9166 zfs storage pool checkpoint

[unleashed.git] / usr / src / uts / common / fs / zfs / dnode_sync.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 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
 * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
 */

#include <sys/zfs_context.h>
#include <sys/dbuf.h>
#include <sys/dnode.h>
#include <sys/dmu.h>
#include <sys/dmu_tx.h>
#include <sys/dmu_objset.h>
#include <sys/dsl_dataset.h>
#include <sys/spa.h>
#include <sys/range_tree.h>
#include <sys/zfeature.h>

static void
dnode_increase_indirection(dnode_t *dn, dmu_tx_t *tx)
{
        dmu_buf_impl_t *db;
        int txgoff = tx->tx_txg & TXG_MASK;
        int nblkptr = dn->dn_phys->dn_nblkptr;
        int old_toplvl = dn->dn_phys->dn_nlevels - 1;
        int new_level = dn->dn_next_nlevels[txgoff];
        int i;

        rw_enter(&dn->dn_struct_rwlock, RW_WRITER);

        /* this dnode can't be paged out because it's dirty */
        ASSERT(dn->dn_phys->dn_type != DMU_OT_NONE);
        ASSERT(RW_WRITE_HELD(&dn->dn_struct_rwlock));
        ASSERT(new_level > 1 && dn->dn_phys->dn_nlevels > 0);

        db = dbuf_hold_level(dn, dn->dn_phys->dn_nlevels, 0, FTAG);
        ASSERT(db != NULL);

        dn->dn_phys->dn_nlevels = new_level;
        dprintf("os=%p obj=%llu, increase to %d\n", dn->dn_objset,
            dn->dn_object, dn->dn_phys->dn_nlevels);

        /* transfer dnode's block pointers to new indirect block */
        (void) dbuf_read(db, NULL, DB_RF_MUST_SUCCEED|DB_RF_HAVESTRUCT);
        ASSERT(db->db.db_data);
        ASSERT(arc_released(db->db_buf));
        ASSERT3U(sizeof (blkptr_t) * nblkptr, <=, db->db.db_size);
        bcopy(dn->dn_phys->dn_blkptr, db->db.db_data,
            sizeof (blkptr_t) * nblkptr);
        arc_buf_freeze(db->db_buf);

        /* set dbuf's parent pointers to new indirect buf */
        for (i = 0; i < nblkptr; i++) {
                dmu_buf_impl_t *child =
                    dbuf_find(dn->dn_objset, dn->dn_object, old_toplvl, i);

                if (child == NULL)
                        continue;
#ifdef  DEBUG
                DB_DNODE_ENTER(child);
                ASSERT3P(DB_DNODE(child), ==, dn);
                DB_DNODE_EXIT(child);
#endif  /* DEBUG */
                if (child->db_parent && child->db_parent != dn->dn_dbuf) {
                        ASSERT(child->db_parent->db_level == db->db_level);
                        ASSERT(child->db_blkptr !=
                            &dn->dn_phys->dn_blkptr[child->db_blkid]);
                        mutex_exit(&child->db_mtx);
                        continue;
                }
                ASSERT(child->db_parent == NULL ||
                    child->db_parent == dn->dn_dbuf);

                child->db_parent = db;
                dbuf_add_ref(db, child);
                if (db->db.db_data)
                        child->db_blkptr = (blkptr_t *)db->db.db_data + i;
                else
                        child->db_blkptr = NULL;
                dprintf_dbuf_bp(child, child->db_blkptr,
                    "changed db_blkptr to new indirect %s", "");

                mutex_exit(&child->db_mtx);
        }

        bzero(dn->dn_phys->dn_blkptr, sizeof (blkptr_t) * nblkptr);

        dbuf_rele(db, FTAG);

        rw_exit(&dn->dn_struct_rwlock);
}

static void
free_blocks(dnode_t *dn, blkptr_t *bp, int num, dmu_tx_t *tx)
{
        dsl_dataset_t *ds = dn->dn_objset->os_dsl_dataset;
        uint64_t bytesfreed = 0;

        dprintf("ds=%p obj=%llx num=%d\n", ds, dn->dn_object, num);

        for (int i = 0; i < num; i++, bp++) {
                if (BP_IS_HOLE(bp))
                        continue;

                bytesfreed += dsl_dataset_block_kill(ds, bp, tx, B_FALSE);
                ASSERT3U(bytesfreed, <=, DN_USED_BYTES(dn->dn_phys));

