Merge branch 'vendor/OPENSSL'

[dragonfly.git] / sys / vfs / hammer2 / hammer2_vfsops.c

/*
 * Copyright (c) 2011-2015 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/buf.h>
#include <sys/uuid.h>
#include <sys/vfsops.h>
#include <sys/sysctl.h>
#include <sys/socket.h>
#include <sys/objcache.h>

#include <sys/proc.h>
#include <sys/namei.h>
#include <sys/mountctl.h>
#include <sys/dirent.h>
#include <sys/uio.h>

#include <sys/mutex.h>
#include <sys/mutex2.h>

#include "hammer2.h"
#include "hammer2_disk.h"
#include "hammer2_mount.h"
#include "hammer2_lz4.h"

#include "zlib/hammer2_zlib.h"

#define REPORT_REFS_ERRORS 1    /* XXX remove me */

MALLOC_DEFINE(M_OBJCACHE, "objcache", "Object Cache");

struct hammer2_sync_info {
        hammer2_trans_t trans;
        int error;
        int waitfor;
};

TAILQ_HEAD(hammer2_mntlist, hammer2_dev);
TAILQ_HEAD(hammer2_pfslist, hammer2_pfs);
static struct hammer2_mntlist hammer2_mntlist;
static struct hammer2_pfslist hammer2_pfslist;
static struct lock hammer2_mntlk;

int hammer2_debug;
int hammer2_cluster_enable = 1;
int hammer2_hardlink_enable = 1;
int hammer2_flush_pipe = 100;
int hammer2_synchronous_flush = 1;
int hammer2_dio_count;
long hammer2_limit_dirty_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_meta_write;
long hammer2_iod_indr_write;
long hammer2_iod_fmap_write;
long hammer2_iod_volu_write;
long hammer2_ioa_file_read;
long hammer2_ioa_meta_read;
long hammer2_ioa_indr_read;
long hammer2_ioa_fmap_read;
long hammer2_ioa_volu_read;
long hammer2_ioa_fmap_write;
long hammer2_ioa_file_write;
long hammer2_ioa_meta_write;
long hammer2_ioa_indr_write;
long hammer2_ioa_volu_write;

MALLOC_DECLARE(C_BUFFER);
MALLOC_DEFINE(C_BUFFER, "compbuffer", "Buffer used for compression.");

MALLOC_DECLARE(D_BUFFER);
MALLOC_DEFINE(D_BUFFER, "decompbuffer", "Buffer used for decompression.");

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

SYSCTL_INT(_vfs_hammer2, OID_AUTO, debug, CTLFLAG_RW,
           &hammer2_debug, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, cluster_enable, CTLFLAG_RW,
           &hammer2_cluster_enable, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, hardlink_enable, CTLFLAG_RW,
           &hammer2_hardlink_enable, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, flush_pipe, CTLFLAG_RW,
           &hammer2_flush_pipe, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, synchronous_flush, CTLFLAG_RW,
           &hammer2_synchronous_flush, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, limit_dirty_chains, CTLFLAG_RW,
           &hammer2_limit_dirty_chains, 0, "");
SYSCTL_INT(_vfs_hammer2, OID_AUTO, dio_count, CTLFLAG_RD,
           &hammer2_dio_count, 0, "");

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

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_file_write, CTLFLAG_RW,
           &hammer2_iod_file_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_meta_write, CTLFLAG_RW,
           &hammer2_iod_meta_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_indr_write, CTLFLAG_RW,
           &hammer2_iod_indr_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_fmap_write, CTLFLAG_RW,
           &hammer2_iod_fmap_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, iod_volu_write, CTLFLAG_RW,
           &hammer2_iod_volu_write, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_file_read, CTLFLAG_RW,
           &hammer2_ioa_file_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_meta_read, CTLFLAG_RW,
           &hammer2_ioa_meta_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_indr_read, CTLFLAG_RW,
           &hammer2_ioa_indr_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_fmap_read, CTLFLAG_RW,
           &hammer2_ioa_fmap_read, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_volu_read, CTLFLAG_RW,
           &hammer2_ioa_volu_read, 0, "");

SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_file_write, CTLFLAG_RW,
           &hammer2_ioa_file_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_meta_write, CTLFLAG_RW,
           &hammer2_ioa_meta_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_indr_write, CTLFLAG_RW,
           &hammer2_ioa_indr_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_fmap_write, CTLFLAG_RW,
           &hammer2_ioa_fmap_write, 0, "");
SYSCTL_LONG(_vfs_hammer2, OID_AUTO, ioa_volu_write, CTLFLAG_RW,
           &hammer2_ioa_volu_write, 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 vnode *, 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_vget(struct mount *mp, struct vnode *dvp,
                                ino_t ino, struct vnode **vpp);
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_install_volume_header(hammer2_dev_t *hmp);
static int hammer2_sync_scan2(struct mount *mp, struct vnode *vp, void *data);

static void hammer2_update_pmps(hammer2_dev_t *hmp);
static void hammer2_write_thread(void *arg);

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);

/* 
 * Functions for compression in threads,
 * from hammer2_vnops.c
 */
static void hammer2_write_file_core(struct buf *bp, hammer2_trans_t *trans,
                                hammer2_inode_t *ip,
                                const hammer2_inode_data_t *ripdata,
                                hammer2_cluster_t *cparent,
                                hammer2_key_t lbase, int ioflag, int pblksize,
                                int *errorp);
static void hammer2_compress_and_write(struct buf *bp, hammer2_trans_t *trans,
                                hammer2_inode_t *ip,
                                const hammer2_inode_data_t *ripdata,
                                hammer2_cluster_t *cparent,
                                hammer2_key_t lbase, int ioflag,
                                int pblksize, int *errorp,
                                int comp_algo, int check_algo);
static void hammer2_zero_check_and_write(struct buf *bp,
                                hammer2_trans_t *trans, hammer2_inode_t *ip,
                                const hammer2_inode_data_t *ripdata,
                                hammer2_cluster_t *cparent,
                                hammer2_key_t lbase,
                                int ioflag, int pblksize, int *errorp,
                                int check_algo);
static int test_block_zeros(const char *buf, size_t bytes);
static void zero_write(struct buf *bp, hammer2_trans_t *trans,
                                hammer2_inode_t *ip,
                                const hammer2_inode_data_t *ripdata,
                                hammer2_cluster_t *cparent,
                                hammer2_key_t lbase,
                                int *errorp);
static void hammer2_write_bp(hammer2_cluster_t *cluster, struct buf *bp,
                                int ioflag, int pblksize, int *errorp,
                                int check_algo);

/*
 * HAMMER2 vfs operations.
 */
static struct vfsops hammer2_vfsops = {
        .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
};

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

VFS_SET(hammer2_vfsops, hammer2, 0);
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;

        int error;

        error = 0;

        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 = D_BUFFER;
        
        margs_write.objsize = 32768;
        margs_write.mtype = C_BUFFER;
        
        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);

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

        hammer2_limit_dirty_chains = desiredvnodes / 10;

        return (error);
}

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

/*
 * Core PFS allocator.  Used to allocate the pmp structure for PFS cluster
 * mounts and the spmp structure for media (hmp) structures.
 *
 * 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_cluster_t *cluster,
                 const hammer2_inode_data_t *ripdata,
                 hammer2_tid_t modify_tid)
{
        hammer2_chain_t *rchain;
        hammer2_inode_t *iroot;
        hammer2_pfs_t *pmp;
        int count;
        int i;
        int j;

        /*
         * 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 (ripdata) {
                TAILQ_FOREACH(pmp, &hammer2_pfslist, mntentry) {
                        if (bcmp(&pmp->pfs_clid, &ripdata->pfs_clid,
                                 sizeof(pmp->pfs_clid)) == 0) {
                                        break;
                        }
                }
        } else {
                pmp = NULL;
        }

        if (pmp == NULL) {
                pmp = kmalloc(sizeof(*pmp), M_HAMMER2, M_WAITOK | M_ZERO);
                hammer2_trans_manage_init(&pmp->tmanage);
                kmalloc_create(&pmp->minode, "HAMMER2-inodes");
                kmalloc_create(&pmp->mmsg, "HAMMER2-pfsmsg");
                lockinit(&pmp->lock, "pfslk", 0, 0);
                spin_init(&pmp->inum_spin, "hm2pfsalloc_inum");
                RB_INIT(&pmp->inum_tree);
                TAILQ_INIT(&pmp->unlinkq);
                spin_init(&pmp->list_spin, "hm2pfsalloc_list");

                /*
                 * Save the last media transaction id for the flusher.  Set
                 * initial 
                 */
                if (ripdata)
                        pmp->pfs_clid = ripdata->pfs_clid;
                hammer2_mtx_init(&pmp->wthread_mtx, "h2wthr");
                bioq_init(&pmp->wthread_bioq);
                TAILQ_INSERT_TAIL(&hammer2_pfslist, 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_SYNCTHR_FROZEN |
                                         HAMMER2_SYNCTHR_REMASTER;
                */
        }

        /*
         * Create the PFS's root inode.
         */
        if ((iroot = pmp->iroot) == NULL) {
                iroot = hammer2_inode_get(pmp, NULL, NULL);
                pmp->iroot = iroot;
                hammer2_inode_ref(iroot);
                hammer2_inode_unlock(iroot, NULL);
        }

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

        /*
         * When a cluster is passed in we must add the cluster's chains
         * to the PFS's root inode, update pmp->pfs_types[], and update
         * the syncronization threads.
         *
         * 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;

        kprintf("add PFS to pmp %p[%d]\n", pmp, j);

        for (i = 0; i < cluster->nchains; ++i) {
                if (j == HAMMER2_MAXCLUSTER)
                        break;
                rchain = cluster->array[i].chain;
                KKASSERT(rchain->pmp == NULL);
                rchain->pmp = pmp;
                hammer2_chain_ref(rchain);
                iroot->cluster.array[j].chain = rchain;
                pmp->pfs_types[j] = ripdata->pfs_type;
                pmp->pfs_names[j] = kstrdup(ripdata->filename, M_HAMMER2);

