/*
 * Copyright (c) 2011-2023 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * by Daniel Flores (GSOC 2013 - mentored by Matthew Dillon, compression)
 *
 * 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.
 */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/nlookup.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/fcntl.h>
#include <sys/vfsops.h>
#include <sys/sysctl.h>
#include <sys/socket.h>
#include <sys/objcache.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/file.h>

#include "hammer2.h"

TAILQ_HEAD(hammer2_mntlist, hammer2_dev);
static struct hammer2_mntlist hammer2_mntlist;

struct hammer2_pfslist hammer2_pfslist;
struct hammer2_pfslist hammer2_spmplist;
struct lock hammer2_mntlk;

int hammer2_supported_version = HAMMER2_VOL_VERSION_DEFAULT;
int hammer2_debug;
int hammer2_aux_flags;
int hammer2_xop_nthreads;
int hammer2_xop_sgroups;
int hammer2_xop_xgroups;
int hammer2_xop_xbase;
int hammer2_xop_mod;
long hammer2_debug_inode;
int hammer2_cluster_meta_read = 1;      /* physical read-ahead */
int hammer2_cluster_data_read = 4;      /* physical read-ahead */
int hammer2_cluster_write = 0;          /* physical write clustering */
int hammer2_dedup_enable = 1;
int hammer2_always_compress = 0;        /* always try to compress */
int hammer2_flush_pipe = 100;
int hammer2_dio_count;
int hammer2_dio_limit = 256;
int hammer2_bulkfree_tps = 5000;
int hammer2_spread_workers;
int hammer2_limit_saved_depth;
long hammer2_chain_allocs;
long hammer2_limit_saved_chains;
long hammer2_limit_dirty_chains;
long hammer2_limit_dirty_inodes;
long hammer2_count_modified_chains;
long hammer2_iod_file_read;
long hammer2_iod_meta_read;
long hammer2_iod_indr_read;
long hammer2_iod_fmap_read;
long hammer2_iod_volu_read;
long hammer2_iod_file_write;
long hammer2_iod_file_wembed;
long hammer2_iod_file_wzero;
long hammer2_iod_file_wdedup;
long hammer2_iod_meta_write;
long hammer2_iod_indr_write;
long hammer2_iod_fmap_write;
long hammer2_iod_volu_write;
static long hammer2_iod_inode_creates;
static long hammer2_iod_inode_deletes;

long hammer2_process_icrc32;
long hammer2_process_xxhash64;

MALLOC_DECLARE(M_HAMMER2_CBUFFER);
MALLOC_DEFINE(M_HAMMER2_CBUFFER, "HAMMER2-compbuffer",
                "Buffer used for compression.");

MALLOC_DECLARE(M_HAMMER2_DEBUFFER);
MALLOC_DEFINE(M_HAMMER2_DEBUFFER, "HAMMER2-decompbuffer",
                "Buffer used for decompression.");

SYSCTL_NODE(_vfs, OID_AUTO, hammer2, CTLFLAG_RW, 0, "HAMMER2 filesystem");

SYSCTL_INT(_vfs_hammer2, OID_AUTO, supported_version, CTLFLAG_RD,
           &hammer2_supported_version, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, aux_flags, CTLFLAG_RW,
           &hammer2_aux_flags, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, debug, CTLFLAG_RW,
           &hammer2_debug, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, debug_inode, CTLFLAG_RW,
           &hammer2_debug_inode, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, spread_workers, CTLFLAG_RW,
           &hammer2_spread_workers, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, cluster_meta_read, CTLFLAG_RW,
           &hammer2_cluster_meta_read, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, cluster_data_read, CTLFLAG_RW,
           &hammer2_cluster_data_read, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, cluster_write, CTLFLAG_RW,
           &hammer2_cluster_write, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, dedup_enable, CTLFLAG_RW,
           &hammer2_dedup_enable, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, always_compress, CTLFLAG_RW,
           &hammer2_always_compress, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, flush_pipe, CTLFLAG_RW,
           &hammer2_flush_pipe, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, bulkfree_tps, CTLFLAG_RW,
           &hammer2_bulkfree_tps, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, chain_allocs, CTLFLAG_RD,
           &hammer2_chain_allocs, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, limit_saved_chains, CTLFLAG_RW,
           &hammer2_limit_saved_chains, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, limit_saved_depth, CTLFLAG_RW,
           &hammer2_limit_saved_depth, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, limit_dirty_chains, CTLFLAG_RW,
           &hammer2_limit_dirty_chains, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, limit_dirty_inodes, CTLFLAG_RW,
           &hammer2_limit_dirty_inodes, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, count_modified_chains, CTLFLAG_RD,
           &hammer2_count_modified_chains, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, dio_count, CTLFLAG_RD,
           &hammer2_dio_count, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, dio_limit, CTLFLAG_RW,
           &hammer2_dio_limit, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_read, CTLFLAG_RD,
           &hammer2_iod_file_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_meta_read, CTLFLAG_RD,
           &hammer2_iod_meta_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_indr_read, CTLFLAG_RD,
           &hammer2_iod_indr_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_fmap_read, CTLFLAG_RD,
           &hammer2_iod_fmap_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_volu_read, CTLFLAG_RD,
           &hammer2_iod_volu_read, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_write, CTLFLAG_RD,
           &hammer2_iod_file_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_wembed, CTLFLAG_RD,
           &hammer2_iod_file_wembed, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_wzero, CTLFLAG_RD,
           &hammer2_iod_file_wzero, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_wdedup, CTLFLAG_RD,
           &hammer2_iod_file_wdedup, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_meta_write, CTLFLAG_RD,
           &hammer2_iod_meta_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_indr_write, CTLFLAG_RD,
           &hammer2_iod_indr_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_fmap_write, CTLFLAG_RD,
           &hammer2_iod_fmap_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_volu_write, CTLFLAG_RD,
           &hammer2_iod_volu_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_inode_creates, CTLFLAG_RD,
           &hammer2_iod_inode_creates, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_inode_deletes, CTLFLAG_RD,
           &hammer2_iod_inode_deletes, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, process_icrc32, CTLFLAG_RD,
           &hammer2_process_icrc32, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, process_xxhash64, CTLFLAG_RD,
           &hammer2_process_xxhash64, 0, "");

static int hammer2_vfs_init(struct vfsconf *conf);
static int hammer2_vfs_uninit(struct vfsconf *vfsp);
static int hammer2_vfs_mount(struct mount *mp, char *path, caddr_t data,
                                struct ucred *cred);
static int hammer2_remount(hammer2_dev_t *, struct mount *, char *,
                                struct ucred *);
static int hammer2_recovery(hammer2_dev_t *hmp);
static int hammer2_vfs_unmount(struct mount *mp, int mntflags);
static int hammer2_vfs_root(struct mount *mp, struct vnode **vpp);
static int hammer2_vfs_statfs(struct mount *mp, struct statfs *sbp,
                                struct ucred *cred);
static int hammer2_vfs_statvfs(struct mount *mp, struct statvfs *sbp,
                                struct ucred *cred);
static int hammer2_vfs_fhtovp(struct mount *mp, struct vnode *rootvp,
                                struct fid *fhp, struct vnode **vpp);
static int hammer2_vfs_vptofh(struct vnode *vp, struct fid *fhp);
static int hammer2_vfs_checkexp(struct mount *mp, struct sockaddr *nam,
                                int *exflagsp, struct ucred **credanonp);
static int hammer2_vfs_modifying(struct mount *mp);

static void hammer2_update_pmps(hammer2_dev_t *hmp);

static void hammer2_mount_helper(struct mount *mp, hammer2_pfs_t *pmp);
static void hammer2_unmount_helper(struct mount *mp, hammer2_pfs_t *pmp,
                                hammer2_dev_t *hmp);
static int hammer2_fixup_pfses(hammer2_dev_t *hmp);

/*
 * HAMMER2 vfs operations.
 */
static struct vfsops hammer2_vfsops = {
        .vfs_flags      = 0,
        .vfs_init       = hammer2_vfs_init,
        .vfs_uninit     = hammer2_vfs_uninit,
        .vfs_sync       = hammer2_vfs_sync,
        .vfs_mount      = hammer2_vfs_mount,
        .vfs_unmount    = hammer2_vfs_unmount,
        .vfs_root       = hammer2_vfs_root,
        .vfs_statfs     = hammer2_vfs_statfs,
        .vfs_statvfs    = hammer2_vfs_statvfs,
        .vfs_vget       = hammer2_vfs_vget,
        .vfs_vptofh     = hammer2_vfs_vptofh,
        .vfs_fhtovp     = hammer2_vfs_fhtovp,
        .vfs_checkexp   = hammer2_vfs_checkexp,
        .vfs_modifying  = hammer2_vfs_modifying
};

MALLOC_DEFINE(M_HAMMER2, "HAMMER2-mount", "");

VFS_SET(hammer2_vfsops, hammer2, VFCF_MPSAFE);
MODULE_VERSION(hammer2, 1);

static
int
hammer2_vfs_init(struct vfsconf *conf)
{
        static struct objcache_malloc_args margs_read;
        static struct objcache_malloc_args margs_write;
        static struct objcache_malloc_args margs_vop;

        int error;
        int mod;

        error = 0;
        kmalloc_raise_limit(M_HAMMER2, 0);      /* unlimited */

        /*
         * hammer2_xop_nthreads must be a multiple of ncpus,
         * minimum 2 * ncpus.
         */
        mod = ncpus;
        hammer2_xop_mod = mod;
        hammer2_xop_nthreads = mod * 2;
        while (hammer2_xop_nthreads / mod < HAMMER2_XOPGROUPS_MIN ||
               hammer2_xop_nthreads < HAMMER2_XOPTHREADS_MIN)
        {
                hammer2_xop_nthreads += mod;
        }
        hammer2_xop_sgroups = hammer2_xop_nthreads / mod / 2;
        hammer2_xop_xgroups = hammer2_xop_nthreads / mod - hammer2_xop_sgroups;
        hammer2_xop_xbase = hammer2_xop_sgroups * mod;

        /*
         * A large DIO cache is needed to retain dedup enablement masks.
         * The bulkfree code clears related masks as part of the disk block
         * recycling algorithm, preventing it from being used for a later
         * dedup.
         *
         * NOTE: A large buffer cache can actually interfere with dedup
         *       operation because we dedup based on media physical buffers
         *       and not logical buffers.  Try to make the DIO case large
         *       enough to avoid this problem, but also cap it.
         */
        hammer2_dio_limit = nbuf * 2;
        if (hammer2_dio_limit > 100000)
                hammer2_dio_limit = 100000;

        if (HAMMER2_BLOCKREF_BYTES != sizeof(struct hammer2_blockref))
                error = EINVAL;
        if (HAMMER2_INODE_BYTES != sizeof(struct hammer2_inode_data))
                error = EINVAL;
        if (HAMMER2_VOLUME_BYTES != sizeof(struct hammer2_volume_data))
                error = EINVAL;

        if (error)
                kprintf("HAMMER2 structure size mismatch; cannot continue.\n");

        margs_read.objsize = 65536;
        margs_read.mtype = M_HAMMER2_DEBUFFER;

        margs_write.objsize = 32768;
        margs_write.mtype = M_HAMMER2_CBUFFER;

        margs_vop.objsize = sizeof(hammer2_xop_t);
        margs_vop.mtype = M_HAMMER2;

        /*
         * Note thaht for the XOPS cache we want backing store allocations
         * to use M_ZERO.  This is not allowed in objcache_get() (to avoid
         * confusion), so use the backing store function that does it.  This
         * means that initial XOPS objects are zerod but REUSED objects are
         * not.  So we are responsible for cleaning the object up sufficiently
         * for our needs before objcache_put()ing it back (typically just the
         * FIFO indices).
         */
        cache_buffer_read = objcache_create(margs_read.mtype->ks_shortdesc,
                                0, 1, NULL, NULL, NULL,
                                objcache_malloc_alloc,
                                objcache_malloc_free,
                                &margs_read);
        cache_buffer_write = objcache_create(margs_write.mtype->ks_shortdesc,
                                0, 1, NULL, NULL, NULL,
                                objcache_malloc_alloc,
                                objcache_malloc_free,
                                &margs_write);
        cache_xops = objcache_create(margs_vop.mtype->ks_shortdesc,
                                0, 1, NULL, NULL, NULL,
                                objcache_malloc_alloc_zero,
                                objcache_malloc_free,
                                &margs_vop);


        lockinit(&hammer2_mntlk, "mntlk", 0, 0);
        TAILQ_INIT(&hammer2_mntlist);
        TAILQ_INIT(&hammer2_pfslist);
        TAILQ_INIT(&hammer2_spmplist);

        hammer2_limit_dirty_chains = maxvnodes / 10;
        if (hammer2_limit_dirty_chains > HAMMER2_LIMIT_DIRTY_CHAINS)
                hammer2_limit_dirty_chains = HAMMER2_LIMIT_DIRTY_CHAINS;
        if (hammer2_limit_dirty_chains < 1000)
                hammer2_limit_dirty_chains = 1000;

        hammer2_limit_dirty_inodes = maxvnodes / 25;
        if (hammer2_limit_dirty_inodes < 100)
                hammer2_limit_dirty_inodes = 100;
        if (hammer2_limit_dirty_inodes > HAMMER2_LIMIT_DIRTY_INODES)
                hammer2_limit_dirty_inodes = HAMMER2_LIMIT_DIRTY_INODES;

        hammer2_limit_saved_chains = hammer2_limit_dirty_chains * 5;

        return (error);
}

static
int
hammer2_vfs_uninit(struct vfsconf *vfsp __unused)
{
        objcache_destroy(cache_buffer_read);
        objcache_destroy(cache_buffer_write);
        objcache_destroy(cache_xops);
        return 0;
}

