlate(vd, &logical_rs, &physical_rs, &remain_rs);
                if (vd->vdev_trim_last_offset <= physical_rs.rs_start) {
                        vd->vdev_trim_bytes_est += ms_free;
                        mutex_exit(&msp->ms_lock);
                        continue;
                }

                /* Metaslab space before this offset has been trimmed */
                uint64_t last_rs_end = physical_rs.rs_end;
                if (!vdev_xlate_is_empty(&remain_rs)) {
                        vdev_xlate_walk(vd, &remain_rs,
                            vdev_trim_xlate_last_rs_end, &last_rs_end);
                }

                if (vd->vdev_trim_last_offset > last_rs_end) {
                        vd->vdev_trim_bytes_done += ms_free;
                        vd->vdev_trim_bytes_est += ms_free;
                        mutex_exit(&msp->ms_lock);
                        continue;
                }

                /*
                 * If we get here, we're in the middle of trimming this
                 * metaslab.  Load it and walk the free tree for more
                 * accurate progress estimation.
                 */
                VERIFY0(metaslab_load(msp));

                range_tree_t *rt = msp->ms_allocatable;
                zfs_btree_t *bt = &rt->rt_root;
                zfs_btree_index_t idx;
                for (range_seg_t *rs = zfs_btree_first(bt, &idx);
                    rs != NULL; rs = zfs_btree_next(bt, &idx, &idx)) {
                        logical_rs.rs_start = rs_get_start(rs, rt);
                        logical_rs.rs_end = rs_get_end(rs, rt);

                        vdev_xlate_walk(vd, &logical_rs,
                            vdev_trim_xlate_progress, vd);
                }
                mutex_exit(&msp->ms_lock);
        }
}

/*
 * Load from disk the vdev's manual TRIM information.  This includes the
 * state, progress, and options provided when initiating the manual TRIM.
 */
static int
vdev_trim_load(vdev_t *vd)
{
        int err = 0;
        ASSERT(spa_config_held(vd->vdev_spa, SCL_CONFIG, RW_READER) ||
            spa_config_held(vd->vdev_spa, SCL_CONFIG, RW_WRITER));
        ASSERT(vd->vdev_leaf_zap != 0);

        if (vd->vdev_trim_state == VDEV_TRIM_ACTIVE ||
            vd->vdev_trim_state == VDEV_TRIM_SUSPENDED) {
                err = zap_lookup(vd->vdev_spa->spa_meta_objset,
                    vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_LAST_OFFSET,
                    sizeof (vd->vdev_trim_last_offset), 1,
                    &vd->vdev_trim_last_offset);
                if (err == ENOENT) {
                        vd->vdev_trim_last_offset = 0;
                        err = 0;
                }

                if (err == 0) {
                        err = zap_lookup(vd->vdev_spa->spa_meta_objset,
                            vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_RATE,
                            sizeof (vd->vdev_trim_rate), 1,
                            &vd->vdev_trim_rate);
                        if (err == ENOENT) {
                                vd->vdev_trim_rate = 0;
                                err = 0;
                        }
                }

                if (err == 0) {
                        err = zap_lookup(vd->vdev_spa->spa_meta_objset,
                            vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_PARTIAL,
                            sizeof (vd->vdev_trim_partial), 1,
                            &vd->vdev_trim_partial);
                        if (err == ENOENT) {
                                vd->vdev_trim_partial = 0;
                                err = 0;
                        }
                }

                if (err == 0) {
                        err = zap_lookup(vd->vdev_spa->spa_meta_objset,
                            vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_SECURE,
                            sizeof (vd->vdev_trim_secure), 1,
                            &vd->vdev_trim_secure);
                        if (err == ENOENT) {
                                vd->vdev_trim_secure = 0;
                                err = 0;
                        }
                }
        }

        vdev_trim_calculate_progress(vd);

        return (err);
}

static void
vdev_trim_xlate_range_add(void *arg, range_seg64_t *physical_rs)
{
        trim_args_t *ta = arg;
        vdev_t *vd = ta->trim_vdev;

        /*
         * Only a manual trim will be traversing the vdev sequentially.
         * For an auto trim all valid ranges should be added.
         */
        if (ta->trim_type == TRIM_TYPE_MANUAL) {

                /* Only add segments that we have not visited yet */
                if (physical_rs->rs_end <= vd->vdev_trim_last_offset)
                        return;

                /* Pick up where we left off mid-range. */
                if (vd->vdev_trim_last_offset > physical_rs->rs_start) {
                        ASSERT3U(physical_rs->rs_end, >,
                            vd->vdev_trim_last_offset);
                        physical_rs->rs_start = vd->vdev_trim_last_offset;
                }
        }

        ASSERT3U(physical_rs->rs_end, >, physical_rs->rs_start);

        range_tree_add(ta->trim_tree, physical_rs->rs_start,
            physical_rs->rs_end - physical_rs->rs_start);
}

/*
 * Convert the logical range into physical ranges and add them to the
 * range tree passed in the trim_args_t.
 */
static void
vdev_trim_range_add(void *arg, uint64_t start, uint64_t size)
{
        trim_args_t *ta = arg;
        vdev_t *vd = ta->trim_vdev;
        range_seg64_t logical_rs;
        logical_rs.rs_start = start;
        logical_rs.rs_end = start + size;