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

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

        if (i != cluster->nchains) {
                kprintf("hammer2_mount: cluster full!\n");
                /* XXX fatal error? */
        }

        /*
         * 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->pfs_nmasters) {
                pmp->pfs_nmasters = ripdata->pfs_nmasters;
        }

        /*
         * Count visible masters.  Masters are usually added with
         * ripdata->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 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) {
                if (pmp->sync_thrs[i].td)
                        continue;
                if ((pmp->pfs_nmasters > 1 &&
                     (pmp->pfs_types[i] == HAMMER2_PFSTYPE_MASTER)) ||
                    pmp->pfs_types[i] != HAMMER2_PFSTYPE_MASTER) {
                        hammer2_syncthr_create(&pmp->sync_thrs[i], pmp, i,
                                               hammer2_syncthr_primary);
                }
        }

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

/*
 * 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;
        int i;

        /*
         * Cleanup our reference on iroot.  iroot is (should) not be needed
         * by the flush code.
         */
        TAILQ_REMOVE(&hammer2_pfslist, pmp, mntentry);

        iroot = pmp->iroot;
        if (iroot) {
                for (i = 0; i < iroot->cluster.nchains; ++i)
                        hammer2_syncthr_delete(&pmp->sync_thrs[i]);
#if REPORT_REFS_ERRORS
                if (pmp->iroot->refs != 1)
                        kprintf("PMP->IROOT %p REFS WRONG %d\n",
                                pmp->iroot, pmp->iroot->refs);
#else
                KKASSERT(pmp->iroot->refs == 1);
#endif
                /* ref for pmp->iroot */
                hammer2_inode_drop(pmp->iroot);
                pmp->iroot = NULL;
        }

        kmalloc_destroy(&pmp->mmsg);
        kmalloc_destroy(&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)
{
        hammer2_pfs_t *pmp;
        hammer2_inode_t *iroot;
        hammer2_cluster_t *cluster;
        hammer2_chain_t *rchain;
        int didfreeze;
        int i;

again:
        TAILQ_FOREACH(pmp, &hammer2_pfslist, mntentry) {
                if ((iroot = pmp->iroot) == NULL)
                        continue;
                if (hmp->spmp == pmp) {
                        kprintf("unmount hmp %p remove spmp %p\n",
                                hmp, pmp);
                        hmp->spmp = NULL;
                }

                /*
                 * 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.
                 */
                cluster = &iroot->cluster;
                for (i = 0; i < cluster->nchains; ++i) {
                        rchain = cluster->array[i].chain;
                        if (rchain == NULL || rchain->hmp != hmp)
                                continue;
                        break;
                }
                if (i != cluster->nchains) {
                        /*
                         * Make sure all synchronization threads are locked
                         * down.
                         */
                        for (i = 0; i < iroot->cluster.nchains; ++i)
                                hammer2_syncthr_freeze(&pmp->sync_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 < cluster->nchains; ++i) {
                                rchain = cluster->array[i].chain;
                                if (rchain == NULL || rchain->hmp != hmp)
                                        continue;
                                hammer2_syncthr_delete(&pmp->sync_thrs[i]);
                                rchain = cluster->array[i].chain;
                                cluster->array[i].chain = NULL;
                                pmp->pfs_types[i] = 0;
                                if (pmp->pfs_names[i]) {
                                        kfree(pmp->pfs_names[i], M_HAMMER2);
                                        pmp->pfs_names[i] = NULL;
                                }
                                hammer2_chain_drop(rchain);

                                /* focus hint */
                                if (cluster->focus == rchain)
                                        cluster->focus = NULL;
                        }
                        hammer2_mtx_unlock(&iroot->lock);
                        didfreeze = 1;  /* remaster, unfreeze down below */
                } else {
                        didfreeze = 0;
                }

                /*
                 * Cleanup trailing chains.  Do not reorder chains (for now).
                 * XXX might remove more than we intended.
                 */
                while (i > 0) {
                        if (cluster->array[i - 1].chain)
                                break;
                        --i;
                }
                cluster->nchains = i;

                /*
                 * If the PMP has no elements remaining we can destroy it.
                 * (this will transition management threads from frozen->exit).
                 */
                if (cluster->nchains == 0) {
                        kprintf("unmount hmp %p last ref to PMP=%p\n",
                                hmp, pmp);
                        hammer2_pfsfree(pmp);
                        goto again;
                }

                /*
                 * If elements still remain we need to set the REMASTER
                 * flag and unfreeze it.
                 */
                if (didfreeze) {
                        for (i = 0; i < iroot->cluster.nchains; ++i) {
                                hammer2_syncthr_remaster(&pmp->sync_thrs[i]);
                                hammer2_syncthr_unfreeze(&pmp->sync_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;
        hammer2_key_t key_next;
        hammer2_key_t key_dummy;
        hammer2_key_t lhc;
        struct vnode *devvp;
        struct nlookupdata nd;
        hammer2_chain_t *parent;
        hammer2_cluster_t *cluster;
        hammer2_cluster_t *cparent;
        const hammer2_inode_data_t *ripdata;
        hammer2_blockref_t bref;
        struct file *fp;
        char devstr[MNAMELEN];
        size_t size;
        size_t done;
        char *dev;
        char *label;
        int ronly = 1;
        int error;
        int cache_index;
        int i;

        hmp = NULL;
        pmp = NULL;
        dev = NULL;
        label = NULL;
        devvp = NULL;
        cache_index = -1;

        kprintf("hammer2_mount\n");

        if (path == NULL) {
                /*
                 * Root mount
                 */
                bzero(&info, sizeof(info));
                info.cluster_fd = -1;
                return (EOPNOTSUPP);
        } else {
                /*
                 * Non-root mount or updating a mount
                 */
                error = copyin(data, &info, sizeof(info));
                if (error)
                        return (error);

                error = copyinstr(info.volume, devstr, MNAMELEN - 1, &done);
                if (error)
                        return (error);

                /* Extract device and label */
                dev = devstr;
                label = strchr(devstr, '@');
                if (label == NULL ||
                    ((label + 1) - dev) > done) {
                        return (EINVAL);
                }
                *label = '\0';
                label++;
                if (*label == '\0')
                        return (EINVAL);

                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.
                         */
                        pmp = MPTOPMP(mp);
                        cluster = &pmp->iroot->cluster;
                        for (i = 0; i < cluster->nchains; ++i) {
                                if (cluster->array[i].chain == NULL)
                                        continue;
                                hmp = cluster->array[i].chain->hmp;
                                devvp = hmp->devvp;
                                error = hammer2_remount(hmp, mp, path,
                                                        devvp, cred);
                                if (error)
                                        break;
                        }
                        /*hammer2_inode_install_hidden(pmp);*/

                        return error;
                }
        }

        /*
         * HMP device mount
         *
         * Lookup name and verify it refers to a block device.
         */
        error = nlookup_init(&nd, dev, UIO_SYSSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vref(&nd.nl_nch, nd.nl_cred, &devvp);
        nlookup_done(&nd);

        if (error == 0) {
                if (vn_isdisk(devvp, &error))
                        error = vfs_mountedon(devvp);
        }

        /*
         * 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);
        TAILQ_FOREACH(hmp, &hammer2_mntlist, mntentry) {
                if (hmp->devvp == devvp)
                        break;
        }

        /*
         * 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_xid_t xid;

                if (error == 0 && vcount(devvp) > 0)
                        error = EBUSY;

                /*
                 * Now open the device
                 */
                if (error == 0) {
                        ronly = ((mp->mnt_flag & MNT_RDONLY) != 0);
                        vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                        error = vinvalbuf(devvp, V_SAVE, 0, 0);
                        if (error == 0) {
                                error = VOP_OPEN(devvp,
                                                 ronly ? FREAD : FREAD | FWRITE,
                                                 FSCRED, NULL);
                        }
                        vn_unlock(devvp);
                }
                if (error && devvp) {
                        vrele(devvp);
                        devvp = NULL;
                }
                if (error) {
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        return error;
                }
                hmp = kmalloc(sizeof(*hmp), M_HAMMER2, M_WAITOK | M_ZERO);
                ksnprintf(hmp->devrepname, sizeof(hmp->devrepname), "%s", dev);
                hmp->ronly = ronly;
                hmp->devvp = devvp;
                kmalloc_create(&hmp->mchain, "HAMMER2-chains");
                TAILQ_INSERT_TAIL(&hammer2_mntlist, hmp, mntentry);
                RB_INIT(&hmp->iotree);
                spin_init(&hmp->io_spin, "hm2mount_io");
                spin_init(&hmp->list_spin, "hm2mount_list");
                TAILQ_INIT(&hmp->flushq);

                lockinit(&hmp->vollk, "h2vol", 0, 0);

                /*
                 * vchain setup. vchain.data is embedded.
                 * vchain.refs is initialized and will never drop to 0.
                 *
                 * NOTE! voldata is not yet loaded.
                 */
                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;
                hmp->vchain.bref.mirror_tid = hmp->voldata.mirror_tid;

                hammer2_chain_core_init(&hmp->vchain);
                /* hmp->vchain.u.xxx is left NULL */

                /*
                 * 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 RBTREE
                 * so it does not interfere with the volume's topology
                 * RBTREE.
                 */
                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.mirror_tid = hmp->voldata.freemap_tid;
                hmp->fchain.bref.methods =
                        HAMMER2_ENC_CHECK(HAMMER2_CHECK_FREEMAP) |
                        HAMMER2_ENC_COMP(HAMMER2_COMP_NONE);

                hammer2_chain_core_init(&hmp->fchain);
                /* hmp->fchain.u.xxx is left NULL */

                /*
                 * Install the volume header and initialize fields from
                 * voldata.
                 */
                error = hammer2_install_volume_header(hmp);
                if (error) {
                        hammer2_unmount_helper(mp, NULL, hmp);
                        lockmgr(&hammer2_mntlk, LK_RELEASE);
                        hammer2_vfs_unmount(mp, MNT_FORCE);
                        return error;
                }