                /*
                 * Save some useful information on the holes being
                 * punched, including logical size, type, and indirection
                 * level. Retaining birth time enables detection of when
                 * holes are punched for reducing the number of free
                 * records transmitted during a zfs send.
                 */

                uint64_t lsize = BP_GET_LSIZE(bp);
                dmu_object_type_t type = BP_GET_TYPE(bp);
                uint64_t lvl = BP_GET_LEVEL(bp);

                bzero(bp, sizeof (blkptr_t));

                if (spa_feature_is_active(dn->dn_objset->os_spa,
                    SPA_FEATURE_HOLE_BIRTH)) {
                        BP_SET_LSIZE(bp, lsize);
                        BP_SET_TYPE(bp, type);
                        BP_SET_LEVEL(bp, lvl);
                        BP_SET_BIRTH(bp, dmu_tx_get_txg(tx), 0);
                }
        }
        dnode_diduse_space(dn, -bytesfreed);
}

#ifdef ZFS_DEBUG
static void
free_verify(dmu_buf_impl_t *db, uint64_t start, uint64_t end, dmu_tx_t *tx)
{
        int off, num;
        int i, err, epbs;
        uint64_t txg = tx->tx_txg;
        dnode_t *dn;

        DB_DNODE_ENTER(db);
        dn = DB_DNODE(db);
        epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
        off = start - (db->db_blkid * 1<<epbs);
        num = end - start + 1;

        ASSERT3U(off, >=, 0);
        ASSERT3U(num, >=, 0);
        ASSERT3U(db->db_level, >, 0);
        ASSERT3U(db->db.db_size, ==, 1 << dn->dn_phys->dn_indblkshift);
        ASSERT3U(off+num, <=, db->db.db_size >> SPA_BLKPTRSHIFT);
        ASSERT(db->db_blkptr != NULL);

        for (i = off; i < off+num; i++) {
                uint64_t *buf;
                dmu_buf_impl_t *child;
                dbuf_dirty_record_t *dr;
                int j;

                ASSERT(db->db_level == 1);

                rw_enter(&dn->dn_struct_rwlock, RW_READER);
                err = dbuf_hold_impl(dn, db->db_level-1,
                    (db->db_blkid << epbs) + i, TRUE, FALSE, FTAG, &child);
                rw_exit(&dn->dn_struct_rwlock);
                if (err == ENOENT)
                        continue;
                ASSERT(err == 0);
                ASSERT(child->db_level == 0);
                dr = child->db_last_dirty;
                while (dr && dr->dr_txg > txg)
                        dr = dr->dr_next;
                ASSERT(dr == NULL || dr->dr_txg == txg);

                /* data_old better be zeroed */
                if (dr) {
                        buf = dr->dt.dl.dr_data->b_data;
                        for (j = 0; j < child->db.db_size >> 3; j++) {
                                if (buf[j] != 0) {
                                        panic("freed data not zero: "
                                            "child=%p i=%d off=%d num=%d\n",
                                            (void *)child, i, off, num);
                                }
                        }
                }

                /*
                 * db_data better be zeroed unless it's dirty in a
                 * future txg.
                 */
                mutex_enter(&child->db_mtx);
                buf = child->db.db_data;
                if (buf != NULL && child->db_state != DB_FILL &&
                    child->db_last_dirty == NULL) {
                        for (j = 0; j < child->db.db_size >> 3; j++) {
                                if (buf[j] != 0) {
                                        panic("freed data not zero: "
                                            "child=%p i=%d off=%d num=%d\n",
                                            (void *)child, i, off, num);
                                }
                        }
                }
                mutex_exit(&child->db_mtx);

                dbuf_rele(child, FTAG);
        }
        DB_DNODE_EXIT(db);
}
#endif

static void
free_children(dmu_buf_impl_t *db, uint64_t blkid, uint64_t nblks,
    dmu_tx_t *tx)
{
        dnode_t *dn;
        blkptr_t *bp;
        dmu_buf_impl_t *subdb;
        uint64_t start, end, dbstart, dbend;
        unsigned int epbs, shift, i;