/*
 * Core PFS allocator.  Used to allocate or reference the pmp structure
 * for PFS cluster mounts and the spmp structure for media (hmp) structures.
 * The pmp can be passed in or loaded by this function using the chain and
 * inode data.
 *
 * pmp->modify_tid tracks new modify_tid transaction ids for front-end
 * transactions.  Note that synchronization does not use this field.
 * (typically frontend operations and synchronization cannot run on the
 * same PFS node at the same time).
 *
 * XXX check locking
 */
hammer2_pfs_t *
hammer2_pfsalloc(hammer2_chain_t *chain,
                 const hammer2_inode_data_t *ripdata,
                 hammer2_dev_t *force_local)
{
        hammer2_pfs_t *pmp;
        hammer2_inode_t *iroot;
        int count;
        int i;
        int j;

        pmp = NULL;

        /*
         * Locate or create the PFS based on the cluster id.  If ripdata
         * is NULL this is a spmp which is unique and is always allocated.
         *
         * If the device is mounted in local mode all PFSs are considered
         * independent and not part of any cluster (for debugging only).
         */
        if (ripdata) {
                TAILQ_FOREACH(pmp, &hammer2_pfslist, mntentry) {
                        if (force_local != pmp->force_local)
                                continue;
                        if (force_local == NULL &&
                            bcmp(&pmp->pfs_clid, &ripdata->meta.pfs_clid,
                                 sizeof(pmp->pfs_clid)) == 0) {
                                break;
                        } else if (force_local && pmp->pfs_names[0] &&
                            strcmp(pmp->pfs_names[0], (const char *)ripdata->filename) == 0) {
                                break;
                        }
                }
        }

        if (pmp == NULL) {
                pmp = kmalloc(sizeof(*pmp), M_HAMMER2, M_WAITOK | M_ZERO);
                pmp->force_local = force_local;
                hammer2_trans_manage_init(pmp);
                kmalloc_create_obj(&pmp->minode, "HAMMER2-inodes",
                                   sizeof(struct hammer2_inode));
                lockinit(&pmp->lock, "pfslk", 0, 0);
                hammer2_spin_init(&pmp->blockset_spin, "h2blkset");
                hammer2_inum_hash_init(pmp);
                hammer2_spin_init(&pmp->xop_spin, "h2xop");
                TAILQ_INIT(&pmp->syncq);
                TAILQ_INIT(&pmp->depq);
                hammer2_spin_init(&pmp->list_spin, "h2pfsalloc_list");

                /*
                 * Save the last media transaction id for the flusher.  Set
                 * initial
                 */
                if (ripdata) {
                        pmp->pfs_clid = ripdata->meta.pfs_clid;
                        TAILQ_INSERT_TAIL(&hammer2_pfslist, pmp, mntentry);
                } else {
                        pmp->flags |= HAMMER2_PMPF_SPMP;
                        TAILQ_INSERT_TAIL(&hammer2_spmplist, pmp, mntentry);
                }

                /*
                 * The synchronization thread may start too early, make
                 * sure it stays frozen until we are ready to let it go.
                 * XXX
                 */
                /*
                pmp->primary_thr.flags = HAMMER2_THREAD_FROZEN |
                                         HAMMER2_THREAD_REMASTER;
                */
        }

        /*
         * Create the PFS's root inode and any missing XOP helper threads.
         */
        if ((iroot = pmp->iroot) == NULL) {
                iroot = hammer2_inode_get(pmp, NULL, 1, -1);
                if (ripdata)
                        iroot->meta = ripdata->meta;
                pmp->iroot = iroot;
                hammer2_inode_ref(iroot);
                hammer2_inode_unlock(iroot);
        }

        /*
         * Stop here if no chain is passed in.
         */
        if (chain == NULL)
                goto done;

        /*
         * When a chain is passed in we must add it to the PFS's root
         * inode, update pmp->pfs_types[], and update the syncronization
         * threads.
         *
         * When forcing local mode, mark the PFS as a MASTER regardless.
         *
         * At the moment empty spots can develop due to removals or failures.
         * Ultimately we want to re-fill these spots but doing so might
         * confused running code. XXX
         */
        hammer2_inode_ref(iroot);
        hammer2_mtx_ex(&iroot->lock);
        j = iroot->cluster.nchains;

        if (j == HAMMER2_MAXCLUSTER) {
                kprintf("hammer2_pfsalloc: cluster full!\n");
                /* XXX fatal error? */
        } else {
                KKASSERT(chain->pmp == NULL);
                chain->pmp = pmp;
                hammer2_chain_ref(chain);
                iroot->cluster.array[j].chain = chain;
                if (force_local)
                        pmp->pfs_types[j] = HAMMER2_PFSTYPE_MASTER;
                else
                        pmp->pfs_types[j] = ripdata->meta.pfs_type;
                pmp->pfs_names[j] = kstrdup((const char *)ripdata->filename, M_HAMMER2);
                pmp->pfs_hmps[j] = chain->hmp;
                hammer2_spin_ex(&pmp->blockset_spin);
                pmp->pfs_iroot_blocksets[j] = chain->data->ipdata.u.blockset;
                hammer2_spin_unex(&pmp->blockset_spin);

                /*
                 * If the PFS is already mounted we must account
                 * for the mount_count here.
                 */
                if (pmp->mp)
                        ++chain->hmp->mount_count;

                /*
                 * May have to fixup dirty chain tracking.  Previous
                 * pmp was NULL so nothing to undo.
                 */
                if (chain->flags & HAMMER2_CHAIN_MODIFIED)
                        hammer2_pfs_memory_inc(pmp);
                ++j;
        }
        iroot->cluster.nchains = j;

        /*
         * Update nmasters from any PFS inode which is part of the cluster.
         * It is possible that this will result in a value which is too
         * high.  MASTER PFSs are authoritative for pfs_nmasters and will
         * override this value later on.
         *
         * (This informs us of masters that might not currently be
         *  discoverable by this mount).
         */
        if (ripdata && pmp->pfs_nmasters < ripdata->meta.pfs_nmasters) {
                pmp->pfs_nmasters = ripdata->meta.pfs_nmasters;
        }

        /*
         * Count visible masters.  Masters are usually added with
         * ripdata->meta.pfs_nmasters set to 1.  This detects when there
         * are more (XXX and must update the master inodes).
         */
        count = 0;
        for (i = 0; i < iroot->cluster.nchains; ++i) {
                if (pmp->pfs_types[i] == HAMMER2_PFSTYPE_MASTER)
                        ++count;
        }
        if (pmp->pfs_nmasters < count)
                pmp->pfs_nmasters = count;

        /*
         * Create missing synchronization and support threads.
         *
         * Single-node masters (including snapshots) have nothing to
         * synchronize and do not require this thread.
         *
         * Multi-node masters or any number of soft masters, slaves, copy,
         * or other PFS types need the thread.
         *
         * Each thread is responsible for its particular cluster index.
         * We use independent threads so stalls or mismatches related to
         * any given target do not affect other targets.
         */
        for (i = 0; i < iroot->cluster.nchains; ++i) {
                /*
                 * Single-node masters (including snapshots) have nothing
                 * to synchronize and will make direct xops support calls,
                 * thus they do not require this thread.
                 *
                 * Note that there can be thousands of snapshots.  We do not
                 * want to create thousands of threads.
                 */
                if (pmp->pfs_nmasters <= 1 &&
                    pmp->pfs_types[i] == HAMMER2_PFSTYPE_MASTER) {
                        continue;
                }

                /*
                 * Sync support thread
                 */
                if (pmp->sync_thrs[i].td == NULL) {
                        hammer2_thr_create(&pmp->sync_thrs[i], pmp, NULL,
                                           "h2nod", i, -1,
                                           hammer2_primary_sync_thread);
                }
        }

        /*
         * Create missing Xop threads
         *
         * NOTE: We create helper threads for all mounted PFSs or any
         *       PFSs with 2+ nodes (so the sync thread can update them,
         *       even if not mounted).
         */
        if (pmp->mp || iroot->cluster.nchains >= 2)
                hammer2_xop_helper_create(pmp);

        hammer2_mtx_unlock(&iroot->lock);
        hammer2_inode_drop(iroot);
done:
        return pmp;
}

/*
 * Deallocate an element of a probed PFS.  If destroying and this is a
 * MASTER, adjust nmasters.
 *
 * This function does not physically destroy the PFS element in its device
 * under the super-root  (see hammer2_ioctl_pfs_delete()).
 */
void
hammer2_pfsdealloc(hammer2_pfs_t *pmp, int clindex, int destroying)
{
        hammer2_inode_t *iroot;
        hammer2_chain_t *chain;
        int j;

        /*
         * Cleanup our reference on iroot.  iroot is (should) not be needed
         * by the flush code.
         */
        iroot = pmp->iroot;
        if (iroot) {
                /*
                 * Stop synchronizing
                 *
                 * XXX flush after acquiring the iroot lock.
                 * XXX clean out the cluster index from all inode structures.
                 */
                hammer2_thr_delete(&pmp->sync_thrs[clindex]);

                /*
                 * Remove the cluster index from the group.  If destroying
                 * the PFS and this is a master, adjust pfs_nmasters.
                 */
                hammer2_mtx_ex(&iroot->lock);
                chain = iroot->cluster.array[clindex].chain;
                iroot->cluster.array[clindex].chain = NULL;

                switch(pmp->pfs_types[clindex]) {
                case HAMMER2_PFSTYPE_MASTER:
                        if (destroying && pmp->pfs_nmasters > 0)
                                --pmp->pfs_nmasters;
                        /* XXX adjust ripdata->meta.pfs_nmasters */
                        break;
                default:
                        break;
                }
                pmp->pfs_types[clindex] = HAMMER2_PFSTYPE_NONE;

                hammer2_mtx_unlock(&iroot->lock);

                /*
                 * Release the chain.
                 */
                if (chain) {
                        atomic_set_int(&chain->flags, HAMMER2_CHAIN_RELEASE);
                        hammer2_chain_drop(chain);
                }

                /*
                 * Terminate all XOP threads for the cluster index.
                 */
                if (pmp->xop_groups) {
                        for (j = 0; j < hammer2_xop_nthreads; ++j) {
                                hammer2_thr_delete(
                                        &pmp->xop_groups[j].thrs[clindex]);
                        }
                }
        }
}

/*
 * Destroy a PFS, typically only occurs after the last mount on a device
 * has gone away.
 */
static void
hammer2_pfsfree(hammer2_pfs_t *pmp)
{
        hammer2_inode_t *iroot;
        hammer2_chain_t *chain;
        int chains_still_present = 0;
        int i;
        int j;

        /*
         * Cleanup our reference on iroot.  iroot is (should) not be needed
         * by the flush code.
         */
        if (pmp->flags & HAMMER2_PMPF_SPMP)
                TAILQ_REMOVE(&hammer2_spmplist, pmp, mntentry);
        else
                TAILQ_REMOVE(&hammer2_pfslist, pmp, mntentry);

        /*
         * Clean up iroot
         */
        iroot = pmp->iroot;
        if (iroot) {
                for (i = 0; i < iroot->cluster.nchains; ++i) {
                        hammer2_thr_delete(&pmp->sync_thrs[i]);
                        if (pmp->xop_groups) {
                                for (j = 0; j < hammer2_xop_nthreads; ++j)
                                        hammer2_thr_delete(
                                                &pmp->xop_groups[j].thrs[i]);
                        }
                        chain = iroot->cluster.array[i].chain;
                        if (chain && !RB_EMPTY(&chain->core.rbtree)) {
                                kprintf("hammer2: Warning pmp %p still "
                                        "has active chains\n", pmp);
                                chains_still_present = 1;
                        }
                }
                KASSERT(iroot->refs == 1,
                        ("PMP->IROOT %p REFS WRONG %d", iroot, iroot->refs));

                /* ref for iroot */
                hammer2_inode_drop(iroot);
                pmp->iroot = NULL;
        }

        /*
         * Free remaining pmp resources
         */
        if (chains_still_present) {
                kprintf("hammer2: cannot free pmp %p, still in use\n", pmp);
        } else {
                kmalloc_destroy_obj(&pmp->minode);
                kfree(pmp, M_HAMMER2);
        }
}

/*
 * Remove all references to hmp from the pfs list.  Any PFS which becomes
 * empty is terminated and freed.
 *
 * XXX inefficient.
 */
static void
hammer2_pfsfree_scan(hammer2_dev_t *hmp, int which)
{
        hammer2_pfs_t *pmp;
        hammer2_inode_t *iroot;
        hammer2_chain_t *rchain;
        int i;
        int j;
        struct hammer2_pfslist *wlist;

        if (which == 0)
                wlist = &hammer2_pfslist;
        else
                wlist = &hammer2_spmplist;
again:
        TAILQ_FOREACH(pmp, wlist, mntentry) {
                if ((iroot = pmp->iroot) == NULL)
                        continue;

                /*
                 * Determine if this PFS is affected.  If it is we must
                 * freeze all management threads and lock its iroot.
                 *
                 * Freezing a management thread forces it idle, operations
                 * in-progress will be aborted and it will have to start
                 * over again when unfrozen, or exit if told to exit.
                 */
                for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                        if (pmp->pfs_hmps[i] == hmp)
                                break;
                }
                if (i == HAMMER2_MAXCLUSTER)
                        continue;

                hammer2_vfs_sync_pmp(pmp, MNT_WAIT);

