hammer2 - Stabilization pass

[dragonfly.git] / sys / vfs / hammer2 / hammer2_cluster.c

/*
 * Copyright (c) 2013-2015 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@dragonflybsd.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * The cluster module collects multiple chains representing the same
 * information from different nodes into a single entity.  It allows direct
 * access to media data as long as it is not blockref array data (which
 * will obviously have to be different at each node).
 *
 * This module also handles I/O dispatch, status rollup, and various
 * mastership arrangements including quorum operations.  It effectively
 * presents one topology to the vnops layer.
 *
 * Many of the API calls mimic chain API calls but operate on clusters
 * instead of chains.  Please see hammer2_chain.c for more complete code
 * documentation of the API functions.
 *
 * WARNING! This module is *extremely* complex.  It must issue asynchronous
 *          locks and I/O, do quorum and/or master-slave processing, and
 *          it must operate properly even if some nodes are broken (which
 *          can also mean indefinite locks).
 *
 *                              CLUSTER OPERATIONS
 *
 * Cluster operations can be broken down into three pieces:
 *
 * (1) Chain locking and data retrieval.
 *              hammer2_cluster_lock()
 *              hammer2_cluster_parent()
 *
 *      - Most complex functions, quorum management on transaction ids.
 *
 *      - Locking and data accesses must be internally asynchronous.
 *
 *      - Validate and manage cache coherency primitives (cache state
 *        is stored in chain topologies but must be validated by these
 *        functions).
 *
 * (2) Lookups and Scans
 *              hammer2_cluster_lookup()
 *              hammer2_cluster_next()
 *
 *      - Depend on locking & data retrieval functions, but still complex.
 *
 *      - Must do quorum management on transaction ids.
 *
 *      - Lookup and Iteration ops Must be internally asynchronous.
 *
 * (3) Modifying Operations
 *              hammer2_cluster_create()
 *              hammer2_cluster_rename()
 *              hammer2_cluster_delete()
 *              hammer2_cluster_modify()
 *              hammer2_cluster_modsync()
 *
 *      - Can usually punt on failures, operation continues unless quorum
 *        is lost.  If quorum is lost, must wait for resynchronization
 *        (depending on the management mode).
 *
 *      - Must disconnect node on failures (also not flush), remount, and
 *        resynchronize.
 *
 *      - Network links (via kdmsg) are relatively easy to issue as the
 *        complex underworkings of hammer2_chain.c don't have to messed
 *        with (the protocol is at a higher level than block-level).
 *
 *      - Multiple local disk nodes (i.e. block devices) are another matter.
 *        Chain operations have to be dispatched to per-node threads (xN)
 *        because we can't asynchronize potentially very complex chain
 *        operations in hammer2_chain.c (it would be a huge mess).
 *
 *        (these threads are also used to terminate incoming kdmsg ops from
 *        other machines).
 *
 *      - Single-node filesystems do not use threads and will simply call
 *        hammer2_chain.c functions directly.  This short-cut is handled
 *        at the base of each cluster function.
 */
#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/types.h>
#include <sys/lock.h>
#include <sys/uuid.h>

#include "hammer2.h"

/*
 * Returns non-zero if any chain in the cluster needs to be resized.
 * Errored elements are not used in the calculation.
 */
int
hammer2_cluster_need_resize(hammer2_cluster_t *cluster, int bytes)
{
        hammer2_chain_t *chain;
        int i;

        KKASSERT(cluster->flags & HAMMER2_CLUSTER_LOCKED);
        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0)
                        continue;
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                if (chain->error)
                        continue;
                if (chain->bytes != bytes)
                        return 1;
        }
        return 0;
}

/*
 * Returns the bref type of the cluster's foucs.
 *
 * If the cluster is errored, returns HAMMER2_BREF_TYPE_EMPTY (0).
 * The cluster must be locked.
 */
uint8_t
hammer2_cluster_type(hammer2_cluster_t *cluster)
{
        KKASSERT(cluster->flags & HAMMER2_CLUSTER_LOCKED);
        if (cluster->error == 0)
                return(cluster->focus->bref.type);
        return 0;
}

/*
 * Returns non-zero if the cluster's focus is flagged as being modified.
 *
 * If the cluster is errored, returns 0.
 */
int
hammer2_cluster_modified(hammer2_cluster_t *cluster)
{
        KKASSERT(cluster->flags & HAMMER2_CLUSTER_LOCKED);
        if (cluster->error == 0)
                return((cluster->focus->flags & HAMMER2_CHAIN_MODIFIED) != 0);
        return 0;
}

/*
 * Returns the bref of the cluster's focus, sans any data-offset information
 * (since offset information is per-node and wouldn't be useful).
 *
 * Callers use this function to access modify_tid, mirror_tid, type,
 * key, and keybits.
 *
 * If the cluster is errored, returns an empty bref.
 * The cluster must be locked.
 */
void
hammer2_cluster_bref(hammer2_cluster_t *cluster, hammer2_blockref_t *bref)
{
        KKASSERT(cluster->flags & HAMMER2_CLUSTER_LOCKED);
        if (cluster->error == 0) {
                *bref = cluster->focus->bref;
                bref->data_off = 0;
        } else {
                bzero(bref, sizeof(*bref));
        }
}

/*
 * Return non-zero if the chain representing an inode has been flagged
 * as having been unlinked.  Allows the vnode reclaim to avoid loading
 * the inode data from disk e.g. when unmount or recycling old, clean
 * vnodes.
 *
 * The cluster does not need to be locked.
 * The focus cannot be used since the cluster might not be locked.
 */
int
hammer2_cluster_isunlinked(hammer2_cluster_t *cluster)
{
        hammer2_chain_t *chain;
        int flags;
        int i;

        flags = 0;
        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0)
                        continue;
                chain = cluster->array[i].chain;
                if (chain)
                        flags |= chain->flags;
        }
        return (flags & HAMMER2_CHAIN_UNLINKED);
}

/*
 * Set a bitmask of flags in all chains related to a cluster.
 * The cluster should probably be locked.
 *
 * XXX Only operate on FEMOD elements?
 */
void
hammer2_cluster_set_chainflags(hammer2_cluster_t *cluster, uint32_t flags)
{
        hammer2_chain_t *chain;
        int i;

        for (i = 0; i < cluster->nchains; ++i) {
                chain = cluster->array[i].chain;
                if (chain)
                        atomic_set_int(&chain->flags, flags);
        }
}

/*
 * Set a bitmask of flags in all chains related to a cluster.
 * The cluster should probably be locked.
 *
 * XXX Only operate on FEMOD elements?
 */
void
hammer2_cluster_clr_chainflags(hammer2_cluster_t *cluster, uint32_t flags)
{
        hammer2_chain_t *chain;
        int i;

        for (i = 0; i < cluster->nchains; ++i) {
                chain = cluster->array[i].chain;
                if (chain)
                        atomic_clear_int(&chain->flags, flags);
        }
}

/*
 * Flag the cluster for flushing recursively up to the root.  Despite the
 * work it does, this is relatively benign.  It just makes sure that the
 * flusher has top-down visibility to this cluster.
 *
 * Errored chains are not flagged for flushing.
 *
 * The cluster should probably be locked.
 */
void
hammer2_cluster_setflush(hammer2_trans_t *trans, hammer2_cluster_t *cluster)
{
        hammer2_chain_t *chain;
        int i;

        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0)
                        continue;
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                if (chain->error)
                        continue;
                hammer2_chain_setflush(trans, chain);
        }
}

