Reduce dirty records memory usage

[zfs.git] / module / zfs / sa.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) 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2013, 2017 by Delphix. All rights reserved.
 * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
 * Copyright 2023 RackTop Systems, Inc.
 */

#include <sys/zfs_context.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/dmu.h>
#include <sys/dmu_impl.h>
#include <sys/dmu_objset.h>
#include <sys/dmu_tx.h>
#include <sys/dbuf.h>
#include <sys/dnode.h>
#include <sys/zap.h>
#include <sys/sa.h>
#include <sys/sunddi.h>
#include <sys/sa_impl.h>
#include <sys/errno.h>
#include <sys/zfs_context.h>

#ifdef _KERNEL
#include <sys/zfs_znode.h>
#endif

/*
 * ZFS System attributes:
 *
 * A generic mechanism to allow for arbitrary attributes
 * to be stored in a dnode.  The data will be stored in the bonus buffer of
 * the dnode and if necessary a special "spill" block will be used to handle
 * overflow situations.  The spill block will be sized to fit the data
 * from 512 - 128K.  When a spill block is used the BP (blkptr_t) for the
 * spill block is stored at the end of the current bonus buffer.  Any
 * attributes that would be in the way of the blkptr_t will be relocated
 * into the spill block.
 *
 * Attribute registration:
 *
 * Stored persistently on a per dataset basis
 * a mapping between attribute "string" names and their actual attribute
 * numeric values, length, and byteswap function.  The names are only used
 * during registration.  All  attributes are known by their unique attribute
 * id value.  If an attribute can have a variable size then the value
 * 0 will be used to indicate this.
 *
 * Attribute Layout:
 *
 * Attribute layouts are a way to compactly store multiple attributes, but
 * without taking the overhead associated with managing each attribute
 * individually.  Since you will typically have the same set of attributes
 * stored in the same order a single table will be used to represent that
 * layout.  The ZPL for example will usually have only about 10 different
 * layouts (regular files, device files, symlinks,
 * regular files + scanstamp, files/dir with extended attributes, and then
 * you have the possibility of all of those minus ACL, because it would
 * be kicked out into the spill block)
 *
 * Layouts are simply an array of the attributes and their
 * ordering i.e. [0, 1, 4, 5, 2]
 *
 * Each distinct layout is given a unique layout number and that is what's
 * stored in the header at the beginning of the SA data buffer.
 *
 * A layout only covers a single dbuf (bonus or spill).  If a set of
 * attributes is split up between the bonus buffer and a spill buffer then
 * two different layouts will be used.  This allows us to byteswap the
 * spill without looking at the bonus buffer and keeps the on disk format of
 * the bonus and spill buffer the same.
 *
 * Adding a single attribute will cause the entire set of attributes to
 * be rewritten and could result in a new layout number being constructed
 * as part of the rewrite if no such layout exists for the new set of
 * attributes.  The new attribute will be appended to the end of the already
 * existing attributes.
 *
 * Both the attribute registration and attribute layout information are
 * stored in normal ZAP attributes.  Their should be a small number of
 * known layouts and the set of attributes is assumed to typically be quite
 * small.
 *
 * The registered attributes and layout "table" information is maintained
 * in core and a special "sa_os_t" is attached to the objset_t.
 *
 * A special interface is provided to allow for quickly applying
 * a large set of attributes at once.  sa_replace_all_by_template() is
 * used to set an array of attributes.  This is used by the ZPL when
 * creating a brand new file.  The template that is passed into the function
 * specifies the attribute, size for variable length attributes, location of
 * data and special "data locator" function if the data isn't in a contiguous
 * location.
 *
 * Byteswap implications:
 *
 * Since the SA attributes are not entirely self describing we can't do
 * the normal byteswap processing.  The special ZAP layout attribute and
 * attribute registration attributes define the byteswap function and the
 * size of the attributes, unless it is variable sized.
 * The normal ZFS byteswapping infrastructure assumes you don't need
 * to read any objects in order to do the necessary byteswapping.  Whereas
 * SA attributes can only be properly byteswapped if the dataset is opened
 * and the layout/attribute ZAP attributes are available.  Because of this
 * the SA attributes will be byteswapped when they are first accessed by
 * the SA code that will read the SA data.
 */

typedef void (sa_iterfunc_t)(void *hdr, void *addr, sa_attr_type_t,
    uint16_t length, int length_idx, boolean_t, void *userp);

static int sa_build_index(sa_handle_t *hdl, sa_buf_type_t buftype);
static void sa_idx_tab_hold(objset_t *os, sa_idx_tab_t *idx_tab);
static sa_idx_tab_t *sa_find_idx_tab(objset_t *os, dmu_object_type_t bonustype,
    sa_hdr_phys_t *hdr);
static void sa_idx_tab_rele(objset_t *os, void *arg);
static void sa_copy_data(sa_data_locator_t *func, void *start, void *target,
    int buflen);
static int sa_modify_attrs(sa_handle_t *hdl, sa_attr_type_t newattr,
    sa_data_op_t action, sa_data_locator_t *locator, void *datastart,
    uint16_t buflen, dmu_tx_t *tx);

static arc_byteswap_func_t sa_bswap_table[] = {
        byteswap_uint64_array,
        byteswap_uint32_array,
        byteswap_uint16_array,
        byteswap_uint8_array,
        zfs_acl_byteswap,
};

#ifdef HAVE_EFFICIENT_UNALIGNED_ACCESS
#define SA_COPY_DATA(f, s, t, l)                                \
do {                                                            \
        if (f == NULL) {                                        \
                if (l == 8) {                                   \
                        *(uint64_t *)t = *(uint64_t *)s;        \
                } else if (l == 16) {                           \
                        *(uint64_t *)t = *(uint64_t *)s;        \
                        *(uint64_t *)((uintptr_t)t + 8) =       \
                            *(uint64_t *)((uintptr_t)s + 8);    \
                } else {                                        \
                        memcpy(t, s, l);                                \
                }                                               \
        } else {                                                \
                sa_copy_data(f, s, t, l);                       \
        }                                                       \
} while (0)
#else
#define SA_COPY_DATA(f, s, t, l)        sa_copy_data(f, s, t, l)
#endif

/*
 * This table is fixed and cannot be changed.  Its purpose is to
 * allow the SA code to work with both old/new ZPL file systems.
 * It contains the list of legacy attributes.  These attributes aren't
 * stored in the "attribute" registry zap objects, since older ZPL file systems
 * won't have the registry.  Only objsets of type ZFS_TYPE_FILESYSTEM will
 * use this static table.
 */
static const sa_attr_reg_t sa_legacy_attrs[] = {
        {"ZPL_ATIME", sizeof (uint64_t) * 2, SA_UINT64_ARRAY, 0},
        {"ZPL_MTIME", sizeof (uint64_t) * 2, SA_UINT64_ARRAY, 1},
        {"ZPL_CTIME", sizeof (uint64_t) * 2, SA_UINT64_ARRAY, 2},
        {"ZPL_CRTIME", sizeof (uint64_t) * 2, SA_UINT64_ARRAY, 3},
        {"ZPL_GEN", sizeof (uint64_t), SA_UINT64_ARRAY, 4},
        {"ZPL_MODE", sizeof (uint64_t), SA_UINT64_ARRAY, 5},
        {"ZPL_SIZE", sizeof (uint64_t), SA_UINT64_ARRAY, 6},
        {"ZPL_PARENT", sizeof (uint64_t), SA_UINT64_ARRAY, 7},
        {"ZPL_LINKS", sizeof (uint64_t), SA_UINT64_ARRAY, 8},
        {"ZPL_XATTR", sizeof (uint64_t), SA_UINT64_ARRAY, 9},
        {"ZPL_RDEV", sizeof (uint64_t), SA_UINT64_ARRAY, 10},
        {"ZPL_FLAGS", sizeof (uint64_t), SA_UINT64_ARRAY, 11},
        {"ZPL_UID", sizeof (uint64_t), SA_UINT64_ARRAY, 12},
        {"ZPL_GID", sizeof (uint64_t), SA_UINT64_ARRAY, 13},
        {"ZPL_PAD", sizeof (uint64_t) * 4, SA_UINT64_ARRAY, 14},
        {"ZPL_ZNODE_ACL", 88, SA_UINT8_ARRAY, 15},
};

/*
 * This is only used for objects of type DMU_OT_ZNODE
 */
static const sa_attr_type_t sa_legacy_zpl_layout[] = {
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
};

/*
 * Special dummy layout used for buffers with no attributes.
 */
static const sa_attr_type_t sa_dummy_zpl_layout[] = { 0 };

static const size_t sa_legacy_attr_count = ARRAY_SIZE(sa_legacy_attrs);
static kmem_cache_t *sa_cache = NULL;

static int
sa_cache_constructor(void *buf, void *unused, int kmflag)
{
        (void) unused, (void) kmflag;
        sa_handle_t *hdl = buf;

        mutex_init(&hdl->sa_lock, NULL, MUTEX_DEFAULT, NULL);
        return (0);
}

static void
sa_cache_destructor(void *buf, void *unused)
{
        (void) unused;
        sa_handle_t *hdl = buf;
        mutex_destroy(&hdl->sa_lock);
}

void
sa_cache_init(void)
{
        sa_cache = kmem_cache_create("sa_cache",
            sizeof (sa_handle_t), 0, sa_cache_constructor,
            sa_cache_destructor, NULL, NULL, NULL, KMC_RECLAIMABLE);
}

void
sa_cache_fini(void)
{
        if (sa_cache)
                kmem_cache_destroy(sa_cache);
}

static int
layout_num_compare(const void *arg1, const void *arg2)
{
        const sa_lot_t *node1 = (const sa_lot_t *)arg1;
        const sa_lot_t *node2 = (const sa_lot_t *)arg2;

        return (TREE_CMP(node1->lot_num, node2->lot_num));
}

static int
layout_hash_compare(const void *arg1, const void *arg2)
{
        const sa_lot_t *node1 = (const sa_lot_t *)arg1;
        const sa_lot_t *node2 = (const sa_lot_t *)arg2;

        int cmp = TREE_CMP(node1->lot_hash, node2->lot_hash);
        if (likely(cmp))
                return (cmp);

        return (TREE_CMP(node1->lot_instance, node2->lot_instance));
}

static boolean_t
sa_layout_equal(sa_lot_t *tbf, sa_attr_type_t *attrs, int count)
{
        int i;

        if (count != tbf->lot_attr_count)
                return (1);

        for (i = 0; i != count; i++) {
                if (attrs[i] != tbf->lot_attrs[i])
                        return (1);
        }
        return (0);
}

#define SA_ATTR_HASH(attr) (zfs_crc64_table[(-1ULL ^ attr) & 0xFF])

static uint64_t
sa_layout_info_hash(const sa_attr_type_t *attrs, int attr_count)
{
        uint64_t crc = -1ULL;

        for (int i = 0; i != attr_count; i++)
                crc ^= SA_ATTR_HASH(attrs[i]);

        return (crc);
}

static int
sa_get_spill(sa_handle_t *hdl)
{
        int rc;
        if (hdl->sa_spill == NULL) {
                if ((rc = dmu_spill_hold_existing(hdl->sa_bonus, NULL,
                    &hdl->sa_spill)) == 0)
                        VERIFY(0 == sa_build_index(hdl, SA_SPILL));
        } else {
                rc = 0;
        }

        return (rc);
}

/*
 * Main attribute lookup/update function
 * returns 0 for success or non zero for failures
 *
 * Operates on bulk array, first failure will abort further processing
 */
static int
sa_attr_op(sa_handle_t *hdl, sa_bulk_attr_t *bulk, int count,
    sa_data_op_t data_op, dmu_tx_t *tx)
{
        sa_os_t *sa = hdl->sa_os->os_sa;
        int i;
        int error = 0;
        sa_buf_type_t buftypes;

        buftypes = 0;

        ASSERT(count > 0);
        for (i = 0; i != count; i++) {
                ASSERT(bulk[i].sa_attr <= hdl->sa_os->os_sa->sa_num_attrs);

                bulk[i].sa_addr = NULL;
                /* First check the bonus buffer */

                if (hdl->sa_bonus_tab && TOC_ATTR_PRESENT(
                    hdl->sa_bonus_tab->sa_idx_tab[bulk[i].sa_attr])) {
                        SA_ATTR_INFO(sa, hdl->sa_bonus_tab,
                            SA_GET_HDR(hdl, SA_BONUS),
                            bulk[i].sa_attr, bulk[i], SA_BONUS, hdl);
                        if (tx && !(buftypes & SA_BONUS)) {
                                dmu_buf_will_dirty(hdl->sa_bonus, tx);
                                buftypes |= SA_BONUS;
                        }
                }
                if (bulk[i].sa_addr == NULL &&
                    ((error = sa_get_spill(hdl)) == 0)) {
                        if (TOC_ATTR_PRESENT(
                            hdl->sa_spill_tab->sa_idx_tab[bulk[i].sa_attr])) {
                                SA_ATTR_INFO(sa, hdl->sa_spill_tab,
                                    SA_GET_HDR(hdl, SA_SPILL),
                                    bulk[i].sa_attr, bulk[i], SA_SPILL, hdl);
                                if (tx && !(buftypes & SA_SPILL) &&
                                    bulk[i].sa_size == bulk[i].sa_length) {
                                        dmu_buf_will_dirty(hdl->sa_spill, tx);
                                        buftypes |= SA_SPILL;
                                }
                        }
                }
                if (error && error != ENOENT) {
                        return ((error == ECKSUM) ? EIO : error);
                }

                switch (data_op) {
                case SA_LOOKUP:
                        if (bulk[i].sa_addr == NULL)
                                return (SET_ERROR(ENOENT));
                        if (bulk[i].sa_data) {
                                SA_COPY_DATA(bulk[i].sa_data_func,
                                    bulk[i].sa_addr, bulk[i].sa_data,
                                    MIN(bulk[i].sa_size, bulk[i].sa_length));
                        }
                        continue;

                case SA_UPDATE:
                        /* existing rewrite of attr */
                        if (bulk[i].sa_addr &&
                            bulk[i].sa_size == bulk[i].sa_length) {
                                SA_COPY_DATA(bulk[i].sa_data_func,
                                    bulk[i].sa_data, bulk[i].sa_addr,
                                    bulk[i].sa_length);
                                continue;
                        } else if (bulk[i].sa_addr) { /* attr size change */
                                error = sa_modify_attrs(hdl, bulk[i].sa_attr,
                                    SA_REPLACE, bulk[i].sa_data_func,
                                    bulk[i].sa_data, bulk[i].sa_length, tx);
                        } else { /* adding new attribute */
                                error = sa_modify_attrs(hdl, bulk[i].sa_attr,
                                    SA_ADD, bulk[i].sa_data_func,
                                    bulk[i].sa_data, bulk[i].sa_length, tx);
                        }
                        if (error)
                                return (error);
                        break;
                default:
                        break;
                }
        }
        return (error);
}

static sa_lot_t *
sa_add_layout_entry(objset_t *os, const sa_attr_type_t *attrs, int attr_count,
    uint64_t lot_num, uint64_t hash, boolean_t zapadd, dmu_tx_t *tx)
{
        sa_os_t *sa = os->os_sa;
        sa_lot_t *tb, *findtb;
        int i;
        avl_index_t loc;

        ASSERT(MUTEX_HELD(&sa->sa_lock));
        tb = kmem_zalloc(sizeof (sa_lot_t), KM_SLEEP);
        tb->lot_attr_count = attr_count;
        tb->lot_attrs = kmem_alloc(sizeof (sa_attr_type_t) * attr_count,
            KM_SLEEP);
        memcpy(tb->lot_attrs, attrs, sizeof (sa_attr_type_t) * attr_count);
        tb->lot_num = lot_num;
        tb->lot_hash = hash;
        tb->lot_instance = 0;

        if (zapadd) {
                char attr_name[8];

                if (sa->sa_layout_attr_obj == 0) {
                        sa->sa_layout_attr_obj = zap_create_link(os,
                            DMU_OT_SA_ATTR_LAYOUTS,
                            sa->sa_master_obj, SA_LAYOUTS, tx);
                }

                (void) snprintf(attr_name, sizeof (attr_name),
                    "%d", (int)lot_num);
                VERIFY(0 == zap_update(os, os->os_sa->sa_layout_attr_obj,
                    attr_name, 2, attr_count, attrs, tx));
        }

        list_create(&tb->lot_idx_tab, sizeof (sa_idx_tab_t),
            offsetof(sa_idx_tab_t, sa_next));

        for (i = 0; i != attr_count; i++) {
                if (sa->sa_attr_table[tb->lot_attrs[i]].sa_length == 0)
                        tb->lot_var_sizes++;
        }

        avl_add(&sa->sa_layout_num_tree, tb);

        /* verify we don't have a hash collision */
        if ((findtb = avl_find(&sa->sa_layout_hash_tree, tb, &loc)) != NULL) {
                for (; findtb && findtb->lot_hash == hash;
                    findtb = AVL_NEXT(&sa->sa_layout_hash_tree, findtb)) {
                        if (findtb->lot_instance != tb->lot_instance)
                                break;
                        tb->lot_instance++;
                }
        }
        avl_add(&sa->sa_layout_hash_tree, tb);
        return (tb);
}

static void
sa_find_layout(objset_t *os, uint64_t hash, sa_attr_type_t *attrs,
    int count, dmu_tx_t *tx, sa_lot_t **lot)
{
        sa_lot_t *tb, tbsearch;
        avl_index_t loc;
        sa_os_t *sa = os->os_sa;
        boolean_t found = B_FALSE;

        mutex_enter(&sa->sa_lock);
        tbsearch.lot_hash = hash;
        tbsearch.lot_instance = 0;
        tb = avl_find(&sa->sa_layout_hash_tree, &tbsearch, &loc);
        if (tb) {
                for (; tb && tb->lot_hash == hash;
                    tb = AVL_NEXT(&sa->sa_layout_hash_tree, tb)) {
                        if (sa_layout_equal(tb, attrs, count) == 0) {
                                found = B_TRUE;
                                break;
                        }
                }
        }
        if (!found) {
                tb = sa_add_layout_entry(os, attrs, count,
                    avl_numnodes(&sa->sa_layout_num_tree), hash, B_TRUE, tx);
        }
        mutex_exit(&sa->sa_lock);
        *lot = tb;
}

static int
sa_resize_spill(sa_handle_t *hdl, uint32_t size, dmu_tx_t *tx)
{
        int error;
        uint32_t blocksize;

        if (size == 0) {
                blocksize = SPA_MINBLOCKSIZE;
        } else if (size > SPA_OLD_MAXBLOCKSIZE) {
                ASSERT(0);
                return (SET_ERROR(EFBIG));
        } else {
                blocksize = P2ROUNDUP_TYPED(size, SPA_MINBLOCKSIZE, uint32_t);
        }

        error = dbuf_spill_set_blksz(hdl->sa_spill, blocksize, tx);
        ASSERT(error == 0);
        return (error);
}

static void
sa_copy_data(sa_data_locator_t *func, void *datastart, void *target, int buflen)
{
        if (func == NULL) {
                memcpy(target, datastart, buflen);
        } else {
                boolean_t start;
                int bytes;
                void *dataptr;
                void *saptr = target;
                uint32_t length;

                start = B_TRUE;
                bytes = 0;
                while (bytes < buflen) {
                        func(&dataptr, &length, buflen, start, datastart);
                        memcpy(saptr, dataptr, length);
                        saptr = (void *)((caddr_t)saptr + length);
                        bytes += length;
                        start = B_FALSE;
                }
        }
}

/*
 * Determine several different values pertaining to system attribute
 * buffers.
 *
 * Return the size of the sa_hdr_phys_t header for the buffer. Each
 * variable length attribute except the first contributes two bytes to
 * the header size, which is then rounded up to an 8-byte boundary.
 *
 * The following output parameters are also computed.
 *
 *  index - The index of the first attribute in attr_desc that will
 *  spill over. Only valid if will_spill is set.
 *
 *  total - The total number of bytes of all system attributes described
 *  in attr_desc.
 *
 *  will_spill - Set when spilling is necessary. It is only set when
 *  the buftype is SA_BONUS.
 */
static int
sa_find_sizes(sa_os_t *sa, sa_bulk_attr_t *attr_desc, int attr_count,
    dmu_buf_t *db, sa_buf_type_t buftype, int full_space, int *index,
    int *total, boolean_t *will_spill)
{
        int var_size_count = 0;
        int i;
        int hdrsize;
        int extra_hdrsize;

        if (buftype == SA_BONUS && sa->sa_force_spill) {
                *total = 0;
                *index = 0;
                *will_spill = B_TRUE;
                return (0);
        }

        *index = -1;
        *total = 0;
        *will_spill = B_FALSE;

        extra_hdrsize = 0;
        hdrsize = (SA_BONUSTYPE_FROM_DB(db) == DMU_OT_ZNODE) ? 0 :
            sizeof (sa_hdr_phys_t);

        ASSERT(IS_P2ALIGNED(full_space, 8));

        for (i = 0; i != attr_count; i++) {
                boolean_t is_var_sz, might_spill_here;
                int tmp_hdrsize;

                *total = P2ROUNDUP(*total, 8);
                *total += attr_desc[i].sa_length;
                if (*will_spill)
                        continue;

                is_var_sz = (SA_REGISTERED_LEN(sa, attr_desc[i].sa_attr) == 0);
                if (is_var_sz)
                        var_size_count++;

                /*
                 * Calculate what the SA header size would be if this
                 * attribute doesn't spill.
                 */
                tmp_hdrsize = hdrsize + ((is_var_sz && var_size_count > 1) ?
                    sizeof (uint16_t) : 0);

                /*
                 * Check whether this attribute spans into the space
                 * that would be used by the spill block pointer should
                 * a spill block be needed.
                 */
                might_spill_here =
                    buftype == SA_BONUS && *index == -1 &&
                    (*total + P2ROUNDUP(tmp_hdrsize, 8)) >
                    (full_space - sizeof (blkptr_t));

                if (is_var_sz && var_size_count > 1) {
                        if (buftype == SA_SPILL ||
                            tmp_hdrsize + *total < full_space) {
                                /*
                                 * Record the extra header size in case this
                                 * increase needs to be reversed due to
                                 * spill-over.
                                 */
                                hdrsize = tmp_hdrsize;
                                if (*index != -1 || might_spill_here)
                                        extra_hdrsize += sizeof (uint16_t);
                        } else {
                                ASSERT(buftype == SA_BONUS);
                                if (*index == -1)
                                        *index = i;
                                *will_spill = B_TRUE;
                                continue;
                        }
                }

                /*
                 * Store index of where spill *could* occur. Then
                 * continue to count the remaining attribute sizes. The
                 * sum is used later for sizing bonus and spill buffer.
                 */
                if (might_spill_here)
                        *index = i;

                if ((*total + P2ROUNDUP(hdrsize, 8)) > full_space &&
                    buftype == SA_BONUS)
                        *will_spill = B_TRUE;
        }

        if (*will_spill)
                hdrsize -= extra_hdrsize;

        hdrsize = P2ROUNDUP(hdrsize, 8);
        return (hdrsize);
}

#define BUF_SPACE_NEEDED(total, header) (total + header)

/*
 * Find layout that corresponds to ordering of attributes
 * If not found a new layout number is created and added to
 * persistent layout tables.
 */
static int
sa_build_layouts(sa_handle_t *hdl, sa_bulk_attr_t *attr_desc, int attr_count,
    dmu_tx_t *tx)
{
        sa_os_t *sa = hdl->sa_os->os_sa;
        uint64_t hash;
        sa_buf_type_t buftype;
        sa_hdr_phys_t *sahdr;
        void *data_start;
        sa_attr_type_t *attrs, *attrs_start;
        int i, lot_count;
        int dnodesize;
        int spill_idx;
        int hdrsize;
        int spillhdrsize = 0;
        int used;
        dmu_object_type_t bonustype;
        sa_lot_t *lot;
        int len_idx;
        int spill_used;
        int bonuslen;
        boolean_t spilling;

        dmu_buf_will_dirty(hdl->sa_bonus, tx);
        bonustype = SA_BONUSTYPE_FROM_DB(hdl->sa_bonus);
        dmu_object_dnsize_from_db(hdl->sa_bonus, &dnodesize);
        bonuslen = DN_BONUS_SIZE(dnodesize);

        /* first determine bonus header size and sum of all attributes */
        hdrsize = sa_find_sizes(sa, attr_desc, attr_count, hdl->sa_bonus,
            SA_BONUS, bonuslen, &spill_idx, &used, &spilling);

        if (used > SPA_OLD_MAXBLOCKSIZE)
                return (SET_ERROR(EFBIG));

        VERIFY0(dmu_set_bonus(hdl->sa_bonus, spilling ?
            MIN(bonuslen - sizeof (blkptr_t), used + hdrsize) :
            used + hdrsize, tx));

        ASSERT((bonustype == DMU_OT_ZNODE && spilling == 0) ||
            bonustype == DMU_OT_SA);

        /* setup and size spill buffer when needed */
        if (spilling) {
                boolean_t dummy;

                if (hdl->sa_spill == NULL) {
                        VERIFY(dmu_spill_hold_by_bonus(hdl->sa_bonus, 0, NULL,
                            &hdl->sa_spill) == 0);
                }
                dmu_buf_will_dirty(hdl->sa_spill, tx);

                spillhdrsize = sa_find_sizes(sa, &attr_desc[spill_idx],
                    attr_count - spill_idx, hdl->sa_spill, SA_SPILL,
                    hdl->sa_spill->db_size, &i, &spill_used, &dummy);

                if (spill_used > SPA_OLD_MAXBLOCKSIZE)
                        return (SET_ERROR(EFBIG));

                if (BUF_SPACE_NEEDED(spill_used, spillhdrsize) >
                    hdl->sa_spill->db_size)
                        VERIFY(0 == sa_resize_spill(hdl,
                            BUF_SPACE_NEEDED(spill_used, spillhdrsize), tx));
        }

        /* setup starting pointers to lay down data */
        data_start = (void *)((uintptr_t)hdl->sa_bonus->db_data + hdrsize);
        sahdr = (sa_hdr_phys_t *)hdl->sa_bonus->db_data;
        buftype = SA_BONUS;

        attrs_start = attrs = kmem_alloc(sizeof (sa_attr_type_t) * attr_count,
            KM_SLEEP);
        lot_count = 0;

        for (i = 0, len_idx = 0, hash = -1ULL; i != attr_count; i++) {
                uint16_t length;

                ASSERT(IS_P2ALIGNED(data_start, 8));
                attrs[i] = attr_desc[i].sa_attr;
                length = SA_REGISTERED_LEN(sa, attrs[i]);
                if (length == 0)
                        length = attr_desc[i].sa_length;

                if (spilling && i == spill_idx) { /* switch to spill buffer */
                        VERIFY(bonustype == DMU_OT_SA);
                        if (buftype == SA_BONUS && !sa->sa_force_spill) {
                                sa_find_layout(hdl->sa_os, hash, attrs_start,
                                    lot_count, tx, &lot);
                                SA_SET_HDR(sahdr, lot->lot_num, hdrsize);
                        }

                        buftype = SA_SPILL;
                        hash = -1ULL;
                        len_idx = 0;

                        sahdr = (sa_hdr_phys_t *)hdl->sa_spill->db_data;
                        sahdr->sa_magic = SA_MAGIC;
                        data_start = (void *)((uintptr_t)sahdr +
                            spillhdrsize);
                        attrs_start = &attrs[i];
                        lot_count = 0;
                }
                hash ^= SA_ATTR_HASH(attrs[i]);
                attr_desc[i].sa_addr = data_start;
                attr_desc[i].sa_size = length;
                SA_COPY_DATA(attr_desc[i].sa_data_func, attr_desc[i].sa_data,
                    data_start, length);
                if (sa->sa_attr_table[attrs[i]].sa_length == 0) {
                        sahdr->sa_lengths[len_idx++] = length;
                }
                data_start = (void *)P2ROUNDUP(((uintptr_t)data_start +
                    length), 8);
                lot_count++;
        }

        sa_find_layout(hdl->sa_os, hash, attrs_start, lot_count, tx, &lot);

        /*
         * Verify that old znodes always have layout number 0.
         * Must be DMU_OT_SA for arbitrary layouts
         */
        VERIFY((bonustype == DMU_OT_ZNODE && lot->lot_num == 0) ||
            (bonustype == DMU_OT_SA && lot->lot_num > 1));

        if (bonustype == DMU_OT_SA) {
                SA_SET_HDR(sahdr, lot->lot_num,
                    buftype == SA_BONUS ? hdrsize : spillhdrsize);
        }

        kmem_free(attrs, sizeof (sa_attr_type_t) * attr_count);
        if (hdl->sa_bonus_tab) {
                sa_idx_tab_rele(hdl->sa_os, hdl->sa_bonus_tab);
                hdl->sa_bonus_tab = NULL;
        }
        if (!sa->sa_force_spill)
                VERIFY(0 == sa_build_index(hdl, SA_BONUS));
        if (hdl->sa_spill) {
                sa_idx_tab_rele(hdl->sa_os, hdl->sa_spill_tab);
                if (!spilling) {
                        /*
                         * remove spill block that is no longer needed.
                         */
                        dmu_buf_rele(hdl->sa_spill, NULL);
                        hdl->sa_spill = NULL;
                        hdl->sa_spill_tab = NULL;
                        VERIFY(0 == dmu_rm_spill(hdl->sa_os,
                            sa_handle_object(hdl), tx));
                } else {
                        VERIFY(0 == sa_build_index(hdl, SA_SPILL));
                }
        }

        return (0);
}

static void
sa_free_attr_table(sa_os_t *sa)
{
        int i;

        if (sa->sa_attr_table == NULL)
                return;

        for (i = 0; i != sa->sa_num_attrs; i++) {
                if (sa->sa_attr_table[i].sa_name)
                        kmem_free(sa->sa_attr_table[i].sa_name,
                            strlen(sa->sa_attr_table[i].sa_name) + 1);
        }

        kmem_free(sa->sa_attr_table,
            sizeof (sa_attr_table_t) * sa->sa_num_attrs);

        sa->sa_attr_table = NULL;
}

static int
sa_attr_table_setup(objset_t *os, const sa_attr_reg_t *reg_attrs, int count)
{
        sa_os_t *sa = os->os_sa;
        uint64_t sa_attr_count = 0;
        uint64_t sa_reg_count = 0;
        int error = 0;
        uint64_t attr_value;
        sa_attr_table_t *tb;
        zap_cursor_t zc;
        zap_attribute_t *za;
        int registered_count = 0;
        int i;
        dmu_objset_type_t ostype = dmu_objset_type(os);

        sa->sa_user_table =
            kmem_zalloc(count * sizeof (sa_attr_type_t), KM_SLEEP);
        sa->sa_user_table_sz = count * sizeof (sa_attr_type_t);

        if (sa->sa_reg_attr_obj != 0) {
                error = zap_count(os, sa->sa_reg_attr_obj,
                    &sa_attr_count);

                /*
                 * Make sure we retrieved a count and that it isn't zero
                 */
                if (error || (error == 0 && sa_attr_count == 0)) {
                        if (error == 0)
                                error = SET_ERROR(EINVAL);
                        goto bail;
                }
                sa_reg_count = sa_attr_count;
        }

        if (ostype == DMU_OST_ZFS && sa_attr_count == 0)
                sa_attr_count += sa_legacy_attr_count;

        /* Allocate attribute numbers for attributes that aren't registered */
        for (i = 0; i != count; i++) {
                boolean_t found = B_FALSE;
                int j;

                if (ostype == DMU_OST_ZFS) {
                        for (j = 0; j != sa_legacy_attr_count; j++) {
                                if (strcmp(reg_attrs[i].sa_name,
                                    sa_legacy_attrs[j].sa_name) == 0) {
                                        sa->sa_user_table[i] =
                                            sa_legacy_attrs[j].sa_attr;
                                        found = B_TRUE;
                                }
                        }
                }
                if (found)
                        continue;

                if (sa->sa_reg_attr_obj)
                        error = zap_lookup(os, sa->sa_reg_attr_obj,
                            reg_attrs[i].sa_name, 8, 1, &attr_value);
                else
                        error = SET_ERROR(ENOENT);
                switch (error) {
                case ENOENT:
                        sa->sa_user_table[i] = (sa_attr_type_t)sa_attr_count;
                        sa_attr_count++;
                        break;
                case 0:
                        sa->sa_user_table[i] = ATTR_NUM(attr_value);
                        break;
                default:
                        goto bail;
                }
        }

        sa->sa_num_attrs = sa_attr_count;
        tb = sa->sa_attr_table =
            kmem_zalloc(sizeof (sa_attr_table_t) * sa_attr_count, KM_SLEEP);

        /*
         * Attribute table is constructed from requested attribute list,
         * previously foreign registered attributes, and also the legacy
         * ZPL set of attributes.
         */

        if (sa->sa_reg_attr_obj) {
                za = zap_attribute_alloc();
                for (zap_cursor_init(&zc, os, sa->sa_reg_attr_obj);
                    (error = zap_cursor_retrieve(&zc, za)) == 0;
                    zap_cursor_advance(&zc)) {
                        uint64_t value;
                        value  = za->za_first_integer;

                        registered_count++;
                        tb[ATTR_NUM(value)].sa_attr = ATTR_NUM(value);
                        tb[ATTR_NUM(value)].sa_length = ATTR_LENGTH(value);
                        tb[ATTR_NUM(value)].sa_byteswap = ATTR_BSWAP(value);
                        tb[ATTR_NUM(value)].sa_registered = B_TRUE;

                        if (tb[ATTR_NUM(value)].sa_name) {
                                continue;
                        }
                        tb[ATTR_NUM(value)].sa_name =
                            kmem_zalloc(strlen(za->za_name) +1, KM_SLEEP);
                        (void) strlcpy(tb[ATTR_NUM(value)].sa_name, za->za_name,
                            strlen(za->za_name) +1);
                }
                zap_cursor_fini(&zc);
                zap_attribute_free(za);
                /*
                 * Make sure we processed the correct number of registered
                 * attributes
                 */
                if (registered_count != sa_reg_count) {
                        ASSERT(error != 0);
                        goto bail;
                }

        }

        if (ostype == DMU_OST_ZFS) {
                for (i = 0; i != sa_legacy_attr_count; i++) {
                        if (tb[i].sa_name)
                                continue;
                        tb[i].sa_attr = sa_legacy_attrs[i].sa_attr;
                        tb[i].sa_length = sa_legacy_attrs[i].sa_length;
                        tb[i].sa_byteswap = sa_legacy_attrs[i].sa_byteswap;
                        tb[i].sa_registered = B_FALSE;
                        tb[i].sa_name =
                            kmem_zalloc(strlen(sa_legacy_attrs[i].sa_name) +1,
                            KM_SLEEP);
                        (void) strlcpy(tb[i].sa_name,
                            sa_legacy_attrs[i].sa_name,
                            strlen(sa_legacy_attrs[i].sa_name) + 1);
                }
        }

        for (i = 0; i != count; i++) {
                sa_attr_type_t attr_id;

                attr_id = sa->sa_user_table[i];
                if (tb[attr_id].sa_name)
                        continue;

                tb[attr_id].sa_length = reg_attrs[i].sa_length;
                tb[attr_id].sa_byteswap = reg_attrs[i].sa_byteswap;
                tb[attr_id].sa_attr = attr_id;
                tb[attr_id].sa_name =
                    kmem_zalloc(strlen(reg_attrs[i].sa_name) + 1, KM_SLEEP);
                (void) strlcpy(tb[attr_id].sa_name, reg_attrs[i].sa_name,
                    strlen(reg_attrs[i].sa_name) + 1);
        }

        sa->sa_need_attr_registration =
            (sa_attr_count != registered_count);

        return (0);
bail:
        kmem_free(sa->sa_user_table, count * sizeof (sa_attr_type_t));
        sa->sa_user_table = NULL;
        sa_free_attr_table(sa);
        ASSERT(error != 0);
        return (error);
}

int
sa_setup(objset_t *os, uint64_t sa_obj, const sa_attr_reg_t *reg_attrs,
    int count, sa_attr_type_t **user_table)
{
        zap_cursor_t zc;
        zap_attribute_t *za;
        sa_os_t *sa;
        dmu_objset_type_t ostype = dmu_objset_type(os);
        sa_attr_type_t *tb;
        int error;

        mutex_enter(&os->os_user_ptr_lock);
        if (os->os_sa) {
                mutex_enter(&os->os_sa->sa_lock);
                mutex_exit(&os->os_user_ptr_lock);
                tb = os->os_sa->sa_user_table;
                mutex_exit(&os->os_sa->sa_lock);
                *user_table = tb;
                return (0);
        }

        sa = kmem_zalloc(sizeof (sa_os_t), KM_SLEEP);
        mutex_init(&sa->sa_lock, NULL, MUTEX_NOLOCKDEP, NULL);
        sa->sa_master_obj = sa_obj;

        os->os_sa = sa;
        mutex_enter(&sa->sa_lock);
        mutex_exit(&os->os_user_ptr_lock);
        avl_create(&sa->sa_layout_num_tree, layout_num_compare,
            sizeof (sa_lot_t), offsetof(sa_lot_t, lot_num_node));
        avl_create(&sa->sa_layout_hash_tree, layout_hash_compare,
            sizeof (sa_lot_t), offsetof(sa_lot_t, lot_hash_node));

        if (sa_obj) {
                error = zap_lookup(os, sa_obj, SA_LAYOUTS,
                    8, 1, &sa->sa_layout_attr_obj);
                if (error != 0 && error != ENOENT)
                        goto fail;
                error = zap_lookup(os, sa_obj, SA_REGISTRY,
                    8, 1, &sa->sa_reg_attr_obj);
                if (error != 0 && error != ENOENT)
                        goto fail;
        }

        if ((error = sa_attr_table_setup(os, reg_attrs, count)) != 0)
                goto fail;

        if (sa->sa_layout_attr_obj != 0) {
                uint64_t layout_count;

                error = zap_count(os, sa->sa_layout_attr_obj,
                    &layout_count);

                /*
                 * Layout number count should be > 0
                 */
                if (error || (error == 0 && layout_count == 0)) {
                        if (error == 0)
                                error = SET_ERROR(EINVAL);
                        goto fail;
                }

                za = zap_attribute_alloc();
                for (zap_cursor_init(&zc, os, sa->sa_layout_attr_obj);
                    (error = zap_cursor_retrieve(&zc, za)) == 0;
                    zap_cursor_advance(&zc)) {
                        sa_attr_type_t *lot_attrs;
                        uint64_t lot_num;

                        lot_attrs = kmem_zalloc(sizeof (sa_attr_type_t) *
                            za->za_num_integers, KM_SLEEP);

                        if ((error = (zap_lookup(os, sa->sa_layout_attr_obj,
                            za->za_name, 2, za->za_num_integers,
                            lot_attrs))) != 0) {
                                kmem_free(lot_attrs, sizeof (sa_attr_type_t) *
                                    za->za_num_integers);
                                break;
                        }
                        VERIFY0(ddi_strtoull(za->za_name, NULL, 10,
                            (unsigned long long *)&lot_num));

                        (void) sa_add_layout_entry(os, lot_attrs,
                            za->za_num_integers, lot_num,
                            sa_layout_info_hash(lot_attrs,
                            za->za_num_integers), B_FALSE, NULL);
                        kmem_free(lot_attrs, sizeof (sa_attr_type_t) *
                            za->za_num_integers);
                }
                zap_cursor_fini(&zc);
                zap_attribute_free(za);

                /*
                 * Make sure layout count matches number of entries added
                 * to AVL tree
                 */
                if (avl_numnodes(&sa->sa_layout_num_tree) != layout_count) {
                        ASSERT(error != 0);
                        goto fail;
                }
        }

        /* Add special layout number for old ZNODES */
        if (ostype == DMU_OST_ZFS) {
                (void) sa_add_layout_entry(os, sa_legacy_zpl_layout,
                    sa_legacy_attr_count, 0,
                    sa_layout_info_hash(sa_legacy_zpl_layout,
                    sa_legacy_attr_count), B_FALSE, NULL);

                (void) sa_add_layout_entry(os, sa_dummy_zpl_layout, 0, 1,
                    0, B_FALSE, NULL);
        }
        *user_table = os->os_sa->sa_user_table;
        mutex_exit(&sa->sa_lock);
        return (0);
fail:
        os->os_sa = NULL;
        sa_free_attr_table(sa);
        if (sa->sa_user_table)
                kmem_free(sa->sa_user_table, sa->sa_user_table_sz);
        mutex_exit(&sa->sa_lock);
        avl_destroy(&sa->sa_layout_hash_tree);
        avl_destroy(&sa->sa_layout_num_tree);
        mutex_destroy(&sa->sa_lock);
        kmem_free(sa, sizeof (sa_os_t));
        return ((error == ECKSUM) ? EIO : error);
}

void
sa_tear_down(objset_t *os)
{
        sa_os_t *sa = os->os_sa;
        sa_lot_t *layout;
        void *cookie;

        kmem_free(sa->sa_user_table, sa->sa_user_table_sz);

        /* Free up attr table */

        sa_free_attr_table(sa);

        cookie = NULL;
        while ((layout =
            avl_destroy_nodes(&sa->sa_layout_hash_tree, &cookie))) {
                sa_idx_tab_t *tab;
                while ((tab = list_head(&layout->lot_idx_tab))) {
                        ASSERT(zfs_refcount_count(&tab->sa_refcount));
                        sa_idx_tab_rele(os, tab);
                }
        }

        cookie = NULL;
        while ((layout = avl_destroy_nodes(&sa->sa_layout_num_tree, &cookie))) {
                kmem_free(layout->lot_attrs,
                    sizeof (sa_attr_type_t) * layout->lot_attr_count);
                kmem_free(layout, sizeof (sa_lot_t));
        }

        avl_destroy(&sa->sa_layout_hash_tree);
        avl_destroy(&sa->sa_layout_num_tree);
        mutex_destroy(&sa->sa_lock);

        kmem_free(sa, sizeof (sa_os_t));
        os->os_sa = NULL;
}

static void
sa_build_idx_tab(void *hdr, void *attr_addr, sa_attr_type_t attr,
    uint16_t length, int length_idx, boolean_t var_length, void *userp)
{
        sa_idx_tab_t *idx_tab = userp;

        if (var_length) {
                ASSERT(idx_tab->sa_variable_lengths);
                idx_tab->sa_variable_lengths[length_idx] = length;
        }
        TOC_ATTR_ENCODE(idx_tab->sa_idx_tab[attr], length_idx,
            (uint32_t)((uintptr_t)attr_addr - (uintptr_t)hdr));
}

static void
sa_attr_iter(objset_t *os, sa_hdr_phys_t *hdr, dmu_object_type_t type,
    sa_iterfunc_t func, sa_lot_t *tab, void *userp)
{
        void *data_start;
        sa_lot_t *tb = tab;
        sa_lot_t search;
        avl_index_t loc;
        sa_os_t *sa = os->os_sa;
        int i;
        uint16_t *length_start = NULL;
        uint8_t length_idx = 0;

        if (tab == NULL) {
                search.lot_num = SA_LAYOUT_NUM(hdr, type);
                tb = avl_find(&sa->sa_layout_num_tree, &search, &loc);
                ASSERT(tb);
        }

        if (IS_SA_BONUSTYPE(type)) {
                data_start = (void *)P2ROUNDUP(((uintptr_t)hdr +
                    offsetof(sa_hdr_phys_t, sa_lengths) +
                    (sizeof (uint16_t) * tb->lot_var_sizes)), 8);
                length_start = hdr->sa_lengths;
        } else {
                data_start = hdr;
        }

        for (i = 0; i != tb->lot_attr_count; i++) {
                int attr_length, reg_length;
                uint8_t idx_len;

                reg_length = sa->sa_attr_table[tb->lot_attrs[i]].sa_length;
                IMPLY(reg_length == 0, IS_SA_BONUSTYPE(type));
                if (reg_length) {
                        attr_length = reg_length;
                        idx_len = 0;
                } else {
                        attr_length = length_start[length_idx];
                        idx_len = length_idx++;
                }

                func(hdr, data_start, tb->lot_attrs[i], attr_length,
                    idx_len, reg_length == 0 ? B_TRUE : B_FALSE, userp);

                data_start = (void *)P2ROUNDUP(((uintptr_t)data_start +
                    attr_length), 8);
        }
}

static void
sa_byteswap_cb(void *hdr, void *attr_addr, sa_attr_type_t attr,
    uint16_t length, int length_idx, boolean_t variable_length, void *userp)
{
        (void) hdr, (void) length_idx, (void) variable_length;
        sa_handle_t *hdl = userp;
        sa_os_t *sa = hdl->sa_os->os_sa;

        sa_bswap_table[sa->sa_attr_table[attr].sa_byteswap](attr_addr, length);
}

static void
sa_byteswap(sa_handle_t *hdl, sa_buf_type_t buftype)
{
        sa_hdr_phys_t *sa_hdr_phys = SA_GET_HDR(hdl, buftype);
        dmu_buf_impl_t *db;
        int num_lengths = 1;
        int i;
        sa_os_t *sa __maybe_unused = hdl->sa_os->os_sa;

        ASSERT(MUTEX_HELD(&sa->sa_lock));
        if (sa_hdr_phys->sa_magic == SA_MAGIC)
                return;

        db = SA_GET_DB(hdl, buftype);

        if (buftype == SA_SPILL) {
                arc_release(db->db_buf, NULL);
                arc_buf_thaw(db->db_buf);
        }

        sa_hdr_phys->sa_magic = BSWAP_32(sa_hdr_phys->sa_magic);
        sa_hdr_phys->sa_layout_info = BSWAP_16(sa_hdr_phys->sa_layout_info);

        /*
         * Determine number of variable lengths in header
         * The standard 8 byte header has one for free and a
         * 16 byte header would have 4 + 1;
         */
        if (SA_HDR_SIZE(sa_hdr_phys) > 8)
                num_lengths += (SA_HDR_SIZE(sa_hdr_phys) - 8) >> 1;
        for (i = 0; i != num_lengths; i++)
                sa_hdr_phys->sa_lengths[i] =
                    BSWAP_16(sa_hdr_phys->sa_lengths[i]);

        sa_attr_iter(hdl->sa_os, sa_hdr_phys, DMU_OT_SA,
            sa_byteswap_cb, NULL, hdl);

        if (buftype == SA_SPILL)
                arc_buf_freeze(((dmu_buf_impl_t *)hdl->sa_spill)->db_buf);
}

static int
sa_build_index(sa_handle_t *hdl, sa_buf_type_t buftype)
{
        sa_hdr_phys_t *sa_hdr_phys;
        dmu_buf_impl_t *db = SA_GET_DB(hdl, buftype);
        dmu_object_type_t bonustype = SA_BONUSTYPE_FROM_DB(db);
        sa_os_t *sa = hdl->sa_os->os_sa;
        sa_idx_tab_t *idx_tab;

        sa_hdr_phys = SA_GET_HDR(hdl, buftype);

        mutex_enter(&sa->sa_lock);

        /* Do we need to byteswap? */

        /* only check if not old znode */
        if (IS_SA_BONUSTYPE(bonustype) && sa_hdr_phys->sa_magic != SA_MAGIC &&
            sa_hdr_phys->sa_magic != 0) {
                if (BSWAP_32(sa_hdr_phys->sa_magic) != SA_MAGIC) {
                        mutex_exit(&sa->sa_lock);
                        zfs_dbgmsg("Buffer Header: %x != SA_MAGIC:%x "
                            "object=%#llx\n", sa_hdr_phys->sa_magic, SA_MAGIC,
                            (u_longlong_t)db->db.db_object);
                        return (SET_ERROR(EIO));
                }
                sa_byteswap(hdl, buftype);
        }

        idx_tab = sa_find_idx_tab(hdl->sa_os, bonustype, sa_hdr_phys);

        if (buftype == SA_BONUS)
                hdl->sa_bonus_tab = idx_tab;
        else
                hdl->sa_spill_tab = idx_tab;

        mutex_exit(&sa->sa_lock);
        return (0);
}

static void
sa_evict_sync(void *dbu)
{
        (void) dbu;
        panic("evicting sa dbuf\n");
}

static void
sa_idx_tab_rele(objset_t *os, void *arg)
{
        sa_os_t *sa = os->os_sa;
        sa_idx_tab_t *idx_tab = arg;

        if (idx_tab == NULL)
                return;

        mutex_enter(&sa->sa_lock);
        if (zfs_refcount_remove(&idx_tab->sa_refcount, NULL) == 0) {
                list_remove(&idx_tab->sa_layout->lot_idx_tab, idx_tab);
                if (idx_tab->sa_variable_lengths)
                        kmem_free(idx_tab->sa_variable_lengths,
                            sizeof (uint16_t) *
                            idx_tab->sa_layout->lot_var_sizes);
                zfs_refcount_destroy(&idx_tab->sa_refcount);
                kmem_free(idx_tab->sa_idx_tab,
                    sizeof (uint32_t) * sa->sa_num_attrs);
                kmem_free(idx_tab, sizeof (sa_idx_tab_t));
        }
        mutex_exit(&sa->sa_lock);
}

static void
sa_idx_tab_hold(objset_t *os, sa_idx_tab_t *idx_tab)
{
        sa_os_t *sa __maybe_unused = os->os_sa;

        ASSERT(MUTEX_HELD(&sa->sa_lock));
        (void) zfs_refcount_add(&idx_tab->sa_refcount, NULL);
}

void
sa_spill_rele(sa_handle_t *hdl)
{
        mutex_enter(&hdl->sa_lock);
        if (hdl->sa_spill) {
                sa_idx_tab_rele(hdl->sa_os, hdl->sa_spill_tab);
                dmu_buf_rele(hdl->sa_spill, NULL);
                hdl->sa_spill = NULL;
                hdl->sa_spill_tab = NULL;
        }
        mutex_exit(&hdl->sa_lock);
}

void
sa_handle_destroy(sa_handle_t *hdl)
{
        dmu_buf_t *db = hdl->sa_bonus;

        mutex_enter(&hdl->sa_lock);
        (void) dmu_buf_remove_user(db, &hdl->sa_dbu);

        if (hdl->sa_bonus_tab)
                sa_idx_tab_rele(hdl->sa_os, hdl->sa_bonus_tab);

        if (hdl->sa_spill_tab)
                sa_idx_tab_rele(hdl->sa_os, hdl->sa_spill_tab);

        dmu_buf_rele(hdl->sa_bonus, NULL);

        if (hdl->sa_spill)
                dmu_buf_rele(hdl->sa_spill, NULL);
        mutex_exit(&hdl->sa_lock);

        kmem_cache_free(sa_cache, hdl);
}

int
sa_handle_get_from_db(objset_t *os, dmu_buf_t *db, void *userp,
    sa_handle_type_t hdl_type, sa_handle_t **handlepp)
{
        int error = 0;
        sa_handle_t *handle = NULL;
#ifdef ZFS_DEBUG
        dmu_object_info_t doi;

        dmu_object_info_from_db(db, &doi);
        ASSERT(doi.doi_bonus_type == DMU_OT_SA ||
            doi.doi_bonus_type == DMU_OT_ZNODE);
#endif
        /* find handle, if it exists */
        /* if one doesn't exist then create a new one, and initialize it */

        if (hdl_type == SA_HDL_SHARED)
                handle = dmu_buf_get_user(db);

        if (handle == NULL) {
                sa_handle_t *winner = NULL;

                handle = kmem_cache_alloc(sa_cache, KM_SLEEP);
                handle->sa_dbu.dbu_evict_func_sync = NULL;
                handle->sa_dbu.dbu_evict_func_async = NULL;
                handle->sa_userp = userp;
                handle->sa_bonus = db;
                handle->sa_os = os;
                handle->sa_spill = NULL;
                handle->sa_bonus_tab = NULL;
                handle->sa_spill_tab = NULL;

                error = sa_build_index(handle, SA_BONUS);

                if (hdl_type == SA_HDL_SHARED) {
                        dmu_buf_init_user(&handle->sa_dbu, sa_evict_sync, NULL,
                            NULL);
                        winner = dmu_buf_set_user_ie(db, &handle->sa_dbu);
                }

                if (winner != NULL) {
                        kmem_cache_free(sa_cache, handle);
                        handle = winner;
                }
        }
        *handlepp = handle;

        return (error);
}

int
sa_handle_get(objset_t *objset, uint64_t objid, void *userp,
    sa_handle_type_t hdl_type, sa_handle_t **handlepp)
{
        dmu_buf_t *db;
        int error;

        if ((error = dmu_bonus_hold(objset, objid, NULL, &db)))
                return (error);

        return (sa_handle_get_from_db(objset, db, userp, hdl_type,
            handlepp));
}

int
sa_buf_hold(objset_t *objset, uint64_t obj_num, const void *tag, dmu_buf_t **db)
{
        return (dmu_bonus_hold(objset, obj_num, tag, db));
}

void
sa_buf_rele(dmu_buf_t *db, const void *tag)
{
        dmu_buf_rele(db, tag);
}

static int
sa_lookup_impl(sa_handle_t *hdl, sa_bulk_attr_t *bulk, int count)
{
        ASSERT(hdl);
        ASSERT(MUTEX_HELD(&hdl->sa_lock));
        return (sa_attr_op(hdl, bulk, count, SA_LOOKUP, NULL));
}

static int
sa_lookup_locked(sa_handle_t *hdl, sa_attr_type_t attr, void *buf,
    uint32_t buflen)
{
        int error;
        sa_bulk_attr_t bulk;

        VERIFY3U(buflen, <=, SA_ATTR_MAX_LEN);

        bulk.sa_attr = attr;
        bulk.sa_data = buf;
        bulk.sa_length = buflen;
        bulk.sa_data_func = NULL;

        ASSERT(hdl);
        error = sa_lookup_impl(hdl, &bulk, 1);
        return (error);
}

int
sa_lookup(sa_handle_t *hdl, sa_attr_type_t attr, void *buf, uint32_t buflen)
{
        int error;

        mutex_enter(&hdl->sa_lock);
        error = sa_lookup_locked(hdl, attr, buf, buflen);
        mutex_exit(&hdl->sa_lock);

        return (error);
}

/*
 * Return size of an attribute
 */

static int
sa_size_locked(sa_handle_t *hdl, sa_attr_type_t attr, int *size)
{
        sa_bulk_attr_t bulk;
        int error;

        bulk.sa_data = NULL;
        bulk.sa_attr = attr;
        bulk.sa_data_func = NULL;

        ASSERT(hdl);
        ASSERT(MUTEX_HELD(&hdl->sa_lock));
        if ((error = sa_attr_op(hdl, &bulk, 1, SA_LOOKUP, NULL)) != 0) {
                return (error);
        }
        *size = bulk.sa_size;

        return (0);
}

int
sa_size(sa_handle_t *hdl, sa_attr_type_t attr, int *size)
{
        int error;

        mutex_enter(&hdl->sa_lock);
        error = sa_size_locked(hdl, attr, size);
        mutex_exit(&hdl->sa_lock);

        return (error);
}

#ifdef _KERNEL
int
sa_lookup_uio(sa_handle_t *hdl, sa_attr_type_t attr, zfs_uio_t *uio)
{
        int error;
        sa_bulk_attr_t bulk;

        bulk.sa_data = NULL;
        bulk.sa_attr = attr;
        bulk.sa_data_func = NULL;

        ASSERT(hdl);

        mutex_enter(&hdl->sa_lock);
        if ((error = sa_attr_op(hdl, &bulk, 1, SA_LOOKUP, NULL)) == 0) {
                error = zfs_uiomove((void *)bulk.sa_addr, MIN(bulk.sa_size,
                    zfs_uio_resid(uio)), UIO_READ, uio);
        }
        mutex_exit(&hdl->sa_lock);
        return (error);
}

/*
 * For the existed object that is upgraded from old system, its ondisk layout
 * has no slot for the project ID attribute. But quota accounting logic needs
 * to access related slots by offset directly. So we need to adjust these old
 * objects' layout to make the project ID to some unified and fixed offset.
 */
int
sa_add_projid(sa_handle_t *hdl, dmu_tx_t *tx, uint64_t projid)
{
        znode_t *zp = sa_get_userdata(hdl);
        dmu_buf_t *db = sa_get_db(hdl);
        zfsvfs_t *zfsvfs = ZTOZSB(zp);
        int count = 0, err = 0;
        sa_bulk_attr_t *bulk, *attrs;
        zfs_acl_locator_cb_t locate = { 0 };
        uint64_t uid, gid, mode, rdev, xattr = 0, parent, gen, links;
        uint64_t crtime[2], mtime[2], ctime[2], atime[2];
        zfs_acl_phys_t znode_acl = { 0 };
        char scanstamp[AV_SCANSTAMP_SZ];
        char *dxattr_obj = NULL;
        int dxattr_size = 0;

        if (zp->z_acl_cached == NULL) {
                zfs_acl_t *aclp;

                mutex_enter(&zp->z_acl_lock);
                err = zfs_acl_node_read(zp, B_FALSE, &aclp, B_FALSE);
                mutex_exit(&zp->z_acl_lock);
                if (err != 0 && err != ENOENT)
                        return (err);
        }

        bulk = kmem_zalloc(sizeof (sa_bulk_attr_t) * ZPL_END, KM_SLEEP);
        attrs = kmem_zalloc(sizeof (sa_bulk_attr_t) * ZPL_END, KM_SLEEP);
        mutex_enter(&hdl->sa_lock);
        mutex_enter(&zp->z_lock);

        err = sa_lookup_locked(hdl, SA_ZPL_PROJID(zfsvfs), &projid,
            sizeof (uint64_t));
        if (unlikely(err == 0))
                /* Someone has added project ID attr by race. */
                err = EEXIST;
        if (err != ENOENT)
                goto out;

        /* First do a bulk query of the attributes that aren't cached */
        if (zp->z_is_sa) {
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MODE(zfsvfs), NULL,
                    &mode, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_GEN(zfsvfs), NULL,
                    &gen, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_UID(zfsvfs), NULL,
                    &uid, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_GID(zfsvfs), NULL,
                    &gid, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_PARENT(zfsvfs), NULL,
                    &parent, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_ATIME(zfsvfs), NULL,
                    &atime, 16);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MTIME(zfsvfs), NULL,
                    &mtime, 16);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CTIME(zfsvfs), NULL,
                    &ctime, 16);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CRTIME(zfsvfs), NULL,
                    &crtime, 16);
                if (Z_ISBLK(ZTOTYPE(zp)) || Z_ISCHR(ZTOTYPE(zp)))
                        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_RDEV(zfsvfs), NULL,
                            &rdev, 8);
        } else {
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_ATIME(zfsvfs), NULL,
                    &atime, 16);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MTIME(zfsvfs), NULL,
                    &mtime, 16);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CTIME(zfsvfs), NULL,
                    &ctime, 16);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_CRTIME(zfsvfs), NULL,
                    &crtime, 16);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_GEN(zfsvfs), NULL,
                    &gen, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MODE(zfsvfs), NULL,
                    &mode, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_PARENT(zfsvfs), NULL,
                    &parent, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_XATTR(zfsvfs), NULL,
                    &xattr, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_RDEV(zfsvfs), NULL,
                    &rdev, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_UID(zfsvfs), NULL,
                    &uid, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_GID(zfsvfs), NULL,
                    &gid, 8);
                SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_ZNODE_ACL(zfsvfs), NULL,
                    &znode_acl, 88);
        }
        err = sa_bulk_lookup_locked(hdl, bulk, count);
        if (err != 0)
                goto out;

        err = sa_lookup_locked(hdl, SA_ZPL_XATTR(zfsvfs), &xattr, 8);
        if (err != 0 && err != ENOENT)
                goto out;

        err = sa_size_locked(hdl, SA_ZPL_DXATTR(zfsvfs), &dxattr_size);
        if (err != 0 && err != ENOENT)
                goto out;
        if (dxattr_size != 0) {
                dxattr_obj = vmem_alloc(dxattr_size, KM_SLEEP);
                err = sa_lookup_locked(hdl, SA_ZPL_DXATTR(zfsvfs), dxattr_obj,
                    dxattr_size);
                if (err != 0 && err != ENOENT)
                        goto out;
        }

        zp->z_projid = projid;
        zp->z_pflags |= ZFS_PROJID;
        links = ZTONLNK(zp);
        count = 0;
        err = 0;

        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_MODE(zfsvfs), NULL, &mode, 8);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_SIZE(zfsvfs), NULL,
            &zp->z_size, 8);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_GEN(zfsvfs), NULL, &gen, 8);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_UID(zfsvfs), NULL, &uid, 8);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_GID(zfsvfs), NULL, &gid, 8);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_PARENT(zfsvfs), NULL, &parent, 8);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_FLAGS(zfsvfs), NULL,
            &zp->z_pflags, 8);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_ATIME(zfsvfs), NULL, &atime, 16);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_MTIME(zfsvfs), NULL, &mtime, 16);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_CTIME(zfsvfs), NULL, &ctime, 16);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_CRTIME(zfsvfs), NULL,
            &crtime, 16);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_LINKS(zfsvfs), NULL, &links, 8);
        SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_PROJID(zfsvfs), NULL, &projid, 8);

        if (Z_ISBLK(ZTOTYPE(zp)) || Z_ISCHR(ZTOTYPE(zp)))
                SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_RDEV(zfsvfs), NULL,
                    &rdev, 8);

        if (zp->z_acl_cached != NULL) {
                SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_DACL_COUNT(zfsvfs), NULL,
                    &zp->z_acl_cached->z_acl_count, 8);
                if (zp->z_acl_cached->z_version < ZFS_ACL_VERSION_FUID)
                        zfs_acl_xform(zp, zp->z_acl_cached, CRED());
                locate.cb_aclp = zp->z_acl_cached;
                SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_DACL_ACES(zfsvfs),
                    zfs_acl_data_locator, &locate,
                    zp->z_acl_cached->z_acl_bytes);
        }

        if (xattr)
                SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_XATTR(zfsvfs), NULL,
                    &xattr, 8);

        if (zp->z_pflags & ZFS_BONUS_SCANSTAMP) {
                memcpy(scanstamp,
                    (caddr_t)db->db_data + ZFS_OLD_ZNODE_PHYS_SIZE,
                    AV_SCANSTAMP_SZ);
                SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_SCANSTAMP(zfsvfs), NULL,
                    scanstamp, AV_SCANSTAMP_SZ);
                zp->z_pflags &= ~ZFS_BONUS_SCANSTAMP;
        }

        if (dxattr_obj) {
                SA_ADD_BULK_ATTR(attrs, count, SA_ZPL_DXATTR(zfsvfs),
                    NULL, dxattr_obj, dxattr_size);
        }

        VERIFY(dmu_set_bonustype(db, DMU_OT_SA, tx) == 0);
        VERIFY(sa_replace_all_by_template_locked(hdl, attrs, count, tx) == 0);
        if (znode_acl.z_acl_extern_obj) {
                VERIFY(0 == dmu_object_free(zfsvfs->z_os,
                    znode_acl.z_acl_extern_obj, tx));
        }

        zp->z_is_sa = B_TRUE;

out:
        mutex_exit(&zp->z_lock);
        mutex_exit(&hdl->sa_lock);
        kmem_free(attrs, sizeof (sa_bulk_attr_t) * ZPL_END);
        kmem_free(bulk, sizeof (sa_bulk_attr_t) * ZPL_END);
        if (dxattr_obj)
                vmem_free(dxattr_obj, dxattr_size);
        return (err);
}
#endif

static sa_idx_tab_t *
sa_find_idx_tab(objset_t *os, dmu_object_type_t bonustype, sa_hdr_phys_t *hdr)
{
        sa_idx_tab_t *idx_tab;
        sa_os_t *sa = os->os_sa;
        sa_lot_t *tb, search;
        avl_index_t loc;

        /*
         * Deterimine layout number.  If SA node and header == 0 then
         * force the index table to the dummy "1" empty layout.
         *
         * The layout number would only be zero for a newly created file
         * that has not added any attributes yet, or with crypto enabled which
         * doesn't write any attributes to the bonus buffer.
         */

        search.lot_num = SA_LAYOUT_NUM(hdr, bonustype);

        tb = avl_find(&sa->sa_layout_num_tree, &search, &loc);

        /* Verify header size is consistent with layout information */
        ASSERT(tb);
        ASSERT((IS_SA_BONUSTYPE(bonustype) &&
            SA_HDR_SIZE_MATCH_LAYOUT(hdr, tb)) || !IS_SA_BONUSTYPE(bonustype) ||
            (IS_SA_BONUSTYPE(bonustype) && hdr->sa_layout_info == 0));

        /*
         * See if any of the already existing TOC entries can be reused?
         */

        for (idx_tab = list_head(&tb->lot_idx_tab); idx_tab;
            idx_tab = list_next(&tb->lot_idx_tab, idx_tab)) {
                boolean_t valid_idx = B_TRUE;
                int i;

                if (tb->lot_var_sizes != 0 &&
                    idx_tab->sa_variable_lengths != NULL) {
                        for (i = 0; i != tb->lot_var_sizes; i++) {
                                if (hdr->sa_lengths[i] !=
                                    idx_tab->sa_variable_lengths[i]) {
                                        valid_idx = B_FALSE;
                                        break;
                                }
                        }
                }
                if (valid_idx) {
                        sa_idx_tab_hold(os, idx_tab);
                        return (idx_tab);
                }
        }

        /* No such luck, create a new entry */
        idx_tab = kmem_zalloc(sizeof (sa_idx_tab_t), KM_SLEEP);
        idx_tab->sa_idx_tab =
            kmem_zalloc(sizeof (uint32_t) * sa->sa_num_attrs, KM_SLEEP);
        idx_tab->sa_layout = tb;
        zfs_refcount_create(&idx_tab->sa_refcount);
        if (tb->lot_var_sizes)
                idx_tab->sa_variable_lengths = kmem_alloc(sizeof (uint16_t) *
                    tb->lot_var_sizes, KM_SLEEP);

        sa_attr_iter(os, hdr, bonustype, sa_build_idx_tab,
            tb, idx_tab);
        sa_idx_tab_hold(os, idx_tab);   /* one hold for consumer */
        sa_idx_tab_hold(os, idx_tab);   /* one for layout */
        list_insert_tail(&tb->lot_idx_tab, idx_tab);
        return (idx_tab);
}

void
sa_default_locator(void **dataptr, uint32_t *len, uint32_t total_len,
    boolean_t start, void *userdata)
{
        ASSERT(start);

        *dataptr = userdata;
        *len = total_len;
}

static void
sa_attr_register_sync(sa_handle_t *hdl, dmu_tx_t *tx)
{
        uint64_t attr_value = 0;
        sa_os_t *sa = hdl->sa_os->os_sa;
        sa_attr_table_t *tb = sa->sa_attr_table;
        int i;

        mutex_enter(&sa->sa_lock);

        if (!sa->sa_need_attr_registration || sa->sa_master_obj == 0) {
                mutex_exit(&sa->sa_lock);
                return;
        }

        if (sa->sa_reg_attr_obj == 0) {
                sa->sa_reg_attr_obj = zap_create_link(hdl->sa_os,
                    DMU_OT_SA_ATTR_REGISTRATION,
                    sa->sa_master_obj, SA_REGISTRY, tx);
        }
        for (i = 0; i != sa->sa_num_attrs; i++) {
                if (sa->sa_attr_table[i].sa_registered)
                        continue;
                ATTR_ENCODE(attr_value, tb[i].sa_attr, tb[i].sa_length,
                    tb[i].sa_byteswap);
                VERIFY(0 == zap_update(hdl->sa_os, sa->sa_reg_attr_obj,
                    tb[i].sa_name, 8, 1, &attr_value, tx));
                tb[i].sa_registered = B_TRUE;
        }
        sa->sa_need_attr_registration = B_FALSE;
        mutex_exit(&sa->sa_lock);
}

/*
 * Replace all attributes with attributes specified in template.
 * If dnode had a spill buffer then those attributes will be
 * also be replaced, possibly with just an empty spill block
 *
 * This interface is intended to only be used for bulk adding of
 * attributes for a new file.  It will also be used by the ZPL
 * when converting and old formatted znode to native SA support.
 */
int
sa_replace_all_by_template_locked(sa_handle_t *hdl, sa_bulk_attr_t *attr_desc,
    int attr_count, dmu_tx_t *tx)
{
        sa_os_t *sa = hdl->sa_os->os_sa;

        if (sa->sa_need_attr_registration)
                sa_attr_register_sync(hdl, tx);
        return (sa_build_layouts(hdl, attr_desc, attr_count, tx));
}

int
sa_replace_all_by_template(sa_handle_t *hdl, sa_bulk_attr_t *attr_desc,
    int attr_count, dmu_tx_t *tx)
{
        int error;

        mutex_enter(&hdl->sa_lock);
        error = sa_replace_all_by_template_locked(hdl, attr_desc,
            attr_count, tx);
        mutex_exit(&hdl->sa_lock);
        return (error);
}

/*
 * Add/remove a single attribute or replace a variable-sized attribute value
 * with a value of a different size, and then rewrite the entire set
 * of attributes.
 * Same-length attribute value replacement (including fixed-length attributes)
 * is handled more efficiently by the upper layers.
 */
static int
sa_modify_attrs(sa_handle_t *hdl, sa_attr_type_t newattr,
    sa_data_op_t action, sa_data_locator_t *locator, void *datastart,
    uint16_t buflen, dmu_tx_t *tx)
{
        sa_os_t *sa = hdl->sa_os->os_sa;
        dmu_buf_impl_t *db = (dmu_buf_impl_t *)hdl->sa_bonus;
        sa_bulk_attr_t *attr_desc;
        void *old_data[2];
        int bonus_attr_count = 0;
        int bonus_data_size = 0;
        int spill_data_size = 0;
        int spill_attr_count = 0;
        int error;
        uint16_t length, reg_length;
        int i, j, k, length_idx;
        sa_hdr_phys_t *hdr;
        sa_idx_tab_t *idx_tab;
        int attr_count;
        int count;

        ASSERT(MUTEX_HELD(&hdl->sa_lock));

        /* First make of copy of the old data */

        DB_DNODE_ENTER(db);
        if (DB_DNODE(db)->dn_bonuslen != 0) {
                bonus_data_size = hdl->sa_bonus->db_size;
                old_data[0] = kmem_alloc(bonus_data_size, KM_SLEEP);
                memcpy(old_data[0], hdl->sa_bonus->db_data,
                    hdl->sa_bonus->db_size);
                bonus_attr_count = hdl->sa_bonus_tab->sa_layout->lot_attr_count;
        } else {
                old_data[0] = NULL;
        }
        DB_DNODE_EXIT(db);

        /* Bring spill buffer online if it isn't currently */

        if ((error = sa_get_spill(hdl)) == 0) {
                spill_data_size = hdl->sa_spill->db_size;
                old_data[1] = vmem_alloc(spill_data_size, KM_SLEEP);
                memcpy(old_data[1], hdl->sa_spill->db_data,
                    hdl->sa_spill->db_size);
                spill_attr_count =
                    hdl->sa_spill_tab->sa_layout->lot_attr_count;
        } else if (error && error != ENOENT) {
                if (old_data[0])
                        kmem_free(old_data[0], bonus_data_size);
                return (error);
        } else {
                old_data[1] = NULL;
        }

        /* build descriptor of all attributes */

        attr_count = bonus_attr_count + spill_attr_count;
        if (action == SA_ADD)
                attr_count++;
        else if (action == SA_REMOVE)
                attr_count--;

        attr_desc = kmem_zalloc(sizeof (sa_bulk_attr_t) * attr_count, KM_SLEEP);

        /*
         * loop through bonus and spill buffer if it exists, and
         * build up new attr_descriptor to reset the attributes
         */
        k = j = 0;
        count = bonus_attr_count;
        hdr = SA_GET_HDR(hdl, SA_BONUS);
        idx_tab = SA_IDX_TAB_GET(hdl, SA_BONUS);
        for (; ; k++) {
                /*
                 * Iterate over each attribute in layout.  Fetch the
                 * size of variable-length attributes needing rewrite
                 * from sa_lengths[].
                 */
                for (i = 0, length_idx = 0; i != count; i++) {
                        sa_attr_type_t attr;

                        attr = idx_tab->sa_layout->lot_attrs[i];
                        reg_length = SA_REGISTERED_LEN(sa, attr);
                        if (reg_length == 0) {
                                length = hdr->sa_lengths[length_idx];
                                length_idx++;
                        } else {
                                length = reg_length;
                        }
                        if (attr == newattr) {
                                /*
                                 * There is nothing to do for SA_REMOVE,
                                 * so it is just skipped.
                                 */
                                if (action == SA_REMOVE)
                                        continue;

                                /*
                                 * Duplicate attributes are not allowed, so the
                                 * action can not be SA_ADD here.
                                 */
                                ASSERT3S(action, ==, SA_REPLACE);

                                /*
                                 * Only a variable-sized attribute can be
                                 * replaced here, and its size must be changing.
                                 */
                                ASSERT3U(reg_length, ==, 0);
                                ASSERT3U(length, !=, buflen);
                                SA_ADD_BULK_ATTR(attr_desc, j, attr,
                                    locator, datastart, buflen);
                        } else {
                                SA_ADD_BULK_ATTR(attr_desc, j, attr,
                                    NULL, (void *)
                                    (TOC_OFF(idx_tab->sa_idx_tab[attr]) +
                                    (uintptr_t)old_data[k]), length);
                        }
                }
                if (k == 0 && hdl->sa_spill) {
                        hdr = SA_GET_HDR(hdl, SA_SPILL);
                        idx_tab = SA_IDX_TAB_GET(hdl, SA_SPILL);
                        count = spill_attr_count;
                } else {
                        break;
                }
        }
        if (action == SA_ADD) {
                reg_length = SA_REGISTERED_LEN(sa, newattr);
                IMPLY(reg_length != 0, reg_length == buflen);
                SA_ADD_BULK_ATTR(attr_desc, j, newattr, locator,
                    datastart, buflen);
        }
        ASSERT3U(j, ==, attr_count);

        error = sa_build_layouts(hdl, attr_desc, attr_count, tx);

        if (old_data[0])
                kmem_free(old_data[0], bonus_data_size);
        if (old_data[1])
                vmem_free(old_data[1], spill_data_size);
        kmem_free(attr_desc, sizeof (sa_bulk_attr_t) * attr_count);

        return (error);
}

static int
sa_bulk_update_impl(sa_handle_t *hdl, sa_bulk_attr_t *bulk, int count,
    dmu_tx_t *tx)
{
        int error;
        sa_os_t *sa = hdl->sa_os->os_sa;
        dmu_object_type_t bonustype;
        dmu_buf_t *saved_spill;

        ASSERT(hdl);
        ASSERT(MUTEX_HELD(&hdl->sa_lock));

        bonustype = SA_BONUSTYPE_FROM_DB(SA_GET_DB(hdl, SA_BONUS));
        saved_spill = hdl->sa_spill;

        /* sync out registration table if necessary */
        if (sa->sa_need_attr_registration)
                sa_attr_register_sync(hdl, tx);

        error = sa_attr_op(hdl, bulk, count, SA_UPDATE, tx);
        if (error == 0 && !IS_SA_BONUSTYPE(bonustype) && sa->sa_update_cb)
                sa->sa_update_cb(hdl, tx);

        /*
         * If saved_spill is NULL and current sa_spill is not NULL that
         * means we increased the refcount of the spill buffer through
         * sa_get_spill() or dmu_spill_hold_by_dnode().  Therefore we
         * must release the hold before calling dmu_tx_commit() to avoid
         * making a copy of this buffer in dbuf_sync_leaf() due to the
         * reference count now being greater than 1.
         */
        if (!saved_spill && hdl->sa_spill) {
                if (hdl->sa_spill_tab) {
                        sa_idx_tab_rele(hdl->sa_os, hdl->sa_spill_tab);
                        hdl->sa_spill_tab = NULL;
                }

                dmu_buf_rele(hdl->sa_spill, NULL);
                hdl->sa_spill = NULL;
        }

        return (error);
}

/*
 * update or add new attribute
 */
int
sa_update(sa_handle_t *hdl, sa_attr_type_t type,
    void *buf, uint32_t buflen, dmu_tx_t *tx)
{
        int error;
        sa_bulk_attr_t bulk;

        VERIFY3U(buflen, <=, SA_ATTR_MAX_LEN);

        bulk.sa_attr = type;
        bulk.sa_data_func = NULL;
        bulk.sa_length = buflen;
        bulk.sa_data = buf;

        mutex_enter(&hdl->sa_lock);
        error = sa_bulk_update_impl(hdl, &bulk, 1, tx);
        mutex_exit(&hdl->sa_lock);
        return (error);
}

int
sa_bulk_lookup_locked(sa_handle_t *hdl, sa_bulk_attr_t *attrs, int count)
{
        ASSERT(hdl);
        ASSERT(MUTEX_HELD(&hdl->sa_lock));
        return (sa_lookup_impl(hdl, attrs, count));
}

int
sa_bulk_lookup(sa_handle_t *hdl, sa_bulk_attr_t *attrs, int count)
{
        int error;

        ASSERT(hdl);
        mutex_enter(&hdl->sa_lock);
        error = sa_bulk_lookup_locked(hdl, attrs, count);
        mutex_exit(&hdl->sa_lock);
        return (error);
}

int
sa_bulk_update(sa_handle_t *hdl, sa_bulk_attr_t *attrs, int count, dmu_tx_t *tx)
{
        int error;

        ASSERT(hdl);
        mutex_enter(&hdl->sa_lock);
        error = sa_bulk_update_impl(hdl, attrs, count, tx);
        mutex_exit(&hdl->sa_lock);
        return (error);
}

int
sa_remove(sa_handle_t *hdl, sa_attr_type_t attr, dmu_tx_t *tx)
{
        int error;

        mutex_enter(&hdl->sa_lock);
        error = sa_modify_attrs(hdl, attr, SA_REMOVE, NULL,
            NULL, 0, tx);
        mutex_exit(&hdl->sa_lock);
        return (error);
}

void
sa_object_info(sa_handle_t *hdl, dmu_object_info_t *doi)
{
        dmu_object_info_from_db(hdl->sa_bonus, doi);
}

void
sa_object_size(sa_handle_t *hdl, uint32_t *blksize, u_longlong_t *nblocks)
{
        dmu_object_size_from_db(hdl->sa_bonus,
            blksize, nblocks);
}

void
sa_set_userp(sa_handle_t *hdl, void *ptr)
{
        hdl->sa_userp = ptr;
}

dmu_buf_t *
sa_get_db(sa_handle_t *hdl)
{
        return (hdl->sa_bonus);
}

void *
sa_get_userdata(sa_handle_t *hdl)
{
        return (hdl->sa_userp);
}

void
sa_register_update_callback_locked(objset_t *os, sa_update_cb_t *func)
{
        ASSERT(MUTEX_HELD(&os->os_sa->sa_lock));
        os->os_sa->sa_update_cb = func;
}

void
sa_register_update_callback(objset_t *os, sa_update_cb_t *func)
{

        mutex_enter(&os->os_sa->sa_lock);
        sa_register_update_callback_locked(os, func);
        mutex_exit(&os->os_sa->sa_lock);
}

uint64_t
sa_handle_object(sa_handle_t *hdl)
{
        return (hdl->sa_bonus->db_object);
}

boolean_t
sa_enabled(objset_t *os)
{
        return (os->os_sa == NULL);
}

int
sa_set_sa_object(objset_t *os, uint64_t sa_object)
{
        sa_os_t *sa = os->os_sa;

        if (sa->sa_master_obj)
                return (1);

        sa->sa_master_obj = sa_object;

        return (0);
}

int
sa_hdrsize(void *arg)
{
        sa_hdr_phys_t *hdr = arg;

        return (SA_HDR_SIZE(hdr));
}

void
sa_handle_lock(sa_handle_t *hdl)
{
        ASSERT(hdl);
        mutex_enter(&hdl->sa_lock);
}

void
sa_handle_unlock(sa_handle_t *hdl)
{
        ASSERT(hdl);
        mutex_exit(&hdl->sa_lock);
}

#ifdef _KERNEL
EXPORT_SYMBOL(sa_handle_get);
EXPORT_SYMBOL(sa_handle_get_from_db);
EXPORT_SYMBOL(sa_handle_destroy);
EXPORT_SYMBOL(sa_buf_hold);
EXPORT_SYMBOL(sa_buf_rele);
EXPORT_SYMBOL(sa_spill_rele);
EXPORT_SYMBOL(sa_lookup);
EXPORT_SYMBOL(sa_update);
EXPORT_SYMBOL(sa_remove);
EXPORT_SYMBOL(sa_bulk_lookup);
EXPORT_SYMBOL(sa_bulk_lookup_locked);
EXPORT_SYMBOL(sa_bulk_update);
EXPORT_SYMBOL(sa_size);
EXPORT_SYMBOL(sa_object_info);
EXPORT_SYMBOL(sa_object_size);
EXPORT_SYMBOL(sa_get_userdata);
EXPORT_SYMBOL(sa_set_userp);
EXPORT_SYMBOL(sa_get_db);
EXPORT_SYMBOL(sa_handle_object);
EXPORT_SYMBOL(sa_register_update_callback);
EXPORT_SYMBOL(sa_setup);
EXPORT_SYMBOL(sa_replace_all_by_template);
EXPORT_SYMBOL(sa_replace_all_by_template_locked);
EXPORT_SYMBOL(sa_enabled);
EXPORT_SYMBOL(sa_cache_init);
EXPORT_SYMBOL(sa_cache_fini);
EXPORT_SYMBOL(sa_set_sa_object);
EXPORT_SYMBOL(sa_hdrsize);
EXPORT_SYMBOL(sa_handle_lock);
EXPORT_SYMBOL(sa_handle_unlock);
EXPORT_SYMBOL(sa_lookup_uio);
EXPORT_SYMBOL(sa_add_projid);
#endif /* _KERNEL */