                /*
                 * Make sure all synchronization threads are locked
                 * down.
                 */
                for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                        if (pmp->pfs_hmps[i] == NULL)
                                continue;
                        hammer2_thr_freeze_async(&pmp->sync_thrs[i]);
                        if (pmp->xop_groups) {
                                for (j = 0; j < hammer2_xop_nthreads; ++j) {
                                        hammer2_thr_freeze_async(
                                                &pmp->xop_groups[j].thrs[i]);
                                }
                        }
                }
                for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                        if (pmp->pfs_hmps[i] == NULL)
                                continue;
                        hammer2_thr_freeze(&pmp->sync_thrs[i]);
                        if (pmp->xop_groups) {
                                for (j = 0; j < hammer2_xop_nthreads; ++j) {
                                        hammer2_thr_freeze(
                                                &pmp->xop_groups[j].thrs[i]);
                                }
                        }
                }

                /*
                 * Lock the inode and clean out matching chains.
                 * Note that we cannot use hammer2_inode_lock_*()
                 * here because that would attempt to validate the
                 * cluster that we are in the middle of ripping
                 * apart.
                 *
                 * WARNING! We are working directly on the inodes
                 *          embedded cluster.
                 */
                hammer2_mtx_ex(&iroot->lock);

                /*
                 * Remove the chain from matching elements of the PFS.
                 */
                for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                        if (pmp->pfs_hmps[i] != hmp)
                                continue;
                        hammer2_thr_delete(&pmp->sync_thrs[i]);
                        if (pmp->xop_groups) {
                                for (j = 0; j < hammer2_xop_nthreads; ++j) {
                                        hammer2_thr_delete(
                                                &pmp->xop_groups[j].thrs[i]);
                                }
                        }
                        rchain = iroot->cluster.array[i].chain;
                        iroot->cluster.array[i].chain = NULL;
                        pmp->pfs_types[i] = HAMMER2_PFSTYPE_NONE;
                        if (pmp->pfs_names[i]) {
                                kfree(pmp->pfs_names[i], M_HAMMER2);
                                pmp->pfs_names[i] = NULL;
                        }
                        if (rchain) {
                                hammer2_chain_drop(rchain);
                                /* focus hint */
                                if (iroot->cluster.focus == rchain)
                                        iroot->cluster.focus = NULL;
                        }
                        pmp->pfs_hmps[i] = NULL;
                }
                hammer2_mtx_unlock(&iroot->lock);

                /*
                 * Cleanup trailing chains.  Gaps may remain.
                 */
                for (i = HAMMER2_MAXCLUSTER - 1; i >= 0; --i) {
                        if (pmp->pfs_hmps[i])
                                break;
                }
                iroot->cluster.nchains = i + 1;

                /*
                 * If the PMP has no elements remaining we can destroy it.
                 * (this will transition management threads from frozen->exit).
                 */
                if (iroot->cluster.nchains == 0) {
                        /*
                         * If this was the hmp's spmp, we need to clean
                         * a little more stuff out.
                         */
                        if (hmp->spmp == pmp) {
                                hmp->spmp = NULL;
                                hmp->vchain.pmp = NULL;
                                hmp->fchain.pmp = NULL;
                        }

                        /*
                         * Free the pmp and restart the loop
                         */
                        KKASSERT(TAILQ_EMPTY(&pmp->syncq));
                        KKASSERT(TAILQ_EMPTY(&pmp->depq));
                        hammer2_pfsfree(pmp);
                        goto again;
                }

                /*
                 * If elements still remain we need to set the REMASTER
                 * flag and unfreeze it.
                 */
                for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                        if (pmp->pfs_hmps[i] == NULL)
                                continue;
                        hammer2_thr_remaster(&pmp->sync_thrs[i]);
                        hammer2_thr_unfreeze(&pmp->sync_thrs[i]);
                        if (pmp->xop_groups) {
                                for (j = 0; j < hammer2_xop_nthreads; ++j) {
                                        hammer2_thr_remaster(
                                                &pmp->xop_groups[j].thrs[i]);
                                        hammer2_thr_unfreeze(
                                                &pmp->xop_groups[j].thrs[i]);
                                }
                        }
                }
        }
}

/*
 * Mount or remount HAMMER2 fileystem from physical media
 *
 *      mountroot
 *              mp              mount point structure
 *              path            NULL
 *              data            <unused>
 *              cred            <unused>
 *
 *      mount
 *              mp              mount point structure
 *              path            path to mount point
 *              data            pointer to argument structure in user space
 *                      volume  volume path (device@LABEL form)
 *                      hflags  user mount flags
 *              cred            user credentials
 *
 * RETURNS:     0       Success
 *              !0      error number
 */
static
int
hammer2_vfs_mount(struct mount *mp, char *path, caddr_t data,
                  struct ucred *cred)
{
        struct hammer2_mount_info info;
        hammer2_pfs_t *pmp;
        hammer2_pfs_t *spmp;
        hammer2_dev_t *hmp, *hmp_tmp;
        hammer2_dev_t *force_local;
        hammer2_key_t key_next;
        hammer2_key_t key_dummy;
        hammer2_key_t lhc;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        const hammer2_inode_data_t *ripdata;
        hammer2_devvp_list_t devvpl;
        hammer2_devvp_t *e, *e_tmp;
        struct file *fp;
        char devstr[MNAMELEN];
        size_t size;
        size_t done;
        char *label;
        int ronly = ((mp->mnt_flag & MNT_RDONLY) != 0);
        int error;
        int i;

        hmp = NULL;
        pmp = NULL;
        label = NULL;
        bzero(&info, sizeof(info));

        if (path) {
                /*
                 * Non-root mount or updating a mount
                 */
                error = copyin(data, &info, sizeof(info));
                if (error)
                        return (error);
        }

        if (mp->mnt_flag & MNT_UPDATE) {
                /*
                 * Update mount.  Note that pmp->iroot->cluster is
                 * an inode-embedded cluster and thus cannot be
                 * directly locked.
                 *
                 * XXX HAMMER2 needs to implement NFS export via
                 *     mountctl.
                 */
                hammer2_cluster_t *cluster;

                error = 0;
                pmp = MPTOPMP(mp);
                pmp->hflags = info.hflags;
                cluster = &pmp->iroot->cluster;
                for (i = 0; i < cluster->nchains; ++i) {
                        if (cluster->array[i].chain == NULL)
                                continue;
                        hmp = cluster->array[i].chain->hmp;
                        error = hammer2_remount(hmp, mp, path, cred);
                        if (error)
                                break;
                }

                return error;
        }

        if (path == NULL) {
                /*
                 * Root mount
                 */
                info.cluster_fd = -1;
                ksnprintf(devstr, sizeof(devstr), "%s",
                          mp->mnt_stat.f_mntfromname);
                done = strlen(devstr) + 1;
                kprintf("hammer2_mount: root devstr=\"%s\"\n", devstr);
        } else {
                error = copyinstr(info.volume, devstr, MNAMELEN - 1, &done);
                if (error)
                        return (error);
                kprintf("hammer2_mount: devstr=\"%s\"\n", devstr);
        }

        /*
         * Extract device and label, automatically mount @BOOT, @ROOT, or @DATA
         * if no label specified, based on the partition id.  Error out if no
         * label or device (with partition id) is specified.  This is strictly
         * a convenience to match the default label created by newfs_hammer2,
         * our preference is that a label always be specified.
         *
         * NOTE: We allow 'mount @LABEL <blah>'... that is, a mount command
         *       that does not specify a device, as long as some H2 label
         *       has already been mounted from that device.  This makes
         *       mounting snapshots a lot easier.
         */
        label = strchr(devstr, '@');
        if (label && ((label + 1) - devstr) > done) {
                kprintf("hammer2_mount: bad label %s/%zd\n", devstr, done);
                return (EINVAL);
        }
        if (label == NULL || label[1] == 0) {
                char slice;

                if (label == NULL)
                        label = devstr + strlen(devstr);
                else
                        *label = '\0';          /* clean up trailing @ */

                slice = label[-1];
                switch(slice) {
                case 'a':
                        label = "BOOT";
                        break;
                case 'd':
                        label = "ROOT";
                        break;
                default:
                        label = "DATA";
                        break;
                }
        } else {
                *label = '\0';
                label++;
        }

        kprintf("hammer2_mount: device=\"%s\" label=\"%s\" rdonly=%d\n",
                devstr, label, ronly);

        /*
         * Initialize all device vnodes.
         */
        TAILQ_INIT(&devvpl);
        error = hammer2_init_devvp(devstr, path == NULL, &devvpl);
        if (error) {
                kprintf("hammer2: failed to initialize devvp in %s\n", devstr);
                hammer2_cleanup_devvp(&devvpl);
                return error;
        }

        /*
         * Determine if the device has already been mounted.  After this
         * check hmp will be non-NULL if we are doing the second or more
         * hammer2 mounts from the same device.
         */
        lockmgr(&hammer2_mntlk, LK_EXCLUSIVE);
        if (!TAILQ_EMPTY(&devvpl)) {
                /*
                 * Match the device.  Due to the way devfs works,
                 * we may not be able to directly match the vnode pointer,
                 * so also check to see if the underlying device matches.
                 */
                TAILQ_FOREACH(hmp_tmp, &hammer2_mntlist, mntentry) {
                        TAILQ_FOREACH(e_tmp, &hmp_tmp->devvpl, entry) {
                                int devvp_found = 0;
                                TAILQ_FOREACH(e, &devvpl, entry) {
                                        KKASSERT(e->devvp);
                                        if (e_tmp->devvp == e->devvp)
                                                devvp_found = 1;
                                        if (e_tmp->devvp->v_rdev &&
                                            e_tmp->devvp->v_rdev == e->devvp->v_rdev)
                                                devvp_found = 1;
                                }
                                if (!devvp_found)
                                        goto next_hmp;
                        }
                        hmp = hmp_tmp;
                        kprintf("hammer2_mount: hmp=%p matched\n", hmp);
                        break;
next_hmp:
                        continue;
                }

                /*
                 * If no match this may be a fresh H2 mount, make sure
                 * the device is not mounted on anything else.
                 */
                if (hmp == NULL) {
                        TAILQ_FOREACH(e, &devvpl, entry) {
                                struct vnode *devvp = e->devvp;
                                KKASSERT(devvp);
                                error = vfs_mountedon(devvp);
                                if (error) {
                                        kprintf("hammer2_mount: %s mounted %d\n",
                                                e->path, error);
                                        hammer2_cleanup_devvp(&devvpl);
                                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                                        return error;
                                }
                        }
                }
        } else {
                /*
                 * Match the label to a pmp already probed.
                 */
                TAILQ_FOREACH(pmp, &hammer2_pfslist, mntentry) {
                        for (i = 0; i < HAMMER2_MAXCLUSTER; ++i) {
                                if (pmp->pfs_names[i] &&
                                    strcmp(pmp->pfs_names[i], label) == 0) {
                                        hmp = pmp->pfs_hmps[i];
                                        break;
                                }
                        }
                        if (hmp)
                                break;
                }
                if (hmp == NULL) {
                        kprintf("hammer2_mount: PFS label \"%s\" not found\n",
                                label);
                        hammer2_cleanup_devvp(&devvpl);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        return ENOENT;
                }
        }

        /*
         * Open the device if this isn't a secondary mount and construct
         * the H2 device mount (hmp).
         */
        if (hmp == NULL) {
                hammer2_chain_t *schain;
                hammer2_xop_head_t xop;

                /*
                 * Now open the device
                 */
                KKASSERT(!TAILQ_EMPTY(&devvpl));
                error = hammer2_open_devvp(&devvpl, ronly);
                if (error) {
                        hammer2_close_devvp(&devvpl, ronly);
                        hammer2_cleanup_devvp(&devvpl);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        return error;
                }

                /*
                 * Construct volumes and link with device vnodes.
                 */
                hmp = kmalloc(sizeof(*hmp), M_HAMMER2, M_WAITOK | M_ZERO);
                hmp->devvp = NULL;
                error = hammer2_init_volumes(mp, &devvpl, hmp->volumes,
                                             &hmp->voldata, &hmp->volhdrno,
                                             &hmp->devvp);
                if (error) {
                        hammer2_close_devvp(&devvpl, ronly);
                        hammer2_cleanup_devvp(&devvpl);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        kfree(hmp, M_HAMMER2);
                        return error;
                }
                if (!hmp->devvp) {
                        kprintf("hammer2: failed to initialize root volume\n");
                        hammer2_unmount_helper(mp, NULL, hmp);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        hammer2_vfs_unmount(mp, MNT_FORCE);
                        return EINVAL;
                }

                ksnprintf(hmp->devrepname, sizeof(hmp->devrepname), "%s", devstr);
                hmp->ronly = ronly;
                hmp->hflags = info.hflags & HMNT2_DEVFLAGS;
                kmalloc_create_obj(&hmp->mchain, "HAMMER2-chains",
                                   sizeof(struct hammer2_chain));
                kmalloc_create_obj(&hmp->mio, "HAMMER2-dio",
                                   sizeof(struct hammer2_io));
                kmalloc_create(&hmp->mmsg, "HAMMER2-msg");
                TAILQ_INSERT_TAIL(&hammer2_mntlist, hmp, mntentry);
                hammer2_io_hash_init(hmp);
                hammer2_spin_init(&hmp->list_spin, "h2mount_list");

                lockinit(&hmp->vollk, "h2vol", 0, 0);
                lockinit(&hmp->bulklk, "h2bulk", 0, 0);
                lockinit(&hmp->bflock, "h2bflk", 0, 0);