                /*
                 * Really important to get these right or flush will get
                 * confused.
                 */
                hmp->spmp = hammer2_pfsalloc(NULL, NULL, 0);
                kprintf("alloc spmp %p tid %016jx\n",
                        hmp->spmp, hmp->voldata.mirror_tid);
                spmp = hmp->spmp;

                /*
                 * Dummy-up vchain and fchain's modify_tid.  mirror_tid
                 * is inherited from the volume header.
                 */
                xid = 0;
                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,
                                      &cache_index, 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;

                /*
                 * 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 = &hammer2_chain_rdata(schain)->ipdata;
                KKASSERT(schain->pmp == NULL);
                spmp->pfs_clid = ripdata->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.
                 */
                cluster = hammer2_cluster_from_chain(schain);
                hammer2_inode_drop(spmp->iroot);
                spmp->iroot = NULL;
                spmp->iroot = hammer2_inode_get(spmp, NULL, cluster);
                spmp->spmp_hmp = hmp;
                spmp->pfs_types[0] = ripdata->pfs_type;
                hammer2_inode_ref(spmp->iroot);
                hammer2_inode_unlock(spmp->iroot, cluster);
                schain = NULL;
                /* leave spmp->iroot with one ref */

                if ((mp->mnt_flag & MNT_RDONLY) == 0) {
                        error = hammer2_recovery(hmp);
                        /* XXX do something with error */
                }
                hammer2_update_pmps(hmp);
                hammer2_iocom_init(hmp);

                /*
                 * Ref the cluster management messaging descriptor.  The mount
                 * program deals with the other end of the communications pipe.
                 */
                fp = holdfp(curproc->p_fd, info.cluster_fd, -1);
                if (fp) {
                        hammer2_cluster_reconnect(hmp, fp);
                } else {
                        kprintf("hammer2_mount: bad cluster_fd!\n");
                }
        } else {
                spmp = hmp->spmp;
        }

        /*
         * 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.
         */
        cparent = hammer2_inode_lock(spmp->iroot, HAMMER2_RESOLVE_ALWAYS);
        lhc = hammer2_dirhash(label, strlen(label));
        cluster = hammer2_cluster_lookup(cparent, &key_next,
                                      lhc, lhc + HAMMER2_DIRHASH_LOMASK,
                                      0);
        while (cluster) {
                if (hammer2_cluster_type(cluster) == HAMMER2_BREF_TYPE_INODE &&
                    strcmp(label,
                       hammer2_cluster_rdata(cluster)->ipdata.filename) == 0) {
                        break;
                }
                cluster = hammer2_cluster_next(cparent, cluster, &key_next,
                                            key_next,
                                            lhc + HAMMER2_DIRHASH_LOMASK, 0);
        }
        hammer2_inode_unlock(spmp->iroot, cparent);

        /*
         * PFS could not be found?
         */
        if (cluster == NULL) {
                kprintf("hammer2_mount: PFS label not found\n");
                hammer2_unmount_helper(mp, NULL, hmp);
                lockmgr(&hammer2_mntlk, LK_RELEASE);
                hammer2_vfs_unmount(mp, MNT_FORCE);

                return EINVAL;
        }

        /*
         * Acquire the pmp structure (it should have already been allocated
         * via hammer2_update_pmps() so do not pass cluster in to add to
         * available chains).
         *
         * Check if the cluster has already been mounted.  A cluster can
         * only be mounted once, use null mounts to mount additional copies.
         */
        ripdata = &hammer2_cluster_rdata(cluster)->ipdata;
        hammer2_cluster_bref(cluster, &bref);
        pmp = hammer2_pfsalloc(NULL, ripdata, bref.modify_tid);
        hammer2_cluster_unlock(cluster);
        hammer2_cluster_drop(cluster);

        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;
        }

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

        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);

        /*
         * A mounted PFS needs a write thread for logical buffers and
         * a hidden directory for deletions of open files.  These features
         * are not used by unmounted PFSs.
         *
         * The logical file buffer bio write thread handles things like
         * physical block assignment and compression.
         */
        pmp->wthread_destroy = 0;
        lwkt_create(hammer2_write_thread, pmp,
                    &pmp->wthread_td, NULL, 0, -1, "h2pfs-%s", label);

        /*
         * With the cluster operational install ihidden.
         * (only applicable to pfs mounts, not applicable to spmp)
         */
        hammer2_inode_install_hidden(pmp);

        /*
         * 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);

        copyinstr(info.volume, mp->mnt_stat.f_mntfromname, MNAMELEN - 1, &size);
        bzero(mp->mnt_stat.f_mntfromname + size, MNAMELEN - size);
        bzero(mp->mnt_stat.f_mntonname, sizeof(mp->mnt_stat.f_mntonname));
        copyinstr(path, mp->mnt_stat.f_mntonname,
                  sizeof(mp->mnt_stat.f_mntonname) - 1,
                  &size);

        /*
         * 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_cluster_t *cparent;
        hammer2_cluster_t *cluster;
        hammer2_blockref_t bref;
        hammer2_pfs_t *spmp;
        hammer2_pfs_t *pmp;
        hammer2_key_t key_next;

        /*
         * 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;
        cparent = hammer2_inode_lock(spmp->iroot, HAMMER2_RESOLVE_ALWAYS);
        cluster = hammer2_cluster_lookup(cparent, &key_next,
                                         HAMMER2_KEY_MIN,
                                         HAMMER2_KEY_MAX,
                                         0);
        while (cluster) {
                if (hammer2_cluster_type(cluster) != HAMMER2_BREF_TYPE_INODE)
                        continue;
                ripdata = &hammer2_cluster_rdata(cluster)->ipdata;
                hammer2_cluster_bref(cluster, &bref);
                kprintf("ADD LOCAL PFS: %s\n", ripdata->filename);

                pmp = hammer2_pfsalloc(cluster, ripdata, bref.modify_tid);
                cluster = hammer2_cluster_next(cparent, cluster,
                                               &key_next,
                                               key_next,
                                               HAMMER2_KEY_MAX,
                                               0);
        }
        hammer2_inode_unlock(spmp->iroot, cparent);
}

/*
 * Handle bioq for strategy write
 */
static
void
hammer2_write_thread(void *arg)
{
        hammer2_pfs_t *pmp;
        struct bio *bio;
        struct buf *bp;
        hammer2_trans_t trans;
        struct vnode *vp;
        hammer2_inode_t *ip;
        hammer2_cluster_t *cparent;
        const hammer2_inode_data_t *ripdata;
        hammer2_key_t lbase;
        int lblksize;
        int pblksize;
        int error;
        
        pmp = arg;
        
        hammer2_mtx_ex(&pmp->wthread_mtx);
        for (;;) {
                /*
                 * Wait for work.  Break out and destroy the thread only if
                 * requested and no work remains.
                 */
                if (bioq_first(&pmp->wthread_bioq) == NULL) {
                        if (pmp->wthread_destroy)
                                break;
                        mtxsleep(&pmp->wthread_bioq, &pmp->wthread_mtx,
                                 0, "h2bioqw", 0);
                        continue;
                }

                /*
                 * Special transaction for logical buffer cache writes.
                 */
                hammer2_trans_init(&trans, pmp, HAMMER2_TRANS_BUFCACHE);

                while ((bio = bioq_takefirst(&pmp->wthread_bioq)) != NULL) {
                        /*
                         * dummy bio for synchronization.  The transaction
                         * must be terminated.
                         */
                        if (bio->bio_buf == NULL) {
                                bio->bio_flags |= BIO_DONE;
                                /* bio will become invalid after DONE set */
                                wakeup(bio);
                                break;
                        }

                        /*
                         * else normal bio processing
                         */
                        hammer2_mtx_unlock(&pmp->wthread_mtx);

                        hammer2_lwinprog_drop(pmp);
                        
                        error = 0;
                        bp = bio->bio_buf;
                        vp = bp->b_vp;
                        ip = VTOI(vp);

                        /*
                         * Inode is modified, flush size and mtime changes
                         * to ensure that the file size remains consistent
                         * with the buffers being flushed.
                         *
                         * NOTE: The inode_fsync() call only flushes the
                         *       inode's meta-data state, it doesn't try
                         *       to flush underlying buffers or chains.
                         *
                         * NOTE: hammer2_write_file_core() may indirectly
                         *       modify and modsync the inode.
                         */
                        cparent = hammer2_inode_lock(ip,
                                                     HAMMER2_RESOLVE_ALWAYS);
                        if (ip->flags & (HAMMER2_INODE_RESIZED |
                                         HAMMER2_INODE_MTIME)) {
                                hammer2_inode_fsync(&trans, ip, cparent);
                        }
                        ripdata = &hammer2_cluster_rdata(cparent)->ipdata;
                        lblksize = hammer2_calc_logical(ip, bio->bio_offset,
                                                        &lbase, NULL);
                        pblksize = hammer2_calc_physical(ip, ripdata, lbase);
                        hammer2_write_file_core(bp, &trans, ip, ripdata,
                                                cparent,
                                                lbase, IO_ASYNC,
                                                pblksize, &error);
                        /* ripdata can be invalid after call */
                        hammer2_inode_unlock(ip, cparent);
                        if (error) {
                                kprintf("hammer2: error in buffer write\n");
                                bp->b_flags |= B_ERROR;
                                bp->b_error = EIO;
                        }
                        biodone(bio);
                        hammer2_mtx_ex(&pmp->wthread_mtx);
                }
                hammer2_trans_done(&trans);
        }
        pmp->wthread_destroy = -1;
        wakeup(&pmp->wthread_destroy);
        
        hammer2_mtx_unlock(&pmp->wthread_mtx);
}

void
hammer2_bioq_sync(hammer2_pfs_t *pmp)
{
        struct bio sync_bio;

        bzero(&sync_bio, sizeof(sync_bio));     /* dummy with no bio_buf */
        hammer2_mtx_ex(&pmp->wthread_mtx);
        if (pmp->wthread_destroy == 0 &&
            TAILQ_FIRST(&pmp->wthread_bioq.queue)) {
                bioq_insert_tail(&pmp->wthread_bioq, &sync_bio);
                while ((sync_bio.bio_flags & BIO_DONE) == 0)
                        mtxsleep(&sync_bio, &pmp->wthread_mtx, 0, "h2bioq", 0);
        }
        hammer2_mtx_unlock(&pmp->wthread_mtx);
}