/*
 * Set the check mode for the cluster.
 * Errored elements of the cluster are ignored.
 *
 * The cluster must be locked and modified.
 */
void
hammer2_cluster_setmethod_check(hammer2_trans_t *trans,
                                hammer2_cluster_t *cluster,
                                int check_algo)
{
        hammer2_chain_t *chain;
        int i;

        KKASSERT(cluster->flags & HAMMER2_CLUSTER_LOCKED);
        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0) {
                        cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
                        continue;
                }
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                if (chain->error)
                        continue;
                KKASSERT(chain->flags & HAMMER2_CHAIN_MODIFIED);
                chain->bref.methods &= ~HAMMER2_ENC_CHECK(-1);
                chain->bref.methods |= HAMMER2_ENC_CHECK(check_algo);
        }
}

/*
 * Create a degenerate cluster with one ref from a single locked chain.
 * The returned cluster will be focused on the chain and inherit its
 * error state.
 *
 * The chain's lock and reference are transfered to the new cluster, so
 * the caller should not try to unlock the chain separately.
 *
 * We fake the flags.
 */
hammer2_cluster_t *
hammer2_cluster_from_chain(hammer2_chain_t *chain)
{
        hammer2_cluster_t *cluster;

        cluster = kmalloc(sizeof(*cluster), M_HAMMER2, M_WAITOK | M_ZERO);
        cluster->array[0].chain = chain;
        cluster->array[0].flags = HAMMER2_CITEM_FEMOD;
        cluster->nchains = 1;
        cluster->focus = chain;
        cluster->focus_index = 0;
        cluster->pmp = chain->pmp;
        cluster->refs = 1;
        cluster->error = chain->error;
        cluster->flags = HAMMER2_CLUSTER_LOCKED |
                         HAMMER2_CLUSTER_WRHARD |
                         HAMMER2_CLUSTER_RDHARD |
                         HAMMER2_CLUSTER_MSYNCED |
                         HAMMER2_CLUSTER_SSYNCED;

        return cluster;
}

/*
 * Add a reference to a cluster and its underlying chains.
 *
 * We must also ref the underlying chains in order to allow ref/unlock
 * sequences to later re-lock.
 */
void
hammer2_cluster_ref(hammer2_cluster_t *cluster)
{
        atomic_add_int(&cluster->refs, 1);
}

/*
 * Drop the caller's reference to the cluster.  When the ref count drops to
 * zero this function frees the cluster and drops all underlying chains.
 *
 * In-progress read I/Os are typically detached from the cluster once the
 * first one returns (the remaining stay attached to the DIOs but are then
 * ignored and drop naturally).
 */
void
hammer2_cluster_drop(hammer2_cluster_t *cluster)
{
        hammer2_chain_t *chain;
        int i;

        KKASSERT(cluster->refs > 0);
        if (atomic_fetchadd_int(&cluster->refs, -1) == 1) {
                cluster->focus = NULL;          /* safety XXX chg to assert */
                cluster->focus_index = 0;

                for (i = 0; i < cluster->nchains; ++i) {
                        chain = cluster->array[i].chain;
                        if (chain) {
                                hammer2_chain_drop(chain);
                                cluster->array[i].chain = NULL; /* safety */
                        }
                }
                cluster->nchains = 0;                           /* safety */

                kfree(cluster, M_HAMMER2);
                /* cluster is invalid */
        }
}

void
hammer2_cluster_wait(hammer2_cluster_t *cluster)
{
        tsleep(cluster->focus, 0, "h2clcw", 1);
}

/*
 * Lock a cluster.  Cluster must already be referenced.  Focus is maintained. 
 *
 * WARNING! This function expects the caller to handle resolution of the
 *          cluster.  We never re-resolve the cluster in this function,
 *          because it might be used to temporarily unlock/relock a cparent
 *          in an iteration or recursrion, and the cparents elements do not
 *          necessarily match.
 */
void
hammer2_cluster_lock_except(hammer2_cluster_t *cluster, int idx, int how)
{
        hammer2_chain_t *chain;
        int i;

        /* cannot be on inode-embedded cluster template, must be on copy */
        KKASSERT(cluster->refs > 0);
        KKASSERT((cluster->flags & HAMMER2_CLUSTER_INODE) == 0);
        if (cluster->flags & HAMMER2_CLUSTER_LOCKED) {
                panic("hammer2_cluster_lock: cluster %p already locked!\n",
                        cluster);
        }
        atomic_set_int(&cluster->flags, HAMMER2_CLUSTER_LOCKED);

        /*
         * Lock chains and resolve state.
         */
        for (i = 0; i < cluster->nchains; ++i) {
                if (i == idx)
                        continue;
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                hammer2_chain_lock(chain, how);
        }
}

void
hammer2_cluster_lock(hammer2_cluster_t *cluster, int how)
{
        hammer2_cluster_lock_except(cluster, -1, how);
}

/*
 * Calculate the clustering state for the cluster and set its focus.
 * This routine must be called with care.  For example, it should not
 * normally be called after relocking a non-leaf cluster because parent
 * clusters help iterations and each element might be at a slightly different
 * indirect node (each node's topology is independently indexed).
 *
 * HAMMER2_CITEM_FEMOD flags which elements can be modified by normal
 * operations.  Typically this is only set on a quorum of MASTERs or
 * on a SOFT_MASTER.  Also as a degenerate case on SUPROOT.  If a SOFT_MASTER
 * is present, this bit is *not* set on a quorum of MASTERs.  The
 * synchronization code ignores this bit, but all hammer2_cluster_*() calls
 * that create/modify/delete elements use it.
 *
 * The chains making up the cluster may be narrowed down based on quorum
 * acceptability, and if RESOLVE_RDONLY is specified the chains can be
 * narrowed down to a single chain as long as the entire subtopology is known
 * to be intact.  So, for example, we can narrow a read-only op to a single
 * fast SLAVE but if we focus a CACHE chain we must still retain at least
 * a SLAVE to ensure that the subtopology can be accessed.
 *
 * RESOLVE_RDONLY operations are effectively as-of so the quorum does not need
 * to be maintained once the topology is validated as-of the top level of
 * the operation.
 *
 * If a failure occurs the operation must be aborted by higher-level code and
 * retried. XXX
 */
void
hammer2_cluster_resolve(hammer2_cluster_t *cluster)
{
        hammer2_chain_t *chain;
        hammer2_chain_t *focus;
        hammer2_pfs_t *pmp;
        hammer2_tid_t quorum_tid;
        hammer2_tid_t last_best_quorum_tid;
        int focus_pfs_type;
        uint32_t nflags;
        int ttlmasters;
        int ttlslaves;
        int nmasters;
        int nslaves;
        int nquorum;
        int smpresent;
        int i;

        cluster->error = 0;
        cluster->focus = NULL;

        focus_pfs_type = 0;
        nflags = 0;
        ttlmasters = 0;
        ttlslaves = 0;
        nmasters = 0;
        nslaves = 0;

        /*
         * Calculate quorum
         */
        pmp = cluster->pmp;
        KKASSERT(pmp != NULL || cluster->nchains == 0);
        nquorum = pmp ? pmp->pfs_nmasters / 2 + 1 : 0;
        smpresent = 0;

        /*
         * Pass 1
         *
         * NOTE: A NULL chain is not necessarily an error, it could be
         *       e.g. a lookup failure or the end of an iteration.
         *       Process normally.
         */
        for (i = 0; i < cluster->nchains; ++i) {
                chain = cluster->array[i].chain;
                if (chain && chain->error) {
                        if (cluster->focus == NULL || cluster->focus == chain) {
                                /* error will be overridden by valid focus */
                                cluster->error = chain->error;
                        }