                /*
                 * vchain setup. vchain.data is embedded.
                 * vchain.refs is initialized and will never drop to 0.
                 */
                hmp->vchain.hmp = hmp;
                hmp->vchain.refs = 1;
                hmp->vchain.data = (void *)&hmp->voldata;
                hmp->vchain.bref.type = HAMMER2_BREF_TYPE_VOLUME;
                hmp->vchain.bref.data_off = 0 | HAMMER2_PBUFRADIX;
                hammer2_chain_init(&hmp->vchain);

                /*
                 * fchain setup.  fchain.data is embedded.
                 * fchain.refs is initialized and will never drop to 0.
                 *
                 * The data is not used but needs to be initialized to
                 * pass assertion muster.  We use this chain primarily
                 * as a placeholder for the freemap's top-level radix tree
                 * so it does not interfere with the volume's topology
                 * radix tree.
                 */
                hmp->fchain.hmp = hmp;
                hmp->fchain.refs = 1;
                hmp->fchain.data = (void *)&hmp->voldata.freemap_blockset;
                hmp->fchain.bref.type = HAMMER2_BREF_TYPE_FREEMAP;
                hmp->fchain.bref.data_off = 0 | HAMMER2_PBUFRADIX;
                hmp->fchain.bref.methods =
                        HAMMER2_ENC_CHECK(HAMMER2_CHECK_FREEMAP) |
                        HAMMER2_ENC_COMP(HAMMER2_COMP_NONE);
                hammer2_chain_init(&hmp->fchain);

                /*
                 * Initialize volume header related fields.
                 */
                KKASSERT(hmp->voldata.magic == HAMMER2_VOLUME_ID_HBO ||
                         hmp->voldata.magic == HAMMER2_VOLUME_ID_ABO);
                hmp->volsync = hmp->voldata;
                hmp->free_reserved = hmp->voldata.allocator_size / 20;
                /*
                 * Must use hmp instead of volume header for these two
                 * in order to handle volume versions transparently.
                 */
                if (hmp->voldata.version >= HAMMER2_VOL_VERSION_MULTI_VOLUMES) {
                        hmp->nvolumes = hmp->voldata.nvolumes;
                        hmp->total_size = hmp->voldata.total_size;
                } else {
                        hmp->nvolumes = 1;
                        hmp->total_size = hmp->voldata.volu_size;
                }
                KKASSERT(hmp->nvolumes > 0);

                /*
                 * Move devvpl entries to hmp.
                 */
                TAILQ_INIT(&hmp->devvpl);
                while ((e = TAILQ_FIRST(&devvpl)) != NULL) {
                        TAILQ_REMOVE(&devvpl, e, entry);
                        TAILQ_INSERT_TAIL(&hmp->devvpl, e, entry);
                }
                KKASSERT(TAILQ_EMPTY(&devvpl));
                KKASSERT(!TAILQ_EMPTY(&hmp->devvpl));

                /*
                 * Really important to get these right or the flush and
                 * teardown code will get confused.
                 */
                hmp->spmp = hammer2_pfsalloc(NULL, NULL, NULL);
                spmp = hmp->spmp;
                spmp->pfs_hmps[0] = hmp;

                /*
                 * Dummy-up vchain and fchain's modify_tid.  mirror_tid
                 * is inherited from the volume header.
                 */
                hmp->vchain.bref.mirror_tid = hmp->voldata.mirror_tid;
                hmp->vchain.bref.modify_tid = hmp->vchain.bref.mirror_tid;
                hmp->vchain.pmp = spmp;
                hmp->fchain.bref.mirror_tid = hmp->voldata.freemap_tid;
                hmp->fchain.bref.modify_tid = hmp->fchain.bref.mirror_tid;
                hmp->fchain.pmp = spmp;

                /*
                 * First locate the super-root inode, which is key 0
                 * relative to the volume header's blockset.
                 *
                 * Then locate the root inode by scanning the directory keyspace
                 * represented by the label.
                 */
                parent = hammer2_chain_lookup_init(&hmp->vchain, 0);
                schain = hammer2_chain_lookup(&parent, &key_dummy,
                                      HAMMER2_SROOT_KEY, HAMMER2_SROOT_KEY,
                                      &error, 0);
                hammer2_chain_lookup_done(parent);
                if (schain == NULL) {
                        kprintf("hammer2_mount: invalid super-root\n");
                        hammer2_unmount_helper(mp, NULL, hmp);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        hammer2_vfs_unmount(mp, MNT_FORCE);
                        return EINVAL;
                }
                if (schain->error) {
                        kprintf("hammer2_mount: error %s reading super-root\n",
                                hammer2_error_str(schain->error));
                        hammer2_chain_unlock(schain);
                        hammer2_chain_drop(schain);
                        schain = NULL;
                        hammer2_unmount_helper(mp, NULL, hmp);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        hammer2_vfs_unmount(mp, MNT_FORCE);
                        return EINVAL;
                }

                /*
                 * The super-root always uses an inode_tid of 1 when
                 * creating PFSs.
                 */
                spmp->inode_tid = 1;
                spmp->modify_tid = schain->bref.modify_tid + 1;

                /*
                 * Sanity-check schain's pmp and finish initialization.
                 * Any chain belonging to the super-root topology should
                 * have a NULL pmp (not even set to spmp).
                 */
                ripdata = &schain->data->ipdata;
                KKASSERT(schain->pmp == NULL);
                spmp->pfs_clid = ripdata->meta.pfs_clid;

                /*
                 * Replace the dummy spmp->iroot with a real one.  It's
                 * easier to just do a wholesale replacement than to try
                 * to update the chain and fixup the iroot fields.
                 *
                 * The returned inode is locked with the supplied cluster.
                 */
                hammer2_dummy_xop_from_chain(&xop, schain);
                hammer2_inode_drop(spmp->iroot);
                spmp->iroot = hammer2_inode_get(spmp, &xop, -1, -1);
                spmp->spmp_hmp = hmp;
                spmp->pfs_types[0] = ripdata->meta.pfs_type;
                spmp->ronly = ronly;
                hammer2_inode_ref(spmp->iroot);
                hammer2_inode_unlock(spmp->iroot);
                hammer2_cluster_unlock(&xop.cluster);
                hammer2_chain_drop(schain);
                /* do not call hammer2_cluster_drop() on an embedded cluster */
                schain = NULL;  /* now invalid */
                /* leave spmp->iroot with one ref */

                if (!hmp->ronly) {
                        error = hammer2_recovery(hmp);
                        if (error == 0)
                                error |= hammer2_fixup_pfses(hmp);
                        /* XXX do something with error */
                }
                hammer2_update_pmps(hmp);
                hammer2_iocom_init(hmp);
                hammer2_bulkfree_init(hmp);

                /*
                 * Ref the cluster management messaging descriptor.  The mount
                 * program deals with the other end of the communications pipe.
                 *
                 * Root mounts typically do not supply one.
                 */
                if (info.cluster_fd >= 0) {
                        fp = holdfp(curthread, info.cluster_fd, -1);
                        if (fp) {
                                hammer2_cluster_reconnect(hmp, fp);
                        } else {
                                kprintf("hammer2_mount: bad cluster_fd!\n");
                        }
                }
        } else {
                /* hmp->devvp_list is already constructed. */
                hammer2_cleanup_devvp(&devvpl);
                spmp = hmp->spmp;
                if (info.hflags & HMNT2_DEVFLAGS) {
                        kprintf("hammer2_mount: Warning: mount flags pertaining "
                                "to the whole device may only be specified "
                                "on the first mount of the device: %08x\n",
                                info.hflags & HMNT2_DEVFLAGS);
                }
        }

        /*
         * Force local mount (disassociate all PFSs from their clusters).
         * Used primarily for debugging.
         */
        force_local = (hmp->hflags & HMNT2_LOCAL) ? hmp : NULL;

        /*
         * Lookup the mount point under the media-localized super-root.
         * Scanning hammer2_pfslist doesn't help us because it represents
         * PFS cluster ids which can aggregate several named PFSs together.
         *
         * cluster->pmp will incorrectly point to spmp and must be fixed
         * up later on.
         */
        hammer2_inode_lock(spmp->iroot, 0);
        parent = hammer2_inode_chain(spmp->iroot, 0, HAMMER2_RESOLVE_ALWAYS);
        lhc = hammer2_dirhash(label, strlen(label));
        chain = hammer2_chain_lookup(&parent, &key_next,
                                     lhc, lhc + HAMMER2_DIRHASH_LOMASK,
                                     &error, 0);
        while (chain) {
                if (chain->bref.type == HAMMER2_BREF_TYPE_INODE &&
                    strcmp(label, (char *)chain->data->ipdata.filename) == 0) {
                        break;
                }
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                            key_next,
                                            lhc + HAMMER2_DIRHASH_LOMASK,
                                            &error, 0);
        }
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
        hammer2_inode_unlock(spmp->iroot);

        /*
         * PFS could not be found?
         */
        if (chain == NULL) {
                hammer2_unmount_helper(mp, NULL, hmp);
                lockmgr(&hammer2_mntlk, LK_RELEASE);
                hammer2_vfs_unmount(mp, MNT_FORCE);

                if (error) {
                        kprintf("hammer2_mount: PFS label I/O error\n");
                        return EINVAL;
                } else {
                        kprintf("hammer2_mount: PFS label \"%s\" not found\n",
                                label);
                        return ENOENT;
                }
        }

        /*
         * Acquire the pmp structure (it should have already been allocated
         * via hammer2_update_pmps()).
         */
        if (chain->error) {
                kprintf("hammer2_mount: PFS label I/O error\n");
        } else {
                ripdata = &chain->data->ipdata;
                pmp = hammer2_pfsalloc(NULL, ripdata, force_local);
        }
        hammer2_chain_unlock(chain);
        hammer2_chain_drop(chain);

        /*
         * PFS to mount must exist at this point.
         */
        if (pmp == NULL) {
                kprintf("hammer2_mount: Failed to acquire PFS structure\n");
                hammer2_unmount_helper(mp, NULL, hmp);
                lockmgr(&hammer2_mntlk, LK_RELEASE);
                hammer2_vfs_unmount(mp, MNT_FORCE);
                return EINVAL;
        }

        /*
         * Finish the mount
         */
        kprintf("hammer2_mount: hmp=%p pmp=%p\n", hmp, pmp);

        /* Check if the pmp has already been mounted. */
        if (pmp->mp) {
                kprintf("hammer2_mount: PFS already mounted!\n");
                hammer2_unmount_helper(mp, NULL, hmp);
                lockmgr(&hammer2_mntlk, LK_RELEASE);
                hammer2_vfs_unmount(mp, MNT_FORCE);
                return EBUSY;
        }

        pmp->ronly = ronly;
        pmp->hflags = info.hflags;
        mp->mnt_flag |= MNT_LOCAL;
        mp->mnt_kern_flag |= MNTK_ALL_MPSAFE;   /* all entry pts are SMP */
        mp->mnt_kern_flag |= MNTK_THR_SYNC;     /* new vsyncscan semantics */

        /*
         * required mount structure initializations
         */
        mp->mnt_stat.f_iosize = HAMMER2_PBUFSIZE;
        mp->mnt_stat.f_bsize = HAMMER2_PBUFSIZE;

        mp->mnt_vstat.f_frsize = HAMMER2_PBUFSIZE;
        mp->mnt_vstat.f_bsize = HAMMER2_PBUFSIZE;

        /*
         * Optional fields
         */
        mp->mnt_iosize_max = MAXPHYS;

        /*
         * Connect up mount pointers.
         */
        hammer2_mount_helper(mp, pmp);
        lockmgr(&hammer2_mntlk, LK_RELEASE);

        /*
         * Finish setup
         */
        vfs_getnewfsid(mp);
        vfs_add_vnodeops(mp, &hammer2_vnode_vops, &mp->mnt_vn_norm_ops);
        vfs_add_vnodeops(mp, &hammer2_spec_vops, &mp->mnt_vn_spec_ops);
        vfs_add_vnodeops(mp, &hammer2_fifo_vops, &mp->mnt_vn_fifo_ops);

        if (path) {
                copyinstr(info.volume, mp->mnt_stat.f_mntfromname,
                          MNAMELEN - 1, &size);
                bzero(mp->mnt_stat.f_mntfromname + size, MNAMELEN - size);
        } /* else root mount, already in there */

        bzero(mp->mnt_stat.f_mntonname, sizeof(mp->mnt_stat.f_mntonname));
        if (path) {
                copyinstr(path, mp->mnt_stat.f_mntonname,
                          sizeof(mp->mnt_stat.f_mntonname) - 1,
                          &size);
        } else {
                /* root mount */
                mp->mnt_stat.f_mntonname[0] = '/';
        }

        /*
         * Initial statfs to prime mnt_stat.
         */
        hammer2_vfs_statfs(mp, &mp->mnt_stat, cred);

        return 0;
}

/*
 * Scan PFSs under the super-root and create hammer2_pfs structures.
 */
static
void
hammer2_update_pmps(hammer2_dev_t *hmp)
{
        const hammer2_inode_data_t *ripdata;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_dev_t *force_local;
        hammer2_pfs_t *spmp;
        hammer2_key_t key_next;
        int error;

        /*
         * Force local mount (disassociate all PFSs from their clusters).
         * Used primarily for debugging.
         */
        force_local = (hmp->hflags & HMNT2_LOCAL) ? hmp : NULL;