        /*
         * There is a small possibility that this block will not be cached:
         *   1 - if level > 1 and there are no children with level <= 1
         *   2 - if this block was evicted since we read it from
         *       dmu_tx_hold_free().
         */
        if (db->db_state != DB_CACHED)
                (void) dbuf_read(db, NULL, DB_RF_MUST_SUCCEED);

        dbuf_release_bp(db);
        bp = db->db.db_data;

        DB_DNODE_ENTER(db);
        dn = DB_DNODE(db);
        epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
        ASSERT3U(epbs, <, 31);
        shift = (db->db_level - 1) * epbs;
        dbstart = db->db_blkid << epbs;
        start = blkid >> shift;
        if (dbstart < start) {
                bp += start - dbstart;
        } else {
                start = dbstart;
        }
        dbend = ((db->db_blkid + 1) << epbs) - 1;
        end = (blkid + nblks - 1) >> shift;
        if (dbend <= end)
                end = dbend;

        ASSERT3U(start, <=, end);

        if (db->db_level == 1) {
                FREE_VERIFY(db, start, end, tx);
                free_blocks(dn, bp, end-start+1, tx);
        } else {
                for (uint64_t id = start; id <= end; id++, bp++) {
                        if (BP_IS_HOLE(bp))
                                continue;
                        rw_enter(&dn->dn_struct_rwlock, RW_READER);
                        VERIFY0(dbuf_hold_impl(dn, db->db_level - 1,
                            id, TRUE, FALSE, FTAG, &subdb));
                        rw_exit(&dn->dn_struct_rwlock);
                        ASSERT3P(bp, ==, subdb->db_blkptr);

                        free_children(subdb, blkid, nblks, tx);
                        dbuf_rele(subdb, FTAG);
                }
        }

        /* If this whole block is free, free ourself too. */
        for (i = 0, bp = db->db.db_data; i < 1 << epbs; i++, bp++) {
                if (!BP_IS_HOLE(bp))
                        break;
        }
        if (i == 1 << epbs) {
                /*
                 * We only found holes. Grab the rwlock to prevent
                 * anybody from reading the blocks we're about to
                 * zero out.
                 */
                rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
                bzero(db->db.db_data, db->db.db_size);
                rw_exit(&dn->dn_struct_rwlock);
                free_blocks(dn, db->db_blkptr, 1, tx);
        } else {
                /*
                 * Partial block free; must be marked dirty so that it
                 * will be written out.
                 */
                ASSERT(db->db_dirtycnt > 0);
        }

        DB_DNODE_EXIT(db);
        arc_buf_freeze(db->db_buf);
}

/*
 * Traverse the indicated range of the provided file
 * and "free" all the blocks contained there.
 */
static void
dnode_sync_free_range_impl(dnode_t *dn, uint64_t blkid, uint64_t nblks,
    dmu_tx_t *tx)
{
        blkptr_t *bp = dn->dn_phys->dn_blkptr;
        int dnlevel = dn->dn_phys->dn_nlevels;
        boolean_t trunc = B_FALSE;

        if (blkid > dn->dn_phys->dn_maxblkid)
                return;

        ASSERT(dn->dn_phys->dn_maxblkid < UINT64_MAX);
        if (blkid + nblks > dn->dn_phys->dn_maxblkid) {
                nblks = dn->dn_phys->dn_maxblkid - blkid + 1;
                trunc = B_TRUE;
        }