/* 
 * Return a chain suitable for I/O, creating the chain if necessary
 * and assigning its physical block.  The cluster will be in a modified
 * state.
 *
 * cparent can wind up being anything.
 *
 * NOTE: Special case for data embedded in inode.
 */
static
hammer2_cluster_t *
hammer2_assign_physical(hammer2_trans_t *trans,
                        hammer2_inode_t *ip, hammer2_cluster_t *cparent,
                        hammer2_key_t lbase, int pblksize, int *errorp)
{
        hammer2_cluster_t *cluster;
        hammer2_cluster_t *dparent;
        hammer2_key_t key_dummy;
        int pradix = hammer2_getradix(pblksize);

        /*
         * Locate the chain associated with lbase, return a locked chain.
         * However, do not instantiate any data reference (which utilizes a
         * device buffer) because we will be using direct IO via the
         * logical buffer cache buffer.
         */
        *errorp = 0;
        KKASSERT(pblksize >= HAMMER2_ALLOC_MIN);
retry:
        dparent = hammer2_cluster_lookup_init(cparent, 0);
        cluster = hammer2_cluster_lookup(dparent, &key_dummy,
                                     lbase, lbase,
                                     HAMMER2_LOOKUP_NODATA);

        if (cluster == NULL) {
                /*
                 * We found a hole, create a new chain entry.
                 *
                 * NOTE: DATA chains are created without device backing
                 *       store (nor do we want any).
                 */
                *errorp = hammer2_cluster_create(trans, dparent, &cluster,
                                               lbase, HAMMER2_PBUFRADIX,
                                               HAMMER2_BREF_TYPE_DATA,
                                               pblksize, 0);
                if (cluster == NULL) {
                        hammer2_cluster_lookup_done(dparent);
                        panic("hammer2_cluster_create: par=%p error=%d\n",
                                dparent->focus, *errorp);
                        goto retry;
                }
                /*ip->delta_dcount += pblksize;*/
        } else {
                switch (hammer2_cluster_type(cluster)) {
                case HAMMER2_BREF_TYPE_INODE:
                        /*
                         * The data is embedded in the inode, which requires
                         * a bit more finess.
                         */
                        hammer2_cluster_modify_ip(trans, ip, cluster, 0);
                        break;
                case HAMMER2_BREF_TYPE_DATA:
                        if (hammer2_cluster_need_resize(cluster, pblksize)) {
                                hammer2_cluster_resize(trans, ip,
                                                     dparent, cluster,
                                                     pradix,
                                                     HAMMER2_MODIFY_OPTDATA);
                        }

                        /*
                         * DATA buffers must be marked modified whether the
                         * data is in a logical buffer or not.  We also have
                         * to make this call to fixup the chain data pointers
                         * after resizing in case this is an encrypted or
                         * compressed buffer.
                         */
                        hammer2_cluster_modify(trans, cluster,
                                               HAMMER2_MODIFY_OPTDATA);
                        break;
                default:
                        panic("hammer2_assign_physical: bad type");
                        /* NOT REACHED */
                        break;
                }
        }

        /*
         * Cleanup.  If cluster wound up being the inode itself, i.e.
         * the DIRECTDATA case for offset 0, then we need to update cparent.
         * The caller expects cparent to not become stale.
         */
        hammer2_cluster_lookup_done(dparent);
        /* dparent = NULL; safety */
        return (cluster);
}

/* 
 * bio queued from hammer2_vnops.c.
 *
 * The core write function which determines which path to take
 * depending on compression settings.  We also have to locate the
 * related clusters so we can calculate and set the check data for
 * the blockref.
 */
static
void
hammer2_write_file_core(struct buf *bp, hammer2_trans_t *trans,
                        hammer2_inode_t *ip,
                        const hammer2_inode_data_t *ripdata,
                        hammer2_cluster_t *cparent,
                        hammer2_key_t lbase, int ioflag, int pblksize,
                        int *errorp)
{
        hammer2_cluster_t *cluster;

        switch(HAMMER2_DEC_ALGO(ripdata->comp_algo)) {
        case HAMMER2_COMP_NONE:
                /*
                 * We have to assign physical storage to the buffer
                 * we intend to dirty or write now to avoid deadlocks
                 * in the strategy code later.
                 *
                 * This can return NOOFFSET for inode-embedded data.
                 * The strategy code will take care of it in that case.
                 */
                cluster = hammer2_assign_physical(trans, ip, cparent,
                                                lbase, pblksize,
                                                errorp);
                if (cluster->ddflag) {
                        hammer2_inode_data_t *wipdata;

                        wipdata = hammer2_cluster_modify_ip(trans, ip,
                                                            cluster, 0);
                        KKASSERT(wipdata->op_flags & HAMMER2_OPFLAG_DIRECTDATA);
                        KKASSERT(bp->b_loffset == 0);
                        bcopy(bp->b_data, wipdata->u.data,
                              HAMMER2_EMBEDDED_BYTES);
                        hammer2_cluster_modsync(cluster);
                } else {
                        hammer2_write_bp(cluster, bp, ioflag, pblksize,
                                         errorp, ripdata->check_algo);
                }
                /* ripdata can become invalid */
                if (cluster) {
                        hammer2_cluster_unlock(cluster);
                        hammer2_cluster_drop(cluster);
                }
                break;
        case HAMMER2_COMP_AUTOZERO:
                /*
                 * Check for zero-fill only
                 */
                hammer2_zero_check_and_write(bp, trans, ip,
                                    ripdata, cparent, lbase,
                                    ioflag, pblksize, errorp,
                                    ripdata->check_algo);
                break;
        case HAMMER2_COMP_LZ4:
        case HAMMER2_COMP_ZLIB:
        default:
                /*
                 * Check for zero-fill and attempt compression.
                 */
                hammer2_compress_and_write(bp, trans, ip,
                                           ripdata, cparent,
                                           lbase, ioflag,
                                           pblksize, errorp,
                                           ripdata->comp_algo,
                                           ripdata->check_algo);
                break;
        }
}

/*
 * Generic function that will perform the compression in compression
 * write path. The compression algorithm is determined by the settings
 * obtained from inode.
 */
static
void
hammer2_compress_and_write(struct buf *bp, hammer2_trans_t *trans,
        hammer2_inode_t *ip, const hammer2_inode_data_t *ripdata,
        hammer2_cluster_t *cparent,
        hammer2_key_t lbase, int ioflag, int pblksize,
        int *errorp, int comp_algo, int check_algo)
{
        hammer2_cluster_t *cluster;
        hammer2_chain_t *chain;
        int comp_size;
        int comp_block_size;
        int i;
        char *comp_buffer;

        if (test_block_zeros(bp->b_data, pblksize)) {
                zero_write(bp, trans, ip, ripdata, cparent, lbase, errorp);
                return;
        }

        comp_size = 0;
        comp_buffer = NULL;

        KKASSERT(pblksize / 2 <= 32768);
                
        if (ip->comp_heuristic < 8 || (ip->comp_heuristic & 7) == 0) {
                z_stream strm_compress;
                int comp_level;
                int ret;

                switch(HAMMER2_DEC_ALGO(comp_algo)) {
                case HAMMER2_COMP_LZ4:
                        comp_buffer = objcache_get(cache_buffer_write,
                                                   M_INTWAIT);
                        comp_size = LZ4_compress_limitedOutput(
                                        bp->b_data,
                                        &comp_buffer[sizeof(int)],
                                        pblksize,
                                        pblksize / 2 - sizeof(int));
                        /*
                         * We need to prefix with the size, LZ4
                         * doesn't do it for us.  Add the related
                         * overhead.
                         */
                        *(int *)comp_buffer = comp_size;
                        if (comp_size)
                                comp_size += sizeof(int);
                        break;
                case HAMMER2_COMP_ZLIB:
                        comp_level = HAMMER2_DEC_LEVEL(comp_algo);
                        if (comp_level == 0)
                                comp_level = 6; /* default zlib compression */
                        else if (comp_level < 6)
                                comp_level = 6;
                        else if (comp_level > 9)
                                comp_level = 9;
                        ret = deflateInit(&strm_compress, comp_level);
                        if (ret != Z_OK) {
                                kprintf("HAMMER2 ZLIB: fatal error "
                                        "on deflateInit.\n");
                        }