        /*
         * Lookup mount point under the media-localized super-root.
         *
         * cluster->pmp will incorrectly point to spmp and must be fixed
         * up later on.
         */
        spmp = hmp->spmp;
        hammer2_inode_lock(spmp->iroot, 0);
        parent = hammer2_inode_chain(spmp->iroot, 0, HAMMER2_RESOLVE_ALWAYS);
        chain = hammer2_chain_lookup(&parent, &key_next,
                                         HAMMER2_KEY_MIN, HAMMER2_KEY_MAX,
                                         &error, 0);
        while (chain) {
                if (chain->error) {
                        kprintf("I/O error scanning PFS labels\n");
                } else if (chain->bref.type != HAMMER2_BREF_TYPE_INODE) {
                        kprintf("Non inode chain type %d under super-root\n",
                                chain->bref.type);
                } else {
                        ripdata = &chain->data->ipdata;
                        hammer2_pfsalloc(chain, ripdata, force_local);
                }
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next, HAMMER2_KEY_MAX,
                                           &error, 0);
        }
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
        hammer2_inode_unlock(spmp->iroot);
}

static
int
hammer2_remount(hammer2_dev_t *hmp, struct mount *mp, char *path __unused,
                struct ucred *cred)
{
        hammer2_pfs_t *pmp;
        hammer2_volume_t *vol;
        struct vnode *devvp;
        int i, ronly_save, error, result = 0;

        pmp = MPTOPMP(mp);
        ronly_save = pmp->ronly;
        if (pmp->ronly == 1 && (mp->mnt_kern_flag & MNTK_WANTRDWR))
                pmp->ronly = 0;
        else if (pmp->ronly == 0 && (mp->mnt_flag & MNT_RDONLY))
                pmp->ronly = 1;

        if (!(hmp->ronly && (mp->mnt_kern_flag & MNTK_WANTRDWR)))
                return 0;

        for (i = 0; i < hmp->nvolumes; ++i) {
                vol = &hmp->volumes[i];
                devvp = vol->dev->devvp;
                KKASSERT(devvp);
                vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                VOP_OPEN(devvp, FREAD | FWRITE, FSCRED, NULL);
                vn_unlock(devvp);
                error = 0;
                if (vol->id == HAMMER2_ROOT_VOLUME) {
                        error = hammer2_recovery(hmp);
                        if (error == 0)
                                error |= hammer2_fixup_pfses(hmp);
                }
                vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                if (error == 0) {
                        VOP_CLOSE(devvp, FREAD, NULL);
                } else {
                        VOP_CLOSE(devvp, FREAD | FWRITE, NULL);
                }
                vn_unlock(devvp);
                result |= error;
        }
        if (result == 0) {
                kprintf("hammer2: enable read/write\n");
                hmp->ronly = 0;
                hmp->spmp->ronly = 0; /* never used */
        } else {
                pmp->ronly = ronly_save;
        }

        return result;
}

static
int
hammer2_vfs_unmount(struct mount *mp, int mntflags)
{
        hammer2_pfs_t *pmp;
        int flags;
        int error = 0;

        pmp = MPTOPMP(mp);

        if (pmp == NULL)
                return(0);

        lockmgr(&hammer2_mntlk, LK_EXCLUSIVE);

        /*
         * If mount initialization proceeded far enough we must flush
         * its vnodes and sync the underlying mount points.  Three syncs
         * are required to fully flush the filesystem (freemap updates lag
         * by one flush, and one extra for safety).
         */
        if (mntflags & MNT_FORCE)
                flags = FORCECLOSE;
        else
                flags = 0;
        if (pmp->iroot) {
                error = vflush(mp, 0, flags);
                if (error)
                        goto failed;
                hammer2_vfs_sync(mp, MNT_WAIT);
                hammer2_vfs_sync(mp, MNT_WAIT);
                hammer2_vfs_sync(mp, MNT_WAIT);
        }

        /*
         * Cleanup the frontend support XOPS threads
         */
        hammer2_xop_helper_cleanup(pmp);

        if (pmp->mp)
                hammer2_unmount_helper(mp, pmp, NULL);

        error = 0;
failed:
        lockmgr(&hammer2_mntlk, LK_RELEASE);

        return (error);
}

/*
 * Mount helper, hook the system mount into our PFS.
 * The mount lock is held.
 *
 * We must bump the mount_count on related devices for any
 * mounted PFSs.
 */
static
void
hammer2_mount_helper(struct mount *mp, hammer2_pfs_t *pmp)
{
        hammer2_cluster_t *cluster;
        hammer2_chain_t *rchain;
        int i;

        mp->mnt_data = (qaddr_t)pmp;
        pmp->mp = mp;

        /*
         * After pmp->mp is set we have to adjust hmp->mount_count.
         */
        cluster = &pmp->iroot->cluster;
        for (i = 0; i < cluster->nchains; ++i) {
                rchain = cluster->array[i].chain;
                if (rchain == NULL)
                        continue;
                ++rchain->hmp->mount_count;
        }

        /*
         * Create missing Xop threads
         */
        hammer2_xop_helper_create(pmp);
}

/*
 * Unmount helper, unhook the system mount from our PFS.
 * The mount lock is held.
 *
 * If hmp is supplied a mount responsible for being the first to open
 * the block device failed and the block device and all PFSs using the
 * block device must be cleaned up.
 *
 * If pmp is supplied multiple devices might be backing the PFS and each
 * must be disconnected.  This might not be the last PFS using some of the
 * underlying devices.  Also, we have to adjust our hmp->mount_count
 * accounting for the devices backing the pmp which is now undergoing an
 * unmount.
 */
static
void
hammer2_unmount_helper(struct mount *mp, hammer2_pfs_t *pmp, hammer2_dev_t *hmp)
{
        hammer2_cluster_t *cluster;
        hammer2_chain_t *rchain;
        int dumpcnt;
        int i;

        /*
         * If no device supplied this is a high-level unmount and we have to
         * to disconnect the mount, adjust mount_count, and locate devices
         * that might now have no mounts.
         */
        if (pmp) {
                KKASSERT(hmp == NULL);
                KKASSERT(MPTOPMP(mp) == pmp);
                pmp->mp = NULL;
                mp->mnt_data = NULL;

                /*
                 * After pmp->mp is cleared we have to account for
                 * mount_count.
                 */
                cluster = &pmp->iroot->cluster;
                for (i = 0; i < cluster->nchains; ++i) {
                        rchain = cluster->array[i].chain;
                        if (rchain == NULL)
                                continue;
                        --rchain->hmp->mount_count;
                        /* scrapping hmp now may invalidate the pmp */
                }
again:
                TAILQ_FOREACH(hmp, &hammer2_mntlist, mntentry) {
                        if (hmp->mount_count == 0) {
                                hammer2_unmount_helper(NULL, NULL, hmp);
                                goto again;
                        }
                }
                return;
        }

        /*
         * Try to terminate the block device.  We can't terminate it if
         * there are still PFSs referencing it.
         */
        if (hmp->mount_count)
                return;

        /*
         * Decomission the network before we start messing with the
         * device and PFS.
         */
        hammer2_iocom_uninit(hmp);

        hammer2_bulkfree_uninit(hmp);
        hammer2_pfsfree_scan(hmp, 0);

        /*
         * Cycle the volume data lock as a safety (probably not needed any
         * more).  To ensure everything is out we need to flush at least
         * three times.  (1) The running of the sideq can dirty the
         * filesystem, (2) A normal flush can dirty the freemap, and
         * (3) ensure that the freemap is fully synchronized.
         *
         * The next mount's recovery scan can clean everything up but we want
         * to leave the filesystem in a 100% clean state on a normal unmount.
         */
#if 0
        hammer2_voldata_lock(hmp);
        hammer2_voldata_unlock(hmp);
#endif

        /*
         * Flush whatever is left.  Unmounted but modified PFS's might still
         * have some dirty chains on them.
         */
        hammer2_chain_lock(&hmp->vchain, HAMMER2_RESOLVE_ALWAYS);
        hammer2_chain_lock(&hmp->fchain, HAMMER2_RESOLVE_ALWAYS);

        if (hmp->fchain.flags & HAMMER2_CHAIN_FLUSH_MASK) {
                hammer2_voldata_modify(hmp);
                hammer2_flush(&hmp->fchain, HAMMER2_FLUSH_TOP |
                                            HAMMER2_FLUSH_ALL);
        }
        hammer2_chain_unlock(&hmp->fchain);

        if (hmp->vchain.flags & HAMMER2_CHAIN_FLUSH_MASK) {
                hammer2_flush(&hmp->vchain, HAMMER2_FLUSH_TOP |
                                            HAMMER2_FLUSH_ALL);
        }
        hammer2_chain_unlock(&hmp->vchain);

        if ((hmp->vchain.flags | hmp->fchain.flags) &
            HAMMER2_CHAIN_FLUSH_MASK) {
                kprintf("hammer2_unmount: chains left over after final sync\n");
                kprintf("    vchain %08x\n", hmp->vchain.flags);
                kprintf("    fchain %08x\n", hmp->fchain.flags);

                if (hammer2_debug & 0x0010)
                        Debugger("entered debugger");
        }

        hammer2_pfsfree_scan(hmp, 1);

        KKASSERT(hmp->spmp == NULL);

        /*
         * Finish up with the device vnode
         */
        if (!TAILQ_EMPTY(&hmp->devvpl)) {
                hammer2_close_devvp(&hmp->devvpl, hmp->ronly);
                hammer2_cleanup_devvp(&hmp->devvpl);
        }
        KKASSERT(TAILQ_EMPTY(&hmp->devvpl));

        /*
         * Clear vchain/fchain flags that might prevent final cleanup
         * of these chains.
         */
        if (hmp->vchain.flags & HAMMER2_CHAIN_MODIFIED) {
                atomic_add_long(&hammer2_count_modified_chains, -1);
                atomic_clear_int(&hmp->vchain.flags, HAMMER2_CHAIN_MODIFIED);
                hammer2_pfs_memory_wakeup(hmp->vchain.pmp, -1);
        }
        if (hmp->vchain.flags & HAMMER2_CHAIN_UPDATE) {
                atomic_clear_int(&hmp->vchain.flags, HAMMER2_CHAIN_UPDATE);
        }

        if (hmp->fchain.flags & HAMMER2_CHAIN_MODIFIED) {
                atomic_add_long(&hammer2_count_modified_chains, -1);
                atomic_clear_int(&hmp->fchain.flags, HAMMER2_CHAIN_MODIFIED);
                hammer2_pfs_memory_wakeup(hmp->fchain.pmp, -1);
        }
        if (hmp->fchain.flags & HAMMER2_CHAIN_UPDATE) {
                atomic_clear_int(&hmp->fchain.flags, HAMMER2_CHAIN_UPDATE);
        }

        dumpcnt = 50;
        hammer2_dump_chain(&hmp->vchain, 0, 0, &dumpcnt, 'v', (u_int)-1);
        dumpcnt = 50;
        hammer2_dump_chain(&hmp->fchain, 0, 0, &dumpcnt, 'f', (u_int)-1);

        /*
         * Final drop of embedded freemap root chain to
         * clean up fchain.core (fchain structure is not
         * flagged ALLOCATED so it is cleaned out and then
         * left to rot).
         */
        hammer2_chain_drop(&hmp->fchain);

        /*
         * Final drop of embedded volume root chain to clean
         * up vchain.core (vchain structure is not flagged
         * ALLOCATED so it is cleaned out and then left to
         * rot).
         */
        hammer2_chain_drop(&hmp->vchain);

        hammer2_io_hash_cleanup_all(hmp);
        if (hmp->iofree_count) {
                kprintf("io_cleanup: %d I/O's left hanging\n",
                        hmp->iofree_count);
        }

        TAILQ_REMOVE(&hammer2_mntlist, hmp, mntentry);
        kmalloc_destroy_obj(&hmp->mchain);
        kmalloc_destroy_obj(&hmp->mio);
        kmalloc_destroy(&hmp->mmsg);
        kfree(hmp, M_HAMMER2);
}

int
hammer2_vfs_vget(struct mount *mp, struct vnode *dvp,
                 ino_t ino, struct vnode **vpp)
{
        hammer2_xop_lookup_t *xop;
        hammer2_pfs_t *pmp;
        hammer2_inode_t *ip;
        hammer2_tid_t inum;
        int error;

        inum = (hammer2_tid_t)ino & HAMMER2_DIRHASH_USERMSK;

        error = 0;
        pmp = MPTOPMP(mp);

        /*
         * Easy if we already have it cached
         */
        ip = hammer2_inode_lookup(pmp, inum);
        if (ip) {
                hammer2_inode_lock(ip, HAMMER2_RESOLVE_SHARED);
                *vpp = hammer2_igetv(ip, &error);
                hammer2_inode_unlock(ip);
                hammer2_inode_drop(ip);         /* from lookup */

                return error;
        }

        /*
         * Otherwise we have to find the inode
         */
        xop = hammer2_xop_alloc(pmp->iroot, 0);
        xop->lhc = inum;
        hammer2_xop_start(&xop->head, &hammer2_lookup_desc);
        error = hammer2_xop_collect(&xop->head, 0);

        if (error == 0)
                ip = hammer2_inode_get(pmp, &xop->head, -1, -1);
        hammer2_xop_retire(&xop->head, HAMMER2_XOPMASK_VOP);

        if (ip) {
                *vpp = hammer2_igetv(ip, &error);
                hammer2_inode_unlock(ip);
        } else {
                *vpp = NULL;
                error = ENOENT;
        }
        return (error);
}

static
int
hammer2_vfs_root(struct mount *mp, struct vnode **vpp)
{
        hammer2_pfs_t *pmp;
        struct vnode *vp;
        int error;

        pmp = MPTOPMP(mp);
        if (pmp->iroot == NULL) {
                kprintf("hammer2 (%s): no root inode\n",
                        mp->mnt_stat.f_mntfromname);
                *vpp = NULL;
                return EINVAL;
        }

        error = 0;
        hammer2_inode_lock(pmp->iroot, HAMMER2_RESOLVE_SHARED);

        while (pmp->inode_tid == 0) {
                hammer2_xop_ipcluster_t *xop;
                const hammer2_inode_meta_t *meta;

                xop = hammer2_xop_alloc(pmp->iroot, HAMMER2_XOP_MODIFYING);
                hammer2_xop_start(&xop->head, &hammer2_ipcluster_desc);
                error = hammer2_xop_collect(&xop->head, 0);

                if (error == 0) {
                        meta = &hammer2_xop_gdata(&xop->head)->ipdata.meta;
                        pmp->iroot->meta = *meta;
                        pmp->inode_tid = meta->pfs_inum + 1;
                        hammer2_xop_pdata(&xop->head);
                        /* meta invalid */