                        /*
                         * Must count total masters and slaves whether the
                         * chain is errored or not.
                         */
                        switch (cluster->pmp->pfs_types[i]) {
                        case HAMMER2_PFSTYPE_MASTER:
                                ++ttlmasters;
                                break;
                        case HAMMER2_PFSTYPE_SLAVE:
                                ++ttlslaves;
                                break;
                        }
                        continue;
                }
                switch (cluster->pmp->pfs_types[i]) {
                case HAMMER2_PFSTYPE_MASTER:
                        ++ttlmasters;
                        break;
                case HAMMER2_PFSTYPE_SLAVE:
                        ++ttlslaves;
                        break;
                case HAMMER2_PFSTYPE_SOFT_MASTER:
                        nflags |= HAMMER2_CLUSTER_WRSOFT;
                        nflags |= HAMMER2_CLUSTER_RDSOFT;
                        smpresent = 1;
                        break;
                case HAMMER2_PFSTYPE_SOFT_SLAVE:
                        nflags |= HAMMER2_CLUSTER_RDSOFT;
                        break;
                case HAMMER2_PFSTYPE_SUPROOT:
                        /*
                         * Degenerate cluster representing the super-root
                         * topology on a single device.  Fake stuff so
                         * cluster ops work as expected.
                         */
                        nflags |= HAMMER2_CLUSTER_WRHARD;
                        nflags |= HAMMER2_CLUSTER_RDHARD;
                        cluster->focus_index = i;
                        cluster->focus = chain;
                        cluster->error = chain ? chain->error : 0;
                        break;
                default:
                        break;
                }
        }

        /*
         * Pass 2
         *
         * Resolve masters.  Calculate nmasters for the highest matching
         * TID, if a quorum cannot be attained try the next lower matching
         * TID until we exhaust TIDs.
         *
         * NOTE: A NULL chain is not necessarily an error, it could be
         *       e.g. a lookup failure or the end of an iteration.
         *       Process normally.
         */
        last_best_quorum_tid = HAMMER2_TID_MAX;
        quorum_tid = 0;         /* fix gcc warning */

        while (nmasters < nquorum && last_best_quorum_tid != 0) {
                nmasters = 0;
                quorum_tid = 0;

                for (i = 0; i < cluster->nchains; ++i) {
                        if (cluster->pmp->pfs_types[i] !=
                            HAMMER2_PFSTYPE_MASTER) {
                                continue;
                        }
                        chain = cluster->array[i].chain;

                        if (cluster->array[i].flags & HAMMER2_CITEM_INVALID) {
                                /*
                                 * Invalid as in unsynchronized, cannot be
                                 * used to calculate the quorum.
                                 */
                        } else if (chain == NULL && quorum_tid == 0) {
                                /*
                                 * NULL chain on master matches NULL chains
                                 * on other masters.
                                 */
                                ++nmasters;
                        } else if (quorum_tid < last_best_quorum_tid &&
                                   chain != NULL &&
                                   (quorum_tid < chain->bref.modify_tid ||
                                    nmasters == 0)) {
                                /*
                                 * Better TID located, reset nmasters count.
                                 */
                                nmasters = 1;
                                quorum_tid = chain->bref.modify_tid;
                        } else if (chain &&
                                   quorum_tid == chain->bref.modify_tid) {
                                /*
                                 * TID matches current collection.
                                 */
                                ++nmasters;
                        }
                }
                if (nmasters >= nquorum)
                        break;
                last_best_quorum_tid = quorum_tid;
        }

        /*
         * Pass 3
         *
         * NOTE: A NULL chain is not necessarily an error, it could be
         *       e.g. a lookup failure or the end of an iteration.
         *       Process normally.
         */
        for (i = 0; i < cluster->nchains; ++i) {
                cluster->array[i].flags &= ~HAMMER2_CITEM_FEMOD;
                chain = cluster->array[i].chain;
                if (chain && chain->error) {
                        if (cluster->focus == NULL || cluster->focus == chain) {
                                /* error will be overridden by valid focus */
                                cluster->error = chain->error;
                        }
                        continue;
                }

                switch (cluster->pmp->pfs_types[i]) {
                case HAMMER2_PFSTYPE_MASTER:
                        /*
                         * We must have enough up-to-date masters to reach
                         * a quorum and the master modify_tid must match
                         * the quorum's modify_tid.
                         *
                         * Do not select an errored or out-of-sync master.
                         */
                        if (cluster->array[i].flags & HAMMER2_CITEM_INVALID) {
                                nflags |= HAMMER2_CLUSTER_UNHARD;
                        } else if (nmasters >= nquorum &&
                                   (chain == NULL || chain->error == 0) &&
                                   ((chain == NULL && quorum_tid == 0) ||
                                    (chain != NULL && quorum_tid ==
                                                  chain->bref.modify_tid))) {
                                nflags |= HAMMER2_CLUSTER_WRHARD;
                                nflags |= HAMMER2_CLUSTER_RDHARD;
                                if (!smpresent) {
                                        cluster->array[i].flags |=
                                                        HAMMER2_CITEM_FEMOD;
                                }
                                if (cluster->focus == NULL ||
                                    focus_pfs_type == HAMMER2_PFSTYPE_SLAVE) {
                                        focus_pfs_type = HAMMER2_PFSTYPE_MASTER;
                                        cluster->focus_index = i;
                                        cluster->focus = chain; /* NULL ok */
                                        cluster->error = chain ? chain->error :
                                                                 0;
                                }
                        } else if (chain == NULL || chain->error == 0) {
                                nflags |= HAMMER2_CLUSTER_UNHARD;
                        }
                        break;
                case HAMMER2_PFSTYPE_SLAVE:
                        /*
                         * We must have enough up-to-date masters to reach
                         * a quorum and the slave modify_tid must match the
                         * quorum's modify_tid.
                         *
                         * Do not select an errored slave.
                         */
                        if (cluster->array[i].flags & HAMMER2_CITEM_INVALID) {
                                nflags |= HAMMER2_CLUSTER_UNHARD;
                        } else if (nmasters >= nquorum &&
                                   (chain == NULL || chain->error == 0) &&
                                   ((chain == NULL && quorum_tid == 0) ||
                                    (chain && quorum_tid ==
                                              chain->bref.modify_tid))) {
                                ++nslaves;
                                nflags |= HAMMER2_CLUSTER_RDHARD;
#if 0
                                /* XXX optimize for RESOLVE_RDONLY */
                                if (cluster->focus == NULL) {
                                        focus_pfs_type = HAMMER2_PFSTYPE_SLAVE;
                                        cluster->focus_index = i;
                                        cluster->focus = chain; /* NULL ok */
                                        cluster->error = chain ? chain->error :
                                                                 0;
                                }
#endif
                        } else if (chain == NULL || chain->error == 0) {
                                nflags |= HAMMER2_CLUSTER_UNSOFT;
                        }
                        break;
                case HAMMER2_PFSTYPE_SOFT_MASTER:
                        /*
                         * Directly mounted soft master always wins.  There
                         * should be only one.
                         */
                        KKASSERT(focus_pfs_type != HAMMER2_PFSTYPE_SOFT_MASTER);
                        cluster->focus_index = i;
                        cluster->focus = chain;
                        cluster->error = chain ? chain->error : 0;
                        focus_pfs_type = HAMMER2_PFSTYPE_SOFT_MASTER;
                        cluster->array[i].flags |= HAMMER2_CITEM_FEMOD;
                        break;
                case HAMMER2_PFSTYPE_SOFT_SLAVE:
                        /*
                         * Directly mounted soft slave always wins.  There
                         * should be only one.
                         */
                        KKASSERT(focus_pfs_type != HAMMER2_PFSTYPE_SOFT_SLAVE);
                        if (focus_pfs_type != HAMMER2_PFSTYPE_SOFT_MASTER) {
                                cluster->focus_index = i;
                                cluster->focus = chain;
                                cluster->error = chain ? chain->error : 0;
                                focus_pfs_type = HAMMER2_PFSTYPE_SOFT_SLAVE;
                        }
                        break;
                case HAMMER2_PFSTYPE_SUPROOT:
                        /*
                         * spmp (degenerate case)
                         */
                        KKASSERT(i == 0);
                        cluster->focus_index = i;
                        cluster->focus = chain;
                        cluster->error = chain ? chain->error : 0;
                        focus_pfs_type = HAMMER2_PFSTYPE_SUPROOT;
                        cluster->array[i].flags |= HAMMER2_CITEM_FEMOD;
                        break;
                default:
                        break;
                }
        }

        /*
         * Focus now set, adjust ddflag.  Skip this pass if the focus
         * is bad or if we are at the PFS root (the bref won't match at
         * the PFS root, obviously).
         */
        focus = cluster->focus;
        if (focus) {
                cluster->ddflag =
                        (cluster->focus->bref.type == HAMMER2_BREF_TYPE_INODE);
        } else {
                cluster->ddflag = 0;
                goto skip4;
        }
        if (cluster->focus->flags & HAMMER2_CHAIN_PFSBOUNDARY)
                goto skip4;

        /*
         * Pass 4
         *
         * Validate the elements that were not marked invalid.  They should
         * match.
         */
        for (i = 0; i < cluster->nchains; ++i) {
                int ddflag;

                chain = cluster->array[i].chain;

                if (chain == NULL)
                        continue;
                if (chain == focus)
                        continue;
                if (cluster->array[i].flags & HAMMER2_CITEM_INVALID)
                        continue;

                ddflag = (chain->bref.type == HAMMER2_BREF_TYPE_INODE);
                if (chain->bref.type != focus->bref.type ||
                    chain->bref.key != focus->bref.key ||
                    chain->bref.keybits != focus->bref.keybits ||
                    chain->bref.modify_tid != focus->bref.modify_tid ||
                    chain->bytes != focus->bytes ||
                    ddflag != cluster->ddflag) {
                        cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
                        if (hammer2_debug & 1)
                        kprintf("cluster_resolve: matching modify_tid failed "
                                "bref test: idx=%d type=%02x/%02x "
                                "key=%016jx/%d-%016jx/%d "
                                "mod=%016jx/%016jx bytes=%u/%u\n",
                                i,
                                chain->bref.type, focus->bref.type,
                                chain->bref.key, chain->bref.keybits,
                                focus->bref.key, focus->bref.keybits,
                                chain->bref.modify_tid, focus->bref.modify_tid,
                                chain->bytes, focus->bytes);
                        if (hammer2_debug & 0x4000)
                                panic("cluster_resolve");
                        /* flag issue and force resync? */
                }
        }
skip4:

        if (ttlslaves == 0)
                nflags |= HAMMER2_CLUSTER_NOSOFT;
        if (ttlmasters == 0)
                nflags |= HAMMER2_CLUSTER_NOHARD;

        /*
         * Set SSYNCED or MSYNCED for slaves and masters respectively if
         * all available nodes (even if 0 are available) are fully
         * synchronized.  This is used by the synchronization thread to
         * determine if there is work it could potentially accomplish.
         */
        if (nslaves == ttlslaves)
                nflags |= HAMMER2_CLUSTER_SSYNCED;
        if (nmasters == ttlmasters)
                nflags |= HAMMER2_CLUSTER_MSYNCED;

        /*
         * Determine if the cluster was successfully locked for the
         * requested operation and generate an error code.  The cluster
         * will not be locked (or ref'd) if an error is returned.
         *
         * Caller can use hammer2_cluster_rdok() and hammer2_cluster_wrok()
         * to determine if reading or writing is possible.  If writing, the
         * cluster still requires a call to hammer2_cluster_modify() first.
         */
        atomic_set_int(&cluster->flags, nflags);
        atomic_clear_int(&cluster->flags, HAMMER2_CLUSTER_ZFLAGS & ~nflags);
}

/*
 * This is used by the sync thread to force non-NULL elements of a copy
 * of the pmp->iroot cluster to be good which is required to prime the
 * sync.
 */
void
hammer2_cluster_forcegood(hammer2_cluster_t *cluster)
{
        int i;

        for (i = 0; i < cluster->nchains; ++i) {
                if (cluster->array[i].chain)
                        cluster->array[i].flags &= ~HAMMER2_CITEM_INVALID;
        }
}

/*
 * Copy a cluster, returned a ref'd cluster.  All underlying chains
 * are also ref'd, but not locked.  Focus state is also copied.
 *
 * Original cluster does not have to be locked but usually is.
 * New cluster will not be flagged as locked.
 *
 * Callers using this function to initialize a new cluster from an inode
 * generally lock and resolve the resulting cluster.
 *
 * Callers which use this function to save/restore a cluster structure
 * generally retain the focus state and do not re-resolve it.  Caller should
 * not try to re-resolve internal (cparent) node state during an iteration
 * as the individual tracking elements of cparent in an iteration may not
 * match even though they are correct.
 */
hammer2_cluster_t *
hammer2_cluster_copy(hammer2_cluster_t *ocluster)
{
        hammer2_pfs_t *pmp = ocluster->pmp;
        hammer2_cluster_t *ncluster;
        hammer2_chain_t *chain;
        int i;

        ncluster = kmalloc(sizeof(*ncluster), M_HAMMER2, M_WAITOK | M_ZERO);
        ncluster->pmp = pmp;
        ncluster->nchains = ocluster->nchains;
        ncluster->refs = 1;

        for (i = 0; i < ocluster->nchains; ++i) {
                chain = ocluster->array[i].chain;
                ncluster->array[i].chain = chain;
                ncluster->array[i].flags = ocluster->array[i].flags;
                if (chain)
                        hammer2_chain_ref(chain);
        }
        ncluster->focus_index = ocluster->focus_index;
        ncluster->focus = ocluster->focus;
        ncluster->flags = ocluster->flags & ~(HAMMER2_CLUSTER_LOCKED |
                                              HAMMER2_CLUSTER_INODE);

        return (ncluster);
}

/*
 * Unlock a cluster.  Refcount and focus is maintained.
 */
void
hammer2_cluster_unlock_except(hammer2_cluster_t *cluster, int idx)
{
        hammer2_chain_t *chain;
        int i;

        if ((cluster->flags & HAMMER2_CLUSTER_LOCKED) == 0) {
                kprintf("hammer2_cluster_unlock: cluster %p not locked\n",
                        cluster);
        }
        KKASSERT(cluster->flags & HAMMER2_CLUSTER_LOCKED);
        KKASSERT(cluster->refs > 0);
        atomic_clear_int(&cluster->flags, HAMMER2_CLUSTER_LOCKED);

        for (i = 0; i < cluster->nchains; ++i) {
                if (i == idx)
                        continue;
                chain = cluster->array[i].chain;
                if (chain)
                        hammer2_chain_unlock(chain);
        }
}

void
hammer2_cluster_unlock(hammer2_cluster_t *cluster)
{
        hammer2_cluster_unlock_except(cluster, -1);
}

/*
 * Resize the cluster's physical storage allocation in-place.  This may
 * replace the cluster's chains.
 */
void
hammer2_cluster_resize(hammer2_trans_t *trans, hammer2_inode_t *ip,
                       hammer2_cluster_t *cparent, hammer2_cluster_t *cluster,
                       int nradix, int flags)
{
        hammer2_chain_t *chain;
        int i;

        KKASSERT(cparent->pmp == cluster->pmp);         /* can be NULL */
        KKASSERT(cparent->nchains == cluster->nchains);

        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0) {
                        cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
                        continue;
                }
                chain = cluster->array[i].chain;
                if (chain) {
                        KKASSERT(cparent->array[i].chain);
                        hammer2_chain_resize(trans, ip,
                                             cparent->array[i].chain, chain,
                                             nradix, flags);
                }
        }
}

/*
 * Set an inode's cluster modified, marking the related chains RW and
 * duplicating them if necessary.
 *
 * The passed-in chain is a localized copy of the chain previously acquired
 * when the inode was locked (and possilby replaced in the mean time), and
 * must also be updated.  In fact, we update it first and then synchronize
 * the inode's cluster cache.
 */
hammer2_inode_data_t *
hammer2_cluster_modify_ip(hammer2_trans_t *trans, hammer2_inode_t *ip,
                          hammer2_cluster_t *cluster, int flags)
{
        atomic_set_int(&ip->flags, HAMMER2_INODE_MODIFIED);
        hammer2_cluster_modify(trans, cluster, flags);

        hammer2_inode_repoint(ip, NULL, cluster);
        if (ip->vp)
                vsetisdirty(ip->vp);
        return (&hammer2_cluster_wdata(cluster)->ipdata);
}

/*
 * Adjust the cluster's chains to allow modification and adjust the
 * focus.  Data will be accessible on return.
 *
 * If our focused master errors on modify, re-resolve the cluster to
 * try to select a different master.
 */
void
hammer2_cluster_modify(hammer2_trans_t *trans, hammer2_cluster_t *cluster,
                       int flags)
{
        hammer2_chain_t *chain;
        int resolve_again;
        int i;

        resolve_again = 0;
        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0) {
                        cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
                        continue;
                }
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                if (chain->error)
                        continue;
                hammer2_chain_modify(trans, chain, flags);
                if (cluster->focus == chain && chain->error) {
                        cluster->error = chain->error;
                        resolve_again = 1;
                }
        }
        if (resolve_again)
                hammer2_cluster_resolve(cluster);
}

/*
 * Synchronize modifications from the focus to other chains in a cluster.
 * Convenient because nominal API users can just modify the contents of the
 * focus (at least for non-blockref data).
 *
 * Nominal front-end operations only edit non-block-table data in a single
 * chain.  This code copies such modifications to the other chains in the
 * cluster.  Blocktable modifications are handled on a chain-by-chain basis
 * by both the frontend and the backend and will explode in fireworks if
 * blindly copied.
 */
void
hammer2_cluster_modsync(hammer2_cluster_t *cluster)
{
        hammer2_chain_t *focus;
        hammer2_chain_t *scan;
        const hammer2_inode_data_t *ripdata;
        hammer2_inode_data_t *wipdata;
        int i;

        focus = cluster->focus;
        KKASSERT(focus->flags & HAMMER2_CHAIN_MODIFIED);

        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0)
                        continue;
                scan = cluster->array[i].chain;
                if (scan == NULL || scan == focus)
                        continue;
                if (scan->error)
                        continue;
                KKASSERT(scan->flags & HAMMER2_CHAIN_MODIFIED);
                KKASSERT(focus->bytes == scan->bytes &&
                         focus->bref.type == scan->bref.type);
                switch(focus->bref.type) {
                case HAMMER2_BREF_TYPE_INODE:
                        ripdata = &focus->data->ipdata;
                        wipdata = &scan->data->ipdata;
                        if ((ripdata->op_flags &
                            HAMMER2_OPFLAG_DIRECTDATA) == 0) {
                                bcopy(ripdata, wipdata,
                                      offsetof(hammer2_inode_data_t, u));
                                break;
                        }
                        /* fall through to full copy */
                case HAMMER2_BREF_TYPE_DATA:
                        bcopy(focus->data, scan->data, focus->bytes);
                        break;
                case HAMMER2_BREF_TYPE_FREEMAP_NODE:
                case HAMMER2_BREF_TYPE_FREEMAP_LEAF:
                case HAMMER2_BREF_TYPE_FREEMAP:
                case HAMMER2_BREF_TYPE_VOLUME:
                        panic("hammer2_cluster_modsync: illegal node type");
                        /* NOT REACHED */
                        break;
                default:
                        panic("hammer2_cluster_modsync: unknown node type");
                        break;
                }
        }
}

/*
 * Lookup initialization/completion API.  Returns a locked, fully resolved
 * cluster with one ref.
 */
hammer2_cluster_t *
hammer2_cluster_lookup_init(hammer2_cluster_t *cparent, int flags)
{
        hammer2_cluster_t *cluster;

        cluster = hammer2_cluster_copy(cparent);
        if (flags & HAMMER2_LOOKUP_SHARED) {
                hammer2_cluster_lock(cluster, HAMMER2_RESOLVE_ALWAYS |
                                              HAMMER2_RESOLVE_SHARED);
        } else {
                hammer2_cluster_lock(cluster, HAMMER2_RESOLVE_ALWAYS);
        }
        hammer2_cluster_resolve(cluster);

        return (cluster);
}

void
hammer2_cluster_lookup_done(hammer2_cluster_t *cparent)
{
        if (cparent) {
                hammer2_cluster_unlock(cparent);
                hammer2_cluster_drop(cparent);
        }
}

/*
 * Locate first match or overlap under parent, return a new, locked, resolved
 * cluster with one ref.
 *
 * Must never be called with HAMMER2_LOOKUP_MATCHIND.
 */
hammer2_cluster_t *
hammer2_cluster_lookup(hammer2_cluster_t *cparent, hammer2_key_t *key_nextp,
                     hammer2_key_t key_beg, hammer2_key_t key_end, int flags)
{
        hammer2_pfs_t *pmp;
        hammer2_cluster_t *cluster;
        hammer2_chain_t *chain;
        hammer2_key_t key_accum;
        hammer2_key_t key_next;
        int null_count;
        int rflags;
        int i;

        KKASSERT((flags & HAMMER2_LOOKUP_MATCHIND) == 0);

        pmp = cparent->pmp;                             /* can be NULL */
        key_accum = *key_nextp;
        null_count = 0;
        if (flags & HAMMER2_LOOKUP_SHARED)
                rflags = HAMMER2_RESOLVE_SHARED;
        else
                rflags = 0;

        cluster = kmalloc(sizeof(*cluster), M_HAMMER2, M_WAITOK | M_ZERO);
        cluster->pmp = pmp;                             /* can be NULL */
        cluster->refs = 1;
        if ((flags & HAMMER2_LOOKUP_NOLOCK) == 0)
                cluster->flags |= HAMMER2_CLUSTER_LOCKED;

        /*
         * Iterating earlier cluster elements with later elements still
         * locked is a problem, so we have to unlock the parent and then
         * re-lock as we go.
         */
        hammer2_cluster_unlock(cparent);
        cparent->flags |= HAMMER2_CLUSTER_LOCKED;

        /*
         * Pass-1, issue lookups.
         */
        for (i = 0; i < cparent->nchains; ++i) {
                cluster->array[i].flags = cparent->array[i].flags;
                key_next = *key_nextp;

                /*
                 * Always relock the parent as we go.
                 */
                if (cparent->array[i].chain) {
                        hammer2_chain_lock(cparent->array[i].chain, rflags);
                }

                /*
                 * Nothing to base the lookup, or parent was not synchronized.
                 */
                if (cparent->array[i].chain == NULL ||
                    (cparent->array[i].flags & HAMMER2_CITEM_INVALID)) {
                        ++null_count;
                        continue;
                }

                chain = hammer2_chain_lookup(&cparent->array[i].chain,
                                             &key_next,
                                             key_beg, key_end,
                                             &cparent->array[i].cache_index,
                                             flags);
                cluster->array[i].chain = chain;
                if (chain == NULL) {
                        ++null_count;
                }
                if (key_accum > key_next)
                        key_accum = key_next;
        }

        /*
         * Cleanup
         */
        cluster->nchains = i;
        *key_nextp = key_accum;

        /*
         * The cluster must be resolved, out of sync elements may be present.
         *
         * If HAMMER2_LOOKUP_ALLNODES is not set focus must be non-NULL.
         */
        if (null_count != i)
                hammer2_cluster_resolve(cluster);
        if (null_count == i ||
            (cluster->focus == NULL &&
             (flags & HAMMER2_LOOKUP_ALLNODES) == 0)) {
                if ((flags & HAMMER2_LOOKUP_NOLOCK) == 0)
                        hammer2_cluster_unlock(cluster);
                hammer2_cluster_drop(cluster);
                cluster = NULL;
        }

        return (cluster);
}

/*
 * Locate next match or overlap under parent, replace the passed-in cluster.
 * The returned cluster is a new, locked, resolved cluster with one ref.
 *
 * Must never be called with HAMMER2_LOOKUP_MATCHIND.
 */
hammer2_cluster_t *
hammer2_cluster_next(hammer2_cluster_t *cparent, hammer2_cluster_t *cluster,
                     hammer2_key_t *key_nextp,
                     hammer2_key_t key_beg, hammer2_key_t key_end, int flags)
{
        hammer2_chain_t *ochain;
        hammer2_chain_t *nchain;
        hammer2_key_t key_accum;
        hammer2_key_t key_next;
        int parent_index;
        int cluster_index;
        int null_count;
        int rflags;
        int i;

        KKASSERT((flags & HAMMER2_LOOKUP_MATCHIND) == 0);

        key_accum = *key_nextp;
        null_count = 0;
        parent_index = cparent->focus_index;    /* save prior focus */
        cluster_index = cluster->focus_index;
        if (flags & HAMMER2_LOOKUP_SHARED)
                rflags = HAMMER2_RESOLVE_SHARED;
        else
                rflags = 0;

        cluster->focus = NULL;          /* XXX needed any more? */
        /*cparent->focus = NULL;*/
        cluster->focus_index = 0;       /* XXX needed any more? */
        /*cparent->focus_index = 0;*/

        cluster->ddflag = 0;

        /*
         * The parent is always locked on entry, the iterator may be locked
         * depending on flags.
         *
         * We must temporarily unlock the passed-in clusters to avoid a
         * deadlock between elements of the cluster with other threads.
         * We will fixup the lock in the loop.
         *
         * Note that this will clear the focus.
         *
         * Reflag the clusters as locked, because we will relock them
         * as we go.
         */
        if ((flags & HAMMER2_LOOKUP_NOLOCK) == 0) {
                hammer2_cluster_unlock(cluster);
                cluster->flags |= HAMMER2_CLUSTER_LOCKED;
        }
        hammer2_cluster_unlock(cparent);
        cparent->flags |= HAMMER2_CLUSTER_LOCKED;

        for (i = 0; i < cparent->nchains; ++i) {
                key_next = *key_nextp;
                ochain = cluster->array[i].chain;

                /*
                 * Always relock the parent as we go.
                 */
                if (cparent->array[i].chain)
                        hammer2_chain_lock(cparent->array[i].chain, rflags);

                /*
                 * Nothing to iterate from.  These cases can occur under
                 * normal operations.  For example, during synchronization
                 * a slave might reach the end of its scan while records
                 * are still left on the master(s).
                 */
                if (ochain == NULL) {
                        ++null_count;
                        continue;
                }
                if (cparent->array[i].chain == NULL ||
                    (cparent->array[i].flags & HAMMER2_CITEM_INVALID) ||
                    (cluster->array[i].flags & HAMMER2_CITEM_INVALID)) {
                        /* ochain has not yet been relocked */
                        hammer2_chain_drop(ochain);
                        cluster->array[i].chain = NULL;
                        ++null_count;
                        continue;
                }

                /*
                 * Relock the child if necessary.  Parent and child will then
                 * be locked as expected by hammer2_chain_next() and flags.
                 */
                if ((flags & HAMMER2_LOOKUP_NOLOCK) == 0)
                        hammer2_chain_lock(ochain, rflags);
                nchain = hammer2_chain_next(&cparent->array[i].chain, ochain,
                                            &key_next, key_beg, key_end,
                                            &cparent->array[i].cache_index,
                                            flags);
                /* ochain now invalid but can still be used for focus check */
                if (parent_index == i) {
                        cparent->focus_index = i;
                        cparent->focus = cparent->array[i].chain;
                }

                cluster->array[i].chain = nchain;
                if (nchain == NULL) {
                        ++null_count;
                }
                if (key_accum > key_next)
                        key_accum = key_next;
        }

        /*
         * Cleanup
         */
        cluster->nchains = i;
        *key_nextp = key_accum;

        /*
         * The cluster must be resolved, out of sync elements may be present.
         *
         * If HAMMER2_LOOKUP_ALLNODES is not set focus must be non-NULL.
         */
        if (null_count != i)
                hammer2_cluster_resolve(cluster);
        if (null_count == i ||
            (cluster->focus == NULL &&
             (flags & HAMMER2_LOOKUP_ALLNODES) == 0)) {
                if ((flags & HAMMER2_LOOKUP_NOLOCK) == 0)
                        hammer2_cluster_unlock(cluster);
                hammer2_cluster_drop(cluster);
                cluster = NULL;
        }
        return(cluster);
}

/*
 * Advance just one chain in the cluster and recalculate the invalid bit.
 * The cluster index is allowed to be flagged invalid on input and is
 * recalculated on return.
 *
 * (used during synchronization to advance past a chain being deleted).
 *
 * The chain being advanced must not be the focus and the clusters in
 * question must have already passed normal cluster_lookup/cluster_next
 * checks.
 *
 * The cluster always remains intact on return, so void function.
 */
void
hammer2_cluster_next_single_chain(hammer2_cluster_t *cparent,
                                  hammer2_cluster_t *cluster,
                                  hammer2_key_t *key_nextp,
                                  hammer2_key_t key_beg,
                                  hammer2_key_t key_end,
                                  int i, int flags)
{
        hammer2_chain_t *ochain;
        hammer2_chain_t *nchain;
        hammer2_chain_t *focus;
        hammer2_key_t key_accum;
        hammer2_key_t key_next;
        int ddflag;

        key_accum = *key_nextp;
        key_next = *key_nextp;
        ochain = cluster->array[i].chain;
        if (ochain == NULL)
                goto done;
        KKASSERT(ochain != cluster->focus);

        nchain = hammer2_chain_next(&cparent->array[i].chain, ochain,
                                    &key_next, key_beg, key_end,
                                    &cparent->array[i].cache_index,
                                    flags);
        /* ochain now invalid */
        if (cparent->focus_index == i)
                cparent->focus = cparent->array[i].chain;

        /*
         * Install nchain.  Note that nchain can be NULL, and can also
         * be in an unlocked state depending on flags.
         */
        cluster->array[i].chain = nchain;
        cluster->array[i].flags &= ~HAMMER2_CITEM_INVALID;

        if (key_accum > key_next)
                key_accum = key_next;

        focus = cluster->focus;
        if (focus == NULL)
                goto done;
        if (nchain == NULL)
                goto done;
#if 0
        if (nchain == focus)    /* ASSERTED NOT TRUE */
                ...
#endif
        ddflag = (nchain->bref.type == HAMMER2_BREF_TYPE_INODE);
        if (nchain->bref.type != focus->bref.type ||
            nchain->bref.key != focus->bref.key ||
            nchain->bref.keybits != focus->bref.keybits ||
            nchain->bref.modify_tid != focus->bref.modify_tid ||
            nchain->bytes != focus->bytes ||
            ddflag != cluster->ddflag) {
                cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
        }

done:
        *key_nextp = key_accum;
#if 0
        /*
         * For now don't re-resolve cluster->flags.
         */
        hammer2_cluster_resolve(cluster);
#endif
}

/*
 * Create a new cluster using the specified key
 */
int
hammer2_cluster_create(hammer2_trans_t *trans, hammer2_cluster_t *cparent,
                     hammer2_cluster_t **clusterp,
                     hammer2_key_t key, int keybits,
                     int type, size_t bytes, int flags)
{
        hammer2_cluster_t *cluster;
        hammer2_pfs_t *pmp;
        int error;
        int i;

        pmp = trans->pmp;                               /* can be NULL */

        if ((cluster = *clusterp) == NULL) {
                cluster = kmalloc(sizeof(*cluster), M_HAMMER2,
                                  M_WAITOK | M_ZERO);
                cluster->pmp = pmp;                     /* can be NULL */
                cluster->refs = 1;
                cluster->flags = HAMMER2_CLUSTER_LOCKED;
        }
        cluster->focus_index = 0;
        cluster->focus = NULL;

        /*
         * NOTE: cluster->array[] entries can initially be NULL.  If
         *       *clusterp is supplied, skip NULL entries, otherwise
         *       create new chains.
         */
        for (i = 0; i < cparent->nchains; ++i) {
                if ((cparent->array[i].flags & HAMMER2_CITEM_FEMOD) == 0) {
                        cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
                        continue;
                }
                if (*clusterp) {
                        if ((cluster->array[i].flags &
                             HAMMER2_CITEM_FEMOD) == 0) {
                                cluster->array[i].flags |=
                                                HAMMER2_CITEM_INVALID;
                                continue;
                        }
                        if (cluster->array[i].chain == NULL)
                                continue;
                }
                error = hammer2_chain_create(trans, &cparent->array[i].chain,
                                             &cluster->array[i].chain, pmp,
                                             key, keybits,
                                             type, bytes, flags);
                if (cparent->focus_index == i)
                        cparent->focus = cparent->array[i].chain;
                KKASSERT(error == 0);
                if (cluster->focus == NULL) {
                        cluster->focus_index = i;
                        cluster->focus = cluster->array[i].chain;
                }
                if (cparent->focus == cparent->array[i].chain) {
                        cluster->focus_index = i;
                        cluster->focus = cluster->array[i].chain;
                }
        }
        cluster->nchains = i;
        *clusterp = cluster;
        hammer2_cluster_resolve(cluster);

        return error;
}

/*
 * Rename a cluster to a new parent.
 *
 * WARNING! Any passed-in bref is probaly from hammer2_cluster_bref(),
 *          So the data_off field is not relevant.  Only the key and
 *          keybits are used.
 */
void
hammer2_cluster_rename(hammer2_trans_t *trans, hammer2_blockref_t *bref,
                       hammer2_cluster_t *cparent, hammer2_cluster_t *cluster,
                       int flags)
{
        hammer2_chain_t *chain;
        hammer2_blockref_t xbref;
        int i;

#if 0
        cluster->focus = NULL;
        cparent->focus = NULL;
        cluster->focus_index = 0;
        cparent->focus_index = 0;
#endif

        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0) {
                        cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
                        continue;
                }
                chain = cluster->array[i].chain;
                if (chain) {
                        if (bref) {
                                xbref = chain->bref;
                                xbref.key = bref->key;
                                xbref.keybits = bref->keybits;
                                hammer2_chain_rename(trans, &xbref,
                                                     &cparent->array[i].chain,
                                                     chain, flags);
                        } else {
                                hammer2_chain_rename(trans, NULL,
                                                     &cparent->array[i].chain,
                                                     chain, flags);
                        }
                        if (cparent->focus_index == i)
                                cparent->focus = cparent->array[i].chain;
                        KKASSERT(cluster->array[i].chain == chain); /*remove*/
                }
        }
}

/*
 * Mark a cluster deleted
 */
void
hammer2_cluster_delete(hammer2_trans_t *trans, hammer2_cluster_t *cparent,
                       hammer2_cluster_t *cluster, int flags)
{
        hammer2_chain_t *chain;
        hammer2_chain_t *parent;
        int i;

        if (cparent == NULL) {
                kprintf("cparent is NULL\n");
                return;
        }

        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0) {
                        cluster->array[i].flags |= HAMMER2_CITEM_INVALID;
                        continue;
                }
                parent = cparent->array[i].chain;
                chain = cluster->array[i].chain;
                if (chain == NULL)
                        continue;
                if (chain->parent != parent) {
                        kprintf("hammer2_cluster_delete: parent "
                                "mismatch chain=%p parent=%p against=%p\n",
                                chain, chain->parent, parent);
                } else {
                        hammer2_chain_delete(trans, parent, chain, flags);
                }
        }
}

/*
 * Create a snapshot of the specified {parent, ochain} with the specified
 * label.  The originating hammer2_inode must be exclusively locked for
 * safety.
 *
 * The ioctl code has already synced the filesystem.
 */
int
hammer2_cluster_snapshot(hammer2_trans_t *trans, hammer2_cluster_t *ocluster,
                       hammer2_ioc_pfs_t *pfs)
{
        hammer2_dev_t *hmp;
        hammer2_cluster_t *ncluster;
        const hammer2_inode_data_t *ripdata;
        hammer2_inode_data_t *wipdata;
        hammer2_chain_t *nchain;
        hammer2_inode_t *nip;
        size_t name_len;
        hammer2_key_t lhc;
        struct vattr vat;
#if 0
        uuid_t opfs_clid;
#endif
        int error;
        int i;

        kprintf("snapshot %s\n", pfs->name);

        name_len = strlen(pfs->name);
        lhc = hammer2_dirhash(pfs->name, name_len);

        /*
         * Get the clid
         */
        ripdata = &hammer2_cluster_rdata(ocluster)->ipdata;
#if 0
        opfs_clid = ripdata->pfs_clid;
#endif
        hmp = ocluster->focus->hmp;     /* XXX find synchronized local disk */

        /*
         * Create the snapshot directory under the super-root
         *
         * Set PFS type, generate a unique filesystem id, and generate
         * a cluster id.  Use the same clid when snapshotting a PFS root,
         * which theoretically allows the snapshot to be used as part of
         * the same cluster (perhaps as a cache).
         *
         * Copy the (flushed) blockref array.  Theoretically we could use
         * chain_duplicate() but it becomes difficult to disentangle
         * the shared core so for now just brute-force it.
         */
        VATTR_NULL(&vat);
        vat.va_type = VDIR;
        vat.va_mode = 0755;
        ncluster = NULL;
        nip = hammer2_inode_create(trans, hmp->spmp->iroot, &vat,
                                   proc0.p_ucred, pfs->name, name_len,
                                   &ncluster,
                                   HAMMER2_INSERT_PFSROOT, &error);

        if (nip) {
                wipdata = hammer2_cluster_modify_ip(trans, nip, ncluster, 0);
                wipdata->pfs_type = HAMMER2_PFSTYPE_MASTER;
                wipdata->pfs_subtype = HAMMER2_PFSSUBTYPE_SNAPSHOT;
                wipdata->op_flags |= HAMMER2_OPFLAG_PFSROOT;
                kern_uuidgen(&wipdata->pfs_fsid, 1);

                /*
                 * Give the snapshot its own private cluster.  As a snapshot
                 * no further synchronization with the original cluster will
                 * be done.
                 */
#if 0
                if (ocluster->focus->flags & HAMMER2_CHAIN_PFSBOUNDARY)
                        wipdata->pfs_clid = opfs_clid;
                else
                        kern_uuidgen(&wipdata->pfs_clid, 1);
#endif
                kern_uuidgen(&wipdata->pfs_clid, 1);

                for (i = 0; i < ncluster->nchains; ++i) {
                        if ((ncluster->array[i].flags &
                             HAMMER2_CITEM_FEMOD) == 0) {
                                ncluster->array[i].flags |=
                                        HAMMER2_CITEM_INVALID;
                                continue;
                        }
                        nchain = ncluster->array[i].chain;
                        if (nchain)
                                nchain->bref.flags |= HAMMER2_BREF_FLAG_PFSROOT;
                }
#if 0
                /* XXX can't set this unless we do an explicit flush, which
                   we also need a pmp assigned to do, else the flush code
                   won't flush ncluster because it thinks it is crossing a
                   flush boundary */
                hammer2_cluster_set_chainflags(ncluster,
                                               HAMMER2_CHAIN_PFSBOUNDARY);
#endif

                /* XXX hack blockset copy */
                /* XXX doesn't work with real cluster */
                KKASSERT(ocluster->nchains == 1);
                wipdata->u.blockset = ripdata->u.blockset;
                hammer2_cluster_modsync(ncluster);
                for (i = 0; i < ncluster->nchains; ++i) {
                        nchain = ncluster->array[i].chain;
                        if (nchain)
                                hammer2_flush(trans, nchain, 1);
                }
                hammer2_inode_unlock(nip, ncluster);
        }
        return (error);
}

/*
 * Return locked parent cluster given a locked child.  The child remains
 * locked on return.  The new parent's focus follows the child's focus
 * and the parent is always resolved.
 *
 * We must temporarily unlock the passed-in cluster to avoid a deadlock
 * between elements of the cluster.
 *
 * We must not try to hammer2_cluster_resolve() cparent.  The individual
 * parent chains for the nodes are the correct parents for the cluster but
 * do not necessarily match, so resolve would likely implode.
 */
hammer2_cluster_t *
hammer2_cluster_parent(hammer2_cluster_t *cluster)
{
        hammer2_cluster_t *cparent;
        int i;

        cparent = hammer2_cluster_copy(cluster);
        hammer2_cluster_unlock(cluster);

        for (i = 0; i < cparent->nchains; ++i) {
                hammer2_chain_t *chain;
                hammer2_chain_t *rchain;

                /*
                 * Calculate parent for each element.  Old chain has an extra
                 * ref for cparent but the lock remains with cluster.
                 */
                chain = cparent->array[i].chain;
                if (chain == NULL)
                        continue;
                while ((rchain = chain->parent) != NULL) {
                        hammer2_chain_ref(rchain);
                        hammer2_chain_lock(rchain, HAMMER2_RESOLVE_ALWAYS);
                        if (chain->parent == rchain)
                                break;
                        hammer2_chain_unlock(rchain);
                        hammer2_chain_drop(rchain);
                }
                cparent->array[i].chain = rchain;
                hammer2_chain_drop(chain);
        }
        cparent->flags |= HAMMER2_CLUSTER_LOCKED;
        /* hammer2_cluster_resolve(cparent); */
        hammer2_cluster_lock(cluster, HAMMER2_RESOLVE_ALWAYS);

        return cparent;
}

/************************************************************************
 *                              CLUSTER I/O                             *
 ************************************************************************
 *
 *
 * WARNING! blockref[] array data is not universal.  These functions should
 *          only be used to access universal data.
 *
 * NOTE!    The rdata call will wait for at least one of the chain I/Os to
 *          complete if necessary.  The I/O's should have already been
 *          initiated by the cluster_lock/chain_lock operation.
 *
 *          The cluster must already be in a modified state before wdata
 *          is called.  The data will already be available for this case.
 */
const hammer2_media_data_t *
hammer2_cluster_rdata(hammer2_cluster_t *cluster)
{
        return(cluster->focus->data);
}

hammer2_media_data_t *
hammer2_cluster_wdata(hammer2_cluster_t *cluster)
{
        KKASSERT(hammer2_cluster_modified(cluster));
        return(cluster->focus->data);
}

/*
 * Load cluster data asynchronously with callback.
 *
 * The callback is made for the first validated data found, or NULL
 * if no valid data is available.
 *
 * NOTE! The cluster structure is either unique or serialized (e.g. embedded
 *       in the inode with an exclusive lock held), the chain structure may be
 *       shared.
 */
void
hammer2_cluster_load_async(hammer2_cluster_t *cluster,
                           void (*callback)(hammer2_iocb_t *iocb), void *ptr)
{
        hammer2_chain_t *chain;
        hammer2_iocb_t *iocb;
        hammer2_dev_t *hmp;
        hammer2_blockref_t *bref;
        int i;

        i = cluster->focus_index;
        chain = cluster->focus;

        iocb = &cluster->iocb;
        iocb->callback = callback;
        iocb->dio = NULL;               /* for already-validated case */
        iocb->cluster = cluster;
        iocb->chain = chain;
        iocb->ptr = ptr;
        iocb->lbase = (off_t)i;
        iocb->flags = 0;
        iocb->error = 0;

        /*
         * Data already validated
         */
        if (chain->data) {
                callback(iocb);
                return;
        }

        /*
         * We must resolve to a device buffer, either by issuing I/O or
         * by creating a zero-fill element.  We do not mark the buffer
         * dirty when creating a zero-fill element (the hammer2_chain_modify()
         * API must still be used to do that).
         *
         * The device buffer is variable-sized in powers of 2 down
         * to HAMMER2_MIN_ALLOC (typically 1K).  A 64K physical storage
         * chunk always contains buffers of the same size. (XXX)
         *
         * The minimum physical IO size may be larger than the variable
         * block size.
         *
         * XXX TODO - handle HAMMER2_CHAIN_INITIAL for case where chain->bytes
         *            matches hammer2_devblksize()?  Or does the freemap's
         *            pre-zeroing handle the case for us?
         */
        bref = &chain->bref;
        hmp = chain->hmp;

#if 0
        /* handled by callback? <- TODO XXX even needed for loads? */
        /*
         * The getblk() optimization for a 100% overwrite can only be used
         * if the physical block size matches the request.
         */
        if ((chain->flags & HAMMER2_CHAIN_INITIAL) &&
            chain->bytes == hammer2_devblksize(chain->bytes)) {
                error = hammer2_io_new(hmp, bref->data_off, chain->bytes, &dio);
                KKASSERT(error == 0);
                iocb->dio = dio;
                callback(iocb);
                return;
        }
#endif

        /*
         * Otherwise issue a read
         */
        hammer2_adjreadcounter(&chain->bref, chain->bytes);
        hammer2_io_getblk(hmp, bref->data_off, chain->bytes, iocb);
}