                        comp_buffer = objcache_get(cache_buffer_write,
                                                   M_INTWAIT);
                        strm_compress.next_in = bp->b_data;
                        strm_compress.avail_in = pblksize;
                        strm_compress.next_out = comp_buffer;
                        strm_compress.avail_out = pblksize / 2;
                        ret = deflate(&strm_compress, Z_FINISH);
                        if (ret == Z_STREAM_END) {
                                comp_size = pblksize / 2 -
                                            strm_compress.avail_out;
                        } else {
                                comp_size = 0;
                        }
                        ret = deflateEnd(&strm_compress);
                        break;
                default:
                        kprintf("Error: Unknown compression method.\n");
                        kprintf("Comp_method = %d.\n", comp_algo);
                        break;
                }
        }

        if (comp_size == 0) {
                /*
                 * compression failed or turned off
                 */
                comp_block_size = pblksize;     /* safety */
                if (++ip->comp_heuristic > 128)
                        ip->comp_heuristic = 8;
        } else {
                /*
                 * compression succeeded
                 */
                ip->comp_heuristic = 0;
                if (comp_size <= 1024) {
                        comp_block_size = 1024;
                } else if (comp_size <= 2048) {
                        comp_block_size = 2048;
                } else if (comp_size <= 4096) {
                        comp_block_size = 4096;
                } else if (comp_size <= 8192) {
                        comp_block_size = 8192;
                } else if (comp_size <= 16384) {
                        comp_block_size = 16384;
                } else if (comp_size <= 32768) {
                        comp_block_size = 32768;
                } else {
                        panic("hammer2: WRITE PATH: "
                              "Weird comp_size value.");
                        /* NOT REACHED */
                        comp_block_size = pblksize;
                }
        }

        cluster = hammer2_assign_physical(trans, ip, cparent,
                                          lbase, comp_block_size,
                                          errorp);
        ripdata = NULL;

        if (*errorp) {
                kprintf("WRITE PATH: An error occurred while "
                        "assigning physical space.\n");
                KKASSERT(cluster == NULL);
                goto done;
        }

        if (cluster->ddflag) {
                hammer2_inode_data_t *wipdata;

                wipdata = &hammer2_cluster_wdata(cluster)->ipdata;
                KKASSERT(wipdata->op_flags & HAMMER2_OPFLAG_DIRECTDATA);
                KKASSERT(bp->b_loffset == 0);
                bcopy(bp->b_data, wipdata->u.data, HAMMER2_EMBEDDED_BYTES);
                hammer2_cluster_modsync(cluster);
        } else
        for (i = 0; i < cluster->nchains; ++i) {
                hammer2_io_t *dio;
                char *bdata;

                /* XXX hackx */

                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0)
                        continue;
                chain = cluster->array[i].chain;        /* XXX */
                if (chain == NULL)
                        continue;
                KKASSERT(chain->flags & HAMMER2_CHAIN_MODIFIED);

                switch(chain->bref.type) {
                case HAMMER2_BREF_TYPE_INODE:
                        panic("hammer2_write_bp: unexpected inode\n");
                        break;
                case HAMMER2_BREF_TYPE_DATA:
                        /*
                         * Optimize out the read-before-write
                         * if possible.
                         */
                        *errorp = hammer2_io_newnz(chain->hmp,
                                                   chain->bref.data_off,
                                                   chain->bytes,
                                                   &dio);
                        if (*errorp) {
                                hammer2_io_brelse(&dio);
                                kprintf("hammer2: WRITE PATH: "
                                        "dbp bread error\n");
                                break;
                        }
                        bdata = hammer2_io_data(dio, chain->bref.data_off);

                        /*
                         * When loading the block make sure we don't
                         * leave garbage after the compressed data.
                         */
                        if (comp_size) {
                                chain->bref.methods =
                                        HAMMER2_ENC_COMP(comp_algo) +
                                        HAMMER2_ENC_CHECK(check_algo);
                                bcopy(comp_buffer, bdata, comp_size);
                                if (comp_size != comp_block_size) {
                                        bzero(bdata + comp_size,
                                              comp_block_size - comp_size);
                                }
                        } else {
                                chain->bref.methods =
                                        HAMMER2_ENC_COMP(
                                                HAMMER2_COMP_NONE) +
                                        HAMMER2_ENC_CHECK(check_algo);
                                bcopy(bp->b_data, bdata, pblksize);
                        }

                        /*
                         * The flush code doesn't calculate check codes for
                         * file data (doing so can result in excessive I/O),
                         * so we do it here.
                         */
                        hammer2_chain_setcheck(chain, bdata);

                        /*
                         * Device buffer is now valid, chain is no longer in
                         * the initial state.
                         *
                         * (No blockref table worries with file data)
                         */
                        atomic_clear_int(&chain->flags, HAMMER2_CHAIN_INITIAL);

                        /* Now write the related bdp. */
                        if (ioflag & IO_SYNC) {
                                /*
                                 * Synchronous I/O requested.
                                 */
                                hammer2_io_bwrite(&dio);
                        /*
                        } else if ((ioflag & IO_DIRECT) &&
                                   loff + n == pblksize) {
                                hammer2_io_bdwrite(&dio);
                        */
                        } else if (ioflag & IO_ASYNC) {
                                hammer2_io_bawrite(&dio);
                        } else {
                                hammer2_io_bdwrite(&dio);
                        }
                        break;
                default:
                        panic("hammer2_write_bp: bad chain type %d\n",
                                chain->bref.type);
                        /* NOT REACHED */
                        break;
                }
        }
done:
        if (cluster) {
                hammer2_cluster_unlock(cluster);
                hammer2_cluster_drop(cluster);
        }
        if (comp_buffer)
                objcache_put(cache_buffer_write, comp_buffer);
}

/*
 * Function that performs zero-checking and writing without compression,
 * it corresponds to default zero-checking path.
 */
static
void
hammer2_zero_check_and_write(struct buf *bp, hammer2_trans_t *trans,
        hammer2_inode_t *ip, const hammer2_inode_data_t *ripdata,
        hammer2_cluster_t *cparent,
        hammer2_key_t lbase, int ioflag, int pblksize, int *errorp,
        int check_algo)
{
        hammer2_cluster_t *cluster;

        if (test_block_zeros(bp->b_data, pblksize)) {
                zero_write(bp, trans, ip, ripdata, cparent, lbase, errorp);
                /* ripdata can become invalid */
        } else {
                cluster = hammer2_assign_physical(trans, ip, cparent,
                                                  lbase, pblksize, errorp);
                hammer2_write_bp(cluster, bp, ioflag, pblksize, errorp,
                                 check_algo);
                /* ripdata can become invalid */
                if (cluster) {
                        hammer2_cluster_unlock(cluster);
                        hammer2_cluster_drop(cluster);
                }
        }
}

/*
 * A function to test whether a block of data contains only zeros,
 * returns TRUE (non-zero) if the block is all zeros.
 */
static
int
test_block_zeros(const char *buf, size_t bytes)
{
        size_t i;

        for (i = 0; i < bytes; i += sizeof(long)) {
                if (*(const long *)(buf + i) != 0)
                        return (0);
        }
        return (1);
}

/*
 * Function to "write" a block that contains only zeros.
 */
static
void
zero_write(struct buf *bp, hammer2_trans_t *trans,
           hammer2_inode_t *ip, const hammer2_inode_data_t *ripdata,
           hammer2_cluster_t *cparent,
           hammer2_key_t lbase, int *errorp __unused)
{
        hammer2_cluster_t *cluster;
        hammer2_key_t key_dummy;

        cparent = hammer2_cluster_lookup_init(cparent, 0);
        cluster = hammer2_cluster_lookup(cparent, &key_dummy, lbase, lbase,
                                     HAMMER2_LOOKUP_NODATA);
        if (cluster) {
                if (cluster->ddflag) {
                        hammer2_inode_data_t *wipdata;

                        wipdata = hammer2_cluster_modify_ip(trans, ip,
                                                            cluster, 0);
                        KKASSERT(wipdata->op_flags & HAMMER2_OPFLAG_DIRECTDATA);
                        KKASSERT(bp->b_loffset == 0);
                        bzero(wipdata->u.data, HAMMER2_EMBEDDED_BYTES);
                        hammer2_cluster_modsync(cluster);
                } else {
                        hammer2_cluster_delete(trans, cparent, cluster,
                                               HAMMER2_DELETE_PERMANENT);
                }
                hammer2_cluster_unlock(cluster);
                hammer2_cluster_drop(cluster);
        }
        hammer2_cluster_lookup_done(cparent);
}

/*
 * Function to write the data as it is, without performing any sort of
 * compression. This function is used in path without compression and
 * default zero-checking path.
 */
static
void
hammer2_write_bp(hammer2_cluster_t *cluster, struct buf *bp, int ioflag,
                                int pblksize, int *errorp, int check_algo)
{
        hammer2_chain_t *chain;
        hammer2_inode_data_t *wipdata;
        hammer2_io_t *dio;
        char *bdata;
        int error;
        int i;

        error = 0;      /* XXX TODO below */

        for (i = 0; i < cluster->nchains; ++i) {
                if ((cluster->array[i].flags & HAMMER2_CITEM_FEMOD) == 0)
                        continue;
                chain = cluster->array[i].chain;        /* XXX */
                if (chain == NULL)
                        continue;
                KKASSERT(chain->flags & HAMMER2_CHAIN_MODIFIED);

                switch(chain->bref.type) {
                case HAMMER2_BREF_TYPE_INODE:
                        wipdata = &hammer2_chain_wdata(chain)->ipdata;
                        KKASSERT(wipdata->op_flags & HAMMER2_OPFLAG_DIRECTDATA);
                        KKASSERT(bp->b_loffset == 0);
                        bcopy(bp->b_data, wipdata->u.data,
                              HAMMER2_EMBEDDED_BYTES);
                        error = 0;
                        break;
                case HAMMER2_BREF_TYPE_DATA:
                        error = hammer2_io_newnz(chain->hmp,
                                                 chain->bref.data_off,
                                                 chain->bytes, &dio);
                        if (error) {
                                hammer2_io_bqrelse(&dio);
                                kprintf("hammer2: WRITE PATH: "
                                        "dbp bread error\n");
                                break;
                        }
                        bdata = hammer2_io_data(dio, chain->bref.data_off);

                        chain->bref.methods = HAMMER2_ENC_COMP(
                                                        HAMMER2_COMP_NONE) +
                                              HAMMER2_ENC_CHECK(check_algo);
                        bcopy(bp->b_data, bdata, chain->bytes);

                        /*
                         * The flush code doesn't calculate check codes for
                         * file data (doing so can result in excessive I/O),
                         * so we do it here.
                         */
                        hammer2_chain_setcheck(chain, bdata);

                        /*
                         * Device buffer is now valid, chain is no longer in
                         * the initial state.
                         *
                         * (No blockref table worries with file data)
                         */
                        atomic_clear_int(&chain->flags, HAMMER2_CHAIN_INITIAL);