                        if (pmp->inode_tid < HAMMER2_INODE_START)
                                pmp->inode_tid = HAMMER2_INODE_START;
                        pmp->modify_tid =
                                xop->head.cluster.focus->bref.modify_tid + 1;
#if 0
                        kprintf("PFS: Starting inode %jd\n",
                                (intmax_t)pmp->inode_tid);
                        kprintf("PMP focus good set nextino=%ld mod=%016jx\n",
                                pmp->inode_tid, pmp->modify_tid);
#endif
                        wakeup(&pmp->iroot);

                        hammer2_xop_retire(&xop->head, HAMMER2_XOPMASK_VOP);

                        /*
                         * Prime the mount info.
                         */
                        hammer2_vfs_statfs(mp, &mp->mnt_stat, NULL);
                        break;
                }

                /*
                 * Loop, try again
                 */
                hammer2_xop_retire(&xop->head, HAMMER2_XOPMASK_VOP);
                hammer2_inode_unlock(pmp->iroot);
                error = tsleep(&pmp->iroot, PCATCH, "h2root", hz);
                hammer2_inode_lock(pmp->iroot, HAMMER2_RESOLVE_SHARED);
                if (error == EINTR)
                        break;
        }

        if (error) {
                hammer2_inode_unlock(pmp->iroot);
                *vpp = NULL;
        } else {
                vp = hammer2_igetv(pmp->iroot, &error);
                hammer2_inode_unlock(pmp->iroot);
                *vpp = vp;
        }

        return (error);
}

/*
 * Filesystem status
 *
 * XXX incorporate ipdata->meta.inode_quota and data_quota
 */
static
int
hammer2_vfs_statfs(struct mount *mp, struct statfs *sbp, struct ucred *cred)
{
        hammer2_pfs_t *pmp;
        hammer2_dev_t *hmp;
        hammer2_blockref_t bref;
        struct statfs tmp;
        int i;

        /*
         * NOTE: iroot might not have validated the cluster yet.
         */
        pmp = MPTOPMP(mp);

        bzero(&tmp, sizeof(tmp));

        for (i = 0; i < pmp->iroot->cluster.nchains; ++i) {
                hmp = pmp->pfs_hmps[i];
                if (hmp == NULL)
                        continue;
                if (pmp->iroot->cluster.array[i].chain)
                        bref = pmp->iroot->cluster.array[i].chain->bref;
                else
                        bzero(&bref, sizeof(bref));

                tmp.f_files = bref.embed.stats.inode_count;
                tmp.f_ffree = 0;
                tmp.f_blocks = hmp->voldata.allocator_size /
                               mp->mnt_vstat.f_bsize;
                tmp.f_bfree = hmp->voldata.allocator_free /
                              mp->mnt_vstat.f_bsize;
                tmp.f_bavail = tmp.f_bfree;

                if (cred && cred->cr_uid != 0) {
                        uint64_t adj;

                        /* 5% */
                        adj = hmp->free_reserved / mp->mnt_vstat.f_bsize;
                        tmp.f_blocks -= adj;
                        tmp.f_bfree -= adj;
                        tmp.f_bavail -= adj;
                }

                mp->mnt_stat.f_blocks = tmp.f_blocks;
                mp->mnt_stat.f_bfree = tmp.f_bfree;
                mp->mnt_stat.f_bavail = tmp.f_bavail;
                mp->mnt_stat.f_files = tmp.f_files;
                mp->mnt_stat.f_ffree = tmp.f_ffree;

                *sbp = mp->mnt_stat;
        }
        return (0);
}

static
int
hammer2_vfs_statvfs(struct mount *mp, struct statvfs *sbp, struct ucred *cred)
{
        hammer2_pfs_t *pmp;
        hammer2_dev_t *hmp;
        hammer2_blockref_t bref;
        struct statvfs tmp;
        int i;

        /*
         * NOTE: iroot might not have validated the cluster yet.
         */
        pmp = MPTOPMP(mp);
        bzero(&tmp, sizeof(tmp));

        for (i = 0; i < pmp->iroot->cluster.nchains; ++i) {
                hmp = pmp->pfs_hmps[i];
                if (hmp == NULL)
                        continue;
                if (pmp->iroot->cluster.array[i].chain)
                        bref = pmp->iroot->cluster.array[i].chain->bref;
                else
                        bzero(&bref, sizeof(bref));

                tmp.f_files = bref.embed.stats.inode_count;
                tmp.f_ffree = 0;
                tmp.f_blocks = hmp->voldata.allocator_size /
                               mp->mnt_vstat.f_bsize;
                tmp.f_bfree = hmp->voldata.allocator_free /
                              mp->mnt_vstat.f_bsize;
                tmp.f_bavail = tmp.f_bfree;

                if (cred && cred->cr_uid != 0) {
                        uint64_t adj;

                        /* 5% */
                        adj = hmp->free_reserved / mp->mnt_vstat.f_bsize;
                        tmp.f_blocks -= adj;
                        tmp.f_bfree -= adj;
                        tmp.f_bavail -= adj;
                }

                mp->mnt_vstat.f_blocks = tmp.f_blocks;
                mp->mnt_vstat.f_bfree = tmp.f_bfree;
                mp->mnt_vstat.f_bavail = tmp.f_bavail;
                mp->mnt_vstat.f_files = tmp.f_files;
                mp->mnt_vstat.f_ffree = tmp.f_ffree;

                *sbp = mp->mnt_vstat;
        }
        return (0);
}

/*
 * Mount-time recovery (RW mounts)
 *
 * Updates to the free block table are allowed to lag flushes by one
 * transaction.  In case of a crash, then on a fresh mount we must do an
 * incremental scan of the last committed transaction id and make sure that
 * all related blocks have been marked allocated.
 */
struct hammer2_recovery_elm {
        TAILQ_ENTRY(hammer2_recovery_elm) entry;
        hammer2_chain_t *chain;
        hammer2_tid_t sync_tid;
};

TAILQ_HEAD(hammer2_recovery_list, hammer2_recovery_elm);

struct hammer2_recovery_info {
        struct hammer2_recovery_list list;
        hammer2_tid_t   mtid;
        int     depth;
};

static int hammer2_recovery_scan(hammer2_dev_t *hmp,
                        hammer2_chain_t *parent,
                        struct hammer2_recovery_info *info,
                        hammer2_tid_t sync_tid);

#define HAMMER2_RECOVERY_MAXDEPTH       10

static
int
hammer2_recovery(hammer2_dev_t *hmp)
{
        struct hammer2_recovery_info info;
        struct hammer2_recovery_elm *elm;
        hammer2_chain_t *parent;
        hammer2_tid_t sync_tid;
        hammer2_tid_t mirror_tid;
        int error;

        hammer2_trans_init(hmp->spmp, 0);

        sync_tid = hmp->voldata.freemap_tid;
        mirror_tid = hmp->voldata.mirror_tid;

        kprintf("hammer2_mount: \"%s\": ", hmp->devrepname);
        if (sync_tid >= mirror_tid) {
                kprintf("no recovery needed\n");
        } else {
                kprintf("freemap recovery %016jx-%016jx\n",
                        sync_tid + 1, mirror_tid);
        }

        TAILQ_INIT(&info.list);
        info.depth = 0;
        parent = hammer2_chain_lookup_init(&hmp->vchain, 0);
        error = hammer2_recovery_scan(hmp, parent, &info, sync_tid);
        hammer2_chain_lookup_done(parent);

        while ((elm = TAILQ_FIRST(&info.list)) != NULL) {
                TAILQ_REMOVE(&info.list, elm, entry);
                parent = elm->chain;
                sync_tid = elm->sync_tid;
                kfree(elm, M_HAMMER2);

                hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
                error |= hammer2_recovery_scan(hmp, parent, &info,
                                              hmp->voldata.freemap_tid);
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);     /* drop elm->chain ref */
        }

        hammer2_trans_done(hmp->spmp, 0);

        return error;
}

static
int
hammer2_recovery_scan(hammer2_dev_t *hmp, hammer2_chain_t *parent,
                      struct hammer2_recovery_info *info,
                      hammer2_tid_t sync_tid)
{
        const hammer2_inode_data_t *ripdata;
        hammer2_chain_t *chain;
        hammer2_blockref_t bref;
        int tmp_error;
        int rup_error;
        int error;
        int first;

        /*
         * Adjust freemap to ensure that the block(s) are marked allocated.
         */
        if (parent->bref.type != HAMMER2_BREF_TYPE_VOLUME) {
                hammer2_freemap_adjust(hmp, &parent->bref,
                                       HAMMER2_FREEMAP_DORECOVER);
        }

        /*
         * Check type for recursive scan
         */
        switch(parent->bref.type) {
        case HAMMER2_BREF_TYPE_VOLUME:
                /* data already instantiated */
                break;
        case HAMMER2_BREF_TYPE_INODE:
                /*
                 * Must instantiate data for DIRECTDATA test and also
                 * for recursion.
                 */
                hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
                ripdata = &parent->data->ipdata;
                if (ripdata->meta.op_flags & HAMMER2_OPFLAG_DIRECTDATA) {
                        /* not applicable to recovery scan */
                        hammer2_chain_unlock(parent);
                        return 0;
                }
                hammer2_chain_unlock(parent);
                break;
        case HAMMER2_BREF_TYPE_INDIRECT:
                /*
                 * Must instantiate data for recursion
                 */
                hammer2_chain_lock(parent, HAMMER2_RESOLVE_ALWAYS);
                hammer2_chain_unlock(parent);
                break;
        case HAMMER2_BREF_TYPE_DIRENT:
        case HAMMER2_BREF_TYPE_DATA:
        case HAMMER2_BREF_TYPE_FREEMAP:
        case HAMMER2_BREF_TYPE_FREEMAP_NODE:
        case HAMMER2_BREF_TYPE_FREEMAP_LEAF:
                /* not applicable to recovery scan */
                return 0;
                break;
        default:
                return HAMMER2_ERROR_BADBREF;
        }

        /*
         * Defer operation if depth limit reached.
         */
        if (info->depth >= HAMMER2_RECOVERY_MAXDEPTH) {
                struct hammer2_recovery_elm *elm;

                elm = kmalloc(sizeof(*elm), M_HAMMER2, M_ZERO | M_WAITOK);
                elm->chain = parent;
                elm->sync_tid = sync_tid;
                hammer2_chain_ref(parent);
                TAILQ_INSERT_TAIL(&info->list, elm, entry);
                /* unlocked by caller */

                return(0);
        }


        /*
         * Recursive scan of the last flushed transaction only.  We are
         * doing this without pmp assignments so don't leave the chains
         * hanging around after we are done with them.
         *
         * error        Cumulative error this level only
         * rup_error    Cumulative error for recursion
         * tmp_error    Specific non-cumulative recursion error
         */
        chain = NULL;
        first = 1;
        rup_error = 0;
        error = 0;

        for (;;) {
                error |= hammer2_chain_scan(parent, &chain, &bref,
                                            &first,
                                            HAMMER2_LOOKUP_NODATA);

                /*
                 * Problem during scan or EOF
                 */
                if (error)
                        break;

                /*
                 * If this is a leaf
                 */
                if (chain == NULL) {
                        if (bref.mirror_tid > sync_tid) {
                                hammer2_freemap_adjust(hmp, &bref,
                                                     HAMMER2_FREEMAP_DORECOVER);
                        }
                        continue;
                }

                /*
                 * This may or may not be a recursive node.
                 */
                atomic_set_int(&chain->flags, HAMMER2_CHAIN_RELEASE);
                if (bref.mirror_tid > sync_tid) {
                        ++info->depth;
                        tmp_error = hammer2_recovery_scan(hmp, chain,
                                                           info, sync_tid);
                        --info->depth;
                } else {
                        tmp_error = 0;
                }

                /*
                 * Flush the recovery at the PFS boundary to stage it for
                 * the final flush of the super-root topology.
                 */
                if (tmp_error == 0 &&
                    (bref.flags & HAMMER2_BREF_FLAG_PFSROOT) &&
                    (chain->flags & HAMMER2_CHAIN_ONFLUSH)) {
                        hammer2_flush(chain, HAMMER2_FLUSH_TOP |
                                             HAMMER2_FLUSH_ALL);
                }
                rup_error |= tmp_error;
        }
        return ((error | rup_error) & ~HAMMER2_ERROR_EOF);
}

/*
 * This fixes up an error introduced in earlier H2 implementations where
 * moving a PFS inode into an indirect block wound up causing the
 * HAMMER2_BREF_FLAG_PFSROOT flag in the bref to get cleared.
 */
static
int
hammer2_fixup_pfses(hammer2_dev_t *hmp)
{
        const hammer2_inode_data_t *ripdata;
        hammer2_chain_t *parent;
        hammer2_chain_t *chain;
        hammer2_key_t key_next;
        hammer2_pfs_t *spmp;
        int error;

        error = 0;