        /*
         * Every range to be trimmed must be part of ms_allocatable.
         * When ZFS_DEBUG_TRIM is set load the metaslab to verify this
         * is always the case.
         */
        if (zfs_flags & ZFS_DEBUG_TRIM) {
                metaslab_t *msp = ta->trim_msp;
                VERIFY0(metaslab_load(msp));
                VERIFY3B(msp->ms_loaded, ==, B_TRUE);
                VERIFY(range_tree_contains(msp->ms_allocatable, start, size));
        }

        ASSERT(vd->vdev_ops->vdev_op_leaf);
        vdev_xlate_walk(vd, &logical_rs, vdev_trim_xlate_range_add, arg);
}

/*
 * Each manual TRIM thread is responsible for trimming the unallocated
 * space for each leaf vdev.  This is accomplished by sequentially iterating
 * over its top-level metaslabs and issuing TRIM I/O for the space described
 * by its ms_allocatable.  While a metaslab is undergoing trimming it is
 * not eligible for new allocations.
 */
static __attribute__((noreturn)) void
vdev_trim_thread(void *arg)
{
        vdev_t *vd = arg;
        spa_t *spa = vd->vdev_spa;
        trim_args_t ta;
        int error = 0;

        /*
         * The VDEV_LEAF_ZAP_TRIM_* entries may have been updated by
         * vdev_trim().  Wait for the updated values to be reflected
         * in the zap in order to start with the requested settings.
         */
        txg_wait_synced(spa_get_dsl(vd->vdev_spa), 0);

        ASSERT(vdev_is_concrete(vd));
        spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

        vd->vdev_trim_last_offset = 0;
        vd->vdev_trim_rate = 0;
        vd->vdev_trim_partial = 0;
        vd->vdev_trim_secure = 0;

        VERIFY0(vdev_trim_load(vd));

        ta.trim_vdev = vd;
        ta.trim_extent_bytes_max = zfs_trim_extent_bytes_max;
        ta.trim_extent_bytes_min = zfs_trim_extent_bytes_min;
        ta.trim_tree = range_tree_create(NULL, RANGE_SEG64, NULL, 0, 0);
        ta.trim_type = TRIM_TYPE_MANUAL;
        ta.trim_flags = 0;

        /*
         * When a secure TRIM has been requested infer that the intent
         * is that everything must be trimmed.  Override the default
         * minimum TRIM size to prevent ranges from being skipped.
         */
        if (vd->vdev_trim_secure) {
                ta.trim_flags |= ZIO_TRIM_SECURE;
                ta.trim_extent_bytes_min = SPA_MINBLOCKSIZE;
        }

        uint64_t ms_count = 0;
        for (uint64_t i = 0; !vd->vdev_detached &&
            i < vd->vdev_top->vdev_ms_count; i++) {
                metaslab_t *msp = vd->vdev_top->vdev_ms[i];

                /*
                 * If we've expanded the top-level vdev or it's our
                 * first pass, calculate our progress.
                 */
                if (vd->vdev_top->vdev_ms_count != ms_count) {
                        vdev_trim_calculate_progress(vd);
                        ms_count = vd->vdev_top->vdev_ms_count;
                }

                spa_config_exit(spa, SCL_CONFIG, FTAG);
                metaslab_disable(msp);
                mutex_enter(&msp->ms_lock);
                VERIFY0(metaslab_load(msp));

                /*
                 * If a partial TRIM was requested skip metaslabs which have
                 * never been initialized and thus have never been written.
                 */
                if (msp->ms_sm == NULL && vd->vdev_trim_partial) {
                        mutex_exit(&msp->ms_lock);
                        metaslab_enable(msp, B_FALSE, B_FALSE);
                        spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
                        vdev_trim_calculate_progress(vd);
                        continue;
                }

                ta.trim_msp = msp;
                range_tree_walk(msp->ms_allocatable, vdev_trim_range_add, &ta);
                range_tree_vacate(msp->ms_trim, NULL, NULL);
                mutex_exit(&msp->ms_lock);

                error = vdev_trim_ranges(&ta);
                metaslab_enable(msp, B_TRUE, B_FALSE);
                spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

                range_tree_vacate(ta.trim_tree, NULL, NULL);
                if (error != 0)
                        break;
        }

        spa_config_exit(spa, SCL_CONFIG, FTAG);

        range_tree_destroy(ta.trim_tree);

        mutex_enter(&vd->vdev_trim_lock);
        if (!vd->vdev_trim_exit_wanted) {
                if (vdev_writeable(vd)) {
                        vdev_trim_change_state(vd, VDEV_TRIM_COMPLETE,
                            vd->vdev_trim_rate, vd->vdev_trim_partial,
                            vd->vdev_trim_secure);
                } else if (vd->vdev_faulted) {
                        vdev_trim_change_state(vd, VDEV_TRIM_CANCELED,
                            vd->vdev_trim_rate, vd->vdev_trim_partial,
                            vd->vdev_trim_secure);
                }
        }
        ASSERT(vd->vdev_trim_thread != NULL || vd->vdev_trim_inflight[0] == 0);