                        if (ioflag & IO_SYNC) {
                                /*
                                 * Synchronous I/O requested.
                                 */
                                hammer2_io_bwrite(&dio);
                        /*
                        } else if ((ioflag & IO_DIRECT) &&
                                   loff + n == pblksize) {
                                hammer2_io_bdwrite(&dio);
                        */
                        } else if (ioflag & IO_ASYNC) {
                                hammer2_io_bawrite(&dio);
                        } else {
                                hammer2_io_bdwrite(&dio);
                        }
                        break;
                default:
                        panic("hammer2_write_bp: bad chain type %d\n",
                              chain->bref.type);
                        /* NOT REACHED */
                        error = 0;
                        break;
                }
                KKASSERT(error == 0);   /* XXX TODO */
        }
        *errorp = error;
}

static
int
hammer2_remount(hammer2_dev_t *hmp, struct mount *mp, char *path,
                struct vnode *devvp, struct ucred *cred)
{
        int error;

        if (hmp->ronly && (mp->mnt_kern_flag & MNTK_WANTRDWR)) {
                error = hammer2_recovery(hmp);
        } else {
                error = 0;
        }
        return error;
}

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);
        }

        if (pmp->wthread_td) {
                hammer2_mtx_ex(&pmp->wthread_mtx);
                pmp->wthread_destroy = 1;
                wakeup(&pmp->wthread_bioq);
                while (pmp->wthread_destroy != -1) {
                        mtxsleep(&pmp->wthread_destroy,
                                &pmp->wthread_mtx, 0,
                                "umount-sleep", 0);
                }
                hammer2_mtx_unlock(&pmp->wthread_mtx);
                pmp->wthread_td = NULL;
        }

        /*
         * Cleanup our reference on ihidden.
         */
        if (pmp->ihidden) {
                hammer2_inode_drop(pmp->ihidden);
                pmp->ihidden = NULL;
        }
        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;
                kprintf("hammer2_mount hmp=%p ++mount_count=%d\n",
                        rchain->hmp, rchain->hmp->mount_count);
        }
}

/*
 * Mount 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 disconnect.  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;
        struct vnode *devvp;
        int dumpcnt;
        int ronly = 0;
        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((void *)(intptr_t)mp->mnt_data == 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;
                        kprintf("hammer2_unmount hmp=%p --mount_count=%d\n",
                                rchain->hmp, 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.
         */
        kprintf("hammer2_unmount hmp=%p mount_count=%d\n",
                hmp, hmp->mount_count);
        if (hmp->mount_count)
                return;

        hammer2_pfsfree_scan(hmp);
        hammer2_dev_exlock(hmp);        /* XXX order */

        /*
         * 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 unlinkq 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
        hammer2_iocom_uninit(hmp);

        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");
        }

        KKASSERT(hmp->spmp == NULL);

        /*
         * Finish up with the device vnode
         */
        if ((devvp = hmp->devvp) != NULL) {
                vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                vinvalbuf(devvp, (ronly ? 0 : V_SAVE), 0, 0);
                hmp->devvp = NULL;
                VOP_CLOSE(devvp, (ronly ? FREAD : FREAD|FWRITE), NULL);
                vn_unlock(devvp);
                vrele(devvp);
                devvp = NULL;
        }

        /*
         * Clear vchain/fchain flags that might prevent final cleanup
         * of these chains.
         */
        if (hmp->vchain.flags & HAMMER2_CHAIN_MODIFIED) {
                atomic_clear_int(&hmp->vchain.flags,
                                 HAMMER2_CHAIN_MODIFIED);
                hammer2_pfs_memory_wakeup(hmp->vchain.pmp);
                hammer2_chain_drop(&hmp->vchain);
        }
        if (hmp->vchain.flags & HAMMER2_CHAIN_UPDATE) {
                atomic_clear_int(&hmp->vchain.flags,
                                 HAMMER2_CHAIN_UPDATE);
                hammer2_chain_drop(&hmp->vchain);
        }

        if (hmp->fchain.flags & HAMMER2_CHAIN_MODIFIED) {
                atomic_clear_int(&hmp->fchain.flags,
                                 HAMMER2_CHAIN_MODIFIED);
                hammer2_pfs_memory_wakeup(hmp->fchain.pmp);
                hammer2_chain_drop(&hmp->fchain);
        }
        if (hmp->fchain.flags & HAMMER2_CHAIN_UPDATE) {
                atomic_clear_int(&hmp->fchain.flags,
                                 HAMMER2_CHAIN_UPDATE);
                hammer2_chain_drop(&hmp->fchain);
        }

        /*
         * 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).
         */
        dumpcnt = 50;
        hammer2_dump_chain(&hmp->vchain, 0, &dumpcnt, 'v');
        dumpcnt = 50;
        hammer2_dump_chain(&hmp->fchain, 0, &dumpcnt, 'f');
        hammer2_dev_unlock(hmp);
        hammer2_chain_drop(&hmp->vchain);

        hammer2_io_cleanup(hmp, &hmp->iotree);
        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(&hmp->mchain);
        kfree(hmp, M_HAMMER2);
}

static
int
hammer2_vfs_vget(struct mount *mp, struct vnode *dvp,
             ino_t ino, struct vnode **vpp)
{
        kprintf("hammer2_vget\n");
        return (EOPNOTSUPP);
}

static
int
hammer2_vfs_root(struct mount *mp, struct vnode **vpp)
{
        hammer2_pfs_t *pmp;
        hammer2_cluster_t *cparent;
        int error;
        struct vnode *vp;

        pmp = MPTOPMP(mp);
        if (pmp->iroot == NULL) {
                *vpp = NULL;
                error = EINVAL;
        } else {
                cparent = hammer2_inode_lock(pmp->iroot,
                                                HAMMER2_RESOLVE_ALWAYS |
                                                HAMMER2_RESOLVE_SHARED);
                vp = hammer2_igetv(pmp->iroot, cparent, &error);
                hammer2_inode_unlock(pmp->iroot, cparent);
                *vpp = vp;
                if (vp == NULL)
                        kprintf("vnodefail\n");
        }

        return (error);
}

/*
 * Filesystem status
 *
 * XXX incorporate ipdata->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;

        pmp = MPTOPMP(mp);
        KKASSERT(pmp->iroot->cluster.nchains >= 1);
        hmp = pmp->iroot->cluster.focus->hmp;   /* iroot retains focus */
        bref = pmp->iroot->cluster.focus->bref; /* no lock */

        mp->mnt_stat.f_files = bref.inode_count;
        mp->mnt_stat.f_ffree = 0;
        mp->mnt_stat.f_blocks = (bref.data_count +
                                 hmp->voldata.allocator_free) /
                                mp->mnt_vstat.f_bsize;
        mp->mnt_stat.f_bfree =  hmp->voldata.allocator_free /
                                mp->mnt_vstat.f_bsize;
        mp->mnt_stat.f_bavail = mp->mnt_stat.f_bfree;

        *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;

        pmp = MPTOPMP(mp);
        KKASSERT(pmp->iroot->cluster.nchains >= 1);
        hmp = pmp->iroot->cluster.focus->hmp;   /* iroot retains focus */
        bref = pmp->iroot->cluster.focus->bref; /* no lock */

        mp->mnt_vstat.f_bsize = HAMMER2_PBUFSIZE;
        mp->mnt_vstat.f_files = bref.inode_count;
        mp->mnt_vstat.f_ffree = 0;
        mp->mnt_vstat.f_blocks = (bref.data_count +
                                 hmp->voldata.allocator_free) /
                                mp->mnt_vstat.f_bsize;
        mp->mnt_vstat.f_bfree = hmp->voldata.allocator_free /
                                mp->mnt_vstat.f_bsize;
        mp->mnt_vstat.f_bavail = mp->mnt_vstat.f_bfree;

        *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.
 *
 * The super-root topology and each PFS has its own transaction id domain,
 * so we must track PFS boundary transitions.
 */
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;
        int     depth;
};

static int hammer2_recovery_scan(hammer2_trans_t *trans, 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)
{
        hammer2_trans_t trans;
        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;
        int cumulative_error = 0;

        hammer2_trans_init(&trans, 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);
        cumulative_error = hammer2_recovery_scan(&trans, 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(&trans, hmp, parent,
                                              &info,
                                              hmp->voldata.freemap_tid);
                hammer2_chain_unlock(parent);
                hammer2_chain_drop(parent);     /* drop elm->chain ref */
                if (error)
                        cumulative_error = error;
        }
        hammer2_trans_done(&trans);

        return cumulative_error;
}

static
int
hammer2_recovery_scan(hammer2_trans_t *trans, 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;
        int cache_index;
        int cumulative_error = 0;
        int error;

        /*
         * Adjust freemap to ensure that the block(s) are marked allocated.
         */
        if (parent->bref.type != HAMMER2_BREF_TYPE_VOLUME) {
                hammer2_freemap_adjust(trans, 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 = &hammer2_chain_rdata(parent)->ipdata;
                if (ripdata->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_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 EDOM;
        }

        /*
         * Defer operation if depth limit reached or if we are crossing a
         * PFS boundary.
         */
        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.
         */
        cache_index = 0;
        chain = hammer2_chain_scan(parent, NULL, &cache_index,
                                   HAMMER2_LOOKUP_NODATA);
        while (chain) {
                atomic_set_int(&chain->flags, HAMMER2_CHAIN_RELEASE);
                if (chain->bref.mirror_tid > sync_tid) {
                        ++info->depth;
                        error = hammer2_recovery_scan(trans, hmp, chain,
                                                      info, sync_tid);
                        --info->depth;
                        if (error)
                                cumulative_error = error;
                }