        /*
         * Lookup mount point under the media-localized super-root.
         *
         * cluster->pmp will incorrectly point to spmp and must be fixed
         * up later on.
         */
        spmp = hmp->spmp;
        hammer2_inode_lock(spmp->iroot, 0);
        parent = hammer2_inode_chain(spmp->iroot, 0, HAMMER2_RESOLVE_ALWAYS);
        chain = hammer2_chain_lookup(&parent, &key_next,
                                         HAMMER2_KEY_MIN, HAMMER2_KEY_MAX,
                                         &error, 0);
        while (chain) {
                if (chain->bref.type != HAMMER2_BREF_TYPE_INODE)
                        continue;
                if (chain->error) {
                        kprintf("I/O error scanning PFS labels\n");
                        error |= chain->error;
                } else if ((chain->bref.flags &
                            HAMMER2_BREF_FLAG_PFSROOT) == 0) {
                        int error2;

                        ripdata = &chain->data->ipdata;
                        hammer2_trans_init(hmp->spmp, 0);
                        error2 = hammer2_chain_modify(chain,
                                                      chain->bref.modify_tid,
                                                      0, 0);
                        if (error2 == 0) {
                                kprintf("hammer2: Correct mis-flagged PFS %s\n",
                                        ripdata->filename);
                                chain->bref.flags |= HAMMER2_BREF_FLAG_PFSROOT;
                        } else {
                                error |= error2;
                        }
                        hammer2_flush(chain, HAMMER2_FLUSH_TOP |
                                             HAMMER2_FLUSH_ALL);
                        hammer2_trans_done(hmp->spmp, 0);
                }
                chain = hammer2_chain_next(&parent, chain, &key_next,
                                           key_next, HAMMER2_KEY_MAX,
                                           &error, 0);
        }
        if (parent) {
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);
        }
        hammer2_inode_unlock(spmp->iroot);

        return error;
}

/*
 * Sync a mount point; this is called periodically on a per-mount basis from
 * the filesystem syncer, and whenever a user issues a sync.
 */
int
hammer2_vfs_sync(struct mount *mp, int waitfor)
{
        int error;

        error = hammer2_vfs_sync_pmp(MPTOPMP(mp), waitfor);

        return error;
}

/*
 * Because frontend operations lock vnodes before we get a chance to
 * lock the related inode, we can't just acquire a vnode lock without
 * risking a deadlock.  The frontend may be holding a vnode lock while
 * also blocked on our SYNCQ flag while trying to get the inode lock.
 *
 * To deal with this situation we can check the vnode lock situation
 * after locking the inode and perform a work-around.
 */
int
hammer2_vfs_sync_pmp(hammer2_pfs_t *pmp, int waitfor)
{
        hammer2_inode_t *ip;
        hammer2_depend_t *depend;
        hammer2_depend_t *depend_next;
        struct vnode *vp;
        uint32_t pass2;
        int error;
        int wakecount;
        int dorestart;

        /*
         * Move all inodes on sideq to syncq.  This will clear sideq.
         * This should represent all flushable inodes.  These inodes
         * will already have refs due to being on syncq or sideq.  We
         * must do this all at once with the spinlock held to ensure that
         * all inode dependencies are part of the same flush.
         *
         * We should be able to do this asynchronously from frontend
         * operations because we will be locking the inodes later on
         * to actually flush them, and that will partition any frontend
         * op using the same inode.  Either it has already locked the
         * inode and we will block, or it has not yet locked the inode
         * and it will block until we are finished flushing that inode.
         *
         * When restarting, only move the inodes flagged as PASS2 from
         * SIDEQ to SYNCQ.  PASS2 propagation by inode_lock4() and
         * inode_depend() are atomic with the spin-lock.
         */
        hammer2_trans_init(pmp, HAMMER2_TRANS_ISFLUSH);
#ifdef HAMMER2_DEBUG_SYNC
        kprintf("FILESYSTEM SYNC BOUNDARY\n");
#endif
        dorestart = 0;

        /*
         * Move inodes from depq to syncq, releasing the related
         * depend structures.
         */
restart:
#ifdef HAMMER2_DEBUG_SYNC
        kprintf("FILESYSTEM SYNC RESTART (%d)\n", dorestart);
#endif
        hammer2_trans_setflags(pmp, 0/*HAMMER2_TRANS_COPYQ*/);
        hammer2_trans_clearflags(pmp, HAMMER2_TRANS_RESCAN);

        /*
         * Move inodes from depq to syncq.  When restarting, only depq's
         * marked pass2 are moved.
         */
        hammer2_spin_ex(&pmp->list_spin);
        depend_next = TAILQ_FIRST(&pmp->depq);
        wakecount = 0;

        while ((depend = depend_next) != NULL) {
                depend_next = TAILQ_NEXT(depend, entry);
                if (dorestart && depend->pass2 == 0)
                        continue;
                TAILQ_FOREACH(ip, &depend->sideq, entry) {
                        KKASSERT(ip->flags & HAMMER2_INODE_SIDEQ);
                        atomic_set_int(&ip->flags, HAMMER2_INODE_SYNCQ);
                        atomic_clear_int(&ip->flags, HAMMER2_INODE_SIDEQ);
                        ip->depend = NULL;
                }

                /*
                 * NOTE: pmp->sideq_count includes both sideq and syncq
                 */
                TAILQ_CONCAT(&pmp->syncq, &depend->sideq, entry);

                depend->count = 0;
                depend->pass2 = 0;
                TAILQ_REMOVE(&pmp->depq, depend, entry);
        }

        hammer2_spin_unex(&pmp->list_spin);
        hammer2_trans_clearflags(pmp, /*HAMMER2_TRANS_COPYQ |*/
                                      HAMMER2_TRANS_WAITING);
        dorestart = 0;

        /*
         * sideq_count may have dropped enough to allow us to unstall
         * the frontend.
         */
        hammer2_pfs_memory_wakeup(pmp, 0);

        /*
         * Now run through all inodes on syncq.
         *
         * Flush transactions only interlock with other flush transactions.
         * Any conflicting frontend operations will block on the inode, but
         * may hold a vnode lock while doing so.
         */
        hammer2_spin_ex(&pmp->list_spin);
        while ((ip = TAILQ_FIRST(&pmp->syncq)) != NULL) {
                /*
                 * Remove the inode from the SYNCQ, transfer the syncq ref
                 * to us.  We must clear SYNCQ to allow any potential
                 * front-end deadlock to proceed.  We must set PASS2 so
                 * the dependency code knows what to do.
                 */
                pass2 = ip->flags;
                cpu_ccfence();
                if (atomic_cmpset_int(&ip->flags,
                              pass2,
                              (pass2 & ~(HAMMER2_INODE_SYNCQ |
                                         HAMMER2_INODE_SYNCQ_WAKEUP)) |
                              HAMMER2_INODE_SYNCQ_PASS2) == 0)
                {
                        continue;
                }
                TAILQ_REMOVE(&pmp->syncq, ip, entry);
                --pmp->sideq_count;
                hammer2_spin_unex(&pmp->list_spin);

                /*
                 * Tickle anyone waiting on ip->flags or the hysteresis
                 * on the dirty inode count.
                 */
                if (pass2 & HAMMER2_INODE_SYNCQ_WAKEUP)
                        wakeup(&ip->flags);
                if (++wakecount >= hammer2_limit_dirty_inodes / 20 + 1) {
                        wakecount = 0;
                        hammer2_pfs_memory_wakeup(pmp, 0);
                }

                /*
                 * Relock the inode, and we inherit a ref from the above.
                 * We will check for a race after we acquire the vnode.
                 */
                hammer2_mtx_ex(&ip->lock);

                /*
                 * We need the vp in order to vfsync() dirty buffers, so if
                 * one isn't attached we can skip it.
                 *
                 * Ordering the inode lock and then the vnode lock has the
                 * potential to deadlock.  If we had left SYNCQ set that could
                 * also deadlock us against the frontend even if we don't hold
                 * any locks, but the latter is not a problem now since we
                 * cleared it.  igetv will temporarily release the inode lock
                 * in a safe manner to work-around the deadlock.
                 *
                 * Unfortunately it is still possible to deadlock when the
                 * frontend obtains multiple inode locks, because all the
                 * related vnodes are already locked (nor can the vnode locks
                 * be released and reacquired without messing up RECLAIM and
                 * INACTIVE sequencing).
                 *
                 * The solution for now is to move the vp back onto SIDEQ
                 * and set dorestart, which will restart the flush after we
                 * exhaust the current SYNCQ.  Note that additional
                 * dependencies may build up, so we definitely need to move
                 * the whole SIDEQ back to SYNCQ when we restart.
                 */
                vp = ip->vp;
                if (vp) {
                        if (vget(vp, LK_EXCLUSIVE|LK_NOWAIT)) {
                                /*
                                 * Failed to get the vnode, requeue the inode
                                 * (PASS2 is already set so it will be found
                                 * again on the restart).  Then unlock.
                                 */
                                vp = NULL;
                                dorestart |= 1;
#ifdef HAMMER2_DEBUG_SYNC
                                kprintf("inum %ld (sync delayed by vnode)\n",
                                        (long)ip->meta.inum);
#endif
                                hammer2_inode_delayed_sideq(ip);

                                hammer2_mtx_unlock(&ip->lock);
                                hammer2_inode_drop(ip);

                                /*
                                 * If PASS2 was previously set we might
                                 * be looping too hard, ask for a delay
                                 * along with the restart.
                                 */
                                if (pass2 & HAMMER2_INODE_SYNCQ_PASS2)
                                        dorestart |= 2;
                                hammer2_spin_ex(&pmp->list_spin);
                                continue;
                        }
                } else {
                        vp = NULL;
                }

                /*
                 * If the inode wound up on a SIDEQ again it will already be
                 * prepped for another PASS2.  In this situation if we flush
                 * it now we will just wind up flushing it again in the same
                 * syncer run, so we might as well not flush it now.
                 */
                if (ip->flags & HAMMER2_INODE_SIDEQ) {
                        hammer2_mtx_unlock(&ip->lock);
                        hammer2_inode_drop(ip);
                        if (vp)
                                vput(vp);
                        dorestart |= 1;
                        hammer2_spin_ex(&pmp->list_spin);
                        continue;
                }

                /*
                 * Ok we have the inode exclusively locked and if vp is
                 * not NULL that will also be exclusively locked.  Do the
                 * meat of the flush.
                 *
                 * vp token needed for v_rbdirty_tree check / vclrisdirty
                 * sequencing.  Though we hold the vnode exclusively so
                 * we shouldn't need to hold the token also in this case.
                 */
                if (vp) {
                        vfsync(vp, MNT_WAIT, 1, NULL, NULL);
                        bio_track_wait(&vp->v_track_write, 0, 0); /* XXX */
                }

                /*
                 * If the inode has not yet been inserted into the tree
                 * we must do so.  Then sync and flush it.  The flush should
                 * update the parent.
                 */
                if (ip->flags & HAMMER2_INODE_DELETING) {
#ifdef HAMMER2_DEBUG_SYNC
                        kprintf("inum %ld destroy\n", (long)ip->meta.inum);
#endif
                        hammer2_inode_chain_des(ip);
                        atomic_add_long(&hammer2_iod_inode_deletes, 1);
                } else if (ip->flags & HAMMER2_INODE_CREATING) {
#ifdef HAMMER2_DEBUG_SYNC
                        kprintf("inum %ld insert\n", (long)ip->meta.inum);
#endif
                        hammer2_inode_chain_ins(ip);
                        atomic_add_long(&hammer2_iod_inode_creates, 1);
                }
#ifdef HAMMER2_DEBUG_SYNC
                kprintf("inum %ld chain-sync\n", (long)ip->meta.inum);
#endif

                /*
                 * Because I kinda messed up the design and index the inodes
                 * under the root inode, along side the directory entries,
                 * we can't flush the inode index under the iroot until the
                 * end.  If we do it now we might miss effects created by
                 * other inodes on the SYNCQ.
                 *
                 * Do a normal (non-FSSYNC) flush instead, which allows the
                 * vnode code to work the same.  We don't want to force iroot
                 * back onto the SIDEQ, and we also don't want the flush code
                 * to update pfs_iroot_blocksets until the final flush later.
                 *
                 * XXX at the moment this will likely result in a double-flush
                 * of the iroot chain.
                 */
                hammer2_inode_chain_sync(ip);
                if (ip == pmp->iroot) {
                        hammer2_inode_chain_flush(ip, HAMMER2_XOP_INODE_STOP);
                } else {
                        hammer2_inode_chain_flush(ip, HAMMER2_XOP_INODE_STOP |
                                                      HAMMER2_XOP_FSSYNC);
                }
                if (vp) {
                        lwkt_gettoken(&vp->v_token);
                        if ((ip->flags & (HAMMER2_INODE_MODIFIED |
                                          HAMMER2_INODE_RESIZED |
                                          HAMMER2_INODE_DIRTYDATA)) == 0 &&
                            RB_EMPTY(&vp->v_rbdirty_tree) &&
                            !bio_track_active(&vp->v_track_write))
                        {
                                vclrisdirty(vp);
                        } else {
                                hammer2_inode_delayed_sideq(ip);
                        }
                        lwkt_reltoken(&vp->v_token);
                        vput(vp);
                        vp = NULL;      /* safety */
                }
                atomic_clear_int(&ip->flags, HAMMER2_INODE_SYNCQ_PASS2);
                hammer2_inode_unlock(ip);       /* unlock+drop */
                /* ip pointer invalid */