        /*
         * Drop the vdev_trim_lock while we sync out the txg since it's
         * possible that a device might be trying to come online and must
         * check to see if it needs to restart a trim. That thread will be
         * holding the spa_config_lock which would prevent the txg_wait_synced
         * from completing.
         */
        mutex_exit(&vd->vdev_trim_lock);
        txg_wait_synced(spa_get_dsl(spa), 0);
        mutex_enter(&vd->vdev_trim_lock);

        vd->vdev_trim_thread = NULL;
        cv_broadcast(&vd->vdev_trim_cv);
        mutex_exit(&vd->vdev_trim_lock);

        thread_exit();
}

/*
 * Initiates a manual TRIM for the vdev_t.  Callers must hold vdev_trim_lock,
 * the vdev_t must be a leaf and cannot already be manually trimming.
 */
void
vdev_trim(vdev_t *vd, uint64_t rate, boolean_t partial, boolean_t secure)
{
        ASSERT(MUTEX_HELD(&vd->vdev_trim_lock));
        ASSERT(vd->vdev_ops->vdev_op_leaf);
        ASSERT(vdev_is_concrete(vd));
        ASSERT3P(vd->vdev_trim_thread, ==, NULL);
        ASSERT(!vd->vdev_detached);
        ASSERT(!vd->vdev_trim_exit_wanted);
        ASSERT(!vd->vdev_top->vdev_removing);
        ASSERT(!vd->vdev_rz_expanding);

        vdev_trim_change_state(vd, VDEV_TRIM_ACTIVE, rate, partial, secure);
        vd->vdev_trim_thread = thread_create(NULL, 0,
            vdev_trim_thread, vd, 0, &p0, TS_RUN, maxclsyspri);
}

/*
 * Wait for the trimming thread to be terminated (canceled or stopped).
 */
static void
vdev_trim_stop_wait_impl(vdev_t *vd)
{
        ASSERT(MUTEX_HELD(&vd->vdev_trim_lock));

        while (vd->vdev_trim_thread != NULL)
                cv_wait(&vd->vdev_trim_cv, &vd->vdev_trim_lock);

        ASSERT3P(vd->vdev_trim_thread, ==, NULL);
        vd->vdev_trim_exit_wanted = B_FALSE;
}

/*
 * Wait for vdev trim threads which were listed to cleanly exit.
 */
void
vdev_trim_stop_wait(spa_t *spa, list_t *vd_list)
{
        (void) spa;
        vdev_t *vd;

        ASSERT(MUTEX_HELD(&spa_namespace_lock));

        while ((vd = list_remove_head(vd_list)) != NULL) {
                mutex_enter(&vd->vdev_trim_lock);
                vdev_trim_stop_wait_impl(vd);
                mutex_exit(&vd->vdev_trim_lock);
        }
}

/*
 * Stop trimming a device, with the resultant trimming state being tgt_state.
 * For blocking behavior pass NULL for vd_list.  Otherwise, when a list_t is
 * provided the stopping vdev is inserted in to the list.  Callers are then
 * required to call vdev_trim_stop_wait() to block for all the trim threads
 * to exit.  The caller must hold vdev_trim_lock and must not be writing to
 * the spa config, as the trimming thread may try to enter the config as a
 * reader before exiting.
 */
void
vdev_trim_stop(vdev_t *vd, vdev_trim_state_t tgt_state, list_t *vd_list)
{
        ASSERT(!spa_config_held(vd->vdev_spa, SCL_CONFIG|SCL_STATE, RW_WRITER));
        ASSERT(MUTEX_HELD(&vd->vdev_trim_lock));
        ASSERT(vd->vdev_ops->vdev_op_leaf);
        ASSERT(vdev_is_concrete(vd));

        /*
         * Allow cancel requests to proceed even if the trim thread has
         * stopped.
         */
        if (vd->vdev_trim_thread == NULL && tgt_state != VDEV_TRIM_CANCELED)
                return;

        vdev_trim_change_state(vd, tgt_state, 0, 0, 0);
        vd->vdev_trim_exit_wanted = B_TRUE;

        if (vd_list == NULL) {
                vdev_trim_stop_wait_impl(vd);
        } else {
                ASSERT(MUTEX_HELD(&spa_namespace_lock));
                list_insert_tail(vd_list, vd);
        }
}

/*
 * Requests that all listed vdevs stop trimming.
 */
static void
vdev_trim_stop_all_impl(vdev_t *vd, vdev_trim_state_t tgt_state,
    list_t *vd_list)
{
        if (vd->vdev_ops->vdev_op_leaf && vdev_is_concrete(vd)) {
                mutex_enter(&vd->vdev_trim_lock);
                vdev_trim_stop(vd, tgt_state, vd_list);
                mutex_exit(&vd->vdev_trim_lock);
                return;
        }

        for (uint64_t i = 0; i < vd->vdev_children; i++) {
                vdev_trim_stop_all_impl(vd->vdev_child[i], tgt_state,
                    vd_list);
        }
}

/*
 * Convenience function to stop trimming of a vdev tree and set all trim
 * thread pointers to NULL.
 */
void
vdev_trim_stop_all(vdev_t *vd, vdev_trim_state_t tgt_state)
{
        spa_t *spa = vd->vdev_spa;
        list_t vd_list;
        vdev_t *vd_l2cache;

        ASSERT(MUTEX_HELD(&spa_namespace_lock));

        list_create(&vd_list, sizeof (vdev_t),
            offsetof(vdev_t, vdev_trim_node));

        vdev_trim_stop_all_impl(vd, tgt_state, &vd_list);