        /* There are no indirect blocks in the object */
        if (dnlevel == 1) {
                if (blkid >= dn->dn_phys->dn_nblkptr) {
                        /* this range was never made persistent */
                        return;
                }
                ASSERT3U(blkid + nblks, <=, dn->dn_phys->dn_nblkptr);
                free_blocks(dn, bp + blkid, nblks, tx);
        } else {
                int shift = (dnlevel - 1) *
                    (dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT);
                int start = blkid >> shift;
                int end = (blkid + nblks - 1) >> shift;
                dmu_buf_impl_t *db;

                ASSERT(start < dn->dn_phys->dn_nblkptr);
                bp += start;
                for (int i = start; i <= end; i++, bp++) {
                        if (BP_IS_HOLE(bp))
                                continue;
                        rw_enter(&dn->dn_struct_rwlock, RW_READER);
                        VERIFY0(dbuf_hold_impl(dn, dnlevel - 1, i,
                            TRUE, FALSE, FTAG, &db));
                        rw_exit(&dn->dn_struct_rwlock);

                        free_children(db, blkid, nblks, tx);
                        dbuf_rele(db, FTAG);
                }
        }

        if (trunc) {
                dn->dn_phys->dn_maxblkid = blkid == 0 ? 0 : blkid - 1;

                uint64_t off = (dn->dn_phys->dn_maxblkid + 1) *
                    (dn->dn_phys->dn_datablkszsec << SPA_MINBLOCKSHIFT);
                ASSERT(off < dn->dn_phys->dn_maxblkid ||
                    dn->dn_phys->dn_maxblkid == 0 ||
                    dnode_next_offset(dn, 0, &off, 1, 1, 0) != 0);
        }
}

typedef struct dnode_sync_free_range_arg {
        dnode_t *dsfra_dnode;
        dmu_tx_t *dsfra_tx;
} dnode_sync_free_range_arg_t;

static void
dnode_sync_free_range(void *arg, uint64_t blkid, uint64_t nblks)
{
        dnode_sync_free_range_arg_t *dsfra = arg;
        dnode_t *dn = dsfra->dsfra_dnode;

        mutex_exit(&dn->dn_mtx);
        dnode_sync_free_range_impl(dn, blkid, nblks, dsfra->dsfra_tx);
        mutex_enter(&dn->dn_mtx);
}

/*
 * Try to kick all the dnode's dbufs out of the cache...
 */
void
dnode_evict_dbufs(dnode_t *dn)
{
        dmu_buf_impl_t db_marker;
        dmu_buf_impl_t *db, *db_next;

        mutex_enter(&dn->dn_dbufs_mtx);
        for (db = avl_first(&dn->dn_dbufs); db != NULL; db = db_next) {

#ifdef  DEBUG
                DB_DNODE_ENTER(db);
                ASSERT3P(DB_DNODE(db), ==, dn);
                DB_DNODE_EXIT(db);
#endif  /* DEBUG */

                mutex_enter(&db->db_mtx);
                if (db->db_state != DB_EVICTING &&
                    refcount_is_zero(&db->db_holds)) {
                        db_marker.db_level = db->db_level;
                        db_marker.db_blkid = db->db_blkid;
                        db_marker.db_state = DB_SEARCH;
                        avl_insert_here(&dn->dn_dbufs, &db_marker, db,
                            AVL_BEFORE);

                        dbuf_destroy(db);

                        db_next = AVL_NEXT(&dn->dn_dbufs, &db_marker);
                        avl_remove(&dn->dn_dbufs, &db_marker);
                } else {
                        db->db_pending_evict = TRUE;
                        mutex_exit(&db->db_mtx);
                        db_next = AVL_NEXT(&dn->dn_dbufs, db);
                }
        }
        mutex_exit(&dn->dn_dbufs_mtx);

        dnode_evict_bonus(dn);
}

void
dnode_evict_bonus(dnode_t *dn)
{
        rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
        if (dn->dn_bonus != NULL) {
                if (refcount_is_zero(&dn->dn_bonus->db_holds)) {
                        mutex_enter(&dn->dn_bonus->db_mtx);
                        dbuf_destroy(dn->dn_bonus);
                        dn->dn_bonus = NULL;
                } else {
                        dn->dn_bonus->db_pending_evict = TRUE;
                }
        }
        rw_exit(&dn->dn_struct_rwlock);
}