                /*
                 * If the inode got dirted after we dropped our locks,
                 * it will have already been moved back to the SIDEQ.
                 */
                hammer2_spin_ex(&pmp->list_spin);
        }
        hammer2_spin_unex(&pmp->list_spin);
        hammer2_pfs_memory_wakeup(pmp, 0);

        if (dorestart || (pmp->trans.flags & HAMMER2_TRANS_RESCAN)) {
                /*
                 * bit 2 is set if something above thinks we might be
                 * looping too hard, try to unclog the frontend
                 * dependency and wait a bit before restarting.
                 *
                 * NOTE: The frontend could be stuck in h2memw, though
                 *       it isn't supposed to be holding vnode locks
                 *       in that case.
                 */
                if (dorestart & 2) {
                        wakeup(&pmp->inmem_dirty_chains);
                        tsleep(&dorestart, 0, "h2syndel", 2);
                }
#ifdef HAMMER2_DEBUG_SYNC
                kprintf("FILESYSTEM SYNC STAGE 1 RESTART\n");
                /*tsleep(&dorestart, 0, "h2STG1-R", hz*20);*/
#endif
                dorestart = 1;
                goto restart;
        }
#ifdef HAMMER2_DEBUG_SYNC
        kprintf("FILESYSTEM SYNC STAGE 2 BEGIN\n");
        /*tsleep(&dorestart, 0, "h2STG2", hz*20);*/
#endif

        /*
         * We have to flush the PFS root last, even if it does not appear to
         * be dirty, because all the inodes in the PFS are indexed under it.
         * The normal flushing of iroot above would only occur if directory
         * entries under the root were changed.
         *
         * Specifying VOLHDR will cause an additionl flush of hmp->spmp
         * for the media making up the cluster.
         */
        if ((ip = pmp->iroot) != NULL) {
                hammer2_inode_ref(ip);
                hammer2_mtx_ex(&ip->lock);
                hammer2_inode_chain_sync(ip);
                hammer2_inode_chain_flush(ip, HAMMER2_XOP_INODE_STOP |
                                              HAMMER2_XOP_FSSYNC |
                                              HAMMER2_XOP_VOLHDR);
                hammer2_inode_unlock(ip);       /* unlock+drop */
        }
#ifdef HAMMER2_DEBUG_SYNC
        kprintf("FILESYSTEM SYNC STAGE 2 DONE\n");
#endif

        /*
         * device bioq sync
         */
        hammer2_bioq_sync(pmp);

        error = 0;      /* XXX */
        hammer2_trans_done(pmp, HAMMER2_TRANS_ISFLUSH);

        return (error);
}

static
int
hammer2_vfs_vptofh(struct vnode *vp, struct fid *fhp)
{
        hammer2_inode_t *ip;

        KKASSERT(MAXFIDSZ >= 16);
        ip = VTOI(vp);
        fhp->fid_len = offsetof(struct fid, fid_data[16]);
        fhp->fid_ext = 0;
        ((hammer2_tid_t *)fhp->fid_data)[0] = ip->meta.inum;
        ((hammer2_tid_t *)fhp->fid_data)[1] = 0;

        return 0;
}

static
int
hammer2_vfs_fhtovp(struct mount *mp, struct vnode *rootvp,
               struct fid *fhp, struct vnode **vpp)
{
        hammer2_tid_t inum;
        int error;

        inum = ((hammer2_tid_t *)fhp->fid_data)[0] & HAMMER2_DIRHASH_USERMSK;
        if (vpp) {
                if (inum == 1)
                        error = hammer2_vfs_root(mp, vpp);
                else
                        error = hammer2_vfs_vget(mp, NULL, inum, vpp);
        } else {
                error = 0;
        }
        return error;
}

static
int
hammer2_vfs_checkexp(struct mount *mp, struct sockaddr *nam,
                 int *exflagsp, struct ucred **credanonp)
{
        hammer2_pfs_t *pmp;
        struct netcred *np;
        int error;

        pmp = MPTOPMP(mp);
        np = vfs_export_lookup(mp, &pmp->export, nam);
        if (np) {
                *exflagsp = np->netc_exflags;
                *credanonp = &np->netc_anon;
                error = 0;
        } else {
                error = EACCES;
        }
        return error;
}

/*
 * This handles hysteresis on regular file flushes.  Because the BIOs are
 * routed to a thread it is possible for an excessive number to build up
 * and cause long front-end stalls long before the runningbuffspace limit
 * is hit, so we implement hammer2_flush_pipe to control the
 * hysteresis.
 *
 * This is a particular problem when compression is used.
 */
void
hammer2_lwinprog_ref(hammer2_pfs_t *pmp)
{
        atomic_add_int(&pmp->count_lwinprog, 1);
}

void
hammer2_lwinprog_drop(hammer2_pfs_t *pmp)
{
        int lwinprog;

        lwinprog = atomic_fetchadd_int(&pmp->count_lwinprog, -1);
        if ((lwinprog & HAMMER2_LWINPROG_WAITING) &&
            (lwinprog & HAMMER2_LWINPROG_MASK) <= hammer2_flush_pipe * 2 / 3) {
                atomic_clear_int(&pmp->count_lwinprog,
                                 HAMMER2_LWINPROG_WAITING);
                wakeup(&pmp->count_lwinprog);
        }
        if ((lwinprog & HAMMER2_LWINPROG_WAITING0) &&
            (lwinprog & HAMMER2_LWINPROG_MASK) <= 0) {
                atomic_clear_int(&pmp->count_lwinprog,
                                 HAMMER2_LWINPROG_WAITING0);
                wakeup(&pmp->count_lwinprog);
        }
}

void
hammer2_lwinprog_wait(hammer2_pfs_t *pmp, int flush_pipe)
{
        int lwinprog;
        int lwflag = (flush_pipe) ? HAMMER2_LWINPROG_WAITING :
                                    HAMMER2_LWINPROG_WAITING0;

        for (;;) {
                lwinprog = pmp->count_lwinprog;
                cpu_ccfence();
                if ((lwinprog & HAMMER2_LWINPROG_MASK) <= flush_pipe)
                        break;
                tsleep_interlock(&pmp->count_lwinprog, 0);
                atomic_set_int(&pmp->count_lwinprog, lwflag);
                lwinprog = pmp->count_lwinprog;
                if ((lwinprog & HAMMER2_LWINPROG_MASK) <= flush_pipe)
                        break;
                tsleep(&pmp->count_lwinprog, PINTERLOCKED, "h2wpipe", hz);
        }
}

/*
 * It is possible for an excessive number of dirty chains or dirty inodes
 * to build up.  When this occurs we start an asynchronous filesystem sync.
 * If the level continues to build up, we stall, waiting for it to drop,
 * with some hysteresis.
 *
 * This relies on the kernel calling hammer2_vfs_modifying() prior to
 * obtaining any vnode locks before making a modifying VOP call.
 */
static int
hammer2_vfs_modifying(struct mount *mp)
{
        if (mp->mnt_flag & MNT_RDONLY)
                return EROFS;
        hammer2_pfs_memory_wait(MPTOPMP(mp));

        return 0;
}

/*
 * Initiate an asynchronous filesystem sync and, with hysteresis,
 * stall if the internal data structure count becomes too bloated.
 */
void
hammer2_pfs_memory_wait(hammer2_pfs_t *pmp)
{
        uint32_t waiting;
        int pcatch;
        int error;
        int started;

        if (pmp == NULL || pmp->mp == NULL)
                return;

        started = 0;

        for (;;) {
                waiting = pmp->inmem_dirty_chains & HAMMER2_DIRTYCHAIN_MASK;
                cpu_ccfence();

                /*
                 * Start the syncer running at 1/2 the limit to try
                 * to avoid sleeping.
                 */
                if (waiting > hammer2_limit_dirty_chains / 2 ||
                    pmp->sideq_count > hammer2_limit_dirty_inodes / 2)
                {
                        trigger_syncer(pmp->mp);
                }

                /*
                 * Stall at the limit waiting for the counts to drop.
                 * This code will typically be woken up once the count
                 * drops below 3/4 the limit, or in one second.
                 */
                if (waiting < hammer2_limit_dirty_chains &&
                    pmp->sideq_count < hammer2_limit_dirty_inodes)
                {
                        break;
                }

                if (started == 0) {
                        trigger_syncer_start(pmp->mp);
                        started = 1;
                }

                /*
                 * Interlocked re-test, sleep, and retry.
                 */
                pcatch = curthread->td_proc ? PCATCH : 0;
                tsleep_interlock(&pmp->inmem_dirty_chains, pcatch);

                atomic_set_int(&pmp->inmem_dirty_chains,
                               HAMMER2_DIRTYCHAIN_WAITING);

                if (waiting < hammer2_limit_dirty_chains &&
                    pmp->sideq_count < hammer2_limit_dirty_inodes) {
                        break;
                }
                error = tsleep(&pmp->inmem_dirty_chains,
                               PINTERLOCKED | pcatch,
                               "h2memw", hz);
                if (error == ERESTART)
                        break;
        }
        if (started)
                trigger_syncer_stop(pmp->mp);
}

/*
 * Wake up any stalled frontend ops waiting, with hysteresis, using
 * 2/3 of the limit.
 */
void
hammer2_pfs_memory_wakeup(hammer2_pfs_t *pmp, int count)
{
        uint32_t waiting;

        if (pmp) {
                waiting = atomic_fetchadd_int(&pmp->inmem_dirty_chains, count);
                /* don't need --waiting to test flag */

                if ((waiting & HAMMER2_DIRTYCHAIN_WAITING) &&
                    (pmp->inmem_dirty_chains & HAMMER2_DIRTYCHAIN_MASK) <=
                    hammer2_limit_dirty_chains * 2 / 3 &&
                    pmp->sideq_count <= hammer2_limit_dirty_inodes * 2 / 3) {
                        atomic_clear_int(&pmp->inmem_dirty_chains,
                                         HAMMER2_DIRTYCHAIN_WAITING);
                        wakeup(&pmp->inmem_dirty_chains);
                }
        }
}

void
hammer2_pfs_memory_inc(hammer2_pfs_t *pmp)
{
        if (pmp) {
                atomic_add_int(&pmp->inmem_dirty_chains, 1);
        }
}

/*
 * Volume header data locks
 */
void
hammer2_voldata_lock(hammer2_dev_t *hmp)
{
        lockmgr(&hmp->vollk, LK_EXCLUSIVE);
}

void
hammer2_voldata_unlock(hammer2_dev_t *hmp)
{
        lockmgr(&hmp->vollk, LK_RELEASE);
}

/*
 * Caller indicates that the volume header is being modified.  Flag
 * the related chain and adjust its transaction id.
 *
 * The transaction id is set to voldata.mirror_tid + 1, similar to
 * what hammer2_chain_modify() does.  Be very careful here, volume
 * data can be updated independently of the rest of the filesystem.
 */
void
hammer2_voldata_modify(hammer2_dev_t *hmp)
{
        if ((hmp->vchain.flags & HAMMER2_CHAIN_MODIFIED) == 0) {
                atomic_add_long(&hammer2_count_modified_chains, 1);
                atomic_set_int(&hmp->vchain.flags, HAMMER2_CHAIN_MODIFIED);
                hammer2_pfs_memory_inc(hmp->vchain.pmp);
                hmp->vchain.bref.mirror_tid = hmp->voldata.mirror_tid + 1;
        }
}

/*
 * Returns 0 if the filesystem has tons of free space
 * Returns 1 if the filesystem has less than 10% remaining
 * Returns 2 if the filesystem has less than 2%/5% (user/root) remaining.
 */
int
hammer2_vfs_enospace(hammer2_inode_t *ip, off_t bytes, struct ucred *cred)
{
        hammer2_pfs_t *pmp;
        hammer2_dev_t *hmp;
        hammer2_off_t free_reserved;
        hammer2_off_t free_nominal;
        int i;

        pmp = ip->pmp;

        if (pmp->free_ticks == 0 || pmp->free_ticks != ticks) {
                free_reserved = HAMMER2_SEGSIZE;
                free_nominal = 0x7FFFFFFFFFFFFFFFLLU;
                for (i = 0; i < pmp->iroot->cluster.nchains; ++i) {
                        hmp = pmp->pfs_hmps[i];
                        if (hmp == NULL)
                                continue;
                        if (pmp->pfs_types[i] != HAMMER2_PFSTYPE_MASTER &&
                            pmp->pfs_types[i] != HAMMER2_PFSTYPE_SOFT_MASTER)
                                continue;

                        if (free_nominal > hmp->voldata.allocator_free)
                                free_nominal = hmp->voldata.allocator_free;
                        if (free_reserved < hmp->free_reserved)
                                free_reserved = hmp->free_reserved;
                }

                /*
                 * SMP races ok
                 */
                pmp->free_reserved = free_reserved;
                pmp->free_nominal = free_nominal;
                pmp->free_ticks = ticks;
        } else {
                free_reserved = pmp->free_reserved;
                free_nominal = pmp->free_nominal;
        }
        if (cred && cred->cr_uid != 0) {
                if ((int64_t)(free_nominal - bytes) <
                    (int64_t)free_reserved) {
                        return 2;
                }
        } else {
                if ((int64_t)(free_nominal - bytes) <
                    (int64_t)free_reserved / 2) {
                        return 2;
                }
        }
        if ((int64_t)(free_nominal - bytes) < (int64_t)free_reserved * 2)
                return 1;
        return 0;
}