        /*
         * Iterate over cache devices and request stop trimming the
         * whole device in case we export the pool or remove the cache
         * device prematurely.
         */
        for (int i = 0; i < spa->spa_l2cache.sav_count; i++) {
                vd_l2cache = spa->spa_l2cache.sav_vdevs[i];
                vdev_trim_stop_all_impl(vd_l2cache, tgt_state, &vd_list);
        }

        vdev_trim_stop_wait(spa, &vd_list);

        if (vd->vdev_spa->spa_sync_on) {
                /* Make sure that our state has been synced to disk */
                txg_wait_synced(spa_get_dsl(vd->vdev_spa), 0);
        }

        list_destroy(&vd_list);
}

/*
 * Conditionally restarts a manual TRIM given its on-disk state.
 */
void
vdev_trim_restart(vdev_t *vd)
{
        ASSERT(MUTEX_HELD(&spa_namespace_lock) ||
            vd->vdev_spa->spa_load_thread == curthread);
        ASSERT(!spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER));

        if (vd->vdev_leaf_zap != 0) {
                mutex_enter(&vd->vdev_trim_lock);
                uint64_t trim_state = VDEV_TRIM_NONE;
                int err = zap_lookup(vd->vdev_spa->spa_meta_objset,
                    vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_STATE,
                    sizeof (trim_state), 1, &trim_state);
                ASSERT(err == 0 || err == ENOENT);
                vd->vdev_trim_state = trim_state;

                uint64_t timestamp = 0;
                err = zap_lookup(vd->vdev_spa->spa_meta_objset,
                    vd->vdev_leaf_zap, VDEV_LEAF_ZAP_TRIM_ACTION_TIME,
                    sizeof (timestamp), 1, &timestamp);
                ASSERT(err == 0 || err == ENOENT);
                vd->vdev_trim_action_time = timestamp;

                if ((vd->vdev_trim_state == VDEV_TRIM_SUSPENDED ||
                    vd->vdev_offline) && !vd->vdev_top->vdev_rz_expanding) {
                        /* load progress for reporting, but don't resume */
                        VERIFY0(vdev_trim_load(vd));
                } else if (vd->vdev_trim_state == VDEV_TRIM_ACTIVE &&
                    vdev_writeable(vd) && !vd->vdev_top->vdev_removing &&
                    !vd->vdev_top->vdev_rz_expanding &&
                    vd->vdev_trim_thread == NULL) {
                        VERIFY0(vdev_trim_load(vd));
                        vdev_trim(vd, vd->vdev_trim_rate,
                            vd->vdev_trim_partial, vd->vdev_trim_secure);
                }

                mutex_exit(&vd->vdev_trim_lock);
        }

        for (uint64_t i = 0; i < vd->vdev_children; i++) {
                vdev_trim_restart(vd->vdev_child[i]);
        }
}

/*
 * Used by the automatic TRIM when ZFS_DEBUG_TRIM is set to verify that
 * every TRIM range is contained within ms_allocatable.
 */
static void
vdev_trim_range_verify(void *arg, uint64_t start, uint64_t size)
{
        trim_args_t *ta = arg;
        metaslab_t *msp = ta->trim_msp;

        VERIFY3B(msp->ms_loaded, ==, B_TRUE);
        VERIFY3U(msp->ms_disabled, >, 0);
        VERIFY(range_tree_contains(msp->ms_allocatable, start, size));
}

/*
 * Each automatic TRIM thread is responsible for managing the trimming of a
 * top-level vdev in the pool.  No automatic TRIM state is maintained on-disk.
 *
 * N.B. This behavior is different from a manual TRIM where a thread
 * is created for each leaf vdev, instead of each top-level vdev.
 */
static __attribute__((noreturn)) void
vdev_autotrim_thread(void *arg)
{
        vdev_t *vd = arg;
        spa_t *spa = vd->vdev_spa;
        int shift = 0;

        mutex_enter(&vd->vdev_autotrim_lock);
        ASSERT3P(vd->vdev_top, ==, vd);
        ASSERT3P(vd->vdev_autotrim_thread, !=, NULL);
        mutex_exit(&vd->vdev_autotrim_lock);
        spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

        while (!vdev_autotrim_should_stop(vd)) {
                int txgs_per_trim = MAX(zfs_trim_txg_batch, 1);
                uint64_t extent_bytes_max = zfs_trim_extent_bytes_max;
                uint64_t extent_bytes_min = zfs_trim_extent_bytes_min;

                /*
                 * All of the metaslabs are divided in to groups of size
                 * num_metaslabs / zfs_trim_txg_batch.  Each of these groups
                 * is composed of metaslabs which are spread evenly over the
                 * device.
                 *
                 * For example, when zfs_trim_txg_batch = 32 (default) then
                 * group 0 will contain metaslabs 0, 32, 64, ...;
                 * group 1 will contain metaslabs 1, 33, 65, ...;
                 * group 2 will contain metaslabs 2, 34, 66, ...; and so on.
                 *
                 * On each pass through the while() loop one of these groups
                 * is selected.  This is accomplished by using a shift value
                 * to select the starting metaslab, then striding over the
                 * metaslabs using the zfs_trim_txg_batch size.  This is
                 * done to accomplish two things.
                 *
                 * 1) By dividing the metaslabs in to groups, and making sure
                 *    that each group takes a minimum of one txg to process.
                 *    Then zfs_trim_txg_batch controls the minimum number of
                 *    txgs which must occur before a metaslab is revisited.
                 *
                 * 2) Selecting non-consecutive metaslabs distributes the
                 *    TRIM commands for a group evenly over the entire device.
                 *    This can be advantageous for certain types of devices.
                 */
                for (uint64_t i = shift % txgs_per_trim; i < vd->vdev_ms_count;
                    i += txgs_per_trim) {
                        metaslab_t *msp = vd->vdev_ms[i];
                        range_tree_t *trim_tree;
                        boolean_t issued_trim = B_FALSE;
                        boolean_t wait_aborted = B_FALSE;