                /*
                 * Flush the recovery at the PFS boundary to stage it for
                 * the final flush of the super-root topology.
                 */
                if ((chain->bref.flags & HAMMER2_BREF_FLAG_PFSROOT) &&
                    (chain->flags & HAMMER2_CHAIN_ONFLUSH)) {
                        hammer2_flush(trans, chain, 1);
                }
                chain = hammer2_chain_scan(parent, chain, &cache_index,
                                           HAMMER2_LOOKUP_NODATA);
        }

        return cumulative_error;
}

/*
 * Sync a mount point; this is called on a per-mount basis from the
 * filesystem syncer process periodically and whenever a user issues
 * a sync.
 */
int
hammer2_vfs_sync(struct mount *mp, int waitfor)
{
        struct hammer2_sync_info info;
        hammer2_inode_t *iroot;
        hammer2_chain_t *chain;
        hammer2_chain_t *parent;
        hammer2_pfs_t *pmp;
        hammer2_dev_t *hmp;
        int flags;
        int error;
        int total_error;
        int i;
        int j;

        pmp = MPTOPMP(mp);
        iroot = pmp->iroot;
        KKASSERT(iroot);
        KKASSERT(iroot->pmp == pmp);

        /*
         * We can't acquire locks on existing vnodes while in a transaction
         * without risking a deadlock.  This assumes that vfsync() can be
         * called without the vnode locked (which it can in DragonFly).
         * Otherwise we'd have to implement a multi-pass or flag the lock
         * failures and retry.
         *
         * The reclamation code interlocks with the sync list's token
         * (by removing the vnode from the scan list) before unlocking
         * the inode, giving us time to ref the inode.
         */
        /*flags = VMSC_GETVP;*/
        flags = 0;
        if (waitfor & MNT_LAZY)
                flags |= VMSC_ONEPASS;

#if 0
        /*
         * Preflush the vnodes using a normal transaction before interlocking
         * with a flush transaction.
         */
        hammer2_trans_init(&info.trans, pmp, 0);
        info.error = 0;
        info.waitfor = MNT_NOWAIT;
        vsyncscan(mp, flags | VMSC_NOWAIT, hammer2_sync_scan2, &info);
        hammer2_trans_done(&info.trans);
#endif

        /*
         * Start our flush transaction.  This does not return until all
         * concurrent transactions have completed and will prevent any
         * new transactions from running concurrently, except for the
         * buffer cache transactions.
         *
         * For efficiency do an async pass before making sure with a
         * synchronous pass on all related buffer cache buffers.  It
         * should theoretically not be possible for any new file buffers
         * to be instantiated during this sequence.
         */
        hammer2_trans_init(&info.trans, pmp, HAMMER2_TRANS_ISFLUSH |
                                             HAMMER2_TRANS_PREFLUSH);
        hammer2_run_unlinkq(&info.trans, pmp);

        info.error = 0;
        info.waitfor = MNT_NOWAIT;
        vsyncscan(mp, flags | VMSC_NOWAIT, hammer2_sync_scan2, &info);
        info.waitfor = MNT_WAIT;
        vsyncscan(mp, flags, hammer2_sync_scan2, &info);

        /*
         * Clear PREFLUSH.  This prevents (or asserts on) any new logical
         * buffer cache flushes which occur during the flush.  Device buffers
         * are not affected.
         */
        hammer2_bioq_sync(info.trans.pmp);
        atomic_clear_int(&info.trans.flags, HAMMER2_TRANS_PREFLUSH);

        total_error = 0;

        /*
         * Flush all nodes to synchronize the PFSROOT subtopology to the media.
         *
         * Note that this flush will not be visible on crash recovery until
         * we flush the super-root topology in the next loop.
         */
        for (i = 0; iroot && i < iroot->cluster.nchains; ++i) {
                chain = iroot->cluster.array[i].chain;
                if (chain == NULL)
                        continue;

                hammer2_chain_ref(chain);
                hammer2_chain_lock(chain, HAMMER2_RESOLVE_ALWAYS);
                if (chain->flags & HAMMER2_CHAIN_FLUSH_MASK) {
                        hammer2_flush(&info.trans, chain, 1);
                        parent = chain->parent;
                        KKASSERT(chain->pmp != parent->pmp);
                        hammer2_chain_setflush(&info.trans, parent);
                }
                hammer2_chain_unlock(chain);
                hammer2_chain_drop(chain);
        }
        hammer2_trans_done(&info.trans);

        /*
         * Flush all volume roots to synchronize PFS flushes with the
         * storage media volume header.  This will flush the freemap and
         * the superroot topology but stops when it reaches a PFSROOT
         * (which we already flushed above).
         *
         * This is the last step which connects the volume root to the
         * PFSROOT dirs flushed above.
         *
         * Each spmp (representing the hmp's super-root) requires its own
         * transaction.
         */
        for (i = 0; iroot && i < iroot->cluster.nchains; ++i) {
                hammer2_chain_t *tmp;

                chain = iroot->cluster.array[i].chain;
                if (chain == NULL)
                        continue;

                hmp = chain->hmp;

                /*
                 * We only have to flush each hmp once
                 */
                for (j = i - 1; j >= 0; --j) {
                        if ((tmp = iroot->cluster.array[j].chain) != NULL) {
                                if (tmp->hmp == hmp)
                                        break;
                        }
                }
                if (j >= 0)
                        continue;

                /*
                 * spmp transaction.  The super-root is never directly
                 * mounted so there shouldn't be any vnodes, let alone any
                 * dirty vnodes associated with it.
                 */
                hammer2_trans_init(&info.trans, hmp->spmp,
                                   HAMMER2_TRANS_ISFLUSH);

                /*
                 * Media mounts have two 'roots', vchain for the topology
                 * and fchain for the free block table.  Flush both.
                 *
                 * Note that the topology and free block table are handled
                 * independently, so the free block table can wind up being
                 * ahead of the topology.  We depend on the bulk free scan
                 * code to deal with any loose ends.
                 */
                hammer2_chain_ref(&hmp->vchain);
                hammer2_chain_lock(&hmp->vchain, HAMMER2_RESOLVE_ALWAYS);
                hammer2_chain_ref(&hmp->fchain);
                hammer2_chain_lock(&hmp->fchain, HAMMER2_RESOLVE_ALWAYS);
                if (hmp->fchain.flags & HAMMER2_CHAIN_FLUSH_MASK) {
                        /*
                         * This will also modify vchain as a side effect,
                         * mark vchain as modified now.
                         */
                        hammer2_voldata_modify(hmp);
                        chain = &hmp->fchain;
                        hammer2_flush(&info.trans, chain, 1);
                        KKASSERT(chain == &hmp->fchain);
                }
                hammer2_chain_unlock(&hmp->fchain);
                hammer2_chain_unlock(&hmp->vchain);
                hammer2_chain_drop(&hmp->fchain);
                /* vchain dropped down below */

                hammer2_chain_lock(&hmp->vchain, HAMMER2_RESOLVE_ALWAYS);
                if (hmp->vchain.flags & HAMMER2_CHAIN_FLUSH_MASK) {
                        chain = &hmp->vchain;
                        hammer2_flush(&info.trans, chain, 1);
                        KKASSERT(chain == &hmp->vchain);
                }
                hammer2_chain_unlock(&hmp->vchain);
                hammer2_chain_drop(&hmp->vchain);

                error = 0;

                /*
                 * We can't safely flush the volume header until we have
                 * flushed any device buffers which have built up.
                 *
                 * XXX this isn't being incremental
                 */
                vn_lock(hmp->devvp, LK_EXCLUSIVE | LK_RETRY);
                error = VOP_FSYNC(hmp->devvp, MNT_WAIT, 0);
                vn_unlock(hmp->devvp);

                /*
                 * The flush code sets CHAIN_VOLUMESYNC to indicate that the
                 * volume header needs synchronization via hmp->volsync.
                 *
                 * XXX synchronize the flag & data with only this flush XXX
                 */
                if (error == 0 &&
                    (hmp->vchain.flags & HAMMER2_CHAIN_VOLUMESYNC)) {
                        struct buf *bp;

                        /*
                         * Synchronize the disk before flushing the volume
                         * header.
                         */
                        bp = getpbuf(NULL);
                        bp->b_bio1.bio_offset = 0;
                        bp->b_bufsize = 0;
                        bp->b_bcount = 0;
                        bp->b_cmd = BUF_CMD_FLUSH;
                        bp->b_bio1.bio_done = biodone_sync;
                        bp->b_bio1.bio_flags |= BIO_SYNC;
                        vn_strategy(hmp->devvp, &bp->b_bio1);
                        biowait(&bp->b_bio1, "h2vol");
                        relpbuf(bp, NULL);

                        /*
                         * Then we can safely flush the version of the
                         * volume header synchronized by the flush code.
                         */
                        i = hmp->volhdrno + 1;
                        if (i >= HAMMER2_NUM_VOLHDRS)
                                i = 0;
                        if (i * HAMMER2_ZONE_BYTES64 + HAMMER2_SEGSIZE >
                            hmp->volsync.volu_size) {
                                i = 0;
                        }
                        kprintf("sync volhdr %d %jd\n",
                                i, (intmax_t)hmp->volsync.volu_size);
                        bp = getblk(hmp->devvp, i * HAMMER2_ZONE_BYTES64,
                                    HAMMER2_PBUFSIZE, 0, 0);
                        atomic_clear_int(&hmp->vchain.flags,
                                         HAMMER2_CHAIN_VOLUMESYNC);
                        bcopy(&hmp->volsync, bp->b_data, HAMMER2_PBUFSIZE);
                        bawrite(bp);
                        hmp->volhdrno = i;
                }
                if (error)
                        total_error = error;

                hammer2_trans_done(&info.trans);        /* spmp trans */
        }
        return (total_error);
}

/*
 * Sync passes.
 */
static int
hammer2_sync_scan2(struct mount *mp, struct vnode *vp, void *data)
{
        struct hammer2_sync_info *info = data;
        hammer2_inode_t *ip;
        int error;

        /*
         * Degenerate cases.  Note that ip == NULL typically means the
         * syncer vnode itself and we don't want to vclrisdirty() in that
         * situation.
         */
        ip = VTOI(vp);
        if (ip == NULL) {
                return(0);
        }
        if (vp->v_type == VNON || vp->v_type == VBAD) {
                vclrisdirty(vp);
                return(0);
        }