static void
dnode_undirty_dbufs(list_t *list)
{
        dbuf_dirty_record_t *dr;

        while (dr = list_head(list)) {
                dmu_buf_impl_t *db = dr->dr_dbuf;
                uint64_t txg = dr->dr_txg;

                if (db->db_level != 0)
                        dnode_undirty_dbufs(&dr->dt.di.dr_children);

                mutex_enter(&db->db_mtx);
                /* XXX - use dbuf_undirty()? */
                list_remove(list, dr);
                ASSERT(db->db_last_dirty == dr);
                db->db_last_dirty = NULL;
                db->db_dirtycnt -= 1;
                if (db->db_level == 0) {
                        ASSERT(db->db_blkid == DMU_BONUS_BLKID ||
                            dr->dt.dl.dr_data == db->db_buf);
                        dbuf_unoverride(dr);
                } else {
                        mutex_destroy(&dr->dt.di.dr_mtx);
                        list_destroy(&dr->dt.di.dr_children);
                }
                kmem_free(dr, sizeof (dbuf_dirty_record_t));
                dbuf_rele_and_unlock(db, (void *)(uintptr_t)txg);
        }
}

static void
dnode_sync_free(dnode_t *dn, dmu_tx_t *tx)
{
        int txgoff = tx->tx_txg & TXG_MASK;

        ASSERT(dmu_tx_is_syncing(tx));

        /*
         * Our contents should have been freed in dnode_sync() by the
         * free range record inserted by the caller of dnode_free().
         */
        ASSERT0(DN_USED_BYTES(dn->dn_phys));
        ASSERT(BP_IS_HOLE(dn->dn_phys->dn_blkptr));

        dnode_undirty_dbufs(&dn->dn_dirty_records[txgoff]);
        dnode_evict_dbufs(dn);

        /*
         * XXX - It would be nice to assert this, but we may still
         * have residual holds from async evictions from the arc...
         *
         * zfs_obj_to_path() also depends on this being
         * commented out.
         *
         * ASSERT3U(refcount_count(&dn->dn_holds), ==, 1);
         */

        /* Undirty next bits */
        dn->dn_next_nlevels[txgoff] = 0;
        dn->dn_next_indblkshift[txgoff] = 0;
        dn->dn_next_blksz[txgoff] = 0;

        /* ASSERT(blkptrs are zero); */
        ASSERT(dn->dn_phys->dn_type != DMU_OT_NONE);
        ASSERT(dn->dn_type != DMU_OT_NONE);

        ASSERT(dn->dn_free_txg > 0);
        if (dn->dn_allocated_txg != dn->dn_free_txg)
                dmu_buf_will_dirty(&dn->dn_dbuf->db, tx);
        bzero(dn->dn_phys, sizeof (dnode_phys_t));

        mutex_enter(&dn->dn_mtx);
        dn->dn_type = DMU_OT_NONE;
        dn->dn_maxblkid = 0;
        dn->dn_allocated_txg = 0;
        dn->dn_free_txg = 0;
        dn->dn_have_spill = B_FALSE;
        mutex_exit(&dn->dn_mtx);

        ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT);

        dnode_rele(dn, (void *)(uintptr_t)tx->tx_txg);
        /*
         * Now that we've released our hold, the dnode may
         * be evicted, so we musn't access it.
         */
}

/*
 * Write out the dnode's dirty buffers.
 */
void
dnode_sync(dnode_t *dn, dmu_tx_t *tx)
{
        dnode_phys_t *dnp = dn->dn_phys;
        int txgoff = tx->tx_txg & TXG_MASK;
        list_t *list = &dn->dn_dirty_records[txgoff];
        static const dnode_phys_t zerodn = { 0 };
        boolean_t kill_spill = B_FALSE;

        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(dnp->dn_type != DMU_OT_NONE || dn->dn_allocated_txg);
        ASSERT(dnp->dn_type != DMU_OT_NONE ||
            bcmp(dnp, &zerodn, DNODE_SIZE) == 0);
        DNODE_VERIFY(dn);