                        spa_config_exit(spa, SCL_CONFIG, FTAG);
                        metaslab_disable(msp);
                        spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

                        mutex_enter(&msp->ms_lock);

                        /*
                         * Skip the metaslab when it has never been allocated
                         * or when there are no recent frees to trim.
                         */
                        if (msp->ms_sm == NULL ||
                            range_tree_is_empty(msp->ms_trim)) {
                                mutex_exit(&msp->ms_lock);
                                metaslab_enable(msp, B_FALSE, B_FALSE);
                                continue;
                        }

                        /*
                         * Skip the metaslab when it has already been disabled.
                         * This may happen when a manual TRIM or initialize
                         * operation is running concurrently.  In the case
                         * of a manual TRIM, the ms_trim tree will have been
                         * vacated.  Only ranges added after the manual TRIM
                         * disabled the metaslab will be included in the tree.
                         * These will be processed when the automatic TRIM
                         * next revisits this metaslab.
                         */
                        if (msp->ms_disabled > 1) {
                                mutex_exit(&msp->ms_lock);
                                metaslab_enable(msp, B_FALSE, B_FALSE);
                                continue;
                        }

                        /*
                         * Allocate an empty range tree which is swapped in
                         * for the existing ms_trim tree while it is processed.
                         */
                        trim_tree = range_tree_create(NULL, RANGE_SEG64, NULL,
                            0, 0);
                        range_tree_swap(&msp->ms_trim, &trim_tree);
                        ASSERT(range_tree_is_empty(msp->ms_trim));

                        /*
                         * There are two cases when constructing the per-vdev
                         * trim trees for a metaslab.  If the top-level vdev
                         * has no children then it is also a leaf and should
                         * be trimmed.  Otherwise our children are the leaves
                         * and a trim tree should be constructed for each.
                         */
                        trim_args_t *tap;
                        uint64_t children = vd->vdev_children;
                        if (children == 0) {
                                children = 1;
                                tap = kmem_zalloc(sizeof (trim_args_t) *
                                    children, KM_SLEEP);
                                tap[0].trim_vdev = vd;
                        } else {
                                tap = kmem_zalloc(sizeof (trim_args_t) *
                                    children, KM_SLEEP);

                                for (uint64_t c = 0; c < children; c++) {
                                        tap[c].trim_vdev = vd->vdev_child[c];
                                }
                        }

                        for (uint64_t c = 0; c < children; c++) {
                                trim_args_t *ta = &tap[c];
                                vdev_t *cvd = ta->trim_vdev;

                                ta->trim_msp = msp;
                                ta->trim_extent_bytes_max = extent_bytes_max;
                                ta->trim_extent_bytes_min = extent_bytes_min;
                                ta->trim_type = TRIM_TYPE_AUTO;
                                ta->trim_flags = 0;

                                if (cvd->vdev_detached ||
                                    !vdev_writeable(cvd) ||
                                    !cvd->vdev_has_trim ||
                                    cvd->vdev_trim_thread != NULL) {
                                        continue;
                                }

                                /*
                                 * When a device has an attached hot spare, or
                                 * is being replaced it will not be trimmed.
                                 * This is done to avoid adding additional
                                 * stress to a potentially unhealthy device,
                                 * and to minimize the required rebuild time.
                                 */
                                if (!cvd->vdev_ops->vdev_op_leaf)
                                        continue;

                                ta->trim_tree = range_tree_create(NULL,
                                    RANGE_SEG64, NULL, 0, 0);
                                range_tree_walk(trim_tree,
                                    vdev_trim_range_add, ta);
                        }

                        mutex_exit(&msp->ms_lock);
                        spa_config_exit(spa, SCL_CONFIG, FTAG);

                        /*
                         * Issue the TRIM I/Os for all ranges covered by the
                         * TRIM trees.  These ranges are safe to TRIM because
                         * no new allocations will be performed until the call
                         * to metaslab_enabled() below.
                         */
                        for (uint64_t c = 0; c < children; c++) {
                                trim_args_t *ta = &tap[c];

                                /*
                                 * Always yield to a manual TRIM if one has
                                 * been started for the child vdev.
                                 */
                                if (ta->trim_tree == NULL ||
                                    ta->trim_vdev->vdev_trim_thread != NULL) {
                                        continue;
                                }

                                /*
                                 * After this point metaslab_enable() must be
                                 * called with the sync flag set.  This is done
                                 * here because vdev_trim_ranges() is allowed
                                 * to be interrupted (EINTR) before issuing all
                                 * of the required TRIM I/Os.
                                 */
                                issued_trim = B_TRUE;

                                int error = vdev_trim_ranges(ta);
                                if (error)
                                        break;
                        }

                        /*
                         * Verify every range which was trimmed is still
                         * contained within the ms_allocatable tree.
                         */
                        if (zfs_flags & ZFS_DEBUG_TRIM) {
                                mutex_enter(&msp->ms_lock);
                                VERIFY0(metaslab_load(msp));
                                VERIFY3P(tap[0].trim_msp, ==, msp);
                                range_tree_walk(trim_tree,
                                    vdev_trim_range_verify, &tap[0]);
                                mutex_exit(&msp->ms_lock);
                        }

                        range_tree_vacate(trim_tree, NULL, NULL);
                        range_tree_destroy(trim_tree);

                        /*
                         * Wait for couples of kicks, to ensure the trim io is
                         * synced. If the wait is aborted due to
                         * vdev_autotrim_exit_wanted, we need to signal
                         * metaslab_enable() to wait for sync.
                         */
                        if (issued_trim) {
                                wait_aborted = vdev_autotrim_wait_kick(vd,
                                    TXG_CONCURRENT_STATES + TXG_DEFER_SIZE);
                        }

                        metaslab_enable(msp, wait_aborted, B_FALSE);
                        spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

                        for (uint64_t c = 0; c < children; c++) {
                                trim_args_t *ta = &tap[c];

                                if (ta->trim_tree == NULL)
                                        continue;

                                range_tree_vacate(ta->trim_tree, NULL, NULL);
                                range_tree_destroy(ta->trim_tree);
                        }

                        kmem_free(tap, sizeof (trim_args_t) * children);

                        if (vdev_autotrim_should_stop(vd))
                                break;
                }

                spa_config_exit(spa, SCL_CONFIG, FTAG);

                vdev_autotrim_wait_kick(vd, 1);

                shift++;
                spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
        }

        for (uint64_t c = 0; c < vd->vdev_children; c++) {
                vdev_t *cvd = vd->vdev_child[c];
                mutex_enter(&cvd->vdev_trim_io_lock);

                while (cvd->vdev_trim_inflight[1] > 0) {
                        cv_wait(&cvd->vdev_trim_io_cv,
                            &cvd->vdev_trim_io_lock);
                }
                mutex_exit(&cvd->vdev_trim_io_lock);
        }

        spa_config_exit(spa, SCL_CONFIG, FTAG);

        /*
         * When exiting because the autotrim property was set to off, then
         * abandon any unprocessed ms_trim ranges to reclaim the memory.
         */
        if (spa_get_autotrim(spa) == SPA_AUTOTRIM_OFF) {
                for (uint64_t i = 0; i < vd->vdev_ms_count; i++) {
                        metaslab_t *msp = vd->vdev_ms[i];

                        mutex_enter(&msp->ms_lock);
                        range_tree_vacate(msp->ms_trim, NULL, NULL);
                        mutex_exit(&msp->ms_lock);
                }
        }

        mutex_enter(&vd->vdev_autotrim_lock);
        ASSERT(vd->vdev_autotrim_thread != NULL);
        vd->vdev_autotrim_thread = NULL;
        cv_broadcast(&vd->vdev_autotrim_cv);
        mutex_exit(&vd->vdev_autotrim_lock);

        thread_exit();
}

/*
 * Starts an autotrim thread, if needed, for each top-level vdev which can be
 * trimmed.  A top-level vdev which has been evacuated will never be trimmed.
 */
void
vdev_autotrim(spa_t *spa)
{
        vdev_t *root_vd = spa->spa_root_vdev;

        for (uint64_t i = 0; i < root_vd->vdev_children; i++) {
                vdev_t *tvd = root_vd->vdev_child[i];

                mutex_enter(&tvd->vdev_autotrim_lock);
                if (vdev_writeable(tvd) && !tvd->vdev_removing &&
                    tvd->vdev_autotrim_thread == NULL &&
                    !tvd->vdev_rz_expanding) {
                        ASSERT3P(tvd->vdev_top, ==, tvd);

                        tvd->vdev_autotrim_thread = thread_create(NULL, 0,
                            vdev_autotrim_thread, tvd, 0, &p0, TS_RUN,
                            maxclsyspri);
                        ASSERT(tvd->vdev_autotrim_thread != NULL);
                }
                mutex_exit(&tvd->vdev_autotrim_lock);
        }
}

/*
 * Wait for the vdev_autotrim_thread associated with the passed top-level
 * vdev to be terminated (canceled or stopped).
 */
void
vdev_autotrim_stop_wait(vdev_t *tvd)
{
        mutex_enter(&tvd->vdev_autotrim_lock);
        if (tvd->vdev_autotrim_thread != NULL) {
                tvd->vdev_autotrim_exit_wanted = B_TRUE;
                cv_broadcast(&tvd->vdev_autotrim_kick_cv);
                cv_wait(&tvd->vdev_autotrim_cv,
                    &tvd->vdev_autotrim_lock);

                ASSERT3P(tvd->vdev_autotrim_thread, ==, NULL);
                tvd->vdev_autotrim_exit_wanted = B_FALSE;
        }
        mutex_exit(&tvd->vdev_autotrim_lock);
}

void
vdev_autotrim_kick(spa_t *spa)
{
        ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER));

        vdev_t *root_vd = spa->spa_root_vdev;
        vdev_t *tvd;

        for (uint64_t i = 0; i < root_vd->vdev_children; i++) {
                tvd = root_vd->vdev_child[i];

                mutex_enter(&tvd->vdev_autotrim_lock);
                if (tvd->vdev_autotrim_thread != NULL)
                        cv_broadcast(&tvd->vdev_autotrim_kick_cv);
                mutex_exit(&tvd->vdev_autotrim_lock);
        }
}

/*
 * Wait for all of the vdev_autotrim_thread associated with the pool to
 * be terminated (canceled or stopped).
 */
void
vdev_autotrim_stop_all(spa_t *spa)
{
        vdev_t *root_vd = spa->spa_root_vdev;

        for (uint64_t i = 0; i < root_vd->vdev_children; i++)
                vdev_autotrim_stop_wait(root_vd->vdev_child[i]);
}

/*
 * Conditionally restart all of the vdev_autotrim_thread's for the pool.
 */
void
vdev_autotrim_restart(spa_t *spa)
{
        ASSERT(MUTEX_HELD(&spa_namespace_lock) ||
            spa->spa_load_thread == curthread);
        if (spa->spa_autotrim)
                vdev_autotrim(spa);
}

static __attribute__((noreturn)) void
vdev_trim_l2arc_thread(void *arg)
{
        vdev_t          *vd = arg;
        spa_t           *spa = vd->vdev_spa;
        l2arc_dev_t     *dev = l2arc_vdev_get(vd);
        trim_args_t     ta = {0};
        range_seg64_t   physical_rs;

        ASSERT(vdev_is_concrete(vd));
        spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

        vd->vdev_trim_last_offset = 0;
        vd->vdev_trim_rate = 0;
        vd->vdev_trim_partial = 0;
        vd->vdev_trim_secure = 0;

        ta.trim_vdev = vd;
        ta.trim_tree = range_tree_create(NULL, RANGE_SEG64, NULL, 0, 0);
        ta.trim_type = TRIM_TYPE_MANUAL;
        ta.trim_extent_bytes_max = zfs_trim_extent_bytes_max;
        ta.trim_extent_bytes_min = SPA_MINBLOCKSIZE;
        ta.trim_flags = 0;

        physical_rs.rs_start = vd->vdev_trim_bytes_done = 0;
        physical_rs.rs_end = vd->vdev_trim_bytes_est =
            vdev_get_min_asize(vd);

        range_tree_add(ta.trim_tree, physical_rs.rs_start,
            physical_rs.rs_end - physical_rs.rs_start);

        mutex_enter(&vd->vdev_trim_lock);
        vdev_trim_change_state(vd, VDEV_TRIM_ACTIVE, 0, 0, 0);
        mutex_exit(&vd->vdev_trim_lock);

        (void) vdev_trim_ranges(&ta);

        spa_config_exit(spa, SCL_CONFIG, FTAG);
        mutex_enter(&vd->vdev_trim_io_lock);
        while (vd->vdev_trim_inflight[TRIM_TYPE_MANUAL] > 0) {
                cv_wait(&vd->vdev_trim_io_cv, &vd->vdev_trim_io_lock);
        }
        mutex_exit(&vd->vdev_trim_io_lock);

        range_tree_vacate(ta.trim_tree, NULL, NULL);
        range_tree_destroy(ta.trim_tree);

        mutex_enter(&vd->vdev_trim_lock);
        if (!vd->vdev_trim_exit_wanted && vdev_writeable(vd)) {
                vdev_trim_change_state(vd, VDEV_TRIM_COMPLETE,
                    vd->vdev_trim_rate, vd->vdev_trim_partial,
                    vd->vdev_trim_secure);
        }
        ASSERT(vd->vdev_trim_thread != NULL ||
            vd->vdev_trim_inflight[TRIM_TYPE_MANUAL] == 0);

        /*
         * Drop the vdev_trim_lock while we sync out the txg since it's
         * possible that a device might be trying to come online and
         * must check to see if it needs to restart a trim. That thread
         * will be holding the spa_config_lock which would prevent the
         * txg_wait_synced from completing. Same strategy as in
         * vdev_trim_thread().
         */
        mutex_exit(&vd->vdev_trim_lock);
        txg_wait_synced(spa_get_dsl(vd->vdev_spa), 0);
        mutex_enter(&vd->vdev_trim_lock);

        /*
         * Update the header of the cache device here, before
         * broadcasting vdev_trim_cv which may lead to the removal
         * of the device. The same applies for setting l2ad_trim_all to
         * false.
         */
        spa_config_enter(vd->vdev_spa, SCL_L2ARC, vd,
            RW_READER);
        memset(dev->l2ad_dev_hdr, 0, dev->l2ad_dev_hdr_asize);
        l2arc_dev_hdr_update(dev);
        spa_config_exit(vd->vdev_spa, SCL_L2ARC, vd);

        vd->vdev_trim_thread = NULL;
        if (vd->vdev_trim_state == VDEV_TRIM_COMPLETE)
                dev->l2ad_trim_all = B_FALSE;

        cv_broadcast(&vd->vdev_trim_cv);
        mutex_exit(&vd->vdev_trim_lock);

        thread_exit();
}

/*
 * Punches out TRIM threads for the L2ARC devices in a spa and assigns them
 * to vd->vdev_trim_thread variable. This facilitates the management of
 * trimming the whole cache device using TRIM_TYPE_MANUAL upon addition
 * to a pool or pool creation or when the header of the device is invalid.
 */
void
vdev_trim_l2arc(spa_t *spa)
{
        ASSERT(MUTEX_HELD(&spa_namespace_lock));

        /*
         * Locate the spa's l2arc devices and kick off TRIM threads.
         */
        for (int i = 0; i < spa->spa_l2cache.sav_count; i++) {
                vdev_t *vd = spa->spa_l2cache.sav_vdevs[i];
                l2arc_dev_t *dev = l2arc_vdev_get(vd);

                if (dev == NULL || !dev->l2ad_trim_all) {
                        /*
                         * Don't attempt TRIM if the vdev is UNAVAIL or if the
                         * cache device was not marked for whole device TRIM
                         * (ie l2arc_trim_ahead = 0, or the L2ARC device header
                         * is valid with trim_state = VDEV_TRIM_COMPLETE and
                         * l2ad_log_entries > 0).
                         */
                        continue;
                }

                mutex_enter(&vd->vdev_trim_lock);
                ASSERT(vd->vdev_ops->vdev_op_leaf);
                ASSERT(vdev_is_concrete(vd));
                ASSERT3P(vd->vdev_trim_thread, ==, NULL);
                ASSERT(!vd->vdev_detached);
                ASSERT(!vd->vdev_trim_exit_wanted);
                ASSERT(!vd->vdev_top->vdev_removing);
                vdev_trim_change_state(vd, VDEV_TRIM_ACTIVE, 0, 0, 0);
                vd->vdev_trim_thread = thread_create(NULL, 0,
                    vdev_trim_l2arc_thread, vd, 0, &p0, TS_RUN, maxclsyspri);
                mutex_exit(&vd->vdev_trim_lock);
        }
}

/*
 * A wrapper which calls vdev_trim_ranges(). It is intended to be called
 * on leaf vdevs.
 */
int
vdev_trim_simple(vdev_t *vd, uint64_t start, uint64_t size)
{
        trim_args_t ta = {0};
        range_seg64_t physical_rs;
        int error;
        physical_rs.rs_start = start;
        physical_rs.rs_end = start + size;

        ASSERT(vdev_is_concrete(vd));
        ASSERT(vd->vdev_ops->vdev_op_leaf);
        ASSERT(!vd->vdev_detached);
        ASSERT(!vd->vdev_top->vdev_removing);
        ASSERT(!vd->vdev_top->vdev_rz_expanding);

        ta.trim_vdev = vd;
        ta.trim_tree = range_tree_create(NULL, RANGE_SEG64, NULL, 0, 0);
        ta.trim_type = TRIM_TYPE_SIMPLE;
        ta.trim_extent_bytes_max = zfs_trim_extent_bytes_max;
        ta.trim_extent_bytes_min = SPA_MINBLOCKSIZE;
        ta.trim_flags = 0;

        ASSERT3U(physical_rs.rs_end, >=, physical_rs.rs_start);

        if (physical_rs.rs_end > physical_rs.rs_start) {
                range_tree_add(ta.trim_tree, physical_rs.rs_start,
                    physical_rs.rs_end - physical_rs.rs_start);
        } else {
                ASSERT3U(physical_rs.rs_end, ==, physical_rs.rs_start);
        }

        error = vdev_trim_ranges(&ta);

        mutex_enter(&vd->vdev_trim_io_lock);
        while (vd->vdev_trim_inflight[TRIM_TYPE_SIMPLE] > 0) {
                cv_wait(&vd->vdev_trim_io_cv, &vd->vdev_trim_io_lock);
        }
        mutex_exit(&vd->vdev_trim_io_lock);

        range_tree_vacate(ta.trim_tree, NULL, NULL);
        range_tree_destroy(ta.trim_tree);

        return (error);
}

EXPORT_SYMBOL(vdev_trim);
EXPORT_SYMBOL(vdev_trim_stop);
EXPORT_SYMBOL(vdev_trim_stop_all);
EXPORT_SYMBOL(vdev_trim_stop_wait);
EXPORT_SYMBOL(vdev_trim_restart);
EXPORT_SYMBOL(vdev_autotrim);
EXPORT_SYMBOL(vdev_autotrim_stop_all);
EXPORT_SYMBOL(vdev_autotrim_stop_wait);
EXPORT_SYMBOL(vdev_autotrim_restart);
EXPORT_SYMBOL(vdev_trim_l2arc);
EXPORT_SYMBOL(vdev_trim_simple);

ZFS_MODULE_PARAM(zfs_trim, zfs_trim_, extent_bytes_max, UINT, ZMOD_RW,
        "Max size of TRIM commands, larger will be split");

ZFS_MODULE_PARAM(zfs_trim, zfs_trim_, extent_bytes_min, UINT, ZMOD_RW,
        "Min size of TRIM commands, smaller will be skipped");

ZFS_MODULE_PARAM(zfs_trim, zfs_trim_, metaslab_skip, UINT, ZMOD_RW,
        "Skip metaslabs which have never been initialized");

ZFS_MODULE_PARAM(zfs_trim, zfs_trim_, txg_batch, UINT, ZMOD_RW,
        "Min number of txgs to aggregate frees before issuing TRIM");

ZFS_MODULE_PARAM(zfs_trim, zfs_trim_, queue_limit, UINT, ZMOD_RW,
        "Max queued TRIMs outstanding per leaf vdev");