        /*
         * VOP_FSYNC will start a new transaction so replicate some code
         * here to do it inline (see hammer2_vop_fsync()).
         *
         * WARNING: The vfsync interacts with the buffer cache and might
         *          block, we can't hold the inode lock at that time.
         *          However, we MUST ref ip before blocking to ensure that
         *          it isn't ripped out from under us (since we do not
         *          hold a lock on the vnode).
         */
        hammer2_inode_ref(ip);
        atomic_clear_int(&ip->flags, HAMMER2_INODE_MODIFIED);
        if ((ip->flags & HAMMER2_INODE_MODIFIED) ||
            !RB_EMPTY(&vp->v_rbdirty_tree)) {
                vfsync(vp, info->waitfor, 1, NULL, NULL);
        }
        if ((ip->flags & HAMMER2_INODE_MODIFIED) == 0 &&
            RB_EMPTY(&vp->v_rbdirty_tree)) {
                vclrisdirty(vp);
        }

        hammer2_inode_drop(ip);
#if 1
        error = 0;
        if (error)
                info->error = error;
#endif
        return(0);
}

static
int
hammer2_vfs_vptofh(struct vnode *vp, struct fid *fhp)
{
        return (0);
}

static
int
hammer2_vfs_fhtovp(struct mount *mp, struct vnode *rootvp,
               struct fid *fhp, struct vnode **vpp)
{
        return (0);
}

static
int
hammer2_vfs_checkexp(struct mount *mp, struct sockaddr *nam,
                 int *exflagsp, struct ucred **credanonp)
{
        return (0);
}

/*
 * Support code for hammer2_vfs_mount().  Read, verify, and install the volume
 * header into the HMP
 *
 * XXX read four volhdrs and use the one with the highest TID whos CRC
 *     matches.
 *
 * XXX check iCRCs.
 *
 * XXX For filesystems w/ less than 4 volhdrs, make sure to not write to
 *     nonexistant locations.
 *
 * XXX Record selected volhdr and ring updates to each of 4 volhdrs
 */
static
int
hammer2_install_volume_header(hammer2_dev_t *hmp)
{
        hammer2_volume_data_t *vd;
        struct buf *bp;
        hammer2_crc32_t crc0, crc, bcrc0, bcrc;
        int error_reported;
        int error;
        int valid;
        int i;

        error_reported = 0;
        error = 0;
        valid = 0;
        bp = NULL;

        /*
         * There are up to 4 copies of the volume header (syncs iterate
         * between them so there is no single master).  We don't trust the
         * volu_size field so we don't know precisely how large the filesystem
         * is, so depend on the OS to return an error if we go beyond the
         * block device's EOF.
         */
        for (i = 0; i < HAMMER2_NUM_VOLHDRS; i++) {
                error = bread(hmp->devvp, i * HAMMER2_ZONE_BYTES64,
                              HAMMER2_VOLUME_BYTES, &bp);
                if (error) {
                        brelse(bp);
                        bp = NULL;
                        continue;
                }

                vd = (struct hammer2_volume_data *) bp->b_data;
                if ((vd->magic != HAMMER2_VOLUME_ID_HBO) &&
                    (vd->magic != HAMMER2_VOLUME_ID_ABO)) {
                        brelse(bp);
                        bp = NULL;
                        continue;
                }

                if (vd->magic == HAMMER2_VOLUME_ID_ABO) {
                        /* XXX: Reversed-endianness filesystem */
                        kprintf("hammer2: reverse-endian filesystem detected");
                        brelse(bp);
                        bp = NULL;
                        continue;
                }

                crc = vd->icrc_sects[HAMMER2_VOL_ICRC_SECT0];
                crc0 = hammer2_icrc32(bp->b_data + HAMMER2_VOLUME_ICRC0_OFF,
                                      HAMMER2_VOLUME_ICRC0_SIZE);
                bcrc = vd->icrc_sects[HAMMER2_VOL_ICRC_SECT1];
                bcrc0 = hammer2_icrc32(bp->b_data + HAMMER2_VOLUME_ICRC1_OFF,
                                       HAMMER2_VOLUME_ICRC1_SIZE);
                if ((crc0 != crc) || (bcrc0 != bcrc)) {
                        kprintf("hammer2 volume header crc "
                                "mismatch copy #%d %08x/%08x\n",
                                i, crc0, crc);
                        error_reported = 1;
                        brelse(bp);
                        bp = NULL;
                        continue;
                }
                if (valid == 0 || hmp->voldata.mirror_tid < vd->mirror_tid) {
                        valid = 1;
                        hmp->voldata = *vd;
                        hmp->volhdrno = i;
                }
                brelse(bp);
                bp = NULL;
        }
        if (valid) {
                hmp->volsync = hmp->voldata;
                error = 0;
                if (error_reported || bootverbose || 1) { /* 1/DEBUG */
                        kprintf("hammer2: using volume header #%d\n",
                                hmp->volhdrno);
                }
        } else {
                error = EINVAL;
                kprintf("hammer2: no valid volume headers found!\n");
        }
        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);
        }
}

void
hammer2_lwinprog_wait(hammer2_pfs_t *pmp)
{
        int lwinprog;

        for (;;) {
                lwinprog = pmp->count_lwinprog;
                cpu_ccfence();
                if ((lwinprog & HAMMER2_LWINPROG_MASK) < hammer2_flush_pipe)
                        break;
                tsleep_interlock(&pmp->count_lwinprog, 0);
                atomic_set_int(&pmp->count_lwinprog, HAMMER2_LWINPROG_WAITING);
                lwinprog = pmp->count_lwinprog;
                if ((lwinprog & HAMMER2_LWINPROG_MASK) < hammer2_flush_pipe)
                        break;
                tsleep(&pmp->count_lwinprog, PINTERLOCKED, "h2wpipe", hz);
        }
}

/*
 * Manage excessive memory resource use for chain and related
 * structures.
 */
void
hammer2_pfs_memory_wait(hammer2_pfs_t *pmp)
{
        uint32_t waiting;
        uint32_t count;
        uint32_t limit;
#if 0
        static int zzticks;
#endif

        /*
         * Atomic check condition and wait.  Also do an early speedup of
         * the syncer to try to avoid hitting the wait.
         */
        for (;;) {
                waiting = pmp->inmem_dirty_chains;
                cpu_ccfence();
                count = waiting & HAMMER2_DIRTYCHAIN_MASK;

                limit = pmp->mp->mnt_nvnodelistsize / 10;
                if (limit < hammer2_limit_dirty_chains)
                        limit = hammer2_limit_dirty_chains;
                if (limit < 1000)
                        limit = 1000;

#if 0
                if ((int)(ticks - zzticks) > hz) {
                        zzticks = ticks;
                        kprintf("count %ld %ld\n", count, limit);
                }
#endif

                /*
                 * Block if there are too many dirty chains present, wait
                 * for the flush to clean some out.
                 */
                if (count > limit) {
                        tsleep_interlock(&pmp->inmem_dirty_chains, 0);
                        if (atomic_cmpset_int(&pmp->inmem_dirty_chains,
                                               waiting,
                                       waiting | HAMMER2_DIRTYCHAIN_WAITING)) {
                                speedup_syncer(pmp->mp);
                                tsleep(&pmp->inmem_dirty_chains, PINTERLOCKED,
                                       "chnmem", hz);
                        }
                        continue;       /* loop on success or fail */
                }

                /*
                 * Try to start an early flush before we are forced to block.
                 */
                if (count > limit * 7 / 10)
                        speedup_syncer(pmp->mp);
                break;
        }
}

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

void
hammer2_pfs_memory_wakeup(hammer2_pfs_t *pmp)
{
        uint32_t waiting;

        if (pmp == NULL)
                return;

        for (;;) {
                waiting = pmp->inmem_dirty_chains;
                cpu_ccfence();
                if (atomic_cmpset_int(&pmp->inmem_dirty_chains,
                                       waiting,
                                       (waiting - 1) &
                                        ~HAMMER2_DIRTYCHAIN_WAITING)) {
                        break;
                }
        }

        if (waiting & HAMMER2_DIRTYCHAIN_WAITING)
                wakeup(&pmp->inmem_dirty_chains);
}

/*
 * Debugging
 */
void
hammer2_dump_chain(hammer2_chain_t *chain, int tab, int *countp, char pfx)
{
        hammer2_chain_t *scan;
        hammer2_chain_t *parent;

        --*countp;
        if (*countp == 0) {
                kprintf("%*.*s...\n", tab, tab, "");
                return;
        }
        if (*countp < 0)
                return;
        kprintf("%*.*s%c-chain %p.%d %016jx/%d mir=%016jx\n",
                tab, tab, "", pfx,
                chain, chain->bref.type,
                chain->bref.key, chain->bref.keybits,
                chain->bref.mirror_tid);

        kprintf("%*.*s      [%08x] (%s) refs=%d",
                tab, tab, "",
                chain->flags,
                ((chain->bref.type == HAMMER2_BREF_TYPE_INODE &&
                chain->data) ?  (char *)chain->data->ipdata.filename : "?"),
                chain->refs);

        parent = chain->parent;
        if (parent)
                kprintf("\n%*.*s      p=%p [pflags %08x prefs %d",
                        tab, tab, "",
                        parent, parent->flags, parent->refs);
        if (RB_EMPTY(&chain->core.rbtree)) {
                kprintf("\n");
        } else {
                kprintf(" {\n");
                RB_FOREACH(scan, hammer2_chain_tree, &chain->core.rbtree)
                        hammer2_dump_chain(scan, tab + 4, countp, 'a');
                if (chain->bref.type == HAMMER2_BREF_TYPE_INODE && chain->data)
                        kprintf("%*.*s}(%s)\n", tab, tab, "",
                                chain->data->ipdata.filename);
                else
                        kprintf("%*.*s}\n", tab, tab, "");
        }
}