        ASSERT(dn->dn_dbuf == NULL || arc_released(dn->dn_dbuf->db_buf));

        if (dmu_objset_userused_enabled(dn->dn_objset) &&
            !DMU_OBJECT_IS_SPECIAL(dn->dn_object)) {
                mutex_enter(&dn->dn_mtx);
                dn->dn_oldused = DN_USED_BYTES(dn->dn_phys);
                dn->dn_oldflags = dn->dn_phys->dn_flags;
                dn->dn_phys->dn_flags |= DNODE_FLAG_USERUSED_ACCOUNTED;
                mutex_exit(&dn->dn_mtx);
                dmu_objset_userquota_get_ids(dn, B_FALSE, tx);
        } else {
                /* Once we account for it, we should always account for it. */
                ASSERT(!(dn->dn_phys->dn_flags &
                    DNODE_FLAG_USERUSED_ACCOUNTED));
        }

        mutex_enter(&dn->dn_mtx);
        if (dn->dn_allocated_txg == tx->tx_txg) {
                /* The dnode is newly allocated or reallocated */
                if (dnp->dn_type == DMU_OT_NONE) {
                        /* this is a first alloc, not a realloc */
                        dnp->dn_nlevels = 1;
                        dnp->dn_nblkptr = dn->dn_nblkptr;
                }

                dnp->dn_type = dn->dn_type;
                dnp->dn_bonustype = dn->dn_bonustype;
                dnp->dn_bonuslen = dn->dn_bonuslen;
        }
        ASSERT(dnp->dn_nlevels > 1 ||
            BP_IS_HOLE(&dnp->dn_blkptr[0]) ||
            BP_IS_EMBEDDED(&dnp->dn_blkptr[0]) ||
            BP_GET_LSIZE(&dnp->dn_blkptr[0]) ==
            dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT);
        ASSERT(dnp->dn_nlevels < 2 ||
            BP_IS_HOLE(&dnp->dn_blkptr[0]) ||
            BP_GET_LSIZE(&dnp->dn_blkptr[0]) == 1 << dnp->dn_indblkshift);

        if (dn->dn_next_type[txgoff] != 0) {
                dnp->dn_type = dn->dn_type;
                dn->dn_next_type[txgoff] = 0;
        }

        if (dn->dn_next_blksz[txgoff] != 0) {
                ASSERT(P2PHASE(dn->dn_next_blksz[txgoff],
                    SPA_MINBLOCKSIZE) == 0);
                ASSERT(BP_IS_HOLE(&dnp->dn_blkptr[0]) ||
                    dn->dn_maxblkid == 0 || list_head(list) != NULL ||
                    dn->dn_next_blksz[txgoff] >> SPA_MINBLOCKSHIFT ==
                    dnp->dn_datablkszsec ||
                    !range_tree_is_empty(dn->dn_free_ranges[txgoff]));
                dnp->dn_datablkszsec =
                    dn->dn_next_blksz[txgoff] >> SPA_MINBLOCKSHIFT;
                dn->dn_next_blksz[txgoff] = 0;
        }

        if (dn->dn_next_bonuslen[txgoff] != 0) {
                if (dn->dn_next_bonuslen[txgoff] == DN_ZERO_BONUSLEN)
                        dnp->dn_bonuslen = 0;
                else
                        dnp->dn_bonuslen = dn->dn_next_bonuslen[txgoff];
                ASSERT(dnp->dn_bonuslen <= DN_MAX_BONUSLEN);
                dn->dn_next_bonuslen[txgoff] = 0;
        }

        if (dn->dn_next_bonustype[txgoff] != 0) {
                ASSERT(DMU_OT_IS_VALID(dn->dn_next_bonustype[txgoff]));
                dnp->dn_bonustype = dn->dn_next_bonustype[txgoff];
                dn->dn_next_bonustype[txgoff] = 0;
        }

        boolean_t freeing_dnode = dn->dn_free_txg > 0 &&
            dn->dn_free_txg <= tx->tx_txg;

        /*
         * Remove the spill block if we have been explicitly asked to
         * remove it, or if the object is being removed.
         */
        if (dn->dn_rm_spillblk[txgoff] || freeing_dnode) {
                if (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR)
                        kill_spill = B_TRUE;
                dn->dn_rm_spillblk[txgoff] = 0;
        }

        if (dn->dn_next_indblkshift[txgoff] != 0) {
                ASSERT(dnp->dn_nlevels == 1);
                dnp->dn_indblkshift = dn->dn_next_indblkshift[txgoff];
                dn->dn_next_indblkshift[txgoff] = 0;
        }

        /*
         * Just take the live (open-context) values for checksum and compress.
         * Strictly speaking it's a future leak, but nothing bad happens if we
         * start using the new checksum or compress algorithm a little early.
         */
        dnp->dn_checksum = dn->dn_checksum;
        dnp->dn_compress = dn->dn_compress;

        mutex_exit(&dn->dn_mtx);

        if (kill_spill) {
                free_blocks(dn, &dn->dn_phys->dn_spill, 1, tx);
                mutex_enter(&dn->dn_mtx);
                dnp->dn_flags &= ~DNODE_FLAG_SPILL_BLKPTR;
                mutex_exit(&dn->dn_mtx);
        }

        /* process all the "freed" ranges in the file */
        if (dn->dn_free_ranges[txgoff] != NULL) {
                dnode_sync_free_range_arg_t dsfra;
                dsfra.dsfra_dnode = dn;
                dsfra.dsfra_tx = tx;
                mutex_enter(&dn->dn_mtx);
                range_tree_vacate(dn->dn_free_ranges[txgoff],
                    dnode_sync_free_range, &dsfra);
                range_tree_destroy(dn->dn_free_ranges[txgoff]);
                dn->dn_free_ranges[txgoff] = NULL;
                mutex_exit(&dn->dn_mtx);
        }

        if (freeing_dnode) {
                dn->dn_objset->os_freed_dnodes++;
                dnode_sync_free(dn, tx);
                return;
        }

        if (dn->dn_next_nlevels[txgoff]) {
                dnode_increase_indirection(dn, tx);
                dn->dn_next_nlevels[txgoff] = 0;
        }

        if (dn->dn_next_nblkptr[txgoff]) {
                /* this should only happen on a realloc */
                ASSERT(dn->dn_allocated_txg == tx->tx_txg);
                if (dn->dn_next_nblkptr[txgoff] > dnp->dn_nblkptr) {
                        /* zero the new blkptrs we are gaining */
                        bzero(dnp->dn_blkptr + dnp->dn_nblkptr,
                            sizeof (blkptr_t) *
                            (dn->dn_next_nblkptr[txgoff] - dnp->dn_nblkptr));
#ifdef ZFS_DEBUG
                } else {
                        int i;
                        ASSERT(dn->dn_next_nblkptr[txgoff] < dnp->dn_nblkptr);
                        /* the blkptrs we are losing better be unallocated */
                        for (i = dn->dn_next_nblkptr[txgoff];
                            i < dnp->dn_nblkptr; i++)
                                ASSERT(BP_IS_HOLE(&dnp->dn_blkptr[i]));
#endif
                }
                mutex_enter(&dn->dn_mtx);
                dnp->dn_nblkptr = dn->dn_next_nblkptr[txgoff];
                dn->dn_next_nblkptr[txgoff] = 0;
                mutex_exit(&dn->dn_mtx);
        }

        dbuf_sync_list(list, dn->dn_phys->dn_nlevels - 1, tx);

        if (!DMU_OBJECT_IS_SPECIAL(dn->dn_object)) {
                ASSERT3P(list_head(list), ==, NULL);
                dnode_rele(dn, (void *)(uintptr_t)tx->tx_txg);
        }

        /*
         * Although we have dropped our reference to the dnode, it
         * can't be evicted until its written, and we haven't yet
         * initiated the IO for the dnode's dbuf.